Search

Management of familial adenomatous polyposis (FAP) is guided by the cumulative risk of colorectal cancer (CRC) and aggressive fibromatosis/desmoid (AF/D). The first non-Caucasian FAP cohort with cumulative risk estimates for CRC and AF/D shows distinct differences with the Caucasian and other Asian cohorts. The strong correlation between the adenomatous polyposis coli (APC) mutation location with the FAP phenotype and the geoethnic differences in APC mutation spectrum, genetic constitution, lifestyle and sporadic CRC rates, mandates the use of population-specific cumulative risk estimates for CRC and desmoid for counselling and risk management. On genotype–phenotype correlation in 83 individuals with classical FAP and a confirmed pathogenic/likely Pathogenic (P/LP) APC variant (n=76) or obligate carrier of the family variant (n=7), we observed a high cumulative CRC risk of 40% and 85% by 40 and 60 years, respectively. The observed 30% cumulative risk by 50 years for desmoids was higher than previous European and Asian cohorts and was significantly associated with prophylactic surgery (OR: 4.58, 95% CI 1.06 to 19.78) and APC mutation 3′ of codon 1309 (OR: 13.07, 95% CI 3.58 to 47.56) and also 3′ of codon 1444 (OR: 8.0, 95% CI 1.83 to 34.94). Global cooperation is required to establish FAP genotype–phenotype associations and population-specific risk estimates to guide genetic counselling and risk management.

This work describes a family with Duchenne muscular dystrophy (DMD) with a rare case of a symptomatic pregnant woman. The main aim was to perform prenatal molecular diagnosis to provide genetic counseling. The secondary aim was to suggest the molecular mechanisms causing the complex structural variant (cxSV) identified. To accomplish this, we used a multi-technique algorithm including segregation analysis, Multiplex Ligation-dependent Probe Amplification, PCR, X-chromosome inactivation studies, microarrays, whole genome sequencing and bioinformatics. We identified a duplication of exons 38-43 in the DMD gene in all affected and obligate carrier members, proving that this was the DMD-causing mutation. We also observed a skewed X-chromosome inactivation in the symptomatic woman that explained her symptomatology. In addition, we identified a cxSV (duplication of exons 38-43 and deletion of exons 45-54) in the affected boy. The molecular characterization and bioinformatic analyses of the breakpoint junctions allowed us to identify Double Strand Breaks stimulator motifs and suggested the replication-dependent Fork Stalling and Template Switching as the most probable mechanisms leading to the duplication. In addition, the de novo deletion might have been the result of a germline inter-chromosome non-allelic recombination involving the Non-Homologous End Joining mechanism. In conclusion, the diagnostic strategy used allowed us to provide accurate molecular diagnosis and genetic counseling. In addition, the familial molecular diagnosis together with the in-depth characterization of the cxSV helped to determine the chronology of the molecular events, and propose and understand the molecular mechanisms involved in the generation of this complex rearrangement.

Objective: Duchenne muscular dystrophy (DMD) is a severe disorder caused by mutation in the X-linked dystrophin gene, therefor carrier testing is required for all female family members. However, there are cases mutation analysis cannot detect any mutation due to a phenomenon called mosaicism. The case report describes a case of mosaicism in a DMD carrier and discusses the approach in diagnosis and counseling of familial disorder. Case report: The proband was diagnosed with DMD at age six. Sequencing of Dystrophin gene identified a 2-nucleotide deletion c.2032_2033delCA, p.Q678DfsX41. Family investigation suggested that the mother was an obligate carrier of Dystrophin mutation. Sequencing of DNA sample from the mother's peripheral blood did not reveal any mutation, there for we take sample from hair follicle for analysis. The result indicated that the mother was a carrier but was masked from initial analysis by mosaicsism. Conclusion: We suggested that more care need to be taken in identifying cases when no mutation was detected in probable or obligate carrier and prenatal diagnosis should remain an option. Keywords: Duchenne muscular dystrophy, Dystrophin, Mosaicism, Counseling, Prenatal diagnosis

PURPOSE To describe findings in a patient with choroideremia (CHM) and his mother, an obligate CHM carrier. METHODS Case report. RESULTS A 25-year-old man with nyctalopia and poor peripheral vision since childhood, as well as a family history consistent with an X-linked retinal disorder was diagnosed with CHM. His asymptomatic 50-year-old mother, an obligate carrier, was also examined. Fundus examination of the affected man showed significant atrophy of the choroid and retinal pigment epithelium, whereas the carrier woman showed patchy pigmentary mottling. Imaging of the affected man showed diffuse retinal pigment epithelium atrophy on optical coherence tomography and extensive areas of decreased choriocapillaris flow on optical coherence tomography angiography. By contrast, the carrier woman showed subtle retinal pigment epithelium changes on optical coherence tomography and mild flow alterations on optical coherence tomography angiography. CONCLUSION This case demonstrates the findings seen in CHM, and while CHM carrier women are often asymptomatic, they may exhibit a mosaic pattern of pigmentary change on fundus examination. Optical coherence tomography angiography may show mild choroidal flow abnormalities. This finding serves to further characterize the extent of dysfunction in CHM and its carrier state.

Little is known on the causes and pathogenesis of the adipose tissue disorder (familial) Multiple Symmetric Lipomatosis (MSL). In a four-generation MSL-family, we performed whole exome sequencing (WES) in 3 affected individuals and 1 obligate carrier and identified Calcyphosine-like (CAPSL) as the most promising candidate gene for this family. Screening of 21 independent patients excluded CAPSL coding sequence variants as a common monogenic cause, but using immunohistochemistry we found that CAPSL was down-regulated in adipose tissue not only from the index patient but also in 10 independent sporadic MSL-patients. This suggests that CAPSL is regulated in sporadic MSL irrespective of the underlying genetic/multifactorial cause. Furthermore, we cultivated pre-adipocytes from MSL-patients and generated 3T3-L1-based Capsl knockout and overexpressing cell models showing altered autophagy, adipogenesis, lipogenesis and Sirtuin-1 (SIRT1) expression. CAPSL seems to be involved in adipocyte biology and perturbation of autophagy is a potential mechanism in the pathogenesis of MSL. Downregulation of CAPSL and upregulation of UCP1 were common features in MSL fat while the known MSL genes MFN2 and LIPE did not show consistent alterations. CAPSL immunostainings could serve as first diagnostic tools in MSL clinical care with a potential to improve time to diagnosis and healthcare options.

Contains fulltext : 215374.pdf (Publisher’s version ) (Open Access) BACKGROUND: Eight different deletions and point variants of the X-chromosomal gene CNKSR2 have been reported in families with males presenting intellectual disability (ID) and epilepsy. Obligate carrier females with a frameshift variant in the N-terminal protein coding part of CNKSR2 or with a deletion of the complete gene are not affected. Only for one C-terminal nonsense variant, two carrier females were mildly affected by seizures without or with mild motor and language delay. METHODS: Exome sequencing was performed in one female child of a Dutch family, presenting seizures, mild ID, facial dysmorphisms, and abnormalities of the extremities. Potential causative variants were validated by Sanger sequencing. X-chromosome-inactivation (XCI) analysis was performed by methylation-sensitive PCR and fragment-length analysis of the androgen-receptor CAG repeat polymorphism. RESULTS: We identified a de novo variant, c.2304G>A (p.(Trp768*)), in the C-terminal protein coding part of the X-chromosomal gene CNKSR2 in a female patient with seizures and mild ID. Sanger sequencing confirmed the presence of this nonsense variant. XCI analysis showed a mild skewing of X inactivation (20:80) in the blood of our patient. Our variant is the second C-terminal-affecting CNKSR2 variant described in neurologically affected females. CONCLUSION: Our results indicate that CNKSR2 nonsense variants in the C-terminal coding part can result in ID with seizures in female variant carriers.

