Exome copy number variant detection, analysis, and classification in a large cohort of families with undiagnosed rare genetic disease.

Copy number variants (CNVs) are significant contributors to the pathogenicity of rare genetic diseases and, with new innovative methods, can now reliably be identified from exome sequencing. Challenges still remain in accurate classification of CNV pathogenicity. CNV calling using GATK-gCNV was performed on exomes from a cohort of 6,633 families (15,759 individuals) with heterogeneous phenotypes and variable prior genetic testing collected at the Broad Institute Center for Mendelian Genomics of the Genomics Research to Elucidate the Genetics of Rare Diseases consortium and analyzed using the seqr platform. The addition of CNV detection to exome analysis identified causal CNVs for 171 families (2.6%). The estimated sizes of CNVs ranged from 293 bp to 80 Mb. The causal CNVs consisted of 140 deletions, 15 duplications, 3 suspected complex structural variants (SVs), 3 insertions, and 10 complex SVs, the latter two groups being identified by orthogonal confirmation methods. To classify CNV variant pathogenicity, we used the 2020 American College of Medical Genetics and Genomics/ClinGen CNV interpretation standards and developed additional criteria to evaluate allelic and functional data as well as variants on the X chromosome to further advance the framework. We interpreted 151 CNVs as likely pathogenic/pathogenic and 20 CNVs as high-interest variants of uncertain significance. Calling CNVs from existing exome data increases the diagnostic yield for individuals undiagnosed after standard testing approaches, providing a higher-resolution alternative to arrays at a fraction of the cost of genome sequencing. Our improvements to the classification approach advances the systematic framework to assess the pathogenicity of CNVs.

Demonstration of the pathogenicity of a common non-exomic mutation in ABCA4 using iPSC-derived retinal organoids and retrospective clinical data.

Mutations in ABCA4 are the most common cause of Mendelian retinal disease. Clinical evaluation of this gene is challenging because of its extreme allelic diversity, the large fraction of non-exomic mutations, and the wide range of associated disease. We used patient-derived retinal organoids as well as DNA samples and clinical data from a large cohort of patients with ABCA4-associated retinal disease to investigate the pathogenicity of a variant in ABCA4 (IVS30 + 1321 A > G) that occurs heterozygously in 2% of Europeans. We found that this variant causes mis-splicing of the gene in photoreceptor cells such that the resulting protein contains 36 incorrect amino acids followed by a premature stop. We also investigated the phenotype of 10 patients with compound genotypes that included this mutation. Their median age of first vision loss was 39 years, which is in the mildest quintile of a large cohort of patients with ABCA4 disease. We conclude that the IVS30 + 1321 A > G variant can cause disease when paired with a sufficiently deleterious opposing allele in a sufficiently permissive genetic background.

Unique variants in CLCN3, encoding an endosomal anion/proton exchanger, underlie a spectrum of neurodevelopmental disorders.

The genetic causes of global developmental delay (GDD) and intellectual disability (ID) are diverse and include variants in numerous ion channels and transporters. Loss-of-function variants in all five endosomal/lysosomal members of the CLC family of Cl- channels and Cl-/H+ exchangers lead to pathology in mice, humans, or both. We have identified nine variants in CLCN3, the gene encoding CIC-3, in 11 individuals with GDD/ID and neurodevelopmental disorders of varying severity. In addition to a homozygous frameshift variant in two siblings, we identified eight different heterozygous de novo missense variants. All have GDD/ID, mood or behavioral disorders, and dysmorphic features; 9/11 have structural brain abnormalities; and 6/11 have seizures. The homozygous variants are predicted to cause loss of ClC-3 function, resulting in severe neurological disease similar to the phenotype observed in Clcn3-/- mice. Their MRIs show possible neurodegeneration with thin corpora callosa and decreased white matter volumes. Individuals with heterozygous variants had a range of neurodevelopmental anomalies including agenesis of the corpus callosum, pons hypoplasia, and increased gyral folding. To characterize the altered function of the exchanger, electrophysiological analyses were performed in Xenopus oocytes and mammalian cells. Two variants, p.Ile607Thr and p.Thr570Ile, had increased currents at negative cytoplasmic voltages and loss of inhibition by luminal acidic pH. In contrast, two other variants showed no significant difference in the current properties. Overall, our work establishes a role for CLCN3 in human neurodevelopment and shows that both homozygous loss of ClC-3 and heterozygous variants can lead to GDD/ID and neuroanatomical abnormalities.

