Novel Variant in the USP9X Gene Is Associated with Congenital Heart Disease in a Male Patient: A Case Report and Literature Review

Introduction

The X-chromosomal USP9X gene encodes a deubiquitylating enzyme involved in protein turnover and TGF-β signaling during fetal and neuronal development. USP9X variants in females are primarily associated with complete loss-of-function (LOF) alleles, leading to neurodevelopmental delay and intellectual disability, as well as a wide range of congenital anomalies. In contrast, USP9X missense variants in males often result in partial rather than complete LOF, specifically affecting neuronal migration and development. USP9X variants in males are associated with intellectual disability, behavioral disorders, global developmental delay, speech delay, and structural CNS defects. Facial dysmorphisms are found in almost all patients.

Case Presentation

We report the case of an Italian boy presenting dysmorphism, intellectual disability, structural brain anomalies, and congenital heart disease. Using next-generation sequencing analysis, we identified a hemizygous de novo variant in the USP9X gene (c.5470A>G, p.Met1824Val) that was never reported in the literature.

Conclusion

We provide an overview of the available literature on USP9X variants in males, in order to further expand the genotypic and phenotypic landscape of male-restricted X-linked mental retardation syndrome. Our findings confirm the involvement of USP9X variants in neuronal development and corroborate the possible association between the novel USP9X variant and congenital heart malformation.

Expanding allelic and phenotypic spectrum of ZC4H2-related disorder: A novel hypomorphic variant and high prevalence of tethered cord

ZC4H2 (MIM# 300897) is a nuclear factor involved in various cellular processes including proliferation and differentiation of neural stem cells, ventral spinal patterning and osteogenic and myogenic processes. Pathogenic variants in ZC4H2 have been associated with Wieacker-Wolff syndrome (MIM# 314580), an X-linked neurodevelopmental disorder characterized by arthrogryposis, development delay, hypotonia, feeding difficulties, poor growth, skeletal abnormalities, and dysmorphic features. Zebrafish zc4h2 null mutants recapitulated the human phenotype, showed complete loss of vsx2 expression in brain, and exhibited abnormal swimming and balance problems. Here we report 7 new patients (four males and three females) with ZC4H2-related disorder from six unrelated families. Four of the 6 ZC4H2 variants are novel: three missense variants, designated as c.142T>A (p.Tyr48Asn), c.558G>A (p.Met186Ile) and c.602C>T (p.Pro201Leu), and a nonsense variant, c.618C>A (p.Cys206*). Two variants were previously reported : a nonsense variant c.199C>T (p.Arg67*) and a splice site variant (c.225+5G>A). Five patients were on the severe spectrum of clinical findings, two of whom had early death. The male patient harboring the p.Met186Ile variant and the female patient that carries the p.Pro201Leu variant have a relatively mild phenotype. Of note, 4/7 patients had a tethered cord that required a surgical repair. We also demonstrate and discuss previously under-recognized phenotypic features including sleep apnea, arrhythmia, hypoglycemia, and unexpected early death. To study the effect of the missense variants, we performed microinjection of human ZC4H2 wild-type or variant mRNAs into zc4h2 null mutant zebrafish embryos. The p.Met186Ile mRNA variant was able to partially rescue vsx2 expression while p.Tyr48Asn and p.Pro201Leu mRNA variants were not. However, swimming and balance problems could not be rescued by any of these variants. These results suggest that the p.Met186Ile is a hypomorphic allele. Our work expands the genotypes and phenotypes associated with ZC4H2-related disorder and demonstrates that the zebrafish system is a reliable method to determine the pathogenicity of ZC4H2 variants.

The Spanish Fabry women study: a retrospective observational study describing the phenotype of females with GLA variants

BACKGROUND

Fabry disease (FD) is an X-linked condition caused by variants in the GLA gene. Since females have two X chromosomes, they were historically thought to be carriers. Although increased knowledge has shown that females often develop the disease, data from Spain and other countries reported that females were undertreated. The aim of this study was to provide a wider and more recent description of the disease characteristics and associated management of females with a GLA variant in a Spanish cohort.