Data on genetic anticipation in breast cancer are sparse. We sought to evaluate age at diagnosis of breast cancer in daughters with a BRCA mutation and their mothers. A review of all carriers of the BRCA mutation diagnosed with breast cancer at the Genetics Institute of a tertiary medical center in 2000-2013 yielded 80 women who could be paired with a mother with breast cancer who was either a carrier of the BRCA mutation or an obligate carrier according to pedigree analysis. Age at diagnosis, type of mutation (BRCA1, BRCA2), year of birth, and ethnicity were recorded. Paired t-test was used to analyze differences in age at cancer diagnosis between groups and subgroups. Mean age at diagnosis of breast cancer was 50.74 years (range 22-88) in the mothers and 43.85 years (range 24-75) in the daughters. The difference was statistically significant (p < 0.001). These findings were consistent regardless of type of BRCA mutation, ethnicity, or mother's year of birth. However, on separate analysis of pairs in which the mother was diagnosed before the age of 50 years, there was no significant difference in mean age at diagnosis between mothers and daughters (~42 years for both). Daughters who carry a BRCA mutation are diagnosed with breast cancer at an earlier age than their carrier mothers, with the exception of pairs in which the mother was diagnosed before the age of 50 years. Future breast-screening guidelines may need to target specific subpopulations of BRCA mutation carriers.

We observed a hereditary phenotype in Alaskan Huskies that was characterized by polyneuropathy with ocular abnormalities and neuronal vacuolation (POANV). The affected dogs developed a progressive severe ataxia, which led to euthanasia between 8 and 16 months of age. The pedigrees were consistent with a monogenic autosomal recessive inheritance. We localized the causative genetic defect to a 4 Mb interval on chromosome 19 by a combined linkage and homozygosity mapping approach. Whole genome sequencing of one affected dog, an obligate carrier, and an unrelated control revealed a 218-bp SINE insertion into exon 7 of the RAB3GAP1 gene. The SINE insertion was perfectly associated with the disease phenotype in a cohort of 43 Alaskan Huskies, and it was absent from 541 control dogs of diverse other breeds. The SINE insertion induced aberrant splicing and led to a transcript with a greatly altered exon 7. RAB3GAP1 loss-of-function variants in humans cause Warburg Micro Syndrome 1 (WARBM1), which is characterized by additional developmental defects compared to canine POANV, whereas Rab3gap1-deficient mice have a much milder phenotype than either humans or dogs. Thus, the RAB3GAP1 mutant Alaskan Huskies provide an interesting intermediate phenotype that may help to better understand the function of RAB3GAP1 in development. Furthermore, the identification of the presumed causative genetic variant will enable genetic testing to avoid the nonintentional breeding of affected dogs.

Mutations in PSEN1 are the most common cause of early-onset Alzheimer's disease (AD). In this article, we present an Argentine family with autosomal dominant early- and late-onset AD. The proband and 6 family members were available for genetic testing and clinical and neuropsychological assessments. Cerebrospinal fluid biomarkers were analyzed in the proband and a cousin (mutation carrier), who also underwent positron emission tomography using F-18-2-fluoro-2-deoxy-D-glucose and Pittsburgh compound B. Exon sequencing of PSEN1, PSEN2, and APP revealed a novel heterozygous variant in PSEN1 (c.356C>T; p.T119I). Median age of onset in the family was 56 years. However, the proband's uncle showed initial symptoms at age 71. Although no DNA was available, he was an obligate carrier because his daughter (proband's cousin) carried the mutation. Both the proband and his cousin exhibited biomarker evidence (cerebrospinal fluid or imaging) of underlying Alzheimer's pathology. Overall, our results support that the PSEN1 p.T119I variant is likely pathogenic.

Whole-gene duplications and missense variants in the HUWE1 gene (NM_031407.6) have been reported in association with intellectual disability (ID). Increased gene dosage has been observed in males with non-syndromic mild to moderate ID with speech delay. Missense variants reported previously appear to be associated with severe ID in males and mild or no ID in obligate carrier females. Here, we report the largest cohort of patients with HUWE1 variants, consisting of 14 females and 7 males, with 15 different missense variants and one splice site variant. Clinical assessment identified common clinical features consisting of moderate to profound ID, delayed or absent speech, short stature with small hands and feet and facial dysmorphism consisting of a broad nasal tip, deep set eyes, epicanthic folds, short palpebral fissures, and a short philtrum. We describe for the first time that females can be severely affected, despite preferential inactivation of the affected X chromosome. Three females with the c.329 G > A p.Arg110Gln variant, present with a phenotype of mild ID, specific facial features, scoliosis and craniosynostosis, as reported previously in a single patient. In these females, the X inactivation pattern appeared skewed in favour of the affected transcript. In summary, HUWE1 missense variants may cause syndromic ID in both males and females.

Idiopathic hypoparathyroidism has been reported to occur as an X-linked recessive disorder in two multigeneration kindreds. Affected individuals, who are males, suffer from infantile onset of epilepsy and hypocalcemia, which appears to be due to an isolated congenital defect of parathyroid gland development; females are not affected and are normocalcemic. We have performed linkage studies in these two kindreds (5 affected males, 11 obligate carrier females, and 44 unaffected members) and have used cloned human X chromosome sequences identifying restriction fragment length polymorphisms to localize the mutant gene causing this disorder. Our studies established linkage between the X-linked recessive idiopathic hypoparathyroid gene (HPT) and the DXS98 (4D.8) locus, peak LOD score = 3.82 (theta = 0.05), thereby mapping HPT to the distal long arm of the X chromosome (Xq26-Xq27). Multilocus analysis indicated that HPT is proximal to the DXS98 (4D.8) locus but distal to the F9 (Factor IX) locus, thereby revealing bridging markers for the disease. The results of this study will improve genetic counseling of affected families, and further characterization of this gene locus will open the way for elucidating the factors controlling the development and activity of the parathyroid glands.

Christianson syndrome (OMIM 300243), caused by mutations in the X-linked SLC9A6 gene, is characterized by severe global developmental delay and intellectual disability, developmental regression, epilepsy, microcephaly and impaired ocular movements. It shares many common features with Angelman syndrome. Carrier females have been described as having learning difficulties with mild to moderate intellectual disability, behavioural issues and psychiatric illnesses. There is little literature on the carrier female phenotype of Christianson syndrome. We describe a large extended family with three affected males, four carrier females, one presumed carrier female and one obligate carrier female with a c.190G>T, p.E64X mutation known to cause a premature stop codon in SLC9A6. We characterize and expand the clinical phenotype of female SLC9A6 mutation carriers by comparing our described family with female carriers previously discussed in the literature. In particular, we highlight the neurodevelopmental and psychiatric phenotypes observed in our family and previous reports.

