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BackgroundDespite the availability of whole exome (WES) and genome sequencing (WGS), chromosomal microarray (CMA) remains the first-line diagnostic test in most rare disorders diagnostic workup, looking for copy number variations (CNVs), with a diagnostic yield of 10%–20%. The question of the equivalence of CMA and WES in CNV calling is an organisational and economic question, especially when ordering a WGS after a negative CMA and/or WES.MethodsThis study measures the equivalence between CMA and GATK4 exome sequencing depth of coverage method in detecting coding CNVs on a retrospective cohort of 615 unrelated individuals. A prospective detection of WES-CNV on a cohort of 2418 unrelated individuals, including the 615 individuals from the validation cohort, was performed.ResultsOn the retrospective validation cohort, every CNV detectable by the method (ie, a CNV with at least one exon not in a dark zone) was accurately called (64/64 events). In the prospective cohort, 32 diagnoses were performed among the 2418 individuals with CNVs ranging from 704 bp to aneuploidy. An incidental finding was reported. The overall increase in diagnostic yield was of 1.7%, varying from 1.2% in individuals with multiple congenital anomalies to 1.9% in individuals with chronic kidney failure.ConclusionCombining single-nucleotide variant (SNV) and CNV detection increases the suitability of exome sequencing as a first-tier diagnostic test for suspected rare Mendelian disorders. Before considering the prescription of a WGS after a negative WES, a careful reanalysis with updated CNV calling and SNV annotation should be considered.

Two distinct syndromes arise from pathogenic variants in the X-linked gene BCOR (BCL-6 corepressor): oculofaciocardiodental (OFCD) syndrome, which affects females, and a severe microphthalmia (‘Lenz’-type) syndrome affecting males. OFCD is an X-linked dominant syndrome caused by a variety of BCOR null mutations. As it manifests only in females, it is presumed to be lethal in males. The severe male X-linked recessive microphthalmia syndrome (‘Lenz’) usually includes developmental delay in addition to the eye findings and is caused by hypomorphic BCOR variants, mainly by a specific missense variant c.254C > T, p.(Pro85Leu). Here, we detail 16 new cases (11 females with 4 additional, genetically confirmed, affected female relatives; 5 male cases each with unaffected carrier mothers). We describe new variants and broaden the phenotypic description for OFCD to include neuropathy, muscle hypotonia, pituitary underdevelopment, brain atrophy, lipoma and the first description of childhood lymphoma in an OFCD case. Our male X-linked recessive cases show significant new phenotypes: developmental delay (without eye anomalies) in two affected half-brothers with a novel BCOR variant, and one male with high myopia, megalophthalmos, posterior embryotoxon, developmental delay, and heart and bony anomalies with a previously undescribed BCOR splice site variant. Our female OFCD cases and their affected female relatives showed variable features, but consistently had early onset cataracts. We show that a mosaic carrier mother manifested early cataract and dental anomalies. All female carriers of the male X-linked recessive cases for whom genetic confirmation was available showed skewed X-inactivation and were unaffected. In view of the extended phenotype, we suggest a new term of X-linked BCOR-related syndrome.

Induced pluripotent stem cells (iPSCs) have considerably impacted human developmental biology and regenerative medicine, notably because they circumvent the use of cells of embryonic origin and offer the potential to generate patient-specific pluripotent stem cells. However, conventional reprogramming protocols produce developmentally advanced, or primed, human iPSCs (hiPSCs), restricting their use to post-implantation human development modeling. Hence, there is a need for hiPSCs resembling preimplantation naive epiblast. Here, we develop a method to generate naive hiPSCs directly from somatic cells, using OKMS overexpression and specific culture conditions, further enabling parallel generation of their isogenic primed counterparts. We benchmark naive hiPSCs against human preimplantation epiblast and reveal remarkable concordance in their transcriptome, dependency on mitochondrial respiration and X-chromosome status. Collectively, our results are essential for the understanding of pluripotency regulation throughout preimplantation development and generate new opportunities for disease modeling and regenerative medicine. Derivation of human induced pluripotent stem cells (hiPSCs) produces primed hiPSCs that can in turn be converted to naive hiPSCs. Here, the authors directly reprogram somatic cells to form both naive and primed isogenic hiPSCs and confirm the similarity of naive hiPSCs to their in vivo counterparts.