RESULTS

Ninety-seven females from 12 hospitals were included in this retrospective study. Mean age was 50.1 ± 17.2 years. Median follow-up time from GLA variant identification was 36.1 months, and most (70.1%) were identified through family screening. Variants associated with classic/non-classic phenotypes were similarly distributed (40.2%/53.6%). Missense variants were the most prevalent (n = 84, 86.6%). In the overall group, 70.4% had major organ involvement (i.e., cardiac, renal, cerebrovascular, peripheral nervous system or gastrointestinal), and 47.3% also had typical Fabry signs (angiokeratoma, cornea verticillata or increased plasma lyso-Gb3). Cardiac involvement was the most prevalent (49.5%) and the main reason for treatment initiation. A total of 33 (34%) patients received disease-specific therapy, 55% of whom were diagnosed by family screening. Females carrying variants associated with a classic phenotype had higher frequencies of clinical manifestations (92.3%) and were predominant in the treated subgroup (69.7%). Despite this, there were 34 untreated females (56.7% of total untreated), with both phenotypes represented, who had major organ involvement, with 27 of cardiac, renal or cerebrovascular nature. Age or comorbidities in this subgroup were comparable to the treated subgroup (P = 0.8 and P = 0.8, respectively).

CONCLUSIONS

Efforts have been made in recent years to diagnose and treat timely Fabry females in Spain. A high percentage of females with pathogenic variants, regardless of their associated phenotype, will likely develop disease. A proportion of females with severe disease in this cohort received specific treatment. Still a significant number of females, even with same profile as the treated ones, who may be eligible for treatment according to European recommendations, remained untreated. Reasons for this merit further investigation.

A female case with novel KDM5C heterozygous variation presenting with Claes-Jensen type-like phonotype

BACKGROUND

Lysine(K)-specific demethylase 5C (KDM5C) dysfunction causes X-linked syndromic intellectual developmental disorder Claes-Jensen type in male patients. The clinical presentations of female individuals with heterozygous KDM5C variations vary widely and are only now beginning to be characterized in detail.

CASE PRESENTATION

Herein, we identified a novel de novo heterozygous nonsense variation of KDM5C (c.3533C > A, p.S1178X) in a sporadic 4-year-old Chinese girl, who presented with Claes-Jensen type-like phenotypes, such as moderate developmental delay, serious expressive language delay, short stature, microcephaly, and typical facial particularities. Moreover, X-chromosome inactivation (XCI) analysis showed no significant skewed X-inactivation.

CONCLUSION

The report expands the genotype of KDM5C variation in female patients, delineates the phenotype of affected females in this well-known X-linked disorder, and also reinforces the necessity to consider this X-linked gene, KDM5C, in sporadic female patients.

Pathogenic variants of ornithine transcarbamylase deficiency: Nation-wide study in Japan and literature review

Ornithine transcarbamylase deficiency (OTCD) is an X-linked disorder. Several male patients with OTCD suffer from severe hyperammonemic crisis in the neonatal period, whereas others develop late-onset manifestations, including hyperammonemic coma. Females with heterozygous pathogenic variants in the OTC gene may develop a variety of clinical manifestations, ranging from asymptomatic conditions to severe hyperammonemic attacks, owing to skewed lyonization. We reported the variants of CPS1, ASS, ASL and OTC detected in the patients with urea cycle disorders through a nation-wide survey in Japan. In this study, we updated the variant data of OTC in Japanese patients and acquired information regarding genetic variants of OTC from patients with OTCD through an extensive literature review. The 523 variants included 386 substitution (330 missense, 53 nonsense, and 3 silent), eight deletion, two duplication, one deletion-insertion, 55 frame shift, two extension, and 69 no category (1 regulatory and 68 splice site error) mutations. We observed a genotype-phenotype relation between the onset time (neonatal onset or late onset), the severity, and genetic mutation in male OTCD patients because the level of deactivation of OTC significantly depends on the pathogenic OTC variants. In conclusion, genetic information about OTC may help to predict long-term outcomes and determine specific treatment strategies, such as liver transplantation, in patients with OTCD.