Background Acute necrotizing encephalopathy (ANE) is a rare and severe parainfectious central nervous system disease in which previously healthy children develop rapidly progressive coma following viral illness. While most ANE are sporadic, familial autosomal dominant ANE due to mutations in the RANBP2 gene has been recently reported (ANE1 or infection-induced acute encephalopathy-3 (IIAE3)). To date, only few IIAE3 families with ADANE episodes have been described. Objective To report a new family with ADANE, describe clinical and radiological features and discuss differential diagnosis including Leigh syndrome or multiple sclerosis. Observation The family included 3 symptomatic individuals and one 59 year-old asymptomatic obligate carrier. Patients presented acute episodes of encephalopathy few days after common viral infection. Ages of onset ranged from 6 months to 5 years. Episodes not only occurred in childhood but also recurred in adulthood. Initial neurological signs included coma, focal neurological deficits and seizures. MRI showed typical necrotizing lesions primarily in the thalamus and brainstem, and in the temporal lobes and insula. CSF cell count and cultures were normal during episodes. RANBP2 gene screening identified pathogenic heterozygous c.1754C>T mutation (p.Thr585Met). Episodes led to cognitive or physical handicap in 2 patients and were fatal in one child. Conclusion IIAE3 or ADANE due to RANBP2 mutations has a large clinical heterogeneity. Our family illustrates the associated phenotypes from asymptomatic carrier to severe episodes of encephalopathy. Based on MRI features, the genetic IIAE3 diagnosis is important since prophylaxis and symptomatic management of infections may be beneficial, possibly in association with steroid or gammaglobulins.

Simpson-Golabi-Behmel syndrome (SGBS) is an overgrowth/multiple congenital anomalies syndrome with an X-linked inheritance. Most cases of SGBS are attributed to mutations in the glypican 3-gene (GPC3), which is highly expressed in the mesodermal embryonic tissues and involves in a local growth regulation. Typical clinical features include pre/postnatal overgrowth, developmental delay, macrocephaly, characteristic facies with prominent eyes and macroglossia, diaphragmatic hernia, congenital heart defects, kidney anomalies, and skeletal anomalies. Obligate carrier females with GPC3 mutations are usually asymptomatic or with mild symptoms. It is thought that skewed X-inactivation is the underlining mechanism for the female patients to present with findings of SGBS. We identified three siblings with typical SGBS (two male and one female cases) and their mother with very mild symptoms in a family carrying c.256C>T (p.Arg86X) mutation in GPC3. X-inactivation studies on the androgen-receptor gene (AR) and the Fragile XE (FRAXE) gene were performed with blood, buccal swabs, and fibroblasts in the carrier females. The studies with blood showed moderately skewed X-inactivation with paternal X-chromosome being preferentially inactivated (71-80% inactivated) in the female patient with SGBS and no skewing was shown in the mother with very mild symptoms. The X-inactivation studies in the mother showed inactivation of the X-chromosome with the mutation by 57%. This suggests that loss of the functional GPC3 protein by 43% is closed to the threshold to develop the SGBS phenotype. Studies with buccal swabs and fibroblasts failed to show different X-inactivation patterns between the two female individuals.

Isolated hypodontia, or congenital absence of one to six permanent teeth (OMIM 300606), is a common condition that affects about 20% of individuals worldwide. We identified two extended Pakistani pedigrees segregating X-linked hypodontia with variable expressivity. Affected males show no other associated anomalies, and obligate carrier females have normal dentition. We analyzed the families with polymorphic markers in the ectodysplasin A (EDA) gene region and obtained significant linkage to the phenotype in each pedigree (Z(max) 3.29 and 2.65, respectively, at theta = 0.00). Sequence analysis of the coding regions of EDA revealed a novel missense mutation c.1091TC resulting in a methionine to threonine substitution (p.M364T) in the tumor necrosis factor (TNF) homology domain. Met364 is a highly conserved residue located on the outer surface of the EDA protein. From our findings, we suggest that the mutation disturbs but does not destroy the EDA structure, resulting in the partial and unusually mild ED phenotype restricted to hypodontia.

To investigate the choroideremia (CHM) gene of one affected male and one obligate carrier in a Japanese family with choroideremia, and to characterize the related clinical features.We examined one affected man and one carrier woman from a Japanese family. Genomic DNA was extracted from leukocytes of peripheral blood collected from the affected man and his daughter, who is an obligate carrier of choroideremia. Exons 1-15 of the CHM gene were amplified by polymerase chain reaction (PCR) and directly sequenced. We performed ophthalmic examinations including best-corrected visual acuity, slit-lamp examination, fundus examination, electroretinography, and Goldmann perimetry.A novel (967-970+2)delAAAGGT mutation was detected in the CHM gene. The affected man was hemizygous and had night-blindness, chorioretinal atrophy spreading from the posterior pole to the mid-periphery, and bareness of the sclera. His daughter was a heterozygous carrier who had chorioretinal atrophy and mottled appearance of the retinal pigment epithelium.A novel (967-970+2)delAAAGGT mutation existed in the CHM gene of a Japanese family with choroideremia.

Chorionic Villous Biopsy (CVS) for diagnosis of XLP was undertaken at 10 weeks gestation in an obligate carrier. The fetus was found to be male by cytogenetic analysis. XLP (Xq25–q26) is closely linked to the RFLP markers DXS10, DXS37 and DXS42, but only DXS10 (distal to XLP) was informative for prenatal diagnosis in this family. RFLP analysis using this marker gave a 7% risk that the fetus was affected, based on the known recombination frequency between DXS10 and XLP. Further investigation was then undertaken to obtain a rapid and more accurate diagnosis using the three highly polymorphic PCR based markers. These were the AC repeat markers DXS424 (XL5A) and DXS425 (XL90A3) and the tetramer repeat marker within HPRT. DX425 is approximately 10 cM proximal to DXS10 and HPRT but is not known with certainty to map proximal or distal to XLP. DXS424 is proximal to DXS10 and HPRT and was inferred to be proximal to XLP on the basis of map distance from HPRT estimated by linkage analysis of data from CEPH pedigrees. This was confirmed by a recombinant in the XLP family between DXS424 and DXS425, placing DXS424 proximal to XLP. Diagnosis by linkage using DXS424 and DXS425, at least one of which is proximal to XLP, and distal markers DXS10 and HPRT, increased the accuracy of diagnosis using flanking marker analysis to greater than 99% that the fetus was unaffected. HLA DR typing of the CVS showed that the fetus was DR identical to a male sibling with XLP. HLA compatibility was confirmed at delivery by full HLA typing and MLC. Transplantation has been carried out utilising cord and placental blood.

Two mentally handicapped dizygotic twin sisters were found to possess the Fragile-X lesion. They showed different levels of cognitive deficit. The hypothesis that the level of cognitive function in female carriers of the Fragile-X lesion may be influenced by Lyonization is discussed. The mother of the twins was schizophrenic. Although she was an obligate carrier her psychosis was thought not to be causally connected with the Fragile-X status.

