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Female carriers of X‐linked inherited retinal diseases (IRDs) are burdened with potentially passing their disease‐causing variant to future generations, as well as exhibiting signs of retinal disease themselves. This study aimed to investigate carriers' experiences of genetic testing, emotions relating to having affected children, and their knowledge regarding genetic testing and gene therapy. An online survey was advertised to self‐identified carriers worldwide. Two hundred and twenty‐eight carriers completed the survey with mean age of 51 years (SD ± 15.0). A majority of respondents resided in the United States of America (51%), Australia (19%), and the United Kingdom (14%). Most carriers identified with feelings of guilt (70%), concern (91%), and anxiety (88%) for their child. Female carriers who had given birth to children had significantly greater gene therapy knowledge compared to carriers who had not (p < 0.05). Respondents agreed that their eyecare provider and general practitioner helped them understand their condition (63%), however, few carriers reported receiving psychological counselling (9%) or family planning advice (5%). Most respondents (78%) agreed that gene therapy should be available to carriers. This study emphasises the importance of providing appropriate counselling to female carriers and illustrates the motivation of many to participate in emerging treatment options, such as gene therapy. [ABSTRACT FROM AUTHOR]

Preconception carrier screening allows identification of couples at risk to have offspring with autosomal recessive and X-linked disorders. In a current multiethnic world, screening based on self-reported ancestry has limitations. Here we describe the findings of a comprehensive pan-ethnic variant-based carrier screening, using the Israeli Jewish population as a model. The cohort included 1696 individuals (848 couples) tested with the ‘MyScreen’ multigene panel. The panel covers 1206 variants spanning 385 genes, known in different Jewish ethnicities and local Arab, Druze and Bedouin populations. Out of these, 205 variants in 143 genes are Jewish founder variants. We identified 859 (50.6%), carriers of at least one variant in 151 genes. Importantly, 569 (66.2%) of carriers could be missed by the current Israeli screening program. In total, 1:40 (2.5%) of carrier couples were identified by the ‘MyScreen’ panel, compared with 1:144 (0.7%) found by the ethnicity-based screening. Surprisingly, 90 individuals (10.5%) were carriers of variants “unexpected” for their reported origin, and 16 variants were previously unreported in Jewish patients. Our results support the advantages of variant-based comprehensive carrier screening for detection of carriers and at-risk couples in a diverse population with many founder disease-causing variants. [ABSTRACT FROM AUTHOR]

Fabry disease (FD) is an X‐linked genetic disease due to pathogenic variants in GLA. The phenotype varies depending on the GLA variant, alpha‐galactosidase residual activity, patient's age and gender and, for females, X chromosome inactivation. Over 1000 variants have been identified, many through screening protocols more susceptible to disclose non‐pathogenic variants or variants of unknown significance (VUS). This, together with the non‐specificity of some FD symptoms, challenges physicians attempting to interpret GLA variants. The traditional way to interpreting pathogenicity is based on a combined approach using allele frequencies, genomic databases, global and disease‐specific clinical databases, and in silico tools proposed by the American College of Medical Genetics and Genomics. Here, a panel of FD specialists convened to study how expertise may compare with the traditional approach. Several GLA VUS, highly controversial in the literature (p.Ser126Gly, p.Ala143Thr, p.Asp313Tyr), were re‐analyzed through reviews of patients' charts. The same was done for pathogenic GLA variants with some specificities. Our data suggest that input of geneticists and physicians with wide expertise in disease phenotypes, prevalence, inheritance, biomarkers, alleles frequencies, disease‐specific databases, and literature greatly contribute to a more accurate interpretation of the pathogenicity of variants, bringing a significant additional value over the traditional approach. [ABSTRACT FROM AUTHOR]

The article presents a case study of two patients with Simpson-Golabi-Behmel syndrome (SGBS) caused by the loss of-function of the glypican-3 gene (GPC3) and which showed Xq26.2 duplication. It informs about the tandem duplication of GPC3 identified by array comparative genomic hybridization (array-CGH). It also recommends a molecular transcription analysis to assess a possible gene disruption.

