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Parental age can have considerable effects on offspring phenotypes and health. However, intergenerational effects may also have longer term effects on offspring fitness. Few studies have investigated parental age effects on offspring fitness in natural populations while also testing for sex- and environment-specific effects. Further, longitudinal parental age effects may be masked by population-level processes such as the selective disappearance of poor-quality individuals. Here, we used multigenerational data collected on individually marked Seychelles warblers (Acrocephalus sechellensis) to investigate the impact of maternal and paternal age on offspring life span and lifetime reproductive success. We found negative effects of maternal age on female offspring life span and lifetime reproductive success, which were driven by within-mother effects. There was no difference in annual reproductive output of females born to older versus younger mothers, suggesting that the differences in offspring lifetime reproductive success were driven by effects on offspring life span. In contrast, there was no association between paternal age and female offspring life span or either maternal or paternal age and male offspring life span. Lifetime reproductive success, but not annual reproductive success, of male offspring increased with maternal age, but this was driven by between-mother effects. No paternal age effects were found on female offspring lifetime reproductive success but there was a positive between-father effect on male offspring lifetime reproductive success. We did not find strong evidence for environment-dependent parental age effects. Our study provides evidence for parental age effects on the lifetime fitness of offspring and shows that such effects can be sex dependent. These results add to the growing literature indicating the importance of intergenerational effects on long-term offspring performance and highlight that these effects can be an important driver of variation in longevity and fitness in the wild.

The increasing prevalence of advanced paternal age (APA) has mirrored the rise in maternal age. APA is associated with an increased risk of de novo pathogenic single-nucleotide variants, but this topic has been much less frequently discussed than advanced maternal age (AMA). To explore the awareness of pregnant women regarding paternal age effect (PAE) disorders, a self-administered questionnaire survey was conducted for pregnant women at their first prenatal visit before 17 weeks of gestation. A total of 120 valid respondents (95.2%) were included in the analyses. Of these, 63.3% of pregnant women were aware of PAE disorders. This was markedly lower than the 90.8% recognition of maternal age effect (MAE) disorders. One-third of women with awareness of MAE disorders were not aware of PAE disorders. Pregnant women who were parous, older than their male partners, with knowledge of prenatal testing prior to this pregnancy, and with experience of prenatal testing in a prior pregnancy were significantly more aware of PAE disorders than others. Awareness of PAE disorders was not associated with undergoing prenatal testing during the present pregnancy. Our results show that the prevalence of pregnant women’s awareness of PAE disorders was lower than that of MAE disorders. The current study served as a preliminary baseline of information about pregnant women’s awareness of PAE disorders. With the introduction of non-invasive prenatal testing, which has the potential to identify PAE disorders, these findings will help the development of a framework for comprehensive prenatal genetic counseling for APA pregnancies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12687-021-00555-y.

The birth prevalence of each common autosomal trisomy (21, 18 and 13) increases with advancing maternal age and this is the most important epidemiological risk factor. Prevalence during pregnancy is also dependent on gestational age. Other factors claimed to influence prevalence include paternal age, ethnicity, family history, premature reproductive aging, parity, twinning, smoking, environmental exposures, maternal medical conditions, and predispositions. We review the evidence for these associations since they may provide insights into causal mechanisms. When investigating potential co-factors it is important to adequately allow for maternal age and minimize its confounding contribution. This is well illustrated by reports of an inverse paternal age effect where there is strong correlation between parental ages. Gestational age at diagnosis, availability of prenatal screening, diagnostic testing, and elective termination of affected pregnancies and healthcare disparities also confound the studies on ethnicity, medical conditions, and predispositions or environmental factors. Data from twin zygosity studies demonstrate the importance of differences in fetal viability for affected pregnancies. We conclude that existing epidemiological evidence for most of the co-factors discussed should currently be considered tenuous; history of Down syndrome, albeit biased, may be an exception. The co-factors may yet provide clues to hitherto poorly understood causal pathways.

Participation in social behaviors that enhance group-level fitness may be influenced by mutations that affect patterns of social epistasis in human populations. Mutations that cause individuals to not participate in these behaviors may weaken the ability of members of a group to coordinate and regulate behavior, which may in turn negatively affect fitness. To investigate the possibility that de novo mutations degrade these adaptive social behaviors, we examine the effect of paternal age (as a well-established proxy for de novo mutation load) on one such social behavior, namely religious observance, since religiosity may be a group-level cultural adaptation facilitating enhanced social coordination. Using two large samples (Wisconsin Longitudinal Study and AddHealth), each of a different US birth cohort, paternal age was used to hierarchically predict respondent’s level of church attendance after controlling for multiple covariates. The effect is absent in WLS (β = .007, ns, N = 4560); however, it is present in AddHealth (β = − .046, p

The importance of (inherited) genetic impact in reading development is well established. De novo mutation is another important contributor that is recently gathering interest as a major liability of neurodevelopmental disorders, but has been neglected in reading research to date. Paternal age at childbirth (PatAGE) is known as the most prominent risk factor for de novo mutation, which has been repeatedly shown by molecular genetic studies. As one of the first efforts, we performed a preliminary investigation of the relationship between PatAGE, offspring's reading, and brain structure in a longitudinal neuroimaging study following 51 children from kindergarten through third grade. The results showed that greater PatAGE was significantly associated with worse reading, explaining an additional 9.5% of the variance after controlling for a number of confounds—including familial factors and cognitive‐linguistic reading precursors. Moreover, this effect was mediated by volumetric maturation of the left posterior thalamus from ages 5 to 8. Complementary analyses indicated the PatAGE‐related thalamic region was most likely located in the pulvinar nuclei and related to the dorsal attention network by using brain atlases, public datasets, and offspring's diffusion imaging data. Altogether, these findings provide novel insights into neurocognitive mechanisms underlying the PatAGE effect on reading acquisition during its earliest phase and suggest promising areas of future research., In the present study, Xia et al. demonstrate that advanced paternal age at childbirth (PatAGE) is negatively associated with offspring's reading. Moreover, this association is mediated by neuroanatomical maturation in the left posterior thalamus, which is closely linked with the dorsal attention network. These findings suggest a novel pathway through which parents affects their offspring's reading ability and suggest future avenues of research on PatAGE‐related factors, such as de novo mutation, in reading.

The chromosomal aneuploidies associated with advanced maternal age has been widely discussed and debated over decades. The paternal age effect associated with aneuploidies was underreported with limited evidence which left room for analysis and discussion. The researchers in a retrospective study, observed the paternal age of three chromosomal aneuploidies from the Indian population. The paternal age was included in the patient data with confirmed karyotype. The paternal age was divided into two groups: 30 years. With the help of Linear regression analysis the correlation of paternal age with children born with aneuploidies was analysed. The researchers made an interesting observation: paternal age was statistically significant as a confounding risk factor in chromosomal aneuploidy in both age categories for Down and Turner syndrome. These findings highlighted the importance of taking a strategic approach to the treatment of couples who are at risk of cytogenetic abnormalities. The correlation of chromosomal aneuploidies and the effect of young paternal age is an interesting factor raised and opened for further investigation and discussion to the future investigators.

Background Whether paternal age effect on schizophrenia is a causation or just an association due to confounding by selection into late parenthood is still debated. We investigated the association between paternal age and early onset of schizophrenia in offspring, controlling for both paternal and maternal predisposition to schizophrenia as empirically estimated using polygenic risk score (PRS) derived from the Psychiatric Genomics Consortium. Methods Among 2923 sporadic schizophrenia cases selected from the Schizophrenia Trio Genomic Research in Taiwan project, 1649 had parents’ genotyping data. The relationships of paternal schizophrenia PRS to paternal age at first birth (AFB) and of maternal schizophrenia PRS to maternal AFB were examined. A logistic regression model of patients’ early onset of schizophrenia (≤18 years old) on paternal age was conducted. Results Advanced paternal age over 20 years exhibited a trend of an increasing proportion of early onset of schizophrenia (odds ratio per 10-year increase in paternal age = 1.28, p = .007) after adjusting for maternal age, sex, and age. Older paternal AFB also exhibited an increasing trend of paternal schizophrenia PRS. Additionally, a U-shaped relationship between maternal AFB and maternal schizophrenia PRS was observed. After adjusting for both paternal and maternal schizophrenia PRS, the association of paternal age with patients’ early onset of schizophrenia remained (odds ratio = 1.29, p = .04). Conclusions The association between paternal age and early onset of schizophrenia was not confounded by parental PRS for schizophrenia, which partially captures parental genetic vulnerability to schizophrenia. Our findings support an independent role of paternal age per se in increased risk of early onset of schizophrenia in offspring.

