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Unexpectedly intersecting her path with a person with a congenital anomaly gives the writer an opportunity to reflect on her own understanding of patients outside the medical perimeter that ultimately influences her point of view during the hospital encounter., (© 2024 The Author(s). American Journal of Medical Genetics Part C: Seminars in Medical Genetics published by Wiley Periodicals LLC.)

Trithorax-related H3K4 methyltransferases, KMT2C and KMT2D, are critical epigenetic modifiers. Haploinsufficiency of KMT2C was only recently recognized as a cause of neurodevelopmental disorder (NDD), so the clinical and molecular spectrums of the KMT2C-related NDD (now designated as Kleefstra syndrome 2) are largely unknown. We ascertained 98 individuals with rare KMT2C variants, including 75 with protein-truncating variants (PTVs). Notably, ∼15% of KMT2C PTVs were inherited. Although the most highly expressed KMT2C transcript consists of only the last four exons, pathogenic PTVs were found in almost all the exons of this large gene. KMT2C variant interpretation can be challenging due to segmental duplications and clonal hematopoesis-induced artifacts. Using samples from 27 affected individuals, divided into discovery and validation cohorts, we generated a moderate strength disorder-specific KMT2C DNA methylation (DNAm) signature and demonstrate its utility in classifying non-truncating variants. Based on 81 individuals with pathogenic/likely pathogenic variants, we demonstrate that the KMT2C-related NDD is characterized by developmental delay, intellectual disability, behavioral and psychiatric problems, hypotonia, seizures, short stature, and other comorbidities. The facial module of PhenoScore, applied to photographs of 34 affected individuals, reveals that the KMT2C-related facial gestalt is significantly different from the general NDD population. Finally, using PhenoScore and DNAm signatures, we demonstrate that the KMT2C-related NDD is clinically and epigenetically distinct from Kleefstra and Kabuki syndromes. Overall, we define the clinical features, molecular spectrum, and DNAm signature of the KMT2C-related NDD and demonstrate they are distinct from Kleefstra and Kabuki syndromes highlighting the need to rename this condition., Competing Interests: Declaration of interests R.W. is a consultant (equity) for Alamya Health., (Copyright © 2024 American Society of Human Genetics. All rights reserved.)

The calcium/calmodulin-dependent protein kinase type 2 (CAMK2) family consists of four different isozymes, encoded by four different genes-CAMK2A, CAMK2B, CAMK2G, and CAMK2D-of which the first three have been associated recently with neurodevelopmental disorders. CAMK2D is one of the major CAMK2 proteins expressed in the heart and has been associated with cardiac anomalies. Although this CAMK2 isoform is also known to be one of the major CAMK2 subtypes expressed during early brain development, it has never been linked with neurodevelopmental disorders until now. Here we show that CAMK2D plays an important role in neurodevelopment not only in mice but also in humans. We identified eight individuals harboring heterozygous variants in CAMK2D who display symptoms of intellectual disability, delayed speech, behavioral problems, and dilated cardiomyopathy. The majority of the variants tested lead to a gain of function (GoF), which appears to cause both neurological problems and dilated cardiomyopathy. In contrast, loss-of-function (LoF) variants appear to induce only neurological symptoms. Together, we describe a cohort of individuals with neurodevelopmental disorders and cardiac anomalies, harboring pathogenic variants in CAMK2D, confirming an important role for the CAMK2D isozyme in both heart and brain function., Competing Interests: Declaration of interests The Department of Molecular and Human Genetics at Baylor College of Medicine receives revenue from clinical genetic testing completed at Baylor Genetics Laboratories. A.B. and I.M.W. are employees of GeneDx, LLC; H.S. is a consultant for Vasa Therapeutics (Poland)., (Copyright © 2023 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Background: Pathogenic variants in the zinc finger protein coding genes are rare causes of intellectual disability and congenital malformations. Mutations in the ZNF148 gene causing GDACCF syndrome (global developmental delay, absent or hypoplastic corpus callosum, dysmorphic facies; MIM #617260) have been reported in five individuals so far., Methods: As a result of an international collaboration using GeneMatcher Phenome Central Repository and personal communications, here we describe the clinical and molecular genetic characteristics of 22 previously unreported individuals., Results: The core clinical phenotype is characterised by developmental delay particularly in the domain of speech development, postnatal growth retardation, microcephaly and facial dysmorphism. Corpus callosum abnormalities appear less frequently than suggested by previous observations. The identified mutations concerned nonsense or frameshift variants that were mainly located in the last exon of the ZNF148 gene. Heterozygous deletion including the entire ZNF148 gene was found in only one case. Most mutations occurred de novo, but were inherited from an affected parent in two families., Conclusion: The GDACCF syndrome is clinically diverse, and a genotype-first approach, that is, exome sequencing is recommended for establishing a genetic diagnosis rather than a phenotype-first approach. However, the syndrome may be suspected based on some recurrent, recognisable features. Corpus callosum anomalies were not as constant as previously suggested, we therefore recommend to replace the term 'GDACCF syndrome' with ' ZNF148 -related neurodevelopmental disorder'., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