Missense variants in DPYSL5 cause a neurodevelopmental disorder with corpus callosum agenesis and cerebellar abnormalities.

The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and ßIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and ßIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.

Bi-allelic loss-of-function variants in BCAS3 cause a syndromic neurodevelopmental disorder.

BCAS3 microtubule-associated cell migration factor (BCAS3) is a large, highly conserved cytoskeletal protein previously proposed to be critical in angiogenesis and implicated in human embryogenesis and tumorigenesis. Here, we established BCAS3 loss-of-function variants as causative for a neurodevelopmental disorder. We report 15 individuals from eight unrelated families with germline bi-allelic loss-of-function variants in BCAS3. All probands share a global developmental delay accompanied by pyramidal tract involvement, microcephaly, short stature, strabismus, dysmorphic facial features, and seizures. The human phenotype is less severe compared with the Bcas3 knockout mouse model and cannot be explained by angiogenic defects alone. Consistent with being loss-of-function alleles, we observed absence of BCAS3 in probands' primary fibroblasts. By comparing the transcriptomic and proteomic data based on probands' fibroblasts with those of the knockout mouse model, we identified similar dysregulated pathways resulting from over-representation analysis, while the dysregulation of some proposed key interactors could not be confirmed. Together with the results from a tissue-specific Drosophila loss-of-function model, we demonstrate a vital role for BCAS3 in neural tissue development.

A Retrospective Longitudinal Study of 460 Patients with ABCA4-Associated Retinal Disease.

PURPOSE: To investigate the distribution of genotypes and natural history of ABCA4-associated retinal disease in a large cohort of patients seen at a single institution. DESIGN: Retrospective, single-institution cohort review. PARTICIPANTS: Patients seen at the University of Iowa between November 1986 and August 2022 clinically suspected to have disease caused by sequence variations in ABCA4. METHODS: DNA samples from participants were subjected to a tiered testing strategy progressing from allele-specific screening to whole genome sequencing. Charts were reviewed, and clinical data were tabulated. The pathogenic severity of the most common alleles was estimated by studying groups of patients who shared 1 allele. Groups of patients with shared genotypes were reviewed for evidence of modifying factor effects. MAIN OUTCOME MEASURES: Age at first uncorrectable vision loss, best-corrected visual acuity, and the area of the I2e isopter of the Goldmann visual field. RESULTS: A total of 460 patients from 390 families demonstrated convincing clinical features of ABCA4-associated retinal disease. Complete genotypes were identified in 399 patients, and partial genotypes were identified in 61. The median age at first vision loss was 16 years (range, 4-76 years). Two hundred sixty-five families (68%) harbored a unique genotype, and no more than 10 patients shared any single genotype. Review of the patients with shared genotypes revealed evidence of modifying factors that in several cases resulted in a > 15-year difference in age at first vision loss. Two hundred forty-one different alleles were identified among the members of this cohort, and 161 of these (67%) were found in only a single individual. CONCLUSIONS: ABCA4-associated retinal disease ranges from a very severe photoreceptor disease with an onset before 5 years of age to a late-onset retinal pigment epithelium-based condition resembling pattern dystrophy. Modifying factors frequently impact the ABCA4 disease phenotype to a degree that is similar in magnitude to the detectable ABCA4 alleles themselves. It is likely that most patients in any cohort will harbor a unique genotype. The latter observations taken together suggest that patients' clinical findings in most cases will be more useful for predicting their clinical course than their genotype. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Surgical Management of Full-Thickness Macular Holes in Macular Telangiectasia Type 2: A Global Multicenter Study.