Advanced paternal age (APA) is associated with infertility and other reproductive risks. Studies looking at APA and outcomes have used different paternal age cut-offs, which has complicated systematic evaluations of reproductive risk associated with paternal aging. This review of the literature suggests that the impact of paternal aging on adverse reproductive outcomes is small, but significant. Studies suggest the incidence of paternal age effect disorders attributed to de novo autosomal dominant mutations is less than 0.5%. Other risks associated with APA include infertility, miscarriage, birth defects, poor neurodevelopmental outcomes, and childhood cancer. Although the increasing prevalence of APA has mirrored the rise in maternal age, this topic has not received similar attention. In this review, we summarize the available literature on the reproductive risks associated with APA to provide a framework for comprehensive genetic counseling and evidence-based management of APA pregnancies.

The mutation rate is a fundamental evolutionary parameter with direct and appreciable effects on the health and function of individuals. Here, we examine this important parameter in the domestic cat, a beloved companion animal as well as a valuable biomedical model. We estimate a mutation rate of 0.86 × 10-8 per bp per generation for the domestic cat (at an average parental age of 3.8 years). We find evidence for a significant paternal age effect, with more mutations transmitted by older sires. Our analyses suggest that the cat and the human have accrued similar numbers of mutations in the germline before reaching sexual maturity. The per-generation mutation rate in the cat is 28% lower than what has been observed in humans, but is consistent with the shorter generation time in the cat. Using a model of reproductive longevity, which takes into account differences in the reproductive age and time to sexual maturity, we are able to explain much of the difference in per-generation rates between species. We further apply our reproductive longevity model in a novel analysis of mutation spectra and find that the spectrum for the cat resembles the human mutation spectrum at a younger age of reproduction. Together, these results implicate changes in life-history as a driver of mutation rate evolution between species. As the first direct observation of the paternal age effect outside of rodents and primates, our results also suggest a phenomenon that may be universal among mammals.

Paternal aging and the prevalence of neurodevelopmental disorders in offspring are well documented. Yet, the underlying mechanism and the mode of inheritance have not been conclusively established. Advancing paternal age is a subtle and varying phenotype. As such, it is likely that a threshold for cumulative risk may exist that, if surpassed, culminates in a predisposition to disease and ultimately an observed phenotype in offspring. Epigenetic regulation provides a plausible explanation for the nongenetic paternal transmission of disease susceptibility. With the use of whole‐genome methylation sequencing, the data described herein substantiate an increasingly compromised DNA methylation profile as sperm ages and, for the first time, also demonstrate a generational correlation in sperm and blastocyst of an altered methylome associated with advanced paternal age. Methylation alterations are not randomly distributed across the genome, but appear clustered at certain chromosomal locations, and significantly colocalize with regions of nucleosome retention. Genes associated with autism spectrum disorder, schizophrenia, and bipolar disorder are significantly enriched with causative methylation aberrations in both sperm and embryos from aged fathers. The long‐term health burden and societal economic impact of these conditions are substantial and will continue with increasingly prevalent diagnosis. This work provides a mechanistic link between the paternal age effect and offspring neurodevelopmental disorders leading to a better understanding of causation and investigation into potential future therapy., A generational epigenetic correlation was observed for human sperm and blastocyst methylomes in association with advanced paternal age at genes implicated in offspring neurodevelopmental disorders, including autism spectrum disorder, schizophrenia, and bipolar disorder. This work provides a mechanistic link between the paternal age effect and offspring neurodevelopmental disorders leading to a better understanding of causation and clinical management.

Νovel emergence of schizophrenia (SCZ) in its sporadic type has been linked, among many candidate epigenetic factors, with advanced paternal age (PA) and advanced maternal age (MA). The most common hypothesis to the paternal age effect is the increased "de novo mutations" during spermatogenesis, while the maternal age hypothesis, though controversial, is at most based on studies that support higher frequency of perinatal complications. Our sample consisted of 462 subjects with DSM-IV-TR SCZ spectrum disorders from the outpatient unit of Eginition Hospital in Athens, Greece, who were further screened for heritability and were divided in a group of sporadic cases (no reported family history for SCZ related disorders up to 2nd degree relatives) and a group of familial SCZ-spectrum disorder cases (positive reported history for SCZ spectrum). These two groups of patients were compared regarding either paternal or maternal age, while the familial type band was used as a control group. The aim of this retrospective file study was to examine whether advanced parental age may contribute in novel appearance of non-affective psychosis in offspring. Using logistic regression analysis, we found that the risk for the sporadic type, as compared to familial type, showed a significant increase for both advanced MA (OR=4.39, p=0.001) and PA (OR=1.92, p=0.012). After adjusting for confounding effects for the other parent's age and gender, the risk effect for the sporadic type of SCZ remained statistically significant for both advanced MA (OR=4.04, p=0.002) and advanced PA, but with a loss of statistical power (OR=1.72, p=0.049). Few studies have been conducted in Greece concerning the role of parental age in SCZ. Our study is consistent with current literature which indicates that both advanced MA and PA may contribute to an increased risk for emergence of sporadic type of SCZ. Furthermore, it is implied that this risk for the sporadic type as compared to the familial type could be higher for advanced MA than advanced PA. Patients with the sporadic type of SCZ, though clinically indistinguishable from the patients with the familial type of the disorder, may share other pathophysiological underlying mechanisms in which parental age, especially advanced MA, may be a candidate mediator. However, future studies could help clarify the role of both PA and MA in the pathophysiology of the disorder.

Spermatogenesis is a highly complex biological process during which germ cells undergo recurrent rounds of DNA replication and cell division that may predispose to random mutational events. Hence, germ cells are vulnerable to the introduction of a range of de novo mutations, in particular chromosomal aberrations, point mutations and small indels. The main mechanisms through which mutations may occur during spermatogenesis are (i) errors in DNA replication, (ii) inefficient repair of non-replicative DNA damage between cell divisions and (iii) exposure to mutagens during lifetime. Any genetic alteration in the spermatozoa, if not repaired/eliminated, can be passed on to the offspring, potentially leading to malformations, chromosomal anomalies and monogenic diseases. Spontaneous de novo mutations tend to arise and accumulate with a higher frequency during testicular aging. In fact, there is an increased incidence of some chromosomal aberrations and a greater risk of congenital disorders, collectively termed paternal age effect (PAE), in children conceived by fathers with advanced age. PAE disorders are related to well-characterized de novo point mutations leading to a selective advantage on the mutant spermatogonial stem cells that cause a progressive enrichment over time of mutant spermatozoa in the testis.The purpose of this chapter is to provide a summary on the spontaneous genetic alterations that occur during spermatogenesis, focusing on their underlying mechanisms and their consequences in the offspring.

BACKGROUND The effect of maternal age at conception on various aspects of offspring health is well documented and often discussed. We seldom hear about the paternal age effect on offspring health, although the link is now almost as solid as with maternal age. The causes behind this, however, are drastically different between males and females. CONTENT In this review article, we will first examine documented physiological changes linked to paternal age effect. We will start with all morphological aspects of the testis that have been shown to be altered with aging. We will then move on to all the parameters of spermatogenesis that are linked with paternal age at conception. The biggest part of this review will focus on genetic changes associated with paternal age effects. Several studies that have established a strong link between paternal age at conception and the rate of de novo mutations will be reviewed. We will next discuss paternal age effects associated with telomere length and try to better understand the seemingly contradictory results. Finally, severe diseases that affect brain functions and normal development have been associated with older paternal age at conception. In this context, we will discuss the cases of autism spectrum disorder and schizophrenia, as well as several childhood cancers. SUMMARY In many Western civilizations, the age at which parents have their first child has increased substantially in recent decades. It is important to summarize major health issues associated with an increased paternal age at conception to better model public health systems.