Purpose To correlate ophthalmic findings with carrier status for a severe Norrie disease (ND) gene mutation (C95F). Design Prospective interventional case series. Participants Six potential carriers and 1 obligate carrier from a family harboring the mutation. Methods An ophthalmologist blind to the pedigree performed a full ophthalmic examination for the 7 asymptomatic family members. A peripheral blood sample was collected from each for ND gene sequencing. Main Outcome Measures Ophthalmic examination findings (with attention to the presence or absence of retinal findings) and results of ND gene sequencing. Results Three carriers were identified by molecular genetics, and all 3 of them had peripheral retinal abnormality. However, 3 of the 4 genetically identified noncarriers also exhibited peripheral retinal abnormality. Two of these noncarriers with retinal findings were the offspring of a confirmed noncarrier. The genetically identified noncarrier with a normal peripheral retinal examination was the daughter of an obligate carrier. Conclusions The presence of peripheral retinal changes was not useful for carrier prediction in a family harboring ND. There are likely additional loci responsible for phenotypic expression.

Idiopathic infantile nystagmus (IIN) consists of involuntary oscillations of the eyes. The familial form is most commonly X-linked. We recently found mutations in a novel gene FRMD7 (Xq26.2), which provided an opportunity to investigate a genetically defined and homogeneous group of patients with nystagmus. We compared clinical features and eye movement recordings of 90 subjects with mutation in the gene ( FRMD7 group) to 48 subjects without mutations but with clinical IIN (non- FRMD7 group). Fifty-eight female obligate carriers of the mutation were also investigated. The median visual acuity (VA) was 0.2 logMAR (Snellen equivalent 6/9) in both groups and most patients had good stereopsis. The prevalence of strabismus was also similar ( FRMD7 : 7.8%, non- FRMD7 : 10%). The presence of anomalous head posture (AHP) was significantly higher in the non- FRMD7 group ( P < 0.0001). The amplitude of nystagmus was more strongly dependant on the direction of gaze in the FRMD7 group being lower at primary position ( P < 0.0001), compared to non- FRMD7 group ( P = 0.83). Pendular nystagmus waveforms were also more frequent in the FRMD7 group ( P = 0.003). Fifty-three percent of the obligate female carriers of an FRMD7 mutation were clinically affected. The VA's in affected females were slightly better compared to affected males ( P = 0.014). Subnormal optokinetic responses were found in a subgroup of obligate unaffected carriers, which may be interpreted as a sub-clinical manifestation. FRMD7 is a major cause of X-linked IIN. Most clinical and eye movement characteristics were similar in the FRMD7 group and non- FRMD7 group with most patients having good VA and stereopsis and low incidence of strabismus. Fewer patients in the FRMD7 group had AHPs, their amplitude of nystagmus being lower in primary position. Our findings are helpful in the clinical identification of IIN and genetic counselling of nystagmus patients.

BACKGROUND Rare variants (

We further evaluated a previously reported family with an apparently undescribed X‐linked syndrome involving joint contractures, keloids, an increased optic cup‐to‐disc ratio, and renal stones to elucidate the genetic cause. To do this, we obtained medical histories and performed physical examination on 14 individuals in the family, five of whom are affected males and three are obligate carrier females. Linkage analysis was performed on all but one individual and chromosome X‐exome sequencing was done on two affected males. The analysis localized the putative gene to Xq27‐qter and chromosome X‐exome sequencing revealed a mutation in exon 28 (c.4726G>A) of the filamin A (FLNA) gene, predicting that a conserved glycine had been replaced by arginine at amino acid 1576 (p.G1576R). Segregation analysis demonstrated that all known carrier females tested were heterozygous (G/A), all affected males were hemizygous for the mutation (A allele) and all normal males were hemizygous for the normal G allele. The data and the bioinformatic analysis indicate that the G1576R mutation in the FLNA gene is very likely pathogenic in this family. The syndrome affecting the family shares phenotypic overlap with other syndromes caused by FLNA mutations, but appears to be a distinct phenotype, likely representing a unique genetic syndrome.

We report on two families, each with documented consanguinity and two affected with overlapping features of Dandy-Walker malformation, genitourinary abnormalities, intellectual disability, and hearing deficit. This phenotype shares similar findings with many well-known syndromes. However, the clinical findings of this syndrome categorize this as a new syndrome as compared with the phenotype of already established syndromes. Due to parental consanguinity, occurrence in siblings of both genders and the absence of manifestations in obligate carrier parents, an autosomal recessive pattern of inheritance is more likely. The authors believe that these families suggest a novel autosomal recessive cerebello-genital syndrome. Array CGH analyses of an affected did not show pathological deletions or duplications.

Background Germline mutations of the INI1 gene predispose children to the development of rhabdoid tumors. Reports of familial cases, however, are extremely rare. Procedure We have identified a three-generation family in which two half-brothers were diagnosed with central nervous system atypical teratoid/rhabdoid tumors (AT/RT). The two boys, diagnosed at 2 months and 17 months of age, had a germline insertion mutation in exon 4 of the INI1 gene that was inherited from their healthy mother. A maternal uncle died in childhood from a brain tumor and a malignant rhabdoid tumor of the kidney, and presumably carried the same germline mutation. As the mother and uncle had different fathers, the grandmother is also an obligate carrier of the mutation. Conclusion The identification of two unaffected carriers in a family segregating a germline mutation and rhabdoid tumor supports the hypothesis that there may be variable risks of development of rhabdoid tumor in the context of a germline mutation. There may be a developmental window in which most rhabdoid tumors occur. This family highlights the importance of mutation analysis in all patients with a suspected rhabdoid tumor. Pediatr Blood Cancer 2006;47:279–284. © 2005 Wiley-Liss, Inc.

Mutation in a gap junction protein gene (GJB2 also named connexin 26) is a major cause of autosomal recessive congenital deafness, which is responsible for about 80% of the cases in Mediterranean families, but actually little is known about the influence of GJB2 mutations on the hearing of obligate carriers. We examined GJB2 35delG mutation carrier individuals to test the possible presence and incidence of audiometric abnormalities among carriers of 35delG mutations. Tonal audiometric analysis was performed on a 35delG mutation carrier group (H) and on a non-carrier control group (N). Audiometric evaluations in the control group showed the presence of thresholds within normal limits at all frequencies, while carriers of 35delG mutations presented a decrease of hearing principally at 6,000 and 8,000 Hz. The difference at 6,000 and 8,000 Hz between groups H and N is statistically significant.

Summary. Partial or complete factor (F)VIII gene deletions are found in about 5% of families with severe hemophilia A. Relatively few deletions have been well characterized and, of these, recombination occurred between either common repeat elements or non-homologous sequences. In evaluating a family with severe hemophilia A, an exon 24 deletion was suspected when no fragment was obtained on attempted PCR amplifications. A combination of the 5′ primer of exon 23 and the 3′ primer of exon 25 fragments was used with prolonged extension times to amplify a normal 2.9 kb fragment that included exons 23 through 25; the patient's amplified product was 1.6 kb indicating a 1.3 kb deletion. A mixture of normal and patient DNA showed both sized fragments as did that from an obligate carrier. Carrier detection was applied to two women at risk; one was and one was not a carrier. Sequencing the proband's 1.6 kb fragment revealed that a 1328 bp deletion occurred between homologous sequences of 287 and 285 bp in introns 23 and 24, respectively; these share 85% identity. Blast nucleotide search revealed that these represent Alu elements. Comparison with an alignment of each of the two homologous sequences further localized recombination to a 41-bp segment. However, a simple recombination event would not account for the proband's sequence. The most likely explanation is that the homologous recombination was accompanied by incomplete mismatch repair.