The lemur family of protein kinases has gained much interest in recent years as they are involved in a variety of cellular processes including regulation of axonal transport and endosomal trafficking, modulation of synaptic functions, memory and learning, and they are centrally placed in several intracellular signalling pathways. Numerous studies have also implicated role of the lemur kinases in the development and progression of a wide range of cancers, cystic fibrosis, and neurodegenerative diseases. However, parallel discoveries and inaccurate prediction of their kinase activity have resulted in a confusing and misleading nomenclature of these proteins. Herein, a group of international scientists with expertise in lemur family of protein kinases set forth a novel nomenclature to rectify this problem and ultimately help the scientific community by providing consistent information about these molecules., (© 2024. The Author(s).)

Purpose: ARF1 was previously implicated in periventricular nodular heterotopia (PVNH) in only five individuals and systematic clinical characterisation was not available. The aim of this study is to provide a comprehensive description of the phenotypic and genotypic spectrum of ARF1 -related neurodevelopmental disorder., Methods: We collected detailed phenotypes of an international cohort of individuals (n=17) with ARF1 variants assembled through the GeneMatcher platform. Missense variants were structurally modelled, and the impact of several were functionally validated., Results: De novo variants (10 missense, 1 frameshift, 1 splice altering resulting in 9 residues insertion) in ARF1 were identified among 17 unrelated individuals. Detailed phenotypes included intellectual disability (ID), microcephaly, seizures and PVNH. No specific facial characteristics were consistent across all cases, however microretrognathia was common. Various hearing and visual defects were recurrent, and interestingly, some inflammatory features were reported. MRI of the brain frequently showed abnormalities consistent with a neuronal migration disorder., Conclusion: We confirm the role of ARF1 in an autosomal dominant syndrome with a phenotypic spectrum including severe ID, microcephaly, seizures and PVNH due to impaired neuronal migration., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Craniosynostosis (CS) is the most common congenital cranial anomaly. Several Mendelian forms of syndromic CS are well described, but a genetic etiology remains elusive in a substantial fraction of probands. Analysis of exome sequence data from 526 proband-parent trios with syndromic CS identified a marked excess (observed 98, expected 33, p = 4.83 × 10 -20 ) of damaging de novo variants (DNVs) in genes highly intolerant to loss-of-function variation (probability of LoF intolerance > 0.9). 30 probands harbored damaging DNVs in 21 genes that were not previously implicated in CS but are involved in chromatin modification and remodeling (4.7-fold enrichment, p = 1.1 × 10 -11 ). 17 genes had multiple damaging DNVs, and 13 genes (CDK13, NFIX, ADNP, KMT5B, SON, ARID1B, CASK, CHD7, MED13L, PSMD12, POLR2A, CHD3, and SETBP1) surpassed thresholds for genome-wide significance. A recurrent gain-of-function DNV in the retinoic acid receptor alpha (RARA; c.865G>A [p.Gly289Arg]) was identified in two probands with similar CS phenotypes. CS risk genes overlap with those identified for autism and other neurodevelopmental disorders, are highly expressed in cranial neural crest cells, and converge in networks that regulate chromatin modification, gene transcription, and osteoblast differentiation. Our results identify several CS loci and have major implications for genetic testing and counseling., Competing Interests: Declaration of interests S.M., M.M., M.S., and P.K. are employees of GeneDx., (Copyright © 2023 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Congenital myasthenic syndrome (CMS) is a heterogeneous condition associated with 34 different genes, including SLC5A7, which encodes the high-affinity choline transporter 1 (CHT1). CHT1 is expressed in presynaptic neurons of the neuromuscular junction where