Advanced paternal age (APA) is a risk factor for schizophrenia (Sz) and bipolar disorder (BP). Putative mechanisms include heritable genetic factors, de novo mutations, and epigenetic mechanisms. Few studies have explored phenotypic features associated with APA. The Genomic Psychiatry Cohort established a clinically characterized repository of genomic samples from subjects with a Sz-BP diagnosis or unaffected controls, 12,975 with parental age information. We estimated relative risk ratios for Sz, schizoaffective depressed and bipolar types (SA-D, SA-B), and BP with and without history of psychotic features (PF) relative to the control group, comparing each paternal age group to the reference group 20-24 years. All tests were two-sided with adjustment for multiple comparisons. Subjects with fathers age 45+ had significantly higher risk for all diagnoses except for BP w/o PF. APA also bore no significant relation to family psychiatric history. In conclusion, we replicated APA as a risk factor for Sz. To our knowledge, this is the first published report of APA in a BP sample stratified by psychosis history, extending this association only in BP w/PF. This suggests that phenotypic expression of the APA effect in Sz-BP spectrum is psychosis, per se, rather than other aspects of these complex disorders. The lack of a significant relationship between paternal age and familial disease patterns suggests that underlying mechanisms of the paternal age effect may involve a complex interaction of heritable and non-heritable factors. The authors discuss implications and testable hypotheses, starting with a focus on genetic mechanisms and endophenotypic expressions of dopaminergic function. © 2015 Wiley Periodicals, Inc.

Although controversial, increasing paternal age has been shown to negatively affect assisted reproductive technology (ART) outcomes and success rates. Most studies investigating the effect of paternal age on ART outcomes use a donor oocyte model to minimize maternal aneuploidy contribution. This study sought to determine whether increasing paternal age is associated with adverse in vitro fertilization (IVF) outcomes when aneuploidy is minimized using preimplantation genetic screening. There were 573 single thawed euploid embryo transfers from 473 patients undergoing oocyte donor and autologous IVF cycles. Cycles were categorized according to paternal age at oocyte retrieval, and an age adjustment was performed for maternal age in order to evaluate for an isolated paternal age effect. Fertilization rate was found to decrease significantly with increasing paternal age ( P = .04). After controlling for oocyte age, there was no significant difference in pregnancy outcomes across all paternal age categories after euploid embryo transfer, including implantation rate ( P = .23), clinical pregnancy rate ( P = .51), and spontaneous abortion rate ( P = .55). Therefore, if a couple is able to produce and transfer a single thawed euploid embryo, no difference in IVF pregnancy outcomes is identified with increasing paternal age.

The past decades have seen a remarkable shift in the demographics of childbearing in Western countries. The risk for offspring with chromosomal aneuploidies with advancing maternal age is well known, but most studies failed to demonstrate a paternal age effect. Retrospectively, we analyzed two case data sets containing parental ages from pre- and postnatal cases with trisomies 21, 13 and 18. The reference data set contains the parental ages of the general Swiss population. We dichotomized all couples into two distinct groups. In the first group, the mothers' integral age was as least as the father's age or older. We compared the frequency of cases in nine 5-year intervals of maternal age. In addition, we computed logistic regression models for the binary endpoint aneuploidy yes/no where paternal ages were incorporated as linear or quadratic, as well as smooth functions within a generalized additive model framework. We demonstrated that the proportion of younger fathers is uniformly different between cases and controls of live-born trisomy 21 as well, although not reaching significance, for fetuses over all mother's ages. Logistic regression models with different strategies to incorporate paternal ages confirmed our findings. The negative paternal age effect was also found in pre- and postnatal cases taken together with trisomies 13 and 18. The couples with younger fathers face almost twofold odds for a child with Down syndrome (DS). We estimated odds curves for parental ages. If confirmation of these findings can be achieved, the management of couples at risk needs a major correction of the risk stratification.

Telomere length (TL) predicts health and survival across taxa. Variation in TL between individuals is thought to be largely of genetic origin, but telomere inheritance is unusual, because zygotes already express a TL phenotype, the TL of the parental gametes. Offspring TL changes with paternal age in many species including humans, presumably through age-related TL changes in sperm, suggesting an epigenetic inheritance mechanism. However, present evidence is based on cross-sectional analyses, and age at reproduction is confounded with between-father variation in TL. Furthermore, the quantitative importance of epigenetic TL inheritance is unknown. Using longitudinal data of free-living jackdaws Corvus monedula, we show that erythrocyte TL of subsequent offspring decreases with parental age within individual fathers, but not mothers. By cross-fostering eggs, we confirmed the paternal age effect to be independent of paternal age dependent care. Epigenetic inheritance accounted for a minimum of 34% of the variance in offspring TL that was explained by paternal TL. This is a minimum estimate, because it ignores the epigenetic component in paternal TL variation and sperm TL heterogeneity within ejaculates. Our results indicate an important epigenetic component in the heritability of TL with potential consequences for offspring fitness prospects., Author summary Telomeres are DNA-protein structures at chromosome ends and a short telomere length predicts reduced survival in humans, birds and other organisms. Variation in telomere length between individuals is thought to be largely of genetic origin, but telomere inheritance may be unusual because not only genes regulating telomere length are inherited, but a fertilised cell already has a telomere length (from the parental gametes). Using long-term individual-based data of jackdaw families (a small corvid species), we found that as fathers aged, they produced chicks with shorter telomeres. This suggests that telomere length inheritance has an epigenetic component. To investigate to what extent telomere length in the fertilised cell affects telomere length after birth, we compared telomere length over years within fathers with the telomere length of their consecutive offspring. This epigenetic component explained a substantial part (≥ one third) of the telomere length inheritance; whereas there was no such effect of maternal telomere length. The sex difference fits the idea that lifelong sperm formation leads to change in telomere length of the sperm cells, whereas female gametes are all formed before birth and their telomere length does not change over time.

Telomeres are repeating sequences of DNA found at the ends of chromosomes, that shorten in most proliferating tissues as we age and our cells replicate. Shortened telomeres result in a reduced capacity for cell proliferation, and in adults have been shown to predict increased morbidity and earlier mortality. Whereas telomeres tend to shorten with cell replications in most tissues, sperm telomere length appears to run counter to this trend by increasing with each cell division, leading to a lengthening of sperm telomeres as men age. As a result, offspring of older fathers have longer telomere lengths. This finding suggests that the age at which a man conceives his offspring might have important influences on his children’s health and longevity by altering the length of telomeres that they inherit. Abraham Aviv and Ezra Susser are leaders in considering this paternal age at conception (PAC) effect on offspring telomere lengths, and their article in this issue is an important review of this topic. In addition to discussing the basic molecular biology and health implications of the PAC effect, they also briefly consider some of the evolutionary dynamics that are implied by this unusual phenomenon. Here we elaborate on the evolutionary significance of the PAC effect and note some points where our interpretations of the literature differ slightly from those of Aviv and Susser.

Background: A risk of miscarriage increases with increase in parental age. However many studies investigate only the effect of maternal age. This study focused on both the maternal age and paternal age effect on miscarriage.Method: Couples with the pregnancy loss issue were studied with the age range 19 to 50 years. Maternal age and paternal age were analyzed together. The couples composed of a women and man both aged 20-29 years were used as reference group.Results: Universally the risk of miscarriage was found to be higher if the women age was 35 years or more and man with age was 40 years or more. But due to small sample size this has not been proved in this study. Conclusions: The risk of pregnancy loss increases if male and female partners are having advanced age.