The Chudley-Lowry syndrome (ChLS, MIM 309490) is an X-linked recessive condition characterized by moderate to severe mental retardation, short stature, mild obesity, hypogonadism, and distinctive facial features characterized by depressed nasal bridge, anteverted nares, inverted-V-shaped upper lip, and macrostomia. The original Chudley-Lowry family consists of three affected males in two generations. Linkage analysis had localized the gene to a large interval, Xp21-Xq26 and an obligate carrier was demonstrated to have highly skewed X inactivation. The combination of the clinical phenotype, consistent with that of the patients with ATR-X syndrome, the skewed X-inactivation pattern in a carrier female, as well as the mapping interval including band Xq13.3, prompted us to consider the XNP/ATR-X gene being involved in this syndrome. Using RT-PCR analysis, we screened the entire XNP/ATR-X gene and found a mutation in exon 2 (c.109C > T) giving rise to a stop codon at position 37 (p.R37X). Western blot and immunocytochemical analyses using a specific monoclonal antibody directed against XNP/ATR-X showed the protein to be present in lymphoblastoid cells from one affected male, despite the premature stop codon. To explain these discordant results, we further analyzed the 5' region of the XNP/ATR-X gene and found three alternative transcripts, which differ in the presence or absence of exon 2, and the length of exon 1. Our data suggest that ChLS is allelic to the ATR-X syndrome with its less severe phenotype being due to the presence of some XNP/ATR-X protein.

Duchenne and Becker muscular dystrophy (DMD and BMD) are caused by mutations in the dystrophin gene. Large rearrangements in the gene are found in about two,thirds of DMD patients, with similar to60% carrying deletions and 5-10% carrying duplications. Most of the remaining 30-35% of patients are expected to have small nucleotide substitutions, insertions, or deletions. To detect these subtle changes within the coding and splice site determining sequences of the dystrophin gene, we established a semiautomated denaturing gradient gel electrophoresis (DGGE) mutation scanning system. The DGGE scan covers the dystrophin gene with 95 amplicons, PCRed either individually or in a multiplex setup. PCR and pooling were performed semiautomatically, using a pipetting robot and 384-well plates, enabling concurrent amplification of DNA of four patients in one run. Amplification of individual fragments was performed using one PCR program. The products were pooled just before gel loading; DGGE requires only a single gel condition. Validation was performed using DNA samples harboring 39 known DMD variants, all of which could be readily detected. DGGE mutation scanning was applied to analyze 135 DMD/BMD patients and potential DMD carriers without large deletions or duplications. In DNA from 25 out of 44 DMD patients (57%) and from 5 out of 39 BMD patients (13%), we identified clear pathogenic changes. All mutations were different, with the exception of one DMD mutation, which occurred twice. In DNA from 10 out of 44 potential DMD carriers, including four obligate carriers, we detected causative changes, including one pathogenic change in every obligate carrier. In addition to these pathogenic changes, we detected 15 unique unclassified variants, i.e., changes for which a pathogenic nature is uncertain. (C) 2003 Wiley-Liss, Inc.

As general population screening becomes more common, an increasing number of cystic fibrosis (CF) carriers will be identified who do not have a family history of CF. Whether these carriers inform their relatives of their carrier status and whether their relatives are motivated to pursue carrier screening is unknown. We surveyed CF carriers with and without a family history of CF to understand whether and how information dissemination patterns differ, why information is or is not shared, and to what extent relatives are known to undergo testing. CF carriers were identified from a general population carrier screening clinic (group B = 18) or were parents of affected children followed at a CF clinic (group A = 30). CF carriers with a family history told essentially 100% of their living parents, siblings, and half-siblings, while those without a family history told 84% of living parents and 56% of siblings (P < 0.05). Despite the high rate of information dissemination in both groups, few siblings were known to have undergone carrier screening (14/74). Significantly fewer second- and third-degree relatives were informed about carrier status or were known to have undergone carrier screening. Group A was more likely to inform second- and third-degree relatives about carrier status. Our study documents that the frequency and reasons for disclosing CF carrier status differ between individuals with and without a family history of CF despite the fact that the reproductive risks for their relatives are the same.

PURPOSE Mutations at some retinitis pigmentosa (RP) loci are associated with variable penetrance and expressivity, exacerbating diagnostic challenges. The purpose of this study was to dissect the genetic underpinnings of nonsyndromic RP with variable age of onset in a large Mexican family. METHODS We ascertained members of a large, multigenerational pedigree using a complete ophthalmic examination. We performed whole exome sequencing on two affected first cousins, an obligate carrier, and a married-in spouse. Confirmatory sequencing of candidate variants was performed in the entire pedigree, as well as genotyping and mRNA studies to investigate expression changes in the causal locus. RESULTS We identified a 14-base pair (bp) deletion in PRPF31, a gene implicated previously in autosomal dominant (ad) RP. The mutation segregated with the phenotype of all 10 affected females, but also was present in six asymptomatics (two females and four males). Studies in patient cells showed that the penetrance/expressivity of the PRPF31 deletion allele was concordant with the expression levels of wild-type message. However, neither the known PRPF31 modulators nor cis-eQTLs within 1 Mb of the locus could account for the variable expression of message or the clinical phenotype. CONCLUSIONS We have identified a novel 14-bp deletion in PRPF31 as the genetic driver of adRP in a large Mexican family that exhibits nonpenetrance and variable expressivity, known properties of this locus. However, our studies intimate the presence of additional loci that can modify PRPF31 expression.

Paroxysmal kinesigenic dyskinesia is a rare episodic movement disorder that can be isolated or associated with benign infantile seizures as part of choreoathetosis syndrome. Mutations in the PRRT2 gene have been recently identified as a cause of paroxysmal kinesigenic dyskinesia and infantile convulsion and choreoathetosis (ICCA). We reported a PRRT2 heterozygous mutation (c.604-607delTCAC, p.S202Hfs*25) in a 3-generation Chinese family with infantile convulsion and choreoathetosis and paroxysmal kinesigenic dyskinesia. The mutation was present in 5 family members, of which 4 were clinically affected and 1 was an obligate carrier with reduced penetrance of PRRT2. The affected carriers of this mutation presented with a similar type of infantile convulsion during early childhood and developed additional paroxysmal kinesigenic dyskinesia symptoms later in life. In addition, they all had a dramatic clinical response to oxcarbazepine/phenytoin therapy. Reduced penetrance of the PRRT2 mutation in this family could warrant genetic counseling.

Background: X-linked agammaglobulinemia (XLA), caused by mutations in Bruton's tyrosine kinase ( BTK ), is the most common form of inherited antibody deficiency. We previously reported that a flow cytometric evaluation of BTK expression in monocytes could easily detect XLA as well as its carrier. Objective: Our purpose was to perform further flow cytometric analysis in additional XLA families in Japan. Methods: In all, 106 hypogammaglobulinemic males (from 91 families) of various ages with a lack of mature B cells ( Results: Flow cytometric assessment revealed the deficient BTK expression status in 78 families (93 patients), and mutations in BTK were identified in 76 of 78 families with presumed XLA. Of the patients with normal BTK expression, 2 showed missense mutations in which the normal amount of altered BTK transcript would cause the XLA phenotype. As many as 30% of these patients with XLA were clinically or genetically recognized beyond 5 years of age. Higher concentrations (>300 mg/dL) of serum IgG were evident in the cases diagnosed among adults, seemingly preventing severe infections. Fifty-seven of 70 mothers of patients with BTK deficiency were diagnosed as obligate carriers on the basis of a bimodal BTK expression pattern. Nine of the remaining 13 mothers showing nonmosaic BTK expression had no mutations in 2 alleles; surprisingly, the other 4 mothers had the mutated alleles. Conclusions: A diagnostic approach based on flow cytometric assessment for XLA should be initially considered in genetic investigation of antibody deficiencies, regardless of the patient's age. (J Allergy Clin Immunol 2001;108:1012-20.)