it uses the inward sodium gradient to reuptake choline. Biallelic CHT1 mutations often lead to neonatal lethality, and less commonly to non-lethal motor weakness and developmental delays. Here, we report detailed biochemical characterization of two novel mutations in CHT1, p.I294T and p.D349N, which we identified in an 11-year-old patient with a history of neonatal respiratory distress, and subsequent hypotonia and global developmental delay. Heterologous expression of each CHT1 mutant in human embryonic kidney cells showed two different mechanisms of reduced protein function. The p.I294T CHT1 mutant transporter function was detectable, but its abundance and half-life were significantly reduced. In contrast, the p.D349N CHT1 mutant was abundantly expressed at the cell membrane, but transporter function was absent. The residual function of the p.I294T CHT1 mutant may explain the non-lethal form of CMS in this patient, and the divergent mechanisms of reduced CHT1 function that we identified may guide future functional studies of the CHT1 myasthenic syndrome. Based on these in vitro studies that provided a diagnosis, treatment with cholinesterase inhibitor together with physical and occupational therapy significantly improved the patient's strength and quality of life., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The non-POU domain-containing octamer-binding (NONO) protein is involved in multiple steps of gene regulation such as RNA metabolism and DNA repair. Hemizygous pathogenic variants in the NONO gene were confirmed to cause a rare X-linked syndromic disorder. Through our in-house diagnostics and subsequent matchmaking, we identified six unrelated male individuals with pathogenic or likely pathogenic NONO variants. For a detailed comparison, we reviewed all published characterizations of the NONO-associated disorder. The combined cohort consists of 16 live-born males showing developmental delay, corpus callosum anomalies, non-compaction cardiomyopathy and relative macrocephaly as leading symptoms. Seven prenatal literature cases were characterized by cardiac malformations. In this study, we extend the phenotypic spectrum through two more cases with epilepsy as well as two more cases with hematologic anomalies. By RNA expression analysis and structural modeling of a new in-frame splice deletion, we reinforce loss-of-function as the pathomechanism for the NONO-associated syndromic disorder., (© 2022 The Authors. American Journal of Medical Genetics Part A published by Wiley Periodicals LLC.)

Clinical exome sequencing (ES) is the most comprehensive genomic test to identify underlying genetic diseases in Canada. We performed this retrospective cohort study to investigate the diagnostic yield of clinical ES in adulthood. Inclusion criteria were: (1) Adult patients ≥18 years old; (2) Patients underwent clinical ES between January 1 and December 31, 2021; (3) Patients were seen in the Department of Medical Genetics. We reviewed patient charts. We applied American College of Medical Genetics and Genomics and the Association for Molecular Pathology variant classification guidelines for interpretation of variants. Non-parametric Fisher's exact statistical test was used. Seventy-seven patients underwent clinical ES. Fourteen different genetic diseases were confirmed in 15 patients: FBXO11, MYH7, MED13L, NSD2, ANKRD11 (n = 2), SHANK3, RHOBTB2, CDKL5, TRIO, TCF4, SCN1, SMAD3, POGZ, and EIF2B3 diseases. The diagnostic yield of clinical ES was 19.5%. Patients with a genetic diagnosis had a significantly higher frequency of neurodevelopmental disorders than those with no genetic diagnosis (p = 0.00339). The diagnostic yield of clinical ES was the highest in patients with seizures (35.7%), and with progressive neurodegenerative diseases (33.3%). Clinical ES is a helpful genomic test to provide genetic diagnoses to the patients who are referred to medical genetic clinics due to suspected genetic diseases in adulthood to end their diagnostic odyssey. Targeted next generation sequencing panels for specific phenotypes may decrease the cost of genomic test in adulthood., (© 2022 Wiley Periodicals LLC.)