Motivation: As the mean age of parenthood grows, the effect of parental age on genetic disease and child health becomes ever more important. A number of autosomal dominant disorders show a dramatic paternal age effect due to selfish mutations: substitutions that grant spermatogonial stem cells (SSCs) a selective advantage in the testes of the father, but have a deleterious effect in offspring. In this paper we present a computational technique to model the SSC niche in order to examine the phenomenon and draw conclusions across different genes and disorders. Results: We used a Markov chain to model the probabilities of mutation and positive selection with cell divisions. The model was fitted to available data on disease incidence and also mutation assays of sperm donors. Strength of selective advantage is presented for a range of disorders including Apert’s syndrome and achondroplasia. Incidence of the diseases was predicted closely for most disorders and was heavily influenced by the site-specific mutation rate and the number of mutable alleles. The model also successfully predicted a stronger selective advantage for more strongly activating gain-of-function mutations within the same gene. Both positive selection and the rate of copy-error mutations are important in adequately explaining the paternal age effect. Availability and Implementation: C ++/R source codes and documentation including compilation instructions are available under GNU license at https://github.com/anwala/NicheSimulation. Contact: ewhel001@odu.edu Supplementary information: Supplementary data are available at Bioinformatics online.

Popular theory suggests that facial averageness is preferred in a partner for genetic benefits to offspring. However, whether facial averageness is associated with genetic quality is yet to be established. Here, we computed an objective measure of facial averageness for a large sample (N = 1,823) of identical and nonidentical twins and their siblings to test two predictions from the theory that facial averageness reflects genetic quality. First, we use biometrical modelling to estimate the heritability of facial averageness, which is necessary if it reflects genetic quality. We also test for a genetic association between facial averageness and facial attractiveness. Second, we assess whether paternal age at conception (a proxy of mutation load) is associated with facial averageness and facial attractiveness. Our findings are mixed with respect to our hypotheses. While we found that facial averageness does have a genetic component, and a significant phenotypic correlation exists between facial averageness and attractiveness, we did not find a genetic correlation between facial averageness and attractiveness (therefore, we cannot say that the genes that affect facial averageness also affect facial attractiveness) and paternal age at conception was not negatively associated with facial averageness. These findings support some of the previously untested assumptions of the 'genetic benefits' account of facial averageness, but cast doubt on others.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field. Mutations generate sequence diversity and provide a substrate for selection. The rate of de novo mutations is therefore of major importance to evolution. Here we conduct a study of genome-wide mutation rates by sequencing the entire genomes of 78 Icelandic parent-offspring trios at high coverage. We show that in our samples, with an average father's age of 29.7, the average de novo mutation rate is 1.20 × 10(-8) per nucleotide per generation. Most notably, the diversity in mutation rate of single nucleotide polymorphisms is dominated by the age of the father at conception of the child. The effect is an increase of about two mutations per year. An exponential model estimates paternal mutations doubling every 16.5 years. After accounting for random Poisson variation, father's age is estimated to explain nearly all of the remaining variation in the de novo mutation counts. These observations shed light on the importance of the father's age on the risk of diseases such as schizophrenia and autism. National Institutes of Health MH071425 info:eu-repo/grantAgreement/EC/FP7/223423 IAPP-MC-251592 European Community IMI grant EU-AIMS 115300

This study investigated for the first time in the psychiatric literature the effect of parental age on age-of-onset (AO) in bipolar I disorder (BPI) in relation to proband sex and family history (FH) for major psychoses in a sample of 564 BPI probands. All probands, 72.68% of their first-degree and 12.13% of their second-degree relatives were directly interviewed. The FH-method was used for all unavailable relatives. The diagnoses were made according to DSM-IVTR. The impact of parental age on proband early/late AO was evaluated through logistic regression with the cut-off for early AO determined through commingling analysis. We found evidence for a significant influence of increasing paternal age, and especially age ≥35 years, on AO of BPI disorder in the total sample (OR = 0.54, CI: 0.35–0.80), in the female subsample (OR = 0.44, CI: 0.25–0.78), in the sporadic subsample (OR = 0.64, CI: 0.38–0.95), and in the subsample with FH of recurrent unipolar major depression (Mdd-RUP) (OR = 0.55, CI: 0.34–0.87). No significant effect of paternal age on disease AO was found in patients with FH of bipolar (BP), schizoaffective disorders (SA), or schizophrenia (SCZ), nor in males. Mean age was significantly higher in fathers of sporadic cases and of cases with FH of Mdd-RUP than in fathers of cases with FH of BP/SA/SCZ (P = 0.011). Maternal age had no significant effect either in the total sample or in subsamples defined by proband sex or FH. In conclusion, in our sample increasing paternal age lowered the onset of BPI selectively, the effect being related to the female sex and FH-type. © 2012 Wiley Periodicals, Inc.

Autosomal dominant conditions are known to be associated with advanced paternal age, and it has been suggested that retinoblastoma (Rb) also exhibits a paternal age effect due to the paternal origin of most new germline RB1 mutations. To further our understanding of the association of parental age and risk of de novo germline RB1 mutations, we evaluated the effect of parental age in a cohort of Rb survivors in the United States. A cohort of 262 Rb patients was retrospectively identified at one institution, and telephone interviews were conducted with parents of 160 survivors (65.3%). We classified Rb survivors into three groups: those with unilateral Rb were classified as sporadic if they had no or unknown family history of Rb, those with bilateral Rb were classified as having a de novo germline mutation if they had no or unknown family history of Rb, and those with unilateral or bilateral Rb, who had a family history of Rb, were classified as familial. We built two sets of nested logistic regression models to detect an increased odds of the de novo germline mutation classification related to older parental age compared to sporadic and familial Rb classifications. The modeling strategy evaluated effects of continuous increasing maternal and paternal age and 5-year age increases adjusted for the age of the other parent. Mean maternal ages for survivors classified as having de novo germline mutations and sporadic Rb were similar (28.3 and 28.5, respectively) as were mean paternal ages (31.9 and 31.2, respectively), and all were significantly higher than the weighted general US population means. In contrast, maternal and paternal ages for familial Rb did not differ significantly from the weighted US general population means. Although we noted no significant differences between mean maternal and paternal ages between each of the three Rb classification groups, we found increased odds of a survivor being in the de novo germline mutation group for each 5-year increase in paternal age, but these findings were not statistically significant (de novo vs. sporadic ORs 30-34 = 1.7 [0.7-4], ≥ 35 = 1.3 [0.5-3.3]; de novo vs. familial ORs 30-34 = 2.8 [1.0-8.4], ≥ 35 = 1.6 [0.6-4.6]). Our study suggests a weak paternal age effect for Rb resulting from de novo germline mutations consistent with the paternal origin of most of these mutations.

BACKGROUND: Schizophrenia is an aetiologically heterogeneous syndrome, with a strong genetic component. Despite a reduced fertility in this disorder, its prevalence is maintained and could be explained by de novo genetic mutations. Advanced paternal age (APA) is a major source of new mutations in human beings and could thus be associated with an increased risk of developing schizophrenia in offspring. New mutations related to APA have been implicated as a cause of sporadic cases in several autosomal dominant diseases and also in neurodevelopmental diseases, autism, intellectual disabilities, and social functioning. The aim of the present study was to summarize the results of studies investigating the role of APA, and to discuss some interpretations. METHODS: All relevant studies were identified through the National Library of Medicine (PubMed(®) database). Keywords used for research were "age" and "schizophrenia" linked to "paternal or father". We have identified and analysed eight cohort studies, five case-control studies, two meta-analyses, and one review concerning different father's mutations potentially transmitted, two studies comparing paternal age at conception between sporadic versus familial cases of schizophrenia. All studies selected have been published between 2000 and 2009. RESULTS: After controlling for several confounding factors including maternal age, the relative risk of schizophrenia increased from 1.84 to 4.62 in offspring of fathers with an older age of fatherhood. Mother's age showed no significant effects after adjusting for paternal age. There was a significant association between paternal age and risk of developing schizophrenia, there was a weaker association with psychosis. DISCUSSION: The results of these different studies are confirmed by two recent meta-analyses which found an increased risk of schizophrenia in offspring of fathers older than 35 years. Two main hypotheses could explain these results. The first one is based on the presence of new mutations in the spermatogonia, possibly because of accumulating replication errors in spermatogonial cell lines. This hypothesis is confirmed by Malaspina et al. (2002) [19], who found that patients without a family history of schizophrenia had significantly older fathers than probands with a positive family history of schizophrenia. However, this result has not been confirmed by other studies, and paternal age effect could be also explained by a mechanism called imprinting, which is a form of gene regulation. The second hypothesis is based on the fact that fathers with schizophrenia spectrum personality disorder, known to be genetically related to schizophrenia, could have an advanced age at conception. However, regarding this hypothesis, advanced maternal age at conception should be a risk factor for schizophrenia, and this is not the case. Thus, the first hypothesis seems more plausible than the second. APA has been identified as a risk factor for other psychiatric disorders such as autism, bipolar disorder, obsessive-compulsive disorder, and phobia, and thus seems to be a non-specific risk factor. Furthermore, its association with impaired neurocognitive outcomes during infancy and childhood in normal populations raises the question of the phenotype linked to APA. CONCLUSION: APA at conception appears to be a risk factor for schizophrenia. This risk factor probably interacts with genetic factors in a gene-environment interaction. To date, there is no validated cut-off at which the risk is significantly increased in offspring. In the future, studies could benefit from analyzing the phenotype related to APA.