PURPOSE: To report on macular hole repair in macular telangiectasia type 2 (MacTel2). DESIGN: Global, multicenter, retrospective case series. PARTICIPANTS: Patients undergoing surgery for MacTel2-associated full-thickness macular hole (MTMH). METHODS: Standardized data collection sheet distributed to all surgeons. MAIN OUTCOME MEASURES: Anatomic closure and visual outcomes of MTMH. RESULTS: Sixty-three surgeries in 47 patients with MTMH were included from 30 surgeons. Mean age was 68.1 years, with 62% female, 72% White, 21% East or South Asian, 2% African American, and 2% Hispanic or Latino. Procedures included 34 internal limiting membrane (ILM) peeling alone, 22 ILM flaps, 5 autologous retinal transplantations (ARTs), 1 retinotomy, and 1 subretinal bleb. For ILM peeling, preoperative visual acuity (VA) was 0.667 ± 0.423 logarithm of the minimum angle of resolution (logMAR). Minimum hole diameter (MHD) was 305.5 ± 159.4 µm (range, 34-573 µm). Sixteen of 34 ILM peels (47%) resulted in MTMH closure. At postoperative month 6, VA was stable at 0.602 ± 0.516 logMAR (P = 0.65). VA improved by at least 2 lines in 43% and at least 4 lines in 24%. For ILM flaps, preoperative VA was 0.878 ± 0.552 logMAR. MHD was 440.8 ± 175.5 µm (range, 97-697 µm), which was significantly larger than for ILM peels (P < 0.01). Twenty of 22 ILM flaps (90%) resulted in MTMH closure, which was significantly higher than for ILM peels (P < 0.01). At postoperative month 6, VA improved to 0.555 ± 0.405 logMAR (P < 0.05). VA improved by at least 2 lines in 56% and at least 4 lines in 28%. For ARTs, preoperative VA was 1.460 ± 0.391 logMAR. MHD was 390.2 ± 203.7 µm (range, 132-687 µm). All 5 ARTs (100%) resulted in MTMH closure. At postoperative month 6, VA was stable at 1.000 ± 0.246 logMAR (P = 0.08). Visual acuity improved at least 2 lines in 25%. CONCLUSIONS: Surgical closure of macular holes improved VA in 57% of MTMHs. Internal limiting membrane flaps achieved better anatomic and functional outcomes than ILM peeling alone. Autologous retinal transplantation may be an option for refractory MTMHs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Current clinical evidence is insufficient to support HMME-PDT as the first choice of treatment for young children with port wine birthmarks.

BACKGROUND: Port wine birthmark (PWB) is a congenital vascular malformation of the skin. Pulsed dye laser (PDL) is the "gold standard" for the treatment of PWB globally. Hematoporphyrin monomethyl ether (HMME or hemoporfin)-mediated photodynamic therapy (HMME-PDT) has emerged as the first choice for PWB treatment, particularly for young children, in many major hospitals in China during the past several decades. AIM: To evaluate whether HMME-PDT is superior to PDL by comparing the clinical efficacies of both modalities. METHOD: PubMed records were searched for all relevant studies of PWB treatment using PDL (1988-2023) or HMME-PDT (2007-2023). Patient characteristics and clinical efficacies were extracted. Studies with a quartile percentage clearance or similar scale were included. A mean color clearance index (CI) per study was calculated and compared among groups. An overall CI (C0), with data weighted by cohort size, was used to evaluate the final efficacy for each modality. RESULT: A total of 18 HMME-PDT studies with 3910 patients in China were eligible for inclusion in this analysis. Similarly, 40 PDL studies with 5094 patients from nine different countries were eligible for inclusion in this analysis. Over 58% of patients in the HMME-PDT studies were minors (<18 years old). A significant portion (21.3%) were young children (<3 years old). Similarly, 33.2% of patients in the PDL studies were minors. A small proportion (9.3%) was young children. The overall clearance rates for PDL were slightly, but not significantly, higher than those for HMME-PDT in cohorts with patients of all ages (C0, 0.54 vs. 0.48, p = 0.733), subpopulations with only minors (C0, 0.54 vs. 0.46, p = 0.714), and young children (C0, 0.67 vs. 0.50, p = 0.081). Regrettably, there was a lack of long-term data on follow-up evaluations for efficacy and impact of HMME-PDT on young children in general, and central nervous system development in particular, because their blood-brain barriers have a greater permeability as compared to adults. CONCLUSION: PDL shows overall albeit insignificantly higher clearance rates than HMME-PDT in patients of all ages; particularly statistical significance is nearly achieved in young children. Collectively, current evidence is insufficient to support HMME-PDT as the first choice of treatment of PWBs in young children given: (1) overall inferior efficacy as compared to PDL; (2) risk of off-target exposure to meningeal vasculature during the procedure; (3) administration of steriods for mitigation of side effects; -and (4) lack of long-term data on the potential impact of HMME on central nervous system development in young children.