The introduction of next generation sequencing (NGS) technologies has revolutionized the practice of Medical Genetics, and despite initial reticence in its application to prenatal genetics (PG), it is becoming gradually routine, subject to availability. Guidance for the clinical implementation of NGS in PG, in particular whole exome sequencing (ES), has been provided by several professional societies with multiple clinical studies quoting a wide range of testing yields. ES was introduced in our tertiary care center in 2017; however, its use in relation to prenatally assessed cases has been limited to the postnatal period. In this study, we review our approach to prenatal testing including the use of microarray (CMA), and NGS technology (gene panels, ES) over a period of three years. The overall diagnostic yield was 30.4%, with 43.2% of those diagnoses being obtained through CMA, and the majority by using NGS technology (42% through gene panels and 16.6% by ES testing, respectively). Of these, 43.4% of the diagnoses were obtained during ongoing pregnancies. Seventy percent of the abnormal pregnancies tested went undiagnosed. We are providing a contemporary, one tertiary care center retrospective view of a real-life PG practice in the context of an evolving use of NGS within a Canadian public health care system that may apply to many similar jurisdictions around the world.

Purpose and Scope: The aim of this position statement is to provide recommendations for Canadian healthcare professionals regarding the use of genome-wide sequencing (GWS) in the context of diagnostic testing of the fetus during pregnancy. This statement was developed to facilitate clinical translation of GWS as a prenatal diagnostic test and the development of best practices in Canada, but the applicability of this document is broader and aims to help professionals in other healthcare systems., Methods of Statement Development: A multidisciplinary group was assembled to review existing literature on fetal GWS for genetic diagnosis in the context of suspected monogenic diseases and to make recommendations relevant to the Canadian context. The statement was circulated for comments to the Canadian College of Medical Geneticists (CCMG) membership-at-large and, following incorporation of feedback, approved by the CCMG Board of Directors on 19 February 2021., Results and Conclusions: The use of prenatal GWS is indicated for the investigation of multiple fetal anomalies. Its use in the context of isolated fetal anomaly should be guided by available resources and current evidence, which is continually changing. During pregnancy, GWS should be ordered by, or in collaboration with, a medical geneticist. It should be used following detailed phenotyping to interrogate known disease genes, preferably using a trio approach, following detailed fetal phenotyping. Testing should be done with an overall aim to help in the management of the pregnancy, delivery and postnatal care. It should be guided by personal utility of the test for the pregnant person and clinical utility for pregnancy and birth management, as outlined herein. Genetic counselling is crucial in making the parental decision an informed decision. Chromosomal microarray analysis should be completed in parallel or prior to GWS and should be preceded by Quantitative Fluorescent PCR (QF-PCR) for detection of common aneuploidies. In normal circumstances, only pathogenic and likely pathogenic variants with a high likelihood of being associated with the identified fetal anomalies should be reported. Reporting of secondary findings, defined as purposeful analysis of variants in a set of medically actionable genes, should not, by default, be performed in the prenatal context. Laboratories should only report incidental findings that reveal risk of a significant Mendelian condition during infancy and childhood. Should a laboratory have a policy for reporting incidental findings in medically actionable adult-onset conditions, they should only be reported with explicit opt-in consent signed by the tested individuals. Genetic counselling is crucial in disclosing the test results and the implications the results may have for the fetus. It should be emphasised that negative results do not rule out a genetic diagnosis nor guarantee a good prognosis. Postnatal phenotyping and reanalysis of existing data should be considered. Families should be given the opportunity to participate in research studies as appropriate. These recommendations will be routinely re-evaluated as knowledge of the diagnostic and clinical utility of fetal GWS during pregnancy improves., Competing Interests: Competing interests: TN: spouse employed by Illumina., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Mutations in RNA-binding proteins can lead to pleiotropic phenotypes including craniofacial, skeletal, limb, and neurological symptoms. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are involved in nucleic acid binding, transcription, and splicing through direct binding to DNA and RNA, or through interaction with other proteins in the spliceosome. We show a developmental role for Hnrnpul1 in zebrafish, resulting in reduced body and fin growth and missing bones. Defects in craniofacial tendon growth and adult-onset caudal scoliosis are also seen. We demonstrate a role for Hnrnpul1 in alternative splicing and transcriptional regulation using RNA-sequencing, particularly of genes involved in translation, ubiquitination, and DNA damage. Given its cross-species conservation and role in splicing, it would not be surprising if it had a role in human development. Whole-exome sequencing detected a homozygous frameshift variant in HNRNPUL1 in 2 siblings with congenital limb malformations, which is a candidate gene for their limb malformations. Zebrafish Hnrnpul1 mutants suggest an important developmental role of hnRNPUL1 and provide motivation for exploring the potential conservation of ancient regulatory circuits involving hnRNPUL1 in human development., (© The Author(s) 2022. Published by Oxford University Press on behalf of Genetics Society of America.)