A six-generation kindred from Arkansas with X-linked recessive spondyloepiphyseal dysplasia tarda (SEDT) was investigated by genetic linkage and mutation analysis. SEDT had been mapped on the X-chromosome (Xp22.2), and the clinical and radiographic evolution of this kindred had been published. Linkage analysis proved informative for all five polymorphic markers tested, and DXS987 and DXS16 co-segregated with the Arkansas kindred (peak logarithm of the odds scores, 3.54 and 3.36, respectively). Subsequently, dinucleotide deletion in a new gene designated “sedlin” was reported to cause SEDT in three families. In an affected man and obligate carrier woman in the Arkansas kindred, we found a 5-bp deletion in exon 5 of sedlin. The defect causes a frameshift, resulting in eight missense amino acids and premature termination. The 5-bp deletion was then demonstrated to segregate with SEDT in the four living generations, including eight affected males and nine obligate carrier females. Furthermore, the deletion was identified in four females who potentially were heterozygous carriers for SEDT. The mutation was not detected in the two young sons of the consultand (believed to be a carrier because of her subtle radiographic skeletal changes and then shown to have the deletion), but they were too young for x-ray diagnosis. Identification of a defect in sedlin in this SEDT kindred enables carrier detection and presymptomatic diagnosis and reveals an important role for this gene in postnatal endochondral bone formation.

Complex illnesses may result from the interaction or addition of multiple factors. We examined the familial co-distribution of two abnormalities common in schizophrenia: impaired auditory sensory gating and impaired flush response to niacin. In ten families, the obligate carrier parent had sensory-gating deficits, while eight of the ten parents without a family history of schizophrenia had impaired flush response. No parents had both deficits. The data are consistent with a theory suggesting the interaction of these two factors in some cases of schizophrenia.

We characterize the clinical and radiographic evolution of X-linked recessive spondyloepiphyseal dysplasia tarda (SEDT) in a 6-generation kindred from Arkansas (SEDT(AK)). Our observations show the natural progression of SEDT(AK) and enable carrier detection by radiographic study. We find that, SEDT(AK) manifests as a postnatal defect. Affected hemizygous males can have radiographically normal vertebrae at birth. The pathogenesis seems to involve a developmental disturbance in endochondral bone formation that is reflected most dramatically in vertebrae by a radiographically inapparent ring apophysis. This defect leads to distinctive malformation of the anterior margins of the lumbar vertebrae during childhood. Subsequently, there is degeneration of intervertebral discs and destruction of spinal facet joints. In the femur, the head, neck, and distal condyles are abnormally shaped and become distorted so that osteoarthritis of the hip is not uncommon. Obligate carrier females heterozygous for the SEDT(AK) gene defect demonstrate several similar but more subtle skeletal abnormalities beginning in early adult life. These women seem to be troubled frequently by arthralgia by middle age. The cumulative findings in SEDT(AK) implicate a defect in a gene at Xp22.2-22.1 that engenders a relatively mild disturbance in endochondral bone formation, especially in the axial skeleton. Accounts of large, well-characterized SEDT kindreds remain essential to appreciate fully any interfamily variability of disease expression and to understand better the pathogenesis of the SEDT defect on the X chromosome.

Hemophagocytic lymphohistiocytosis (HLH), also referred to as familial erythrophagocytic lymphohistiocytosis, is a rare disorder of infancy associated with proliferation of activated histiocytes and T cells, anemia, thrombocytopenia, and fevers. This disorder appears to be due to the uncontrolled activation of T cells producing IL-2, tumor necrosis factor-alpha, and interferon-gamma. Untreated, the disorder is universally fatal. Various deficits in immune function have been described during acute disease activity including impaired T cell function, impaired monocyte-mediated antibody-dependent cytotoxicity, impaired natural killer cell function, and impaired IL-1 production. We examined natural killer cell function in familial HLH patients to determine whether this finding was consistently associated with the disease. We also examined natural killer cell function in asymptomatic parents and siblings of patients. Impaired natural killer cell function was identified in all patients and in some family members, including obligate carrier parents. This implies that one potential genetic defect in HLH may result in depressed natural killer function, but that this may not be sufficient to reliably predict eventual progression to disease.

Deficiency of iduronate-2-sulphatase (IDS) results in the X linked recessive lysosomal storage disorder Hunter syndrome. Determination of carrier status in families affected by this disorder has been performed using a variety of enzymatic tests. None of these tests has proved to be 100% effective at identifying carriers. The aim of this study was to perform carrier testing in a family affected by the disorder, where testing was complicated by the fact that no surviving affected subjects were available for study. Direct dye primer sequencing of PCR products was used to identify mixed bases in an obligate carrier. Two mixed bases were observed within exon VIII. The first base change (T-->A) at nucleotide position 1150 results in a missense mutation (H342Q), while the second base change (G-->T) at nucleotide position 1151 results in a nonsense mutation (G343X). Four additional female family members were screened for the same mutation. Using this approach it is possible to provide unambiguous information about a subject's carrier status and, unlike biochemical testing, this approach will be equally effective when applied to families with the mild form of this disorder.

Objective: Carrier identification in X-linked immunodeficiency disorders can be based on the demonstration of non-random X inactivation (NRXI) in affected blood cell lineages when growth is impaired in cells expressing the abnormal gene. We examined the utility of seeking evidence of NRXI1 to test the carrier status of women in families affected by X-linked severe combined immunodeficiency (XSCID) and X-linked hypogammaglobulinaemia (XLH),2 to identify as carriers the mothers of boys with SCID or hypogammaglobulinaemia whose phenotype suggested X-linkage and3 to infer X-linkage in boys with SCID or hypogammaglobulinaemia whose disease was not clearly X-linked on the basis either of family history or clinical and immunological characteristics. Methodology: A polymerase chain reaction-based method was used to amplify a polymorphic CAG repeat in the first exon of the androgen receptor gene after selective digestion of the active X chromosome with a methylation-sensitive enzyme, HpaII to distinguish between the paternal and maternal alleles and to identify their methylation status. Results: Heterozygosity was found in 24 of 31 female subjects (77%). As anticipated, NRXI could be demonstrated in all lymphoid cells studied from obligate carriers of XSCID and an obligate carrier of XLH but not on a carrier of X-linked immunodeficiency with hyper-IgM. The finding of NRXI in the mother of a boy with a SCID variant showed her to be a carrier of XSCID and establishes that her son has XSCID, not otherwise evident from available data. Conclusions: This PCR assay provides a rapid method for carrier detection of X-linked immunodeficiencies, and has allowed us to expand the phenotype of XSCID

We report on two brothers and one maternal cousin with severe mental retardation, microcephaly, short stature, cryptorchidism, and spastic diplegia. The patients were born to normal and non-consanguineous parents. All other members of the family, almost exclusively females, were clinically normal, suggesting X linked inheritance. By multipoint linkage analysis with markers spanning the whole X chromosome, we have tentatively assigned the underlying genetic defect to Xp11.4-q21, achieving a maximum lod score of 1.3. This localisation overlaps MRXS3, a syndromic form of mental retardation resembling that found in the family described here, although with a milder presentation. We discuss the possibility that both phenotypes might be allelic variants of the same gene localised in the pericentromeric region of the X chromosome. Analysis of the X inactivation pattern in one potential and three obligate carrier females showed non-random inactivation of the allele linked to the disease. This finding may be interpreted as: (1) a negative selection effect on cells bearing the mutation on the active X chromosome; (2) both the disease causing gene and the X inactivation centre are simultaneously affected by the same alteration, a deletion for instance; or (3) the skewed inactivation is the consequence of an independent event randomly associated with the disease. In any case, the observation of consistent X inactivation supports X linkage of the disease.