The phenotypic spectrum of AMER1-related osteopathia striata with cranial sclerosis: The first Canadian cohort

Osteopathia striata with cranial sclerosis (OSCS; OMIM# 300373) is a rare X-linked disorder caused by mutations of the AMER1 gene. OSCS is traditionally considered a skeletal dysplasia, characterized by cranial sclerosis and longitudinal striations in the long bone metaphyses. However, OSCS affects many body systems and varies significantly in phenotypic severity between individuals. This case series focuses on the phenotypic presentation and development of individuals with OSCS. We provide an account of 12 patients with OSCS, ranging from 5 months to 38 years of age. These patients were diagnosed with OSCS after genetic testing confirmed pathogenic mutations in AMER1. Patient consent was obtained for photos and participation. Data were collected regarding perinatal history, dysmorphic features, and review of systems. This case series documents common facial dysmorphology, as well as rare extraskeletal features of OSCS, including two patients with intestinal malrotation and two patients with pyloric stenosis. We share four apparently nonmosaic males with OSCS (one de novo and three maternal variants). We also provide a clinical update on a patient who was previously published by Chénier et al. (2012). American Journal of Medical Genetics Part A, 158, 2946-2952. More research is needed to investigate the links between genotype and phenotype and assess the long-term comorbidities and overall quality of life of individuals with OSCS.

Clinical Manifestations in a Girl with NAA10-Related Syndrome and Genotype-Phenotype Correlation in Females

Since 2011, eight males with an X-linked recessive disorder (Ogden syndrome, MIM #300855) associated with the same missense variant p.(Ser37Pro) in the NAA10 gene have been described. After the advent of whole exome sequencing, many NAA10 variants have been reported as causative of syndromic or non-syndromic intellectual disability in both males and females. The NAA10 gene lies in the Xq28 region and encodes the catalytic subunit of the major N-terminal acetyltransferase complex NatA, which acetylates almost half the human proteome. Here, we present a young female carrying a de novo NAA10 [NM_003491:c.247C > T, p.(Arg83Cys)] variant. The 18-year-old girl has severely delayed motor and language development, autistic traits, postnatal growth failure, facial dysmorphisms, interventricular septal defect, neuroimaging anomalies and epilepsy. Our attempt is to expand and compare genotype–phenotype correlation in females with NAA10-related syndrome. A detailed clinical description could have relevant consequences for the clinical management of known and newly identified individuals.

Simpson-Golabi-Behmel syndrome: One family, same mutation, different outcome

Simpson-Golabi-Behmel syndrome (SGBS) is a rare X-linked condition characterized by pre and postnatal overgrowth with visceral and skeletal abnormalities. The syndrome is caused mainly by mutations in the X-linked gene GPC3. Clinical presentation of SGBS in affected males is well defined, but there is a lack of knowledge about affected females, with very few reported cases. In total, eight female carriers with clinical expression of SGBS have been reported to date. In the present report, we describe the ninth patient and her family history. The interesting features of our female patient are the Wilms' tumor and the transfontanelar ultrasound findings. The patient's older sister, carrier of the same mutation, has minor facial dysmorphisms but no congenital anomalies and so far, no further clinical findings, as well as her mother and grandmother. There is a lesson to be learned from these rare cases, namely that SGBS may have a significant clinical expression in females, and therefore, screening should be considered in all patients with SGBS regardless of the sex or phenotypic severity.

[Somatic mutations in the androgen receptor gene as the cause of androgen insensitivity syndrome]

Androgen insensitivity syndrome is an X-linked disorder characterized by either complete or partial insensitivity of target tissues to androgens. This disease is caused by mutations in the AR gene located on the Х chromosome. Currently, there are no distinct clinical, biochemical, or hormonal markers that would allow one to differentiate androgen insensitivity syndrome from a number of other forms of 46,XY disorders of sex development. Therefore, final verification of this condition is based on the results of molecular genetic tests. Although more than 1,000 point mutations in the AR gene have been reported, somatic mutations in this gene have been described rather rarely. However, this very type of mutations makes the course of this disease difficult to predict, since various cells in the human body contain both normal and mutant receptors. Somatic mosaicism can cause spontaneous masculization during puberty in individuals born with a completely normal female phenotype. In this case report, we describe the phenotypic and molecular genetic characteristics of eight patients with various forms of androgen insensitivity syndrome caused by somatic mutations in the AR gene.