Increasing Incidence and Decreasing Mortality of Melanoma in Elderly Adults: An Epidemiologic Study in Olmsted County, Minnesota.

BACKGROUND AND OBJECTIVE: Primary cutaneous melanoma incidence is increasing in elderly individuals. This population-based cohort examines incidence and mortality rates among adults aged 61 years and older with cutaneous melanoma. MATERIALS AND METHODS: Using the Rochester Epidemiology Project, patients aged 61 years of age or older with a first lifetime diagnosis of cutaneous melanoma between January 1, 1970 and December 31, 2020 were identified. RESULTS: The age- and sex-adjusted incidence rate increased from 16.4 (95% CI, 8.2-24.6) per 100,000 person-years in 1970 to 1979 to 201.5 (95% CI, 185.1-217.8) per 100,000 person-years in 2011 to 2020 (12.3-fold increase). There was a 16.0x increase in males and an 8.5× increase in females. Melanoma incidence has stabilized in males (1.2-fold increase, p = .11) and continues to significantly increase in females (2.7-fold increase, p < .001). Older age at diagnosis was significantly associated with an increased risk of death (HR 1.23 per 5-year increase in age at diagnosis, 95% CI, 1.02-1.47). CONCLUSION: Melanoma incidence continues to increase since 1970. The incidence has risen in elderly females, but has stabilized in males. Mortality has decreased throughout this period.

Comments on "What is silence? Therefore, what is sound?" - A discussion of Brownian motion and the threshold of hearing (L).

This Letter to the editor is a comment on an article in the JASA Forum by William Yost. It pertains to a reference he made to prior work that indicates the possibility that the human threshold of hearing in the most sensitive region may be limited by Brownian motion of the air molecules, also called thermal noise. I present additional data and my own observations that support this contention.

Lower Extremity Angiosarcoma: A Life-Threatening Complication of Lymphedema.

ABSTRACT: When angiosarcoma, a rare and aggressive tumor of the soft tissue, develops in the setting of chronic lymphedema, it is referred to as Stewart-Treves syndrome. It is usually seen in chronic lymphedema of the upper limbs postmastectomy. Angiosarcoma developing in the lower limb in the setting of chronic lymphedema is rare and has a poor outcome. The presentation of angiosarcoma can vary, ranging from a bleeding papule to a plaque or a subcutaneous mass, which can later progress to ulceration or necrosis. Treatment for Stewart-Treves syndrome is aggressive because of its poor prognosis and usually requires a multidisciplinary approach of surgery, radiation, and chemotherapy. Several theories have been put forth to explain the mechanism of Stewart-Treves syndrome, but it remains ambiguous. The current literature regarding angiosarcoma developing in the setting of chronic lymphedema in the lower limb is limited to single case reports. Herein, the authors report a series of six cases of biopsy-proven angiosarcoma in the setting of lower extremity lymphedema. Providers should include angiosarcoma in the differential diagnosis of ulcerative or vascular tumors arising in the context of lower extremity lymphedema.

De novo CLCN3 variants affecting Gly327 cause severe neurodevelopmental syndrome with brain structural abnormalities.