Objective: Past studies of fetal tetralogy of fallot (ToF) have reported extra-cardiac anomalies (ECAs) in 17%-45%, genetic syndromes in as low as 20% and poor postnatal outcomes. This study sought to examine these factors in a contemporary cohort., Methods: A retrospective review examining 83 fetuses with ToF diagnosed 2012-2019. Referral indication, ToF subtype, additional cardiac, extra-cardiac and genetic diagnoses, pregnancy outcomes and survival were documented., Results: The mean gestational age at diagnosis was 23 ± 4 weeks. Of 94% (78/83) with genetic testing (GT), 30% (23/78, 95%CI 21%-40%) had genetic anomalies (GA), including Trisomy 21 (39%, 9/23), 22q11 deletion (35%, 8/23), Trisomy 13 or 18 (17%, 4/23) and 9% (2/23) others. A further 4% (3/78) had VACTERL association. Forty-one percent (34/83, 95%CI 31%-52%) had ≥1 major ECA of whom 41% (14/34) also had a genetic anomaly., Outcomes: 22% (18/83) pregnancy termination, 5% (4/83) intrauterine death and 72% (60/83) live birth. Of live births, 3% (2/60) experienced neonatal death, 7% late death (4/60) and 90% (54/60) were alive at last follow-up (mean age 3.5 ± 2.4 years)., Conclusion: In a cohort of fetuses with ToF and high rates of GT, compared to previous reports, GA were more common and there were similar rates of ECAs., (© 2022 John Wiley & Sons Ltd.)

Purpose: Adducins interconnect spectrin and actin filaments to form polygonal scaffolds beneath the cell membranes and form ring-like structures in neuronal axons. Adducins regulate mouse neural development, but their function in the human brain is unknown., Methods: We used exome sequencing to uncover ADD1 variants associated with intellectual disability (ID) and brain malformations. We studied ADD1 splice isoforms in mouse and human neocortex development with RNA sequencing, super resolution imaging, and immunoblotting. We investigated 4 variant ADD1 proteins and heterozygous ADD1 cells for protein expression and ADD1-ADD2 dimerization. We studied Add1 functions in vivo using Add1 knockout mice., Results: We uncovered loss-of-function ADD1 variants in 4 unrelated individuals affected by ID and/or structural brain defects. Three additional de novo copy number variations covering the ADD1 locus were associated with ID and brain malformations. ADD1 is highly expressed in the neocortex and the corpus callosum, whereas ADD1 splice isoforms are dynamically expressed between cortical progenitors and postmitotic neurons. Human variants impair ADD1 protein expression and/or dimerization with ADD2. Add1 knockout mice recapitulate corpus callosum dysgenesis and ventriculomegaly phenotypes., Conclusion: Our human and mouse genetics results indicate that pathogenic ADD1 variants cause corpus callosum dysgenesis, ventriculomegaly, and/or ID., Competing Interests: Conflict of Interest R.D.G receives consulting fees from Minovia Therapeutics. All other authors declare no conflicts of interest., (Copyright © 2021 American College of Medical Genetics and Genomics. Published by Elsevier Inc. All rights reserved.)