TAF1-gene editing alters the morphology and function of the cerebellum and cerebral cortex

TAF1/MRSX33 intellectual disability syndrome is an X-linked disorder caused by loss-of-function mutations in the TAF1 gene. How these mutations cause dysmorphology, hypotonia, intellectual and motor defects is unknown. Mouse models which have embryonically targeted TAF1 have failed, possibly due to TAF1 being essential for viability, preferentially expressed in early brain development, and intolerant of mutation. Novel animal models are valuable tools for understanding neuronal pathology. Here, we report the development and characterization of a novel animal model for TAF1 ID syndrome in which the TAF1 gene is deleted in embryonic rats using clustered regularly interspaced short palindromic repeats (CRISPR) associated protein 9 (Cas9) technology and somatic brain transgenesis mediated by lentiviral transduction. Rat pups, post-natal day 3, were subjected to intracerebroventricular (ICV) injection of either gRNA-control or gRNA-TAF1 vectors. Rats were subjected to a battery of behavioral tests followed by histopathological analyses of brains at post-natal day 14 and day 35. TAF1-edited rats exhibited behavioral deficits at both the neonatal and juvenile stages of development. Deletion of TAF1 lead to a hypoplasia and loss of the Purkinje cells. We also observed a decreased in GFAP positive astrocytes and an increase in Iba1 positive microglia within the granular layer of the cerebellum in TAF1-edited animals. Immunostaining revealed a reduction in the expression of the CaV3.1 T-type calcium channel. Abnormal motor symptoms in TAF1-edited rats were associated with irregular cerebellar output caused by changes in the intrinsic activity of the Purkinje cells due to loss of pre-synaptic CaV3.1. This animal model provides a powerful new tool for studies of neuronal dysfunction in conditions associated with TAF1 abnormalities and should prove useful for developing therapeutic strategies to treat TAF1 ID syndrome.

A Hemizygous Deletion Within the PGK1 Gene in Males with PGK1 Deficiency

Phosphoglycerate kinase-1 (PGK1) deficiency is a rare X-linked disorder caused by pathogenic variants in the PGK1 gene. Complete loss-of-function variants have not been reported in this gene, indicating that residual enzyme function is critical for viability in males. Therefore, copy number variants (CNVs) that include single exon or multiple exon deletions or duplications are generally not expected in individuals with PGK1 deficiency. Here we describe a 64-year-old male presenting with a family history (three additional affected males) and a personal history of childhood-onset metabolic myopathy that involves episodes of muscle pain, stiffness after activity, exercise intolerance, and myoglobinuria after exertion. Biochemical analysis on a muscle biopsy indicated significantly reduced activity (15% compared to normal) for phosphoglycerate kinase (PGK1), a glycolytic enzyme encoded by PGK1. A diagnosis of PGK1 deficiency was established by molecular analysis which detected an approximately 886 kb deletion involving the polyadenylation site in the 3'UTR of the PGK1 gene. RNA analysis showed significantly reduced PGK1 transcript levels (30% compared to normal). This is the first deletion reported in the PGK1 gene and is the first pathogenic variant involving the 3'UTR polyadenylation site of this gene. Our report emphasizes the role of 3'UTR variants in human disorders and underscores the need for exploring noncoding regions of disease-associated genes when seeking a molecular diagnosis.

Clinical profile of comorbidity of rare diseases in a Tunisian patient: a case report associating incontinentia pigmenti and Noonan syndrome

Background

Noonan syndrome (NS) is an autosomal dominant multisystem disorder caused by the dysregulation of several genes belonging to the RAS Mitogen Activated Protein Kinase (MAPK) signaling pathway. Incontinentia Pigmenti (IP) is an X-linked, dominantly inherited multisystem disorder.