A recent study revealed that monoallelic missense or biallelic loss-of-function variants in the chloride voltage-gated channel 3 (CLCN3) cause neurodevelopmental disorders resulting in brain abnormalities. Functional studies suggested that some missense variants had varying gain-of-function effects on channel activity. Meanwhile, two patients with homozygous frameshift variants showed severe neuropsychiatric disorders and a range of brain structural abnormalities. Here we describe two patients with de novo CLCN3 variants affecting the same amino acid, Gly327 (p.(Gly327Ser) and p.(Gly327Asp)). They showed severe neurological phenotypes including global developmental delay, intellectual disability, hypotonia, failure to thrive, and various brain abnormalities. They also presented with characteristic brain and ophthalmological abnormalities, hippocampal and retinal degradation, which were observed in patients harboring homozygous loss-of-function variants. These findings were also observed in CLCN3-deficient mice, indicating that the monoallelic missense variant may also have a dominant negative effect. This study will expand the phenotypic spectrum of CLCN3-related disorders.

Intermolecular Pauson-Khand-Type Reaction of Vinyl Iodides with Alkynes and a CO Surrogate.

A strategy for the palladium-catalyzed intermolecular synthesis of polysubstituted cyclopentenones is reported. The three-component reaction utilizes vinyl iodides and internal alkynes to form the carbon framework of the cyclopentenone with Cr(CO)6 serving as an easy to handle, solid CO surrogate, and a hydrosilane as a hydride source. We demonstrate the scope of the reaction which includes a wide range of functional groups. The reaction is regioselective, with the use of linear or branched vinyl iodides resulting in the α- or ß-substituted cyclopentenones, respectively. Further, we show that a two-step sequence from commercially available alkynes can be used to generate cyclopentenone products via formation of the vinyl iodide and subsequent Pauson-Khand-type reaction.

High-resolution mapping and characterization of open chromatin across the genome.

Mapping DNase I hypersensitive (HS) sites is an accurate method of identifying the location of genetic regulatory elements, including promoters, enhancers, silencers, insulators, and locus control regions. We employed high-throughput sequencing and whole-genome tiled array strategies to identify DNase I HS sites within human primary CD4+ T cells. Combining these two technologies, we have created a comprehensive and accurate genome-wide open chromatin map. Surprisingly, only 16%-21% of the identified 94,925 DNase I HS sites are found in promoters or first exons of known genes, but nearly half of the most open sites are in these regions. In conjunction with expression, motif, and chromatin immunoprecipitation data, we find evidence of cell-type-specific characteristics, including the ability to identify transcription start sites and locations of different chromatin marks utilized in these cells. In addition, and unexpectedly, our analyses have uncovered detailed features of nucleosome structure.

MACULAR ATROPHY AND PHENOTYPIC VARIABILITY IN AUTOSOMAL DOMINANT STARGARDT-LIKE MACULAR DYSTROPHY DUE TO PROM1 MUTATION.

PURPOSE: To describe the phenotypic variability and rates of progression of atrophy in patients with PROM1 -associated macular dystrophy. METHODS: Patients in this retrospective, longitudinal case series from a tertiary center had clinical examination and multimodal imaging performed. Areas of retinal pigment epithelium and ellipsoid zone loss over time by optical coherence tomography were calculated by two independent graders. RESULTS: Fifteen patients from five kindreds with an Arg373Cys mutation in PROM1 were studied. The average age was 39 years, and 80% were women. The visual acuity was 20/40 at presentation and 20/57 at last follow-up (average 4.8 years). Three distinct macular phenotypes were observed: 1) central geographic atrophy (13%), 2) multifocal geographic atrophy (20%), and 3) bull's eye maculopathy (67%). The overall rate of atrophy progression was 0.36 mm 2 /year, but the average rate of atrophy progression varied by macular phenotype: 1.08 mm 2 /year for central geographic atrophy, 0.53 mm 2 /year for multifocal geographic atrophy, and 0.23 mm 2 /year for bull's eye maculopathy. CONCLUSION: Patients with PROM1 -associated macular dystrophy demonstrate distinct phenotypes, with bull's eye maculopathy being the most common. The average rate of atrophy progression may be similar to reported rates for ABCA4 -related Stargardt disease and less than age-related macular degeneration. These results provide important measures for following treatment response in future gene and stem cell-based therapies.