This paper presents a computational model for simulating the propagation of de novo mutations and paternal age effects in populations. The model uses data for paternal de novo mutation rates depending on age and demographic data such as age distributions, birth distributions versus age, varying life expectancy, and correlations with fertility. The number of paternal de novo mutations in children increases with the paternal age at conception. This might be of interest considering that the average paternal age has risen significantly in many societies throughout the last century. The model introduced below can superimpose and extrapolate different effects based on demographic dynamics. This includes the assessment of statistically associated neurological disorders in offspring, particularly IQ decay depending on the paternal age and other medical phenotypes which constitute paternal age effects. Yearly paternal mutation rates and correlations with paternal age were used to simulate both, de novo mutation propagation and probabilities for correlating conditions such as IQ decay. The extrapolated effect after several generations of persistently elevated paternal age appears to be drastic. To account for possibly mitigating factors, the paternal age effect has been super-positioned with the Flynn effect in simulated cases. The model automatically generates distributions for varying paternal ages, not just single cases, in convenient 3D distributions. The model simulates each person’s individual reproductive incidents through a particle type approach which is more rigorous than insufficiently adaptive, continuum models based on partial differential equations. The model is not only applicable to humans and yields many valuable conclusions for a wide array of topics including the paternal age effect, correlations with intelligence, evolution, bottlenecks in evolution, as well as the role of de novo mutation.

With congenital central hypoventilation syndrome (CCHS), most patients have a de novo 5–13 polyalanine expansion mutation in PHOX2B. We reported previously that de novo polyalanine expansion mutations were of paternal origin and were derived from unequal sister chromatid exchange during spermatogenesis in six and four informative families, respectively. In this study, we analyzed the relationship between haplotypes and de novo polyalanine expansion in PHOX2B and found that haplotypes carrying rs17884724:A>C were detected frequently in 7-alanine expanded (27-alanine) mutant alleles, which are the most prevalent mutations in CCHS. The allele with rs17884724:A>C made fewer nucleotide mismatches in the misalignment at crossing-over than the allele without rs17884724:A>C. The high frequency of rs17884724:A>C in 7-alanine expansion (27-alanine) mutations also supported the unequal crossover mechanism for polyalanine expansion. We also confirmed the paternal origin of de novo polyalanine expansion mutation and unequal sister chromatid exchange association in three more patients. In spite of paternal bias, the paternal age effect on CCHS incidence was not observed. De novo polyalanine expansion mutations are mainly derived from unequal sister chromatid exchange during spermatogenesis because of replication and/or repair systems that are specific for spermatogenesis.

Genes mutated in congenital malformation syndromes are frequently implicated in oncogenesis, but the causative germline and somatic mutations occur in separate cells at different times of an organism's life. Here we unify these processes to a single cellular event for mutations arising in male germ cells that show a paternal age effect. Screening of 30 spermatocytic seminomas for oncogenic mutations in 17 genes identified 2 mutations in FGFR3 (both 1948A>G, encoding K650E, which causes thanatophoric dysplasia in the germline) and 5 mutations in HRAS. Massively parallel sequencing of sperm DNA showed that levels of the FGFR3 mutation increase with paternal age and that the mutation spectrum at the Lys650 codon is similar to that observed in bladder cancer. Most spermatocytic seminomas show increased immunoreactivity for FGFR3 and/or HRAS. We propose that paternal age-effect mutations activate a common 'selfish' pathway supporting proliferation in the testis, leading to diverse phenotypes in the next generation including fetal lethality, congenital syndromes and cancer predisposition.

In an attempt to resolve conflicting evidence from the literature concerning the existence of a paternal age effect in 46,X,i(Xq) Turner's syndrome, we have analysed data on all known cases ascertained in the main population centres of Scotland and on others ascertained in England, using population controls matched for year of birth. There was a significant (P = 0.02) increase of 2.3 years in the mean paternal age of the Scottish cases, and a smaller and non-significant increase in their mean maternal age. Logistic regression analysis confirmed that the primary association was with paternal, rather than maternal, age. For the English cases, however, there were small and non-significant decreases in their mean maternal and paternal ages. The differences between the two groups were also significant, but cannot be explained by any likely source of ascertainment bias. We therefore conclude that there is no evidence for a universal paternal age effect in this condition, but that at least one mechanism of origin, occurring with variable frequency, may be associated with increased paternal age. Using data from this and earlier published studies, we estimate the incidence of individuals with a 46,X,i(Xq) cell line to be between 3.3 and 13 per 10(5) female livebirths.

The cause of ALS remains largely unknown for the 90% with no known family history, but spontaneous mutation to risk alleles of as yet unidentified genes is possible. It has long been recognized that genetic diseases may be more likely to occur in the last born children of a sibship because increased paternal age is associated with an increased spontaneous point mutation rate in sperm. To test the hypothesis that such a mechanism is responsible for sporadic ALS, we have performed a retrospective analysis of birth order position. We have analyzed sibships of size greater than four using a binomial test for birth position. The 478 pedigrees studied show no birth order effect, suggesting that any genetic contributions to sporadic ALS are more likely to be through deletion in large genes or interactions of common polymorphisms, rather than frequent spontaneous point mutation. This is encouraging for the prospect of finding sporadic ALS susceptibility genes using genome-wide association mapping.

Summary The ‘selfish spermatogonial selection’- model was proposed to explain the paternal age effect (PAE) of some congenital disorders associated with point mutations in male germ cells. According to this, spermatogonia carrying pathogenic mutations gain a selection advantage over non-mutated spermatogonia which leads to an increased number of mutated spermatogonia and consequently spermatozoa over time. Recently, an immunohistochemical approach using the premeiotic marker melanoma antigen family A4 (MAGE A4) was undertaken by the Wilkie group to confirm the presence of microclones of putatively mutated spermatogonia in testes of elderly men. The objective of our study was the age-dependent assessment of testes from men with normal spermatogenesis using MAGE A4 immunohistochemistry to identify and corroborate cellular clusters indicative for ‘selfish spermatogonial selection’ in our cohort. We analyzed testicular tissues obtained from men with normal spermatogenesis assigned to three age groups [(1) 28.8 ± 2.7 years; (2) 48.1 ± 1 years; (3) 71.9 ± 6.8 years, n/group = 8]. We could detect very similar distribution patterns of MAGE A4-positive cells and the presence of several types of microclusters as reported previously. However, these cellular clusters, indicative for clonal expansion, were not only present in testes from elderly men but also in those from age group 1 and 2. Using graphical three-dimensional modelling, we identified that cross-section directions e.g. longitudinal sections might provoke misleading interpretation of spermatogonial clusters, in particular when the tissue processing is limited. Thus, appropriate fixation and embedding is needed for reliable analysis of testicular sections. We therefore propose a more careful interpretation of such spermatogonial clusters and recommend a 3-D analysis to unequivocally determine ‘selfish spermatogonial selection’-manifestations.