L1CAM gene mutations cause neurodevelopmental disorders collectively termed L1 syndrome. Insufficient information about L1CAM variants complicates clinical prognosis, genetic diagnosis and genetic counseling. We combined clinical data, in silico effect predictions and functional analysis of four L1CAM variants, p.I37N, p.T38M, p.M172I and p.D202Y, located to the two N-terminal Ig-like domains present in five families with symptoms of L1 syndrome. Software tools predicted destabilizing effects of p. I37N and p. D202Y but results for p. T38M and p. M172I were inconsistent. Cell surface expression of mutant proteins L1-T38M, L1-M172I and L1-D202Y was normal. Conversely, L1-I37N accumulated in the endoplasmic reticulum (ER) and showed temperature-sensitive protein maturation suggesting that p. I37N induces protein misfolding. L1CAM-mediated cell-cell aggregation was severely impaired by L1CAM variants p. I37N, p. M172I and p. D202Y but was preserved by the variant p. T38M. Our experimental data indicate that protein misfolding and accumulation in the ER affect function of the L1CAM variant p. I37N whereas the variants p. M172I and p. D202Y impair homophilic interaction at the cell surface. [ABSTRACT FROM AUTHOR]

De novo missense mutations and in-frame coding deletions in the X-linked gene SMC1A (structural maintenance of chromosomes 1A), encoding part of the cohesin complex, are known to cause Cornelia de Lange syndrome in both males and females. For a long time, loss-of-function (LoF) mutations in SMC1A were considered incompatible with life, as such mutations had not been reported in neither male nor female patients. However, recently, the authors and others reported LoF mutations in females with intellectual disability ( ID) and epilepsy. Here we present the detailed phenotype of two females with de novo LoF mutations in SMC1A, including a de novo mutation of single base deletion [c.2364del, p.( Asn788Lysfs*10)], predicted to result in a frameshift, and a de novo deletion of exon 16, resulting in an out-of-frame mRNA splice product [p.( Leu808Argfs*6)]. By combining our patients with the other recently reported females carrying SMC1A LoF mutations, we ascertained a phenotypic spectrum of (severe) ID, therapy-resistant epilepsy, absence/delay of speech, hypotonia and small hands and feet. Our data show the existence of a novel phenotypic entity - distinct from CdLS - and caused by de novo SMC1A LoF mutations. [ABSTRACT FROM AUTHOR]

Alport syndrome ( AS) is caused by pathogenic mutations in the genes encoding α3, α4 or α5 chains of collagen IV ( COL4A3/ COL4A4/ COL4A5), resulting in hematuria, chronic renal failure ( CRF), sensorineural hearing loss ( SNHL) and ocular abnormalities. Mutations in the X-linked COL4A5 gene have been identified in 85% of the families ( XLAS). In this study, 22 of 60 probands (37%) of unrelated Portuguese families, with clinical diagnosis of AS and no evidence of autosomal inheritance, had pathogenic COL4A5 mutations detected by Sanger sequencing and/or multiplex-ligation probe amplification, of which 12 (57%) are novel. Males had more severe and earlier renal and extrarenal complications, but microscopic hematuria was a constant finding irrespective of gender. Nonsense and splice site mutations, as well as small and large deletions, were associated with younger age of onset of SNHL in males, and with higher risk of CRF and SNHL in females. Pathogenic COL4A3 or COL4A4 mutations were subsequently identified in more than half of the families without a pathogenic mutation in COL4A5. The lower than expected prevalence of XLAS in Portuguese families warrants the use of next-generation sequencing for simultaneous COL4A3/ COL4A4/ COL4A5 analysis, as first-tier approach to the genetic diagnosis of collagen type IV-related nephropathies. [ABSTRACT FROM AUTHOR]