Local Recurrence Rates of Extramammary Paget Disease Are Lower After Mohs Micrographic Surgery Compared With Wide Local Excision: A Systematic Review and Meta-Analysis.

BACKGROUND: Extramammary Paget disease (EMPD) is a rare, slow growing neoplasm that presents most commonly in the anogenital region of older adults. OBJECTIVE: To analyze the difference in local recurrence rates of EMPD in patients treated with wide local excision (WLE) versus Mohs micrographic surgery (MMS). MATERIALS AND METHODS: A systematic review of the literature and meta-analysis were performed. Inclusion criteria were adults greater than 18 years of age with a diagnosis of EMPD who have undergone surgical intervention and had follow-up data. Studies were independently reviewed by 2 coinvestigators with discrepancies resolved by the principal investigator. RESULTS: Twenty-seven studies met the inclusion criteria. Patients had a 2.67 times higher chance of local recurrence after WLE than MMS (95% confidence interval [CI]:1.47, 4.85; p = .001). Meta-analysis of single-arm studies revealed a 7.3% local recurrence rate after MMS (95% CI: 0.039, 0.107; p < .001) versus a 26.3% recurrence rate after WLE (95% CI: 0.149, 0.376; p < .001). After excluding recurrent tumors, the odds ratio for recurrence in WLE versus MMS was 2.3 (95% CI: 0.285, 18.43, p = .435). CONCLUSION: There is a clinically and statistically increased risk of local recurrence of EMPD after WLE compared with MMS.

Local Recurrence Rates of Malignant Melanoma After Mohs Micrographic Surgery Are Lowest With 5- to 10-mm Initial Margins: A Systematic Review and Meta-Analysis.

BACKGROUND: Current consensus guidelines have discouraged the use of sub-0.5-cm (in situ) and sub-1-cm (invasive) margins when performing Mohs micrographic surgery (Mohs) for melanoma, with minimal evidence to guide this recommendation. OBJECTIVE: To compare melanoma local recurrence rates after Mohs based on initial margin size. MATERIALS AND METHODS: A systematic review and meta-analysis was conducted with search terms including Mohs micrographic surgery, surgical margin, recurrent disease, and melanoma. RESULTS: Forty-three studies were included. The 5- to 10-mm margin category had a statistically significant lower local recurrence compared with 1- to 5-mm and 5-mm categories. Recurrence for 1- to 5-mm, 5-mm, 5- to 10-mm, and 10-mm categories were 2.3% (CI 0.8-3.5, p < .001), 1.4% (CI 0.6-2.2, p < .001), 0.3% (CI 0.2-0.5, p < .001), and 6.1% (CI -6.7 - 18.8, p = .349), respectively. Number of stages for 1 to 5, 5, 5 to 10, and 10-mm categories were 1.8, 1.8, 1.6, and 1.6, respectively. There was no statistically significant difference between the groups (p = .694). CONCLUSION: Five- to 10-mm margins were associated with the lowest local recurrence rates. A 5- to 10-mm initial margin should be considered where other factors (tumor characteristics, anatomical or functional considerations) allow.

Newborn screening for neurodevelopmental diseases: Are we there yet?

In the US, newborn screening (NBS) is a unique health program that supports health equity and screens virtually every baby after birth, and has brought timely treatments to babies since the 1960's. With the decreasing cost of sequencing and the improving methods to interpret genetic data, there is an opportunity to add DNA sequencing as a screening method to facilitate the identification of babies with treatable conditions that cannot be identified in any other scalable way, including highly penetrant genetic neurodevelopmental disorders (NDD). However, the lack of effective dietary or drug-based treatments has made it nearly impossible to consider NDDs in the current NBS framework, yet it is anticipated that any treatment will be maximally effective if started early. Hence there is a critical need for large scale pilot studies to assess if and how NDDs can be effectively screened at birth, if parents desire that information, and what impact early diagnosis may have. Here we attempt to provide an overview of the recent advances in NDD treatments, explore the possible framework of setting up a pilot study to genetically screen for NDDs, highlight key technical, practical, and ethical considerations and challenges, and examine the policy and health system implications.