Autosomal ring chromosomes are rare cytogenetic findings that arise from breakage and fusion of the chromosome ends. Rings are mitotically unstable, usually sporadic and associated with a 'ring syndrome', characterized by a variable phenotype: growth retardation, no significant dysmorphisms and normal to moderately disabled intelligence. We describe the clinical features and molecular characterization of two sisters with ring chromosome 4. Karyotype analysis was performed on both sisters and parents. Chromosome microarray was performed on both sisters to delineate the breakpoint imbalance. Both sisters had a large ring 4 chromosome in the majority of cells analyzed on karyotype. Microarray results were identical in the sisters, showing a 55.8 kb duplication on the terminal 4p arm and a 1.5 Mb deletion on the terminal 4q arm. No genes of interest were identified in these regions. Parental karyotypes on lymphocytes and fibroblasts were normal, with no finding of mosaicism for the ring 4 chromosome. Polymorphic marker analysis revealed the maternal origin of the ring. To our knowledge, this is the first reported instance of a ring 4 chromosome recurring in siblings after extensive parental testing, which suggests this was due to maternal gonadal mosaicism., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Objectives: To document the clinical spectrum and outcomes of fetal double outlet right ventricle (DORV) without heterotaxy in a recent diagnostic era., Methods: Prenatal cases of DORV consecutively diagnosed from 2007 to 2018 were retrospectively identified. Clinical records, including details regarding genetic testing and pre and postnatal imaging were reviewed., Results: DORV was diagnosed in 99 fetuses without heterotaxy. The most common anatomic subtype was subaortic ventricular septal defect (VSD) and normally related great arteries with (n = 45, 45%) or without (n = 13, 13%) pulmonary stenosis. The remainder had a subpulmonic VSD with transposed great arteries (n = 15, 15%), atrioventricular valve atresia (n = 24, 24%), or remote VSD (n = 2, 2%). A genetic diagnosis was found in 32 (34%) of 93 tested. Major extracardiac anomalies were found in 40 (40%), including 17/24 (71%) with and 22/69 (32%) without an abnormal karyotype, with VACTERL association in 9. Genetic and/or extracardiac pathology was identified in 37/58 (64%) with a subaortic VSD, 5/15 (33%) with a subpulmonic VSD, 9/24 (38%) of those with AV valve atresia and 2/2 (100%) with a remote VSD. A genetic abnormality was a significant predictor of fetal demise (9/37 vs 1/62 p < 0.01) or pregnancy termination (12/35 vs 9/64 p = 0.03)., Conclusions: Fetal DORV is associated with a high rate of genetic abnormalities and extracardiac pathology. The presence of genetic abnormalities impacts prenatal outcomes and parental decision-making., (© 2021 John Wiley & Sons Ltd.)