Case presentation

This study is the first report of the coexistence of Noonan (NS) and Incontinentia Pigmenti (IP) syndromes in the same patient. We report on the clinical phenotype and molecular characterization of this patient. The patient was examined by a pluridisciplinary staff of clinicians and geneticist. The clinical diagnosis of NS and IP was confirmed by molecular investigations. The newborn girl came to our clinics due to flagrant dysmorphia and dermatological manifestations. The clinical observations led to characterize the Incontinentia Pigmenti traits and a suspicion of a Noonan syndrome association. Molecular diagnosis was performed by Haloplex resequencing of 29 genes associated with RASopathies and confirmed the NS diagnosis. The common recurrent intragenic deletion mutation in IKBKG gene causing the IP was detected with an improved PCR protocol.

Conclusion

This is the first report in the literature of comorbidity of NS and IP, two rare multisystem syndromes.

[Combined Preimplantation Genetic Testing for Aneuploidy and Monogenic Disease in a Mexican Family Affected by X-linked Hypohidrotic Ectodermal Dysplasia]

Background

Hypohidrotic ectodermal dysplasia (HED) is a genetic skin condition presenting as hypohidrosis, hypodontia, and hypotrichosis, resulting in an important burden for affected families. The most common form of HED has an X-linked inheritance and female carriers have the option of prenatal or preimplantation genetic testing (PGT) to avoid transmission of the disease. A combined PGT for a mutation in EDA gene and aneuploidies in a Mexican carrier of X-linked HED is reported.

Materials and Methods

Ovarian stimulation and assisted reproduction procedures were performed in a private academic medical center. PGT for a novel c.707-1G>A (rs886039466) mutation in EDA gene and chromosomal aneuploidies was performed by massive parallel and Sanger sequencing.

Results

In the first PGT, the transfer of two blastocysts did not result in a pregnancy. An accumulative stimulation approach was decided to improve pregnancy chances for a second PGT procedure. Three ovarian stimulations were performed and 10 blastocysts coming from fresh and vitrified oocytes were genetically analyzed. A single embryo transfer produced a healthy non-carrier euploid girl.

Discussion

PGT combining aneuploidy and mutation analyses is an alternative for female carriers of X-linked and other Mendelian disorders in Latin-American countries. In the era of genomic and personalized medicine, medically assisted reproduction techniques, such as PGT, are shifting from only infertility to preventive genetics.

Duplications of GPC3 and GPC4 genes in symptomatic female carriers of Simpson-Golabi-Behmel syndrome type 1

GPC3 and GPC4 are the only two genes in which mutations are known to cause Simpson-Golabi-Behmel syndrome type 1 (SGBS1). The majority of SGBS1 patients have point mutations or deletions in GPC3. Only one SGBS1 family has been reported with duplication of both GPC3 and GPC4. Although clinical presentation of SGBS1 in affected males is well defined, the phenotype in female carriers is less clear. In total, six female carriers with clinical expression of SGBS1 have been reported to date. In this study, we provide description of two families with rare duplications in both GPC3 and GPC4. These imbalances resulted in SGBS1 in males, while female carriers with skewed X-inactivation exhibited significant features of SGBS1 including congenital heart defect, hernias, intellectual disability and coarse facial features. In family 2, a SGBS diagnosis was not considered in the father until after the diagnosis had been first considered and made in the affected daughter. We emphasize on the importance of testing at risk females and careful examination of those who are found to be carriers of SGBS1. We also discuss and provide supportive evidence for the role of skewed X-inactivation in clinical expression of SGBS1 in female carriers.

First Korean Case of Renpenning Syndrome with Novel Mutation in PQBP1 Diagnosed by Targeted Exome Sequencing, and Literature Review

Renpenning syndrome is a rare X-linked disorder characterized by mental retardation, leanness, microcephaly, facial dysmorphism, short stature, and small testes. This disease is caused by PQBP1 mutations. Herein, we present a literature review and describe the clinical and molecular findings in a Korean boy with Renpenning syndrome. A 23-month-old boy presented with mental retardation, narrow face, bulbous nose, and cardiac anomaly. Interestingly, targeted exome sequencing identified a novel mutation c.559delT (p.Tyr187llefs*8) in the PQBP1 gene, and he was diagnosed as having Renpenning syndrome. In line with previously reported studies, our case suggests that men with mental retardation, short stature, and microcephaly should include Renpenning syndrome as a differential diagnosis.