Advanced paternal age is a well-established risk factor for the development of schizophrenia (SZ),1, 2, 3 and an increased rate of de novo mutations with increasing paternal age has been proposed as the chief explanation for this association.4 However, the paternal age effect could also be as a result of other potential explanations. For example, analyses of Danish registry data revealed that the paternal age effect was attributable to paternal age at birth of the first child in the sibship, rather than to age at birth of the child with SZ,5 which suggests that some explanation other than de novo mutations may explain the reported paternal age association with SZ. Furthermore, advanced maternal age, that has also been implicated in the risk of neurodevelopmental disorders (NDDs) via unknown mechanisms (that is, not de novo mutation), should also be incorporated in this conceptualization.6, 7 Therefore, findings regarding de novo mutations as the explanation for the association between advanced paternal age and SZ are inconclusive because covariates, such as maternal age8 and family size,9 which may index other potential mechanisms than paternally derived de novo mutations, have not been simultaneously considered in most prior analyses.

Autosomal dominant Townes-Brocks syndrome (TBS) is characterized by imperforate anus, triphalangeal and supernumerary thumbs, dysplastic ears and sensorineural hearing loss, and may also involve other organ systems. Strong inter- and intrafamiliar variability is known. Approximately 50% of TBS cases are sporadic and due to de novo mutations in the SALL1 gene. SALL1 encodes a zinc finger protein operating as a transcriptional repressor and localizing to pericentromeric heterochromatin. We traced the parental origin of SALL1 mutations in sporadic TBS by analysis of linkage between SALL1 mutations and exonic or intronic polymorphisms in 16 families with 10 different mutations. Mutations were of paternal origin in 14 of 16 cases (87.5%). Paternal origin was independent of the mutation type. The mean paternal age at conception was 29.9 and the mean maternal age 26.5 years. We conclude that de novo mutations in SALL1 mostly occur on the paternally derived chromosome 16 without an obvious age effect.

Increased paternal age is associated with a greater risk of producing children with genetic disorders originating from de novo germline mutations. Mice mimic the human condition by displaying an age-associated increase in spontaneous mutant frequency in spermatogenic cells. The observed increase in mutant frequency appears to be associated with a decrease in the DNA repair protein, AP endonuclease 1 (APEX1) and Apex1 heterozygous mice display an accelerated paternal age effect as young adults. In this study, we directly tested if APEX1 over-expression in cell lines and transgenic mice could prevent increases in mutagenesis. Cell lines with ectopic expression of APEX1 had increased APEX1 activity and lower spontaneous and induced mutations in the lacI reporter gene relative to the control. Spermatogenic cells obtained from mice transgenic for human APEX1 displayed increased APEX1 activity, were protected from the age-dependent increase in spontaneous germline mutagenesis, and exhibited increased apoptosis in the spermatogonial cell population. These results directly indicate that increases in APEX1 level confer protection against the murine paternal age effect, thus highlighting the role of APEX1 in preserving reproductive health with increasing age and in protection against genotoxin-induced mutagenesis in somatic cells.

A simultaneous four-colour fluorescence in situ hybridisation (FISH) assay was used in human sperm in order to search for a paternal age effect on: (1) the incidence of structural aberrations and aneuploidy of chromosome 9, and (2) the sex ratio in both normal spermatozoa and spermatozoa with a numerical or structural abnormality of chromosome 9. The sperm samples were collected from 18 healthy donors, aged 24–74 years (mean 48.8 years old). Specific probes for the subtelomeric 9q region (9qter), centromeric regions of chromosomes 6 and 9, and the satellite III region of the Y chromosome were used for FISH analysis. A total of 190 117 sperms were evaluated with a minimum of 10 000 sperm scored from each donor. A significant linear increase in the overall level of duplications and deletions for the centromeric and subtelomeric regions of chromosome 9 (P≤0.002), chromosome 9 disomy (P

The lifelong spermatogonial stem cell divisions unique to male germ cell production are thought to contribute to a higher mutation frequency in males. The fact that certain de novo human genetic conditions (e.g., achondroplasia) increase in incidence with the age of the father is consistent with this idea. Although it is assumed that the paternal age effect is the result of an increasing frequency of mutant sperm as a man grows older, no direct molecular measurement of the germ-line mutation frequency has been made to confirm this hypothesis. Using sperm DNA from donors of different ages, we determined the frequency of the nucleotide substitution in the fibroblast growth factor receptor 3 ( FGFR3 ) gene that causes achondroplasia. Surprisingly, the magnitude of the increase in mutation frequency with age appears insufficient to explain why older fathers have a greater chance of having a child with this condition. A number of alternatives may explain this discrepancy, including selection for sperm that carry the mutation or an age-dependent increase in premutagenic lesions that remain unrepaired in sperm and are inefficiently detected by the PCR assay.

Schizophrenia is an etiologically heterogeneous syndrome. It has a strong genetic component and exists in clinically indistinguishable familial and nonfamilial (sporadic) forms. A significant role for de novo genetic mutations in genetic schizophrenia vulnerability is suggested by a strong monotonic increase in schizophrenia risk with advancing paternal age. However, an alternative explanation for the paternal age effect in schizophrenia is that childbearing is delayed in fathers who themselves have genetic schizophrenia vulnerability. In this study, we compared paternal birth ages between patient groups with familial (n = 35) and sporadic (n = 68) patients with DSM-IV schizophrenia from an inpatient schizophrenia research unit. If later age of fathering children is related to having some genetic schizophrenia vulnerability, then paternal birth age should be later in familial schizophrenia cases than in sporadic cases, and any association of father's age and schizophrenia risk in offspring would be a spurious finding, unrelated to etiology. However, if de novo mutations cause sporadic schizophrenia, then patients without a family history of schizophrenia would have older fathers than familial patients. We found that patients without a family history of schizophrenia had significantly older fathers (4.7 years) than familial patients; so later childbirth was not attributable to parental psychiatric illness. These findings support the hypothesis that de novo mutations contribute to the risk for sporadic schizophrenia.

The outcome of schizophrenia is subject to the influence of factors ranging from biological to psychosocial aspects.1–3 After clinical stabilization, where positive psychotic symptoms are expected to have largely subsided, other aspects of the illness, such as relapse, become increasingly pertinent in the course of recovery.4–7 The re-emergence of psychotic symptoms is distressing to the patients and their families,8 and some relapses may even lead to treatment resistance.9 In a recent meta-analytic review on 109 relapse predictors, Alvarez-Jimenez et al10 identified medication discontinuation, persistent SUD, caregivers’ critical comments, and premorbid adjustment to be significant. Further evidence within the early intervention services in different countries has also confirmed these findings.11–13 The continual identification of predictors for relapse, especially in the early phase of the disorder, is therefore the logical next step in research.10,14 Studying etiological factors not only helps us to understand the illness but also suggests ways to find potential subgroups of the disorder that may affect clinical management.15–17 Advanced paternal age has been reported as a risk factor in disease development in several birth and army cohorts,18–22 and as a predisposing factor for a particular subtype of schizophrenia.23–26 Interestingly, a recent meta-analysis has reported both older (30 years or older) and younger (younger than 25 years) fathers increased the risk of schizophrenia; and, in particular, younger paternal age effect was found among male but not female offspring, indicating the potential confounding effect of sex.27 Clinical Implications Advanced paternal age (particularly 40 years and older) has a negative effect on relapse following FEP, even after controlling for medication discontinuation and sex. Our findings raise an interesting research question of how advanced paternal age might contribute to possible biological and psychosocial mechanisms leading to relapse. Limitations The exact timing of relapse was not measured. The relatively short follow-up period also limited the observation. Hence observation may only allow for distinction between a minority of the patients with more serious illness and those running a more benign course. The potential confounding variable of premorbid adjustment, caregivers’ negative comments, and substance abuse were not measured. At present, many studies focus on paternal age as an etiological factor of schizophrenia. Whether paternal age has any effect on the clinical course of illness (for example, relapse) in schizophrenia has not been explored. Evidence has begun to suggest that patients with advanced paternal age have more severe psychotic symptoms after medication withdrawal.26 The preliminary data call for a need to further examine the neurobiological factors, symptoms, treatment effects, and course of illness in patients with older fathers, which may lead to a meaningful differentiation between subtypes of the disorder.26 Therefore, we consider paternal age to be a probable prognostic indicator adversely influencing the outcome of psychotic relapse in schizophrenia. Examining the role of advanced paternal age in early relapse within 12 months from the start of treatment is important because this is the time when most patients would have remitted from the first episode and embarked on a rehabilitation program or resumed work and (or) study. We therefore hypothesized that patients with older fathers have more relapses at 1-year follow-up. We speculated that any identified effect of paternal age in relapse to be unrelated to medication adherence and sex, and that the main hypothesis would still stand when potential confounding factors were considered.