Ectodermal dysplasias (EDs) are a group of genetic disorders characterized by the abnormal development of the ectodermal-derived structures. X-linked hypohidrotic ectodermal dysplasia, resulting from mutations in ED1 gene, is the most common form. The main purpose of this study was to characterize the phenotype spectrum in 45 males harboring ED1 mutations. The study showed that in addition to the involvement of the major ectodermal tissues, the majority of patients also have alterations of several minor ectodermal-derived structures. Characterizing the clinical spectrum resulting from ED1 gene mutations improves diagnosis and can direct clinical care. [ABSTRACT FROM AUTHOR]

Skeletal dysplasias are challenging to diagnose because of their phenotypic variability, genetic heterogeneity, and diverse inheritance patterns. We conducted whole exome sequencing of a Turkish male with a suspected X-linked skeletal dysplasia of unknown etiology as well as his unaffected mother and maternal uncle. Bioinformatic filtering of variants implicated in skeletal system development revealed a novel hemizygous mutation, c.341-(11_9) delAAT, in an intron of TRAPPC2, the causative locus of spondyloepiphyseal dysplasia tarda ( SEDT). We show that this deletion leads to the loss of wild-type TRAPPC2 and the generation of two functionally impaired mRNAs in patient cells. These consequences are predicted to disrupt function of SEDLIN/ TRAPPC2. The clinical and research data were returned, with appropriate caveats, to the patient and informed his disease status and reproductive choices. Our findings expand the allelic repertoire of SEDT and show how prior filtering of the morbid human genome informed by inheritance pattern and phenotype, when combined with appropriate functional tests in patient-derived cells, can expedite discovery, overcome issues of missing data and help interpret variants of unknown significance. Finally, this example shows how the return of a clinically confirmed mutational finding, supported by research allele pathogenicity data, can assist individuals with inherited disorders with life choices. [ABSTRACT FROM AUTHOR]

In a multidisciplinary outpatient clinic for hereditary skin diseases and/or syndromes involving the skin, 7% (30 of 409) of patients were found to have an abnormality involving the X chromosome, a mutation in a gene located on the X chromosome or a clinical diagnosis of an X-linked monogenetic condition. The collaboration of a dermatologist and a clinical geneticist proves to be very valuable in recognizing and diagnosing these conditions. By combining their specific expertize in counselling an individual patient, X-linked diagnoses were recognized and could be confirmed by molecular and/or cytogenetic studies in 24 of 30 cases. Mosaicism plays an important role in many X-linked hereditary skin disorders. From our experience, we extracted clinical clues for specialists working in the field of genetics and/or dermatology for considering X-linked disorders involving the skin. [ABSTRACT FROM AUTHOR]

Craniofrontonasal syndrome ( CFNS) is an X-linked disorder caused by inactivating mutations in the gene for ephrin- B1 ( EFNB1). Paradoxically it shows a more severe phenotype in females than in males. As a result of X inactivation cell populations with and without EFNB1 expression are found in EFNB1+/− females. This is thought to initiate a process termed cellular interference which may be responsible for the phenotype in females. We present a boy with severe clinical features of CFNS. In ∼42% of his blood cells we found a supernumerary ring X chromosome containing EFNB1 but lacking XIST. Mosaicism for cell populations with different levels of EFNB1 expression can explain the severe phenotype of this patient. In vitro experiments in Xenopus tissue showed that cells overexpress ephrinB1 cluster and sort out from wild-type cells. Our report provides further evidence that cellular interference contributes to the paradoxical inheritance pattern of CFNS. [ABSTRACT FROM AUTHOR]

Fabry disease ( FD) is an X-linked lysosomal storage disorder (LSD) caused by the deficiency of the enzyme α-galactosidase. It exhibits a wide clinical spectrum that may lead to a delayed or even missed diagnosis and the real incidence can be underestimated. We report the cases of two unrelated Italian families in whom FD was incidentally diagnosed in two females. In both families, the risk for other lysosomal disorders was known from other members affected by fucosidosis or mucopolysaccharidosis I Hurler/Scheie. Some subjects were simultaneously heterozygous for Fabry and the other lysosomal deficiency. Our study shows that the risk for more than one LSDs can occur in a family pedigree. The diagnosis of Fabry in female probands represents a diagnostic challenge, as symptoms and signs can be variably present because of the random X-chromosome inactivation. [ABSTRACT FROM AUTHOR]