Mutation update for the GPC3 gene involved in Simpson-Golabi-Behmel syndrome and review of the literature

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked multiple congenital anomalies and overgrowth syndrome caused by a defect in the glypican-3 gene (GPC3). Until now, GPC3 mutations have been reported in isolated cases or small series and the global genotypic spectrum of these mutations has never been delineated. In this study, we review the 57 previously described GPC3 mutations and significantly expand this mutational spectrum with the description of 29 novel mutations. Compiling our data and those of the literature, we provide an overview of 86 distinct GPC3 mutations identified in 120 unrelated families, ranging from single nucleotide variations to complex genomic rearrangements and dispersed throughout the entire coding region of GPC3. The vast majority of them are deletions or truncating mutations (frameshift, nonsense mutations) predicted to result in a loss-of-function. Missense mutations are rare and the two which were functionally characterized, impaired GPC3 function by preventing GPC3 cleavage and cell surface addressing respectively. This report by describing for the first time the wide mutational spectrum of GPC3 could help clinicians and geneticists in interpreting GPC3 variants identified incidentally by high-throughput sequencing technologies and also reinforces the need for functional validation of non-truncating mutations (missense, in frame mutations, duplications).

Functional assessment of creatine transporter in control and X-linked SLC6A8-deficient fibroblasts

Creatine transporter is currently the focus of renewed interest with emerging roles in brain neurotransmission and physiology, and the bioenergetics of cancer metastases. We here report on amendments of a standard creatine uptake assay which might help clinical chemistry laboratories to extend their current range of measurements of creatine and metabolites in body fluids to functional enzyme explorations. In this respect, short incubation times and the use of a stable-isotope-labeled substrate (D₃-creatine) preceded by a creatine wash-out step from cultured fibroblast cells by removal of fetal bovine serum (rich in creatine) from the incubation medium are recommended. Together, these measures decreased, by a first order of magnitude, creatine concentrations in the incubation medium at the start of creatine-uptake studies and allowed to functionally discriminate between 4 hemizygous male and 4 heterozygous female patients with X-linked SLC6A8 deficiency, and between this cohort of eight patients and controls. The functional assay corroborated genetic diagnosis of SLC6A8 deficiency. Gene anomalies in our small cohort included splicing site (c.912G > A [p.Ile260_Gln304del], c.778-2A > G and c.1495 + 2 T > G), substitution (c.407C > T) [p.Ala136Val] and deletion (c.635_636delAG [p.Glu212Valfs*84] and c.1324delC [p.Gln442Lysfs*21]) variants with reduced creatine transporter function validating their pathogenicity, including that of a previously unreported c.1324delC variant. The present assay adaptations provide an easy, reliable and discriminative manner for exploring creatine transporter activity and disease variations. It might apply to drug testing or other evaluations in the genetic and metabolic horizons covered by the emerging functions of creatine and its transporter, in a way, however, requiring and completed by additional studies on female patients and blood-brain barrier permeability properties of selected compounds. As a whole, the proposed assay of creatine transporter positively adds to currently existing measurements of this transporter activity, and determining on a large scale the extent of its exact suitability to detect female patients should condition in the future its transfer in clinical practice.

Joint SOGC-CCMG Opinion for Reproductive Genetic Carrier Screening: An Update for All Canadian Providers of Maternity and Reproductive Healthcare in the Era of Direct-to-Consumer Testing

OBJECTIVE

This guideline was written to update Canadian maternity care and reproductive healthcare providers on pre- and postconceptional reproductive carrier screening for women or couples who may be at risk of being carriers for autosomal recessive (AR), autosomal dominant (AD), or X-linked (XL) conditions, with risk of transmission to the fetus. Four previous SOGC- Canadian College of Medical Geneticists (CCMG) guidelines are updated and merged into the current document.

INTENDED USERS

All maternity care (most responsible health provider [MRHP]) and paediatric providers; maternity nursing; nurse practitioner; provincial maternity care administrator; medical student; and postgraduate resident year 1-7.