An unduly pessimistic description of what it means to have an extra X or Y chromosome is frequently given to the parents of an affected fetus or child by geneticists and paediatricians because the source of their information has been biased towards abnormality. In 1967 the Medical Research Council set up a cytogenetic survey of consecutive newborn infants to establish the incidence of the various chromosome abnormalities. The long term follow up of children with sex chromosome abnormalities ascertained in the survey, which screened 34 380 newborns in Edinburgh between 1967 and 1979, has enabled a more balanced prognosis to be reached. Most boys with the karyotypes 47,XXY and 47,XYY and girls with 47,XXX are never diagnosed. While that may suggest that the conditions are of no importance to the affected individuals, I will show using the following results that this is not the case. Based on the incidence at birth obtained from cytogenetic surveys of around 200 000 infants from the UK, Denmark, Canada, the USA, and Japan, an XXY karyotype was found in 1.3 per 1000 male infants, while XYY and XXX occurred with a frequency of 1 per 1000 male or female infants, respectively.1 Using these incidence figures Abramsky and Chapelle2 found that 10% of expected cases of XXY boys were identified at amniocentesis, a further 26% were diagnosed in childhood or adult life on account of hypogonadism, gynaecomastia, infertility, or developmental delay, leaving 64% undiagnosed. Among XYY boys, where there is no advanced paternal age effect, 85% were calculated to be undiagnosed either before or after birth. Abramsky and Chapelle did not include XXX females, but an estimate can be made from the maternal age distribution of 57 affected newborns where 26% were born to mothers over the age of 35 years. It is reasonable to …

SummaryMore than 97% of achondroplasia cases are caused by one of two mutations (G1138A and G1138C) in the fibroblast growth factor receptor 3 (FGFR3) gene, which results in a specific amino acid substitution, G380R. Sporadic cases of achondroplasia have been associated with advanced paternal age, suggesting that these mutations occur preferentially during spermatogenesis. We have determined the parental origin of the achondroplasia mutation in 40 sporadic cases. Three distinct 1-bp polymorphisms were identified in the FGFR3 gene, within close proximity to the achondroplasia mutation site. Ninety-nine families, each with a sporadic case of achondroplasia in a child, were analyzed in this study. In this population, the achondroplasia mutation occurred on the paternal chromosome in all 40 cases in which parental origin was unambiguous. This observation is consistent with the clinical observation of advanced paternal age resulting in new cases of achondroplasia and suggests that factors influencing DNA replication or repair during spermatogenesis, but not during oogenesis, may predispose to the occurrence of the G1138 FGFR3 mutations.

Paternal non-disjunction of chromosome 21 accounts for 5-10% of Down syndrome cases, therefore, relative to the maternally derived cases, little is known about paternally derived trisomy 21. We present the first analysis of recombination and non-disjunction for a large paternally derived population of free trisomy 21 conceptuses ( n = 67). Unlike maternal cases where the ratio of meiosis I (MI) to meiosis II (MII) errors is 3:1, a near 1:1 ratio exists among paternal cases, with a slight excess of MII errors. We found no paternal age effect for the overall population nor when classifying cases according to stage of non-disjunction error. Among 22 MI cases, only five had an observable recombinant event. This differs significantly from the 11 expected events ( P0.02, Fisher's exact), suggesting reduced recombination along the non-disjoined chromosomes 21 involved in paternal MI non-disjunction. No difference in recombination was detected among 27 paternal MII cases as compared with controls. However, cases exhibited a slight increase in the frequency of proximal and medial exchange when compared with controls (0.37 versus 0.28, respectively). Lastly, this study confirmed previous reports of excess male probands among paternally derived trisomy 21 cases. However, we report evidence suggesting an MII stage-specific sex ratio disturbance where 2.5 male probands were found for each female proband. Classification of MII cases based on the position of the exchange event suggested that the proband sex ratio disturbance was restricted to non-telomeric exchange cases. Based on these findings, we propose new models to explain the association between paternally derived trisomy 21 and excessive male probands.

From a series of 1,713 patients with craniosynostosis hospitalized between 1976 and 1996, 237 propositi with metopic synostosis were analyzed. The prevalence of metopic synostosis was estimated in the order of 1 in 15,000 children. Family information was obtained from 184 propositi from 179 families. The male-to-female ratio was 3.3:1. There was no maternal or paternal age effect. A family history was obtained in 10 of the 179 families, giving a 5.6% figure of familial cases. The frequency of twinning was 7.8% with two concordances for metopic synostosis in two monozygotic twin pairs. The male-to-female ratio, the twinning frequency, and the proportion of familial cases in trigonocephaly are very similar to those observed in scaphocephaly, which also involves the longitudinal sutural system. Fetal exposure to valproic acid was noticed in eight cases. The series was divided into two groups: nonsyndromal trigonocephaly (n = 184) and trigonocephaly associated with other malformations (n = 53). The second group included 13 cases of well-delineated syndromes and 40 cases of trigonocephaly associated with one or more malformations, but without any known syndrome, that could be undelineated syndromes. These groups differed significantly in their mental prognosis.

The human mutation rate for base substitutions is much higher in males than in females and increases with paternal age. This effect is mainly, if not entirely, due to the large number of cell divisions in the male germ line. The mutation-rate increase is considerably greater than expected if the mutation rate were simply proportional to the number of cell divisions. In contrast, those mutations that are small deletions or rearrangements do not show the paternal age effect. The observed increase with the age of the father in the incidence of children with different dominant mutations is variable, presumably the result of different mixtures of base substitutions and deletions. In Drosophila , the rate of mutations causing minor deleterious effects is estimated to be about one new mutation per zygote. Because of a larger number of genes and a much larger amount of DNA, the human rate is presumably higher. Recently, the Drosophila data have been reanalyzed and the mutation-rate estimate questioned, but I believe that the totality of evidence supports the original conclusion. The most reasonable way in which a species can cope with a high mutation rate is by quasi-truncation selection, whereby a number of mutant genes are eliminated by one “genetic death.”

Sporadic neurofibromatosis 1 (NF1) occurs in the absence of a family history of the disease and usually results from a new mutation in the germ cell of one of the parents, most commonly the father. Older paternal age may increase the risk for a new germinal NF1 mutation, but the results of studies to address this question conflict. We investigated paternal age in sporadic NF1 by using a case-control study design. Patients who were seen at two specialty NF clinics in Houston, Texas, born between 1970 and 1992 and living in the Houston area and surrounding counties, were studied. Birth certificates with information on the father were found for 89 cases. For each case, two birth certificates were chosen at random from the same year and county of birth. In this way, the control group of 178 individuals was formed. Fathers of patients with NFI were 1.5 years older than fathers of control subjects at the birth of the child, but the difference was only of borderline statistical significance (P = 0.07). This paternal age difference was not changed by adjustment for socioeconomic status or maternal age. These and previous data are consistent with either a small paternal age effect in sporadic NF1 or a bias such as that resulting from the selection of cases and/or controls.

Sperm samples were collected from 18 healthy men of various ages. Multicolor FISH was performed on each sample, using probes for the sex chromosomes and chromosome 1. A minimum of 10,000 sperm per donor was analyzed. The Pearson correlation coefficient was used to determine if there was an association between donor age and disomy frequency for the sex chromosomes.

