Project description:Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the novelty of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n=43) patient cohort to date identified that hypotonia and congenital heart defects are novel prominent features. Both missense variants and putative loss-of-function variants resulted in slow growth in patient derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wildtype littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA-sequencing of patient lymphoblasts and Kmt5b-haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified novel pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.
Project description:Different types of germline de novo SETBP1 variants cause clinically distinct and heterogeneous neurodevelopmental disorders: Schinzel-Giedion syndrome (SGS, via missense variants at a critical degron region) and SETBP1-haploinsufficiency disorder. However, due to the lack of systematic investigation of genotype-phenotype associations of different types of SETBP1 variants, and limited understanding of its roles in neurodevelopment, the extent of clinical heterogeneity and how this relates to underlying pathophysiological mechanisms remain elusive. This imposes challenges for diagnosis. Here, we present a comprehensive investigation of the largest cohort to-date of individuals carrying SETBP1 missense variants outside the degron region (n=18). We performed thorough clinical and speech phenotyping with functional follow-up using cellular assays and transcriptomics. Our findings suggest that such variants cause a clinically and functionally variable developmental syndrome, showing only partial overlaps with classical SGS and SETBP1-haploinsufficiency disorder. We provide evidence of loss-of-function pathophysiological mechanisms impairing ubiquitination, DNA-binding, transcription, and neuronal differentiation capacity and morphologies. In contrast to SGS and SETBP1 haploinsufficiency, these effects are independent of protein abundance. Overall, our study provides important novel insights into diagnosis, patient care, and aetiology of SETBP1-related disorders.
Project description:Different types of germline de novo SETBP1 variants cause clinically distinct and heterogeneous neurodevelopmental disorders: Schinzel-Giedion syndrome (SGS, via missense variants at a critical degron region) and SETBP1-haploinsufficiency disorder. However, due to the lack of systematic investigation of genotype-phenotype associations of different types of SETBP1 variants, and limited understanding of its roles in neurodevelopment, the extent of clinical heterogeneity and how this relates to underlying pathophysiological mechanisms remain elusive. This imposes challenges for diagnosis. Here, we present a comprehensive investigation of the largest cohort to-date of individuals carrying SETBP1 missense variants outside the degron region (n=18). We performed thorough clinical and speech phenotyping with functional follow-up using cellular assays and transcriptomics. Our findings suggest that such variants cause a clinically and functionally variable developmental syndrome, showing only partial overlaps with classical SGS and SETBP1-haploinsufficiency disorder. We provide evidence of loss-of-function pathophysiological mechanisms impairing ubiquitination, DNA-binding, transcription, and neuronal differentiation capacity and morphologies. In contrast to SGS and SETBP1 haploinsufficiency, these effects are independent of protein abundance. Overall, our study provides important novel insights into diagnosis, patient care, and aetiology of SETBP1-related disorders.
Project description:This analysis includes the whole-genome screening of unbalanced chromosomal rearrangements (copy-number variants; CNV) in a boy with neurodevelopmental disorders and epilepsy.
Project description:The increasing availability and affordability of genetic testing has resulted in the identification of numerous novel variants associated with neurodevelopmental disorders. There remains a need for methods to analyze the functional impact of these variants. Some methods, like expressing these variants in cell culture, may be rapid, but lack physiologic context. Other methods, like making a whole mouse model may provide physiologic accuracy, but are costly and time consuming. We recently developed a technique, Breasi-CRISPR, which results in efficient genome editing of neural precursor cells via electroporation of CRISPR-CAS9 reagents into developing mouse brains. Since Breasi-CRISPR is extremely rapid, and enables the analysis of targeted genes in vivo, we wondered if this technique would accelerate the study of monogenic neurodevelopmental disorders. Here, we use Breasi-CRISPR to model megalencephaly postaxial polydactyly polymicrogyria hydrocephalus (MPPH) syndrome. We found that two days after Breasi-CRISPR, we were able to see neurodevelopmental phenotypes known to be associated with MPPH syndrome including increased cyclin D2 protein abundance and an increase in neural progenitor proliferation. Thus, Breasi-CRISPR can efficiently model MPPH syndrome, and may be a powerful method to add to the toolbox of those investigating the functional impact of patient variants in neurodevelopmental disorders.