TARGET POPULATION

Fertile, sexually active females and their fertile, sexually active male partners who are either planning a pregnancy or are pregnant (preferably in the first trimester of pregnancy, but any gestational age is acceptable).

OPTIONS

Women and their partners will be able to obtain appropriate genetic carrier screening information and possible diagnosis of AR, AD, or XL disorders (preferably pre-conception), thereby allowing an informed choice regarding genetic carrier screening and reproductive options (e.g., prenatal diagnosis, preimplantation genetic diagnosis, egg or sperm donation, or adoption).

OUTCOMES

Informed reproductive decisions related to genetic carrier screening and reproductive outcomes based on family history, ethnic background, past obstetrical history, known carrier status, or genetic diagnosis. SOGC REPRODUCTIVE CARRIER SCREENING SUMMARY STATEMENT (2016): Pre-conception or prenatal education and counselling for reproductive carrier screening requires a discussion about testing within the three perinatal genetic carrier screening/diagnosis time periods, which include pre-conception, prenatal, and neonatal for conditions currently being screened for and diagnosed. This new information should be added to the standard reproductive carrier screening protocols that are already being utilized by the most responsible maternity provider through the informed consent process with the patient. (III-A; GRADE low/moderate) SOGC OVERVIEW OF RECOMMENDATIONS QUALITY AND GRADE: There was a strong observational/expert opinion (quality and grade) for the genetic carrier literature with randomized controlled trial evidence being available only for the invasive testing. Both the Canadian Task Force on Preventive Health Care quality and classification and the GRADE evidence quality and grade are provided.

EVIDENCE

MEDLINE; PubMed; government neonatal screening websites; key words/common reproductive genetic carrier screened diseases/previous SOGC Guidelines/medical academic societies (Society of Maternal-Fetal Medicine [SMFM]; American College of Medical Genetics and Genomics; American College of Obstetricians and Gynecologists [ACOG]; CCMG; Royal College Obstetrics and Gynaecology [RCOG] [UK]; American Society of Human Genetics [ASHG]; International Society of Prenatal Diagnosis [ISPD])/provincial neonatal screening policies and programs; search terms (carrier screening, prenatal screening, neonatal genetic/metabolic screening, cystic fibrosis (CF), thalassemia, hemoglobinopathy, hemophilia, Fragile X syndrome (FXS), spinal muscular atrophy, Ashkenazi Jewish carrier screening, genetic carrier screening protocols, AR, AD, XL).

SEARCH PERIOD

10 years (June 2005-September 2015); initial search dates June 30, 2015 and September 15, 2015; completed final search January 4, 2016. Validation of articles was completed by primary authors RD Wilson and I De Bie.

BENEFITS, HARMS, AND COST

Benefits are to provide an evidenced based reproductive genetic carrier screening update consensus based on international opinions and publications for the use of Canadian women, who are planning a pregnancy or who are pregnant and have been identified to be at risk (personal or male partner family or reproductive history) for the transmission of a clinically significant genetic condition to their offspring with associated morbidity and/or mortality. Harm may arise from having counselling and informed testing of the carrier status of the mother, their partner, or their fetus, as well as from declining to have this counselling and informed testing or from not having the opportunity for counselling and informed testing. Costs will ensue both from the provision of opportunities for counselling and testing, as well as when no such opportunities are offered or are declined and the birth of a child with a significant inherited condition and resulting morbidity/mortality occurs; these comprise not only the health care costs to the system but also the social/financial/psychological/emotional costs to the family. These recommendations are based on expert opinion and have not been subjected to a health economics assessment and local or provincial implementation will be required.

GUIDELINE UPDATE

This guideline is an update of four previous joint SOGC-CCMG Genetic Screening Guidelines dated 2002, 2006, 2008, and 2008 developed by the SOGC Genetic Committee in collaboration with the CCMG Prenatal Diagnosis Committee (now Clinical Practice Committee). 2016 CARRIER SCREENING RECOMMENDATIONS.