Osteopathia striata congenita with cranial sclerosis ( OSCS) is a skeletal dysplasia caused by germline deletions of or truncating point mutations in the X-linked gene WTX ( FAM123B, AMER1). Females present with longitudinal striations of sclerotic bone along the long axis of long bones and cranial sclerosis, with a high prevalence of cleft palate and hearing loss. Intellectual disability or neurodevelopmental delay is not observed in females with point mutations in WTX leading to OSCS. One female has been described with a deletion spanning multiple neighbouring genes suggesting that deletion of some neighbouring loci may result in abnormal neurodevelopment. In this cohort of 13 females with OSCS resulting from deletions of WTX, a relationship is observed where deletion of ARHGEF9 and/or MTMR8 in conjunction with WTX results in an additional neurodevelopmental phenotype whereas deletion of ASB12 along with WTX is associated with a good neurodevelopmental prognosis. [ABSTRACT FROM AUTHOR]

Tsurusaki Y, Kosho T, Hatasaki K, Narumi Y, Wakui K, Fukushima Y, Doi H, Saitsu H, Miyake N, Matsumoto N. Exome sequencing in a family with an X-linked lethal malformation syndrome: clinical consequences of hemizygous truncating OFD1 mutations in male patients. Oral-facial-digital syndrome type 1 (OFD1; OMIM #311200) is an X-linked dominant disorder, caused by heterozygous mutations in the OFD1 gene and characterized by facial anomalies, abnormalities in oral tissues, digits, brain, and kidney; and male lethality in the first or second trimester pregnancy. We encountered a family with three affected male neonates having an 'unclassified' X-linked lethal congenital malformation syndrome. Exome sequencing of entire transcripts of the whole X chromosome has identified a novel splicing mutation (c.2388+1G > C) in intron 17 of OFD1, resulting in a premature stop codon at amino acid position 796. The affected males manifested severe multisystem complications in addition to the cardinal features of OFD1 and the carrier female showed only subtle features of OFD1. The present patients and the previously reported male patients from four families (clinical OFD1; Simpson-Golabi-Behmel syndrome, type 2 with an OFD1 mutation; Joubert syndrome-10 with OFD1 mutations) would belong to a single syndrome spectrum caused by truncating OFD1 mutations, presenting with craniofacial features (macrocephaly, depressed or broad nasal bridge, and lip abnormalities), postaxial polydactyly, respiratory insufficiency with recurrent respiratory tract infections in survivors, severe mental or developmental retardation, and brain malformations (hypoplasia or agenesis of corpus callosum and/or cerebellar vermis and posterior fossa abnormalities). [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which discusses a study regarding Simpson-Golabi-Behmel type I (SGBS1), an X-linked overgrowth syndrome diagnosed in a foetus with glypican-3 (GPC3) and glypican-4 (GPC4) gene microduplications.

The article discusses the study on the role of X-linked intellectual disability (XLID) genes in XLID pathogenesis. It states that the duplication of KIAA2022 gene results to gene deficiency and results to intellectual disability and autism. It mentions that whole gene duplication results to gene deficiency.

The article discusses the case of a girl affected by osteopathia striata with cranial sclerosis (OSCS), a rare X-linked dominant skeletal dysplasia due to a novel WTX mutation, who developed Wilms tumor at three years of age. Topics covered include characteristics and cause of OSCS, patient's diagnosis of OSCS made on the basis of medical history and physical examination, and treatment given to the patient.

A letter to the editor is presented in response to the article "Cornelia de Lange syndrome," by M. I. Boyle and colleagues in the 2014 issue.