In a previous study of 99 Ashkenazi Jewish patients with Parkinson disease from Israel who were tested for the six most common mutations for Gaucher disease, 31.3% had at least one Gaucher disease mutation, implying that carrier status per se my be a risk for Parkinson disease. The purpose of this survey was to ascertain the presence of Parkinson disease among Ashkenazi Jewish obligate carriers of Gaucher disease relative to its incidence in a comparable cohort of Ashkenazi Jews who are putatively non-carriers. There was no statistically significant difference in gender or age between the groups (n>100). Among patients, 27.3% reported having a relative with Parkinson disease while among the controls there was a reported 12.3% which was statistically significant (P=0.05). While based completely on subjective reports in a paper-base questionnaire, the results of this survey implicate a high rate of Parkinson disease among individuals with Gaucher disease mutations.

Although familial recurrences of Rett syndrome (RTT) comprise only approximately 1% of the reported cases, it is these cases that hold the key for the understanding of the genetic basis of the disorder. Families in which RTT occurs in mother and daughter, aunt and niece, and half sisters are consistent with dominant inheritance and variable expressivity of the phenotype. Recurrence of RTT in sisters is likely due to germ-line mosaicism in one of the parents, rather than to recessive inheritance. The exclusive occurrence of classic RTT in females led to the hypothesis that it is X-linked and may be lethal in males. In an X-linked dominant disorder, unaffected obligate-carrier females would be expected to show nonrandom or skewed inactivation of the X chromosome bearing the mutant allele. We investigated the X chromosome inactivation (XCI) patterns in the female members of a newly identified family with recurrence of RTT in a maternal aunt and a niece. Skewing of XCI is present in the obligate carrier in this family, supporting the hypothesis that RTT is an X-linked disorder. However, evaluation of the XCI pattern in the mother of affected half sisters shows random XCI, suggesting germ-line mosaicism as the cause of repeated transmission in this family. To determine which regions of the X chromosome were inherited concordantly/discordantly by the probands, we genotyped the individuals in the aunt-niece family and two previously reported pairs of half sisters. These combined exclusion-mapping data allow us to exclude the RTT locus from the interval between DXS1053 in Xp22.2 and DXS1222 in Xq22.3. This represents an extension of the previous exclusion map.

Primary ovarian insufficiency (POI), or premature ovarian failure, results from ovarian follicle depletion with a consequent elevation of FSH levels before age 40 years. We identified a family in which 9 women in 3 consecutive generations developed menopause at approximately age 30 years. We hypothesized a genetic cause with a dominant mode of inheritance.This was a family-based genetic study and a replicate group of women with POI.The study was conducted at an academic medical center.Seven affected women and an obligate carrier and 7 unaffected family members were genotyped. The genes of interest were also sequenced in 38 unrelated women with POI.The DNA from 7 family members was subjected to whole-exome sequencing. The genotypes of interest were confirmed and genotypes of additional family members and unrelated women with POI were determined using Sanger sequencing.A high-impact, deleterious variant that segregated appropriately with POI in the family was required.A heterozygous stop codon (Ser429X) was identified in the eukaryotic translation initiation factor 4E nuclear import factor 1 (eIF4ENIF1) in the proband and all affected women but not in the unaffected family members. The chance that such a high-impact, deleterious variant would segregate appropriately among the affected and unaffected relatives by chance is very low (P.05). There were no additional mutations identified in eIF4ENIF1 or eIF4E in 38 unrelated women with POI.Data demonstrate a new gene associated with dominantly inherited POI. These results highlight the importance of translation initiation factors and their regulators in ovarian function.

Genetic predisposition plays a key role in the development of familial breast cancer. In spite of strong familial clustering of the disease and extensive efforts made during the past decade; however, progress has been slow in identifying genetic predisposition for the majority of familial breast cancer families. The question arises therefore as to whether current approaches are adequate in identifying the unknown genetic predisposition. We analyzed eight members of a BRCA1-, BRCA2-, p53-, and PTEN-negative breast cancer family, of which five had breast cancer, one is an obligate gene carrier, and two were unaffected. We sequenced the entire coding region of the genome for each member using exome sequencing to identify nonsynonymous variants. We identified 55 nonsynonymous germline variants affecting 49 genes in multiple members of the family, of which 22 are predicted to have damaging effects. We validated 20 of the 22 selected variants in the family by Sanger sequencing. Two variants in KAT6B, an acetal transferase gene, were identified in six family members of which five were affected with breast cancer and one is the unaffected obligate carrier. We further examined the presence of the identified variants in a cohort of 40 additional breast cancer cases from 22 familial breast cancer families, but none of the 22 variants was detected in these cases. Sequencing the entire coding exons in KAT6B detects no variants in these cases. Our results show that genetic predisposition for familial breast cancer can be rich in an affected family, but the predisposition can be family-specific. As such, it will be difficult to detect them by applying population-based approach. Our study supports the concept that focusing on each affected family will be required to determine the genetic predisposition for many familial breast cancer families whose genetic dispositions remain unknown.

X-linked recessive myotubular myopathy (XLMTM) is a severe neonatal neuro-muscular disease characterized by muscle weakness, hypotonia, and respiratory problems. The locus for the XLMTM gene (MTM1) has previously been mapped to Xq28 between the markers DXS304 and DXS497 by linkage analyses and by determining the breakpoints of deletion patients. We report linkage analysis data or 20 XLMTM families who were tested using the DNA markers DXS1113, DXS304, DXS455, DXS1684, DXS305 and DXS52 and present two families showing recombination between MTM1 and either DXS304, DXS334 or DXS305. We found each of the families to be informative for at least three markers. Based on these findings we excluded 30 women from being carriers, the carrier status of 17 obligate carrier mothers could be confirmed and eight mothers and sisters were identified as to be at high risk of carrying a MTM1 mutation. By combining recently published data with the results of our recombinant families, we suggest that the MTM1 locus maps between DXS334 and DXS497 narrowing the region of interest from 600 kb to an estimated500 kb interval. This additional refinement in the localization of MTM1 means a further step towards the isolation of the gene in the near future, and allows more reliable and efficient carrier detection and prenatal diagnosis.