13 novel putative mutations in ATP7A found in a cohort of 25 Italian families

ATP7A is a copper-transporting P-type adenosine triphosphatase whose loss of function leads to the Menkes disease, an X-linked copper metabolism multi-organ disorder (1 in 100.000 births). Here we document our experience with the ATP7A linked diseases in Italy. We analyzed the exonic structure of the ATP7A gene in 25 unrelated Italian families and studied the variants of unknown significance. We identified 22 different DNA alterations, 13 of which first reported in this study. The classical Menkes phenotype was present in 21 of the 25 families and was linked with highly damaging mutations (7 nonsense; 4 frame-shift; 2 small in-frame deletions, 2 splice site alterations, 2 gross deletions, and 1 gross duplication). Of the 4 cases with milder variants of the Menkes disease two had a missense mutation, one a leaky splice site alteration and one a nonsense mutation in exon 22. We determined in silico that all the mutations leading to the classical Menkes disease leave no residual activity of ATP7A including the apparently less severe in-frame deletions. Whereas milder forms of the disease are characterized by mutations that allow a limited residual activity of ATP7A, including the nonsense mutation observed.

Lesch-Nyhan syndrome: The saga of metabolic abnormalities and self-injurious behavior

Lesch-Nyhan syndrome (LNS) is an X-linked recessive disorder of purine metabolism caused by a mutation in Xq26.2-q26.3 (OMIM 308000.0004). The presence of the diagnostic triad, i.e. signs of self-injurious behavior (SIB) and results of pedigree analysis and novel molecular biology & genetic testing, confirms the diagnosis of LNS. With a level of hypoxanthine guanine phosphoribosyl-transferase 1 (HPRT1) enzyme activity < 2%, patients develop neurological, neurocognitive, and neuromotor symptoms along with SIB. Described here is a case of 4-year-old boy who was diagnosed with LNS. The boy displayed SIB, i.e. biting of the lips and fingers, and he had cerebral venous sinus thrombosis caused by LNS.

Fabry disease: A fundamental genetic modifier of cardiac function

Fabry disease (FD) is an inherited X-linked metabolic storage disorder triggered by abnormalities in the GLA gene at Xq22, which leads to a deficiency in α-galactosidase A and massive accumulation of intralysosomal glycosphingolipids. Cardiac complications are very common in FD and are the main cause of late morbidity, as well as early mortality in both hemizygous men and heterozygous women. There is a need for a multidisciplinary approach to evaluation and management of FD patients as there is a wide range of presentation of FD, which varies with mutation and other organ involvement/dysfunction. An overview of common cardiac involvement and clinical characteristics in FD including: left ventricular hypertrophy (LVH), conduction abnormalities and arrhythmias, coronary artery disease and valvular infiltrative myopathy are provided in this review. Current therapeutic approaches such as enzyme replacement therapy as well as the emergence of novel therapeutic options such as gene therapy to optimize disease outcomes in FD patients will be highlighted in this paper.

Identification of a novel mutation in a Chinese family with Nance-Horan syndrome by whole exome sequencing

OBJECTIVE

Nance-Horan syndrome (NHS) is a rare X-linked disorder characterized by congenital nuclear cataracts, dental anomalies, and craniofacial dysmorphisms. Mental retardation was present in about 30% of the reported cases. The purpose of this study was to investigate the genetic and clinical features of NHS in a Chinese family.

METHODS

Whole exome sequencing analysis was performed on DNA from an affected male to scan for candidate mutations on the X-chromosome. Sanger sequencing was used to verify these candidate mutations in the whole family. Clinical and ophthalmological examinations were performed on all members of the family.

RESULTS

A combination of exome sequencing and Sanger sequencing revealed a nonsense mutation c.322G>T (E108X) in exon 1 of NHS gene, co-segregating with the disease in the family. The nonsense mutation led to the conversion of glutamic acid to a stop codon (E108X), resulting in truncation of the NHS protein. Multiple sequence alignments showed that codon 108, where the mutation (c.322G>T) occurred, was located within a phylogenetically conserved region. The clinical features in all affected males and female carriers are described in detail.

CONCLUSIONS

We report a nonsense mutation c.322G>T (E108X) in a Chinese family with NHS. Our findings broaden the spectrum of NHS mutations and provide molecular insight into future NHS clinical genetic diagnosis.