Lanosterol synthase (LSS) gene was initially described in families with extensive congenital cataracts. Recently, a study has highlighted LSS associated with hypotrichosis simplex. We expanded the phenotypic spectrum of LSS to a recessive neuroectodermal syndrome formerly named alopecia with mental retardation (APMR) syndrome. It is a rare autosomal recessive condition characterized by hypotrichosis and intellectual disability (ID) or developmental delay (DD), frequently associated with early-onset epilepsy and other dermatological features. Through a multicenter international collaborative study, we identified LSS pathogenic variants in APMR individuals either by exome sequencing or LSS Sanger sequencing. Splicing defects were assessed by transcript analysis and minigene assay. We reported ten APMR individuals from six unrelated families with biallelic variants in LSS. We additionally identified one affected individual with a single rare variant in LSS and an allelic imbalance suggesting a second event. Among the identified variants, two were truncating, seven were missense, and two were splicing variants. Quantification of cholesterol and its precursors did not reveal noticeable imbalance. In the cholesterol biosynthesis pathway, lanosterol synthase leads to the cyclization of (S)-2,3-oxidosqualene into lanosterol. Our data suggest LSS as a major gene causing a rare recessive neuroectodermal syndrome.

Neurodevelopmental proteasomopathies are a group of disorders caused by variants in proteasome subunit genes, that disrupt protein homeostasis and brain development through poorly characterized mechanisms. Here, we report 26 distinct variants in PSMC5 , encoding the AAA⁺ ATPase subunit PSMC5/RPT6, in individuals with syndromic neurodevelopmental conditions. Combining genetic, multi-omics and biochemical approaches across cellular models and Drosophila , we unveil the essential role of proteasomes in sustaining key cellular processes. Loss of PSMC5/RPT6 function impairs proteasome activity, leading to protein aggregation, disruption of mitochondrial homeostasis, and dysregulation of lipid metabolism and immune signaling. It also compromises synaptic balance, neuritogenesis, and neural progenitor cell stemness, causing deficits in higher-order functions, including learning and locomotion. Pharmacological targeting of integrated stress response kinases reveals a mechanistic link between proteotoxic stress and spontaneous type I interferon activation. These findings expand our understanding of proteasome-dependent quality control in neurodevelopment and suggest potential therapeutic strategies for neurodevelopmental proteasomopathies. Variants in the PSMC5 gene impair proteasome function and cellular homeostasis, altering brain development in children. This study reveals underlying molecular mechanisms contributing to this neurodevelopmental phenotype, and suggests therapeutic leads for neurodevelopmental proteasomopathies.

Pathogenic variants in ATP-dependent chromatin remodeling proteins are a recurrent cause of neurodevelopmental disorders (NDDs). The NURF complex consists of BPTF and either the SMARCA5 or SMARCA1 ISWI-chromatin remodeling enzyme. Pathogenic variants in BPTF and SMARCA5 have been previously implicated in NDDs. Here, we describe 35 individuals from 26 families with de novo or maternally inherited variants in the X-linked SMARCA1 gene. This SMARCA1-related NDD is associated with a spectrum of involvement, including mild to severe ID/DD, delayed or regressive speech development, ASD features, facial dysmorphisms, and other variable features. Individuals carrying SMARCA1 truncating variants exhibit a mildly unique genome-wide DNA methylation profile and a high penetrance of macrocephaly. Genetic dissection of the NURF complex using Smarca1 , Smarca5 , and Bptf single and double mouse knockouts reveals the importance of NURF composition and dosage for proper forebrain development. We propose that genetic alterations affecting different NURF components, including SMARCA1 , result in a NDD with a broad clinical spectrum. The authors identify pathogenic variants in the SMARCA1 gene as the cause of a variable neurodevelopmental disorder. Mouse studies suggest diverse genetic mechanisms related to NURF complex composition mediate the phenotype.