Background: Hypertension has been identified as the most common comorbidity in coronavirus disease 2019 (COVID-19) patients, and has been suggested as a risk factor for COVID-19 disease outcomes. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus enters host human cells via binding to host cell angiotensin-converting enzyme 2 (ACE2) receptors. Inhibition of ACE2 has been proposed as a potential therapeutic approach to block SARS-CoV-2 contagion. However, some experts suggest that ACE2 inhibition could worsen the infection. Here, we aimed to study the effect of ACE2 inhibition on the SARS-CoV-2 spike protein binding to ACE2., Method: Crystallographic structures of the SARS-CoV-2 spike protein, the spike receptor-binding domain, native ACE2, and the ACE2 complexed with MLN-4760 were used as the study model structures. The spike proteins were docked to the ACE2 structures and the dynamics of the complexes, ligand-protein, and protein-protein interactions were studied by molecular dynamics simulation for 100 ns., Results: Our result showed that inhibition of ACE2 by MLN-4760 increased the affinity of the SARS-CoV-2 spike protein binding to ACE2. Results also revealed that spike protein binding to the ACE2 inhibited by MLN-4760 restored the enzymatic active conformation of the ACE2 from closed/inactive to open/active conformation by removing MLN-4760 binding from the ligand-binding pocket of ACE2., Conclusion: We conclude that using ACE2 inhibitors can increase the risk of SARS-CoV-2 infection and worsen COVID-19 disease outcome. We also found that the SARS-CoV-2 can abrogate the function of ACE2 inhibitors and rescue the enzymatic activity of ACE2. Therefore, ACE2 inhibition is not a useful treatment against COVID-19 infection., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Inherited retinal dystrophies (IRDs) affect 1 in 3000 individuals worldwide and are genetically heterogeneous, with over 270 identified genes and loci; however, there are still many identified disorders with no current genetic etiology. Whole exome sequencing (WES) provides a hypothesis-free first examination of IRD patients in either a clinical or research setting to identify the genetic cause of disease. We present a study of IRD in ten families from Alberta, Canada, through the lens of novel gene discovery. We identify the genetic etiology of IRDs in three of the families to be variants in known disease-associated genes, previously missed by clinical investigations. In addition, we identify two potentially novel associations: LRP1 in early-onset drusen formation and UBE2U in a multi-system condition presenting with retinoschisis, cataracts, learning disabilities, and developmental delay. We also describe interesting results in our unsolved cases to provide further information to other investigators of these blinding conditions., (© 2021. The Author(s), under exclusive licence to European Society of Human Genetics.)

Teebi hypertelorism syndrome (THS; OMIM 145420) is a rare craniofacial disorder characterized by hypertelorism, prominent forehead, short nose with broad or depressed nasal root. Some cases of THS have been attributed to SPECC1L variants. Homozygous variants in CDH11 truncating the transmembrane and intracellular domains have been implicated in Elsahy-Waters syndrome (EWS; OMIM 211380) with hypertelorism. We report THS due to CDH11 heterozygous missense variants on 19 subjects from 9 families. All affected residues in the extracellular region of Cadherin-11 (CHD11) are highly conserved across vertebrate species and classical cadherins. Six of the variants that cluster around the EC2-EC3 and EC3-EC4 linker regions are predicted to affect Ca 2+ binding that is required for cadherin stability. Two of the additional variants [c.164G > C, p.(Trp55Ser) and c.418G > A, p.(Glu140Lys)] are also notable as they are predicted to directly affect trans-homodimer formation. Immunohistochemical study demonstrates that CDH11 is strongly expressed in human facial mesenchyme. Using multiple functional assays, we show that five variants from the EC1, EC2-EC3 linker, and EC3 regions significantly reduced the cell-substrate trans adhesion activity and one variant from EC3-EC4 linker results in changes in cell morphology, focal adhesion, and migration, suggesting dominant negative effect. Characteristic features in this cohort included depressed nasal root, cardiac and umbilical defects. These features distinguished this phenotype from that seen in SPECC1L-related hypertelorism syndrome and CDH11-related EWS. Our results demonstrate heterozygous variants in CDH11, which decrease cell-cell adhesion and increase cell migratory behavior, cause a form of THS, as termed CDH11-related THS.