Anterior cervical hypertrichosis (ACH) is a rare form of localized hypertrichosis with 15 previously reported cases. ACH has been considered to be a dominant phenotype, either X-linked or autosomal [OMIM 600457]. ACH was associated with hereditary motor and sensory neuropathy (HMSN) in one family, in which the proband also exhibited severe chorioretinal degeneration and optic atrophy, probably as a different entity [OMIM 239840]. A Mexican boy with congenital ACH associated with moderate mental retardation, abnormal EEG, mild microcephaly, hypertrichosis on the back, and hallux valgus is presented here. An equal sex ratio found in 16 reported cases as well as the suggestion of a paternal age effect in one report appear most consistent with an autosomal dominant mode of inheritance for this trait. It remains unclear if isolated ACH, ACH-HMSN, or other associated findings reported in patients with ACH, including unusual features found in our case, are part of ACH or fortuitous associations, due to the small number of affected patients and different ascertainment biases present in previous reports.

Advanced parental age at childbirth has been identified as a risk factor for a number of developmental disorders, including Down’s syndrome,1 Marfan’s syndrome,2 achondroplasia3 and even some cancers.4 There has been considerable recent interest in the potential role of parental age, particularly paternal age, as a risk factor for autism5 and for schizophrenia.6 While claims of an association of parental age and risk for schizophrenia have been made for over 50 years, the issue attracted serious attention after a report by Malaspina et al.6 in a sample of 638 Israeli patients with schizophrenia, which found that the age of their fathers at childbirth significantly increased the odds of their being ill, by upwards of 1.2-fold per decade of advancing age. A number of subsequent studies have provided additional evidence for this association, which in a recent meta-analysis has been found to represent an overall increase of risk of ~1.3-fold, especially for fathers who are 55 years or older at childbirth.7 Maternal age tends not to be significantly associated with risk for schizophrenia.6 The popular interpretation of these data has been that de novo mutations, which are known to become more abundant in sperm of older men,2 are the mechanism. Indeed, a recent high-profile publication by Kong et al.8 demonstrated, in a sample of 78 families, a linear relationship between paternal age and the number of de novo mutations in offspring, with approximately two de novo mutations per year of advancing paternal age. Kong et al.8 interpret their data in the context of evidence that older fathers have increased risk of offspring with developmental disorders such as autism and schizophrenia, suggesting that they are causally linked. There has been considerable front-page mass media attention to the possible conclusion that the two associations (that is, paternal age and risk for schizophrenia and paternal age and de novo mutations) are linked causally, including suggestions that younger males should consider sperm cryopreservation for later parenting (for example, NY Times, 22 August 2012). Despite the intuitive appeal of this causal link, it is conceivable that these two associations, though each valid, may be unrelated. In fact, they have not been linked in the same data, and the conclusion of a causal link is still premature. Indeed, other possibilities for the association with paternal age merit consideration. For example, a recent study of over 2.2 million people in Denmark replicated the paternal age effect on risk for schizophrenia, but suggested that de novo mutations could not account for it.9 These investigators found that the association was explained by the age of the father at the birth of his first child, not by the age at which the father had a child who developed schizophrenia. It is thus conceivable that some fathers have inherited traits that are linked both to higher risk for schizophrenia and to difficulty or slowness in becoming married, or perhaps to parenting. Moreover, there is evidence that very young paternal age also increases risk for schizophrenia, a finding that would not be explained by age-associated de novo mutations.7 Another approach to elucidate the potential role of age-related de novo mutations and risk for schizophrenia is to explore birth order within families. If de novo mutations inherited from fathers are a causative factor for schizophrenia, affected individuals would be more likely to be later born children, particularly in families with older fathers. Interestingly, for schizophrenia, epidemiological studies do not support an overall birth-order effect.10 We tested the association of paternal age and birth order of offspring with schizophrenia in 463 families with an affected offspring and multiple biological siblings (range 2–13). Overall, 155 offspring with schizophrenia were born first and 188 were born last. A null univariate effect of birth order in families with two offspring—the subject with schizophrenia was first born in 97 and second born in 106 (P = 0.575)—echo those of earlier epidemiological studies but are clearly of limited power in this subsample of our family data set. However, statistical models that incorporate father’s age at the birth of an affected offspring in all the families suggest a paternal age association with birth order. Categorizing paternal age groups consistent with prior literature suggests that birth-order patterns between paternal aged groups are significantly different (Table 1A, P = 1.92×10−4). More generally, the overall correlation in the entire sample between birth order of affected offspring and paternal age, corrected for family size, is highly significant (P = 1.26×10−13). Our results are tempered by sample size and potentially unknown ascertainment biases, but they are consistent with the expected effects of de novo mutations on risk for schizophrenia within families. Table 1 Parental age versus birth order Because paternal and maternal ages are correlated in our families (r = 0.70, P < 2 × 10−16), we next considered the possibility that parity and illness status are primarily linked to maternal age, which would implicate a cause of birth-order risk other than de novo mutations. Categorizing maternal age into three typical bins resulted in birth-order patterns that are highly significantly different (Table 1B, P = 1.33 × 10−8). Moreover, overall proband birth order was much more highly correlated with maternal age (P < 2.16 × 10−16) than paternal age, and when both are entered into a multiple regression (adjusting for family size), only maternal age has a significant effect (P = 7.53 × 10−16); paternal age does not (P = 0.995). This statistical approach is the de facto method for untangling highly correlated maternal and paternal age effects in the literature.8 The strong maternal age association might suggest that parity adversely influences intrauterine development, and obstetrical complications (OCs) are also a risk factor for schizophrenia.11 Quantitative ratings of OCs were available for 197 probands, and were actually associated with lower birth order (P = 6.84 × 10−5), consistent with the generally greater frequency of complications in first pregnancies and perhaps a factor in the increased risk of illness in the first-born children of younger mothers. Still, increasing maternal age was independently associated with higher proband birth order even in this smaller subset of subjects (Figure 1, P = 1.81 × 10−15). Figure 1 Plot of maternal age at birth of proband versus his or her birth order. Each point (orange) represents the proband from one family. The boxplots demonstrate the interquartile range of maternal ages for all families that contain a proband born at that ... Our results in families, while not implicating a specific cause of the paternal age association with risk for schizophrenia, support the Danish study9 in suggesting that de novo mutations do not play a prominent role. It is important to emphasize that our data do not speak to the validity of the paternal age association with risk for schizophrenia, which is assumed to be valid. The parental age effects may, for instance, increase risk for schizophrenia through social factors related to parenting,9 or more generally, to epigenetic mechanisms associated with the developmental environment, both intrauterine and postnatal. Our data suggest, however, that the principal mechanism of this association is not de novo mutations. Clearly, more work is needed to determine the degree to which the association of schizophrenia with paternal age is due to paternally derived de novo mutations or to a cause linked to other factors related to childbearing in later middle age or to a combination of both.

Birth rates for older fathers have increased 30% since 1980. When combined with the increased risk for genetic and multifactorial disorders in children conceived by older fathers, paternal age has become an important health issue for modern society. Laboratory research in this area has been minimal, perhaps because of significant experimental barriers, not the least of which is inadequate access to fresh, disease-free human testicular tissue. Regardless, progress has been made and intriguing models supported by experimental evidence have been proposed. The putative mechanisms range from reduced DNA repair activity, leading to increased mutagenesis, to positive selection of germ cells harboring specific disease-causing mutations. There remain many important venues for research in this increasingly relevant phenomenon that impacts future generations.

Item does not contain fulltext Genomic copy number variations (CNVs) and increased parental age are both associated with the risk to develop a variety of clinical neuropsychiatric disorders such as autism, schizophrenia and bipolar disorder. At the same time, it has been shown that the rate of transmitted de novo single nucleotide mutations is increased with paternal age. To address whether paternal age also affects the burden of structural genomic deletions and duplications, we examined various types of CNV burden in a large population sample from the Netherlands. Healthy participants with parental age information (n = 6,773) were collected at different University Medical Centers. CNVs were called with the PennCNV algorithm using Illumina genome-wide SNP array data. We observed no evidence in support of a paternal age effect on CNV load in the offspring. Our results were negative for global measures as well as several proxies for de novo CNV events in this unique sample. While recent studies suggest de novo single nucleotide mutation rate to be dominated by the age of the father at conception, our results strongly suggest that at the level of global CNV burden there is no influence of increased paternal age. While it remains possible that local genomic effects may exist for specific phenotypes, this study indicates that global CNV burden and increased father's age may be independent disease risk factors.