De Novo Pathogenic Variants in N-cadherin Cause a Syndromic Neurodevelopmental Disorder with Corpus Collosum, Axon, Cardiac, Ocular, and Genital Defects.

Cadherins constitute a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion. The extracellular domain of cadherins consists of extracellular cadherin (EC) domains, separated by calcium binding sites. The EC interacts with other cadherin molecules in cis and in trans to mechanically hold apposing cell surfaces together. CDH2 encodes N-cadherin, whose essential roles in neural development include neuronal migration and axon pathfinding. However, CDH2 has not yet been linked to a Mendelian neurodevelopmental disorder. Here, we report de novo heterozygous pathogenic variants (seven missense, two frameshift) in CDH2 in nine individuals with a syndromic neurodevelopmental disorder characterized by global developmental delay and/or intellectual disability, variable axon pathfinding defects (corpus callosum agenesis or hypoplasia, mirror movements, Duane anomaly), and ocular, cardiac, and genital anomalies. All seven missense variants (c.1057G>A [p.Asp353Asn]; c.1789G>A [p.Asp597Asn]; c.1789G>T [p.Asp597Tyr]; c.1802A>C [p.Asn601Thr]; c.1839C>G [p.Cys613Trp]; c.1880A>G [p.Asp627Gly]; c.2027A>G [p.Tyr676Cys]) result in substitution of highly conserved residues, and six of seven cluster within EC domains 4 and 5. Four of the substitutions affect the calcium-binding site in the EC4-EC5 interdomain. We show that cells expressing these variants in the EC4-EC5 domains have a defect in cell-cell adhesion; this defect includes impaired binding in trans with N-cadherin-WT expressed on apposing cells. The two frameshift variants (c.2563_2564delCT [p.Leu855Valfs∗4]; c.2564_2567dupTGTT [p.Leu856Phefs∗5]) are predicted to lead to a truncated cytoplasmic domain. Our study demonstrates that de novo heterozygous variants in CDH2 impair the adhesive activity of N-cadherin, resulting in a multisystemic developmental disorder, that could be named ACOG syndrome (agenesis of corpus callosum, axon pathfinding, cardiac, ocular, and genital defects).

Heterozygous variants in MYH10 associated with neurodevelopmental disorders and congenital anomalies with evidence for primary cilia-dependent defects in Hedgehog signaling.

PURPOSE: Nonmuscle myosin II complexes are master regulators of actin dynamics that play essential roles during embryogenesis with vertebrates possessing 3 nonmuscle myosin II heavy chain genes, MYH9, MYH10, and MYH14. As opposed to MYH9 and MYH14, no recognizable disorder has been associated with MYH10. We sought to define the clinical characteristics and molecular mechanism of a novel autosomal dominant disorder related to MYH10. METHODS: An international collaboration identified the patient cohort. CAS9-mediated knockout cell models were used to explore the mechanism of disease pathogenesis. RESULTS: We identified a cohort of 16 individuals with heterozygous MYH10 variants presenting with a broad spectrum of neurodevelopmental disorders and variable congenital anomalies that affect most organ systems and were recapitulated in animal models of altered MYH10 activity. Variants were typically de novo missense changes with clustering observed in the motor domain. MYH10 knockout cells showed defects in primary ciliogenesis and reduced ciliary length with impaired Hedgehog signaling. MYH10 variant overexpression produced a dominant-negative effect on ciliary length. CONCLUSION: These data presented a novel genetic cause of isolated and syndromic neurodevelopmental disorders related to heterozygous variants in the MYH10 gene with implications for disrupted primary cilia length control and altered Hedgehog signaling in disease pathogenesis.