We report a family in which the normal pattern of X-linked inheritance of hemophilia B (Factor IX deficiency) is complicated by mosaicism in the proband's maternal grandfather. The proband, an infant with severe Factor IX deficiency, was initially thought to be a sporadic case. Testing of other family members identified his mother as a carrier of the disorder, and his asymptomatic maternal grandfather as having very mild FIX deficiency. The causative familial mutation was identified as a two base pair deletion (AG within codons 134-135) in the Factor IX gene. The grandfather was shown to be "heterozygous" for the deletion. Karyotype analysis confirmed him to be 46XY thereby ruling out Klinefelter syndrome. The proband's aunt, who as the daughter of a man with hemophilia is theoretically an obligate carrier, was found not to carry this familial mutation, and thus not to be a carrier of hemophilia B. The grandfather must therefore be an X chromosome somatic and germline mosaic, with consequent segregation of the affected and non-affected Factor IX genes. This observation underlines the importance of confirming carrier status even in those individuals assumed to be obligate carriers, and has implications for genetic counseling.

X linked recessive deafness accounts for only 1.7% of all childhood deafness. Only a few of the at least 28 different X linked syndromes associated with hearing impairment have been characterised at the molecular level. In 1960, a large Norwegian family was reported with early onset progressive sensorineural deafness, which was indexed in McKusick as DFN-1, McKusick 304700. No associated symptoms were described at that time. This family has been restudied clinically. Extensive neurological, neurophysiological, neuroradiological, and biochemical, as well as molecular techniques, have been applied to characterise the X linked recessive syndrome. The family history and extensive characterisation of 16 affected males in five generations confirmed the X linked recessive inheritance and the postlingual progressive nature of the sensorineural deafness. Some obligate carrier females showed signs of minor neuropathy and mild hearing impairment. Restudy of the original DFN-1 family showed that the deafness is part of a progressive X linked recessive syndrome, which includes visual disability leading to cortical blindness, dystonia, fractures, and mental deficiency. Linkage analysis indicated that the gene was linked to locus DXS101 in Xq22 with a lod score of 5.37 (zero recombination). Based on lod-1 support interval of the multipoint analysis, the gene is located in a region spanning from 5 cM proximal to 3 cM distal to this locus. As the proteolipid protein gene (PLP) is within this region and mutations have been shown to be associated with non-classical PMD (Pelizaeus-Merzbacher disease), such as complex X linked hereditary spastic paraplegia, PLP may represent a candidate gene for this disorder. This family represents a new syndrome (Mohr-Tranebjaerg syndrome, MTS) and provides significant new information about a new X linked recessive sydromic type of deafness which was previously thought to be isolated deafness.

Seventeen obligate carriers from nine families with autosomal recessive Usher syndrome type I underwent otological, audiological, vestibular, and ophthalmological examination in order to identify possible manifestations of heterozygosity. Linkage studies were performed and six families showed linkage to chromosome region 11q13.5 while 3 families have so far failed to show linkage to the candidate regions. Eight obligate carriers had an abnormal puretone audiogram. Two different audiometric patterns could be distinguished when hearing loss was corrected for age and sex. Four carriers (24%) had significant sensorineural hearing loss (SNHL) which increased at higher frequencies. The other 13 carriers had SNHL of about 10 dB at 0.25 and 0.5 kHz, but less at higher frequencies. Vestibular findings were generally normal. Electrooculography demonstrated a significant lower mean light peak/dark trough ratio in Usher type I carriers compared to normal control individuals. The methods used in this study were found not to be specific enough to clinically identify carriers of Usher type I syndrome. Nevertheless it is remarkable that a number of obligate carriers showed significant audiological and ophthalmological abnormalities. 29 refs., 1 fig., 3 tabs.

Purpose To investigate the diverse ocular manifestations and identify the causative mutation in a large family with autosomal dominant anterior segment dysgenesis accompanied in some individuals by cerebral vascular disease. Design Retrospective observational case series and laboratory investigation. Methods Forty-five family members from 4 generations underwent ophthalmic examination. Molecular genetic investigation included analysis with single nucleotide polymorphism (SNP) markers and DNA sequencing. Whole exome sequencing was performed in 1 individual. Results A broad range of ocular manifestations was observed. Typical cases presented with corneal clouding, anterior synechiae, and iris hypoplasia. Posterior embryotoxon, corectopia, and early cataract development were also seen. One obligate carrier and several other family members had minor ocular anomalies, thus confounding the scoring of affected and unaffected individuals. Cerebral hemorrhages had occurred in 4 individuals, in 3 at birth or during the first year of life. Seven patients with corneal clouding were considered “definitely affected” for linkage studies. Haplotype mapping revealed that they shared a 14 cM region in the terminal part of chromosome 13q that included the locus for COL4A1 . The affected family members were heterozygous for a novel COL4A1 sequence variant c.4881C>G (p.Asn1627Lys) predicted to be damaging and not found among 185 local blood donors. Exome sequencing showed that this variant was the only one in the candidate region not found in dbSNP. Conclusion Among the family members shown to carry the novel COL4A1 mutation, heterogenous presentations of anterior segment dysgenesis was seen. Testing family members for this mutation also made a definite diagnosis possible in patients with a clinical presentation difficult to classify. In families where anterior segment dysgenesis occurs together with cerebral hemorrhages, genetic analysis of COL4A1 should be considered.

Intellectual disability is common. Aristaless-related homeobox (ARX) gene is one of the most frequently mutated and pleiotropic genes, implicated in 10 different phenotypes. More than half of ∼100 reported cases with ARX mutations are due to a recurrent duplication of 24 bp, c.429_452dup, which leads to polyalanine tract expansion. The excess of affected males among the offspring of the obligate carrier females raised the possibility of transmission ratio distortion for the c.429_452dup mutation. We found a significant deviation from the expected Mendelian 1:1 ratio of transmission in favour of the c.429_452dup ARX mutation. We hypothesise that the preferential transmission of the c.429_452dup mutation may be due to asymmetry of meiosis in the oocyte. Our findings may have implications for genetic counselling of families segregating the c.429_452dup mutation and allude to putative role of ARX in oocyte biology.

Phenotypic variation in amyotrophic lateral sclerosis (ALS) is common, and one atypical form is the flail arm variant (FAV). Some classic ALS patients carry TARDBP mutations, and so we sought to establish whether TARDBP mutations are also present in the FAV of ALS. Mutation analysis of TARDBP, the gene encoding TDP-43, was performed in cohorts of classic and FAV ALS patients. An analysis of mutation effects was performed in patient fibroblasts. Results showed that a novel heterozygous in-frame insertion/deletion (indel), c.1158_1159delAT; c.1158_1159insCACCAACC, was identified in a highly conserved region encoding the glycine-rich area of TDP-43 in a patient with FAV. This indel was confirmed in the proband's mother, an obligate carrier, and was absent from 480 ethnically-matched control individuals. Transcription of the mutant allele was confirmed. Under induced stress, indel-mutant fibroblasts showed a loss of normal nuclear TDP-43 immunoreactivity and formation of cytoplasmic inclusions of TDP-43, consistent with features seen in affected neurons. In conclusion, TARDBP missense mutations have previously been reported in classic ALS and frontotemporal lobar degeneration. The identification of a TARDBP indel mutation in a patient with FAV extends the spectrum of mutations and further supports the role of TDP-43 in a range of neurodegenerative phenotypes.