Purpose: Proline Rich 12 (PRR12) is a gene of unknown function with suspected DNA-binding activity, expressed in developing mice and human brains. Predicted loss-of-function variants in this gene are extremely rare, indicating high intolerance of haploinsufficiency., Methods: Three individuals with intellectual disability and iris anomalies and truncating de novo PRR12 variants were described previously. We add 21 individuals with similar PRR12 variants identified via matchmaking platforms, bringing the total number to 24., Results: We observed 12 frameshift, 6 nonsense, 1 splice-site, and 2 missense variants and one patient with a gross deletion involving PRR12. Three individuals had additional genetic findings, possibly confounding the phenotype. All patients had developmental impairment. Variable structural eye defects were observed in 12/24 individuals (50%) including anophthalmia, microphthalmia, colobomas, optic nerve and iris abnormalities. Additional common features included hypotonia (61%), heart defects (52%), growth failure (54%), and kidney anomalies (35%). PrediXcan analysis showed that phecodes most strongly associated with reduced predicted PRR12 expression were enriched for eye- (7/30) and kidney- (4/30) phenotypes, such as wet macular degeneration and chronic kidney disease., Conclusion: These findings support PRR12 haploinsufficiency as a cause for a novel disorder with a wide clinical spectrum marked chiefly by neurodevelopmental and eye abnormalities.

Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein (SRCAP) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as "non-FLHS SRCAP-related NDD." All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP, there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: Agenesis of the ductus venosus (ADV) has been associated with additional anomalies in up to 83% of cases. We sought to investigate characteristics, co-morbidities and outcomes of ADV in the current era. We hypothesized that rates of cardiac and non-cardiac diagnoses and survival would be higher, due to advances in genetic testing, prenatal diagnosis and surveillance., Methods: A retrospective series of cases diagnosed at our institution from 2007 to 2018 were identified by searching our database. Cardiac and obstetric charts were reviewed for cardiac and extra-cardiac anomalies, genetic results and outcomes., Results: Fourteen cases were diagnosed at a mean gestational age of 23.9 weeks (range 13-33). All had associated genetic, cardiac or extra-cardiac anomalies. Eight (57%) had cardiac anomalies and one other developed cardiomyopathy by 6 months. Extra-cardiac anomalies were present in 93% (13/14) and genetic diagnoses made in 75% (6/8) of those tested. Cardiac output Z-scores were >2 in 60% (6/10) prior to delivery. Two had hydrops, there was one intra-uterine death, 13 live-births and two neonatal deaths., Conclusion: Our cohort had more associated diagnoses and a lower mortality than previously reported. In our experience, high output occurs frequently, however with a relatively low risk of hydrops and intrauterine death., (© 2020 John Wiley & Sons Ltd.)

Weaver syndrome (WS), an overgrowth/intellectual disability syndrome (OGID), is caused by pathogenic variants in the histone methyltransferase EZH2, which encodes a core component of the Polycomb repressive complex-2 (PRC2). Using genome-wide DNA methylation (DNAm) data for 187 individuals with OGID and 969 control subjects, we show that pathogenic variants in EZH2 generate a highly specific and sensitive DNAm signature reflecting the phenotype of WS. This signature can be used to distinguish loss-of-function from gain-of-function missense variants and to detect somatic mosaicism. We also show that the signature can accurately classify sequence variants in EED and SUZ12, which encode two other core components of PRC2, and predict the presence of pathogenic variants in undiagnosed individuals with OGID. The discovery of a functionally relevant signature with utility for diagnostic classification of sequence variants in EZH2, EED, and SUZ12 supports the emerging paradigm shift for implementation of DNAm signatures into diagnostics and translational research., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

A subset of a larger and heterogeneous class of disorders, the congenital myasthenic syndromes (CMS) are caused by pathogenic variants in genes encoding proteins that support the integrity and function of the neuromuscular junction (NMJ). A central component of the NMJ is the sodium-dependent high-affinity choline transporter 1 (CHT1), a solute carrier protein (gene symbol SLC5A7), responsible for the reuptake of choline into nerve termini has recently been implicated as one of several autosomal recessive causes of CMS. We report the identification and functional characterization of a novel pathogenic variant in SLC5A7, c.788C>T (p.Ser263Phe) in an El Salvadorian family with a lethal form of a congenital myasthenic syndrome characterized by fetal akinesia. This study expands the clinical phenotype and insight into a form of fetal akinesia related to CHT1 defects and proposes a genotype-phenotype correlation for the lethal form of SLC5A7-related disorder with potential implications for genetic counseling., (© 2019 Wiley Periodicals, Inc.)