Project description:Neurodevelopmental proteasomopathies represent a distinctive category of neurodevelopmental disorders (NDD) characterized by genetic variations within the 26S proteasome, a protein complex governing eukaryotic cellular protein homeostasis. In our comprehensive study, we identified 23 unique variants in PSMC5, which encodes the AAA-ATPase proteasome subunit PSMC5/Rpt6, causing syndromic NDD in 38 unrelated individuals. Overexpression of PSMC5 variants altered human hippocampal neuron morphology, while PSMC5 knockdown led to impaired reversal learning in flies and loss of excitatory synapses in rat hippocampal neurons. PSMC5 loss-of-function resulted in abnormal protein aggregation, profoundly impacting innate immune signaling, mitophagy rates, and lipid metabolism in affected individuals. Importantly, targeting key components of the integrated stress response, such as PKR and GCN2 kinases, ameliorated immune dysregulations in cells from affected individuals. These findings significantly advance our understanding of the molecular mechanisms underlying neurodevelopmental proteasomopathies, provide links to research in neurodegenerative diseases, and open up potential therapeutic avenues.
Project description:We performed a targeted NGS using the commercial gene panel design ClearSeq Inherited Disease (Agilent Technologies) to identify the pathogenic sequence variants in two boys with neurodevelopmental disorders and epilepsy and their unaffected parents
Project description:The ADAT2/ADAT3 (ADAT) complex catalyzes the adenosine to inosine modification at the wobble position of eukaryotic tRNAs. Mutations in ADAT3, the catalytically inactive subunit of the ADAT2/ADAT3 complex, have been identified in patients presenting with severe neurodevelopmental disorders. Yet, the physiological function of ADAT2/ADAT3 complex during brain development remains totally unknown. Here, we investigated the role of the ADAT2/ADAT3 complex in cortical development. First, we reported 21 new neurodevelopmental disorders patients carrying biallelic variants in ADAT3. Second, we used structural, biochemical, and enzymatic assays to deeply characterized the impact of those variants on ADAT2/ADAT3 structure, biochemical properties, enzymatic activity and tRNAs editing and abundance. Finally, in vivo complementation assays were performed to correlate functional deficits with neuronal migration defects in the developing mouse cortex. Our results showed that maintaining a proper level of ADAT2/ADAT3 catalytic activity is essential for radial migration of projection neurons in the developing mouse cortex. We demonstrated that the identified ADAT3 variants significantly impaired the abundance and, for some, the activity of the complex, leading to a substantial decrease in I34 levels with direct consequence on their steady-state. We correlated the severity of the migration phenotype with the degree of the loss of function caused by the variants. Altogether, our results highlight the critical role of ADAT2/ADAT3 during cortical development and provide cellular and molecular insights into the pathogenic mechanisms underlying ADAT3-related neurodevelopmental disorders.
2025-03-05 | GSE278536 | GEO
Project description:GRIN2A-related disorders: genotypes, functional consequences, and phenotypes
Project description:Pharmaceutical agents, such as antiepileptic medications, can cross fetal barriers and affect the developing brain. Prenatal exposure to the antiepileptic drug valproate (VPA) is associated with an increased risk of neurodevelopmental disorders, including congenital malformations and autism spectrum disorder. VPA-treated animal models and neural organoids proposed defects in intracellular mechanisms such as Wnt signaling underlying VPA-induced neurodevelopmental adversities. However, the influence of extracellular mechanisms on these defects remains unexplored. Here, we showed that VPA treatment disrupted ventricular-like regions, suggesting defects in cell-cell and cell-matrix interactions. Transcriptomics analyses confirmed the disruption of ECM secretion as well as intracellular processes related to microenvironment sensing, such as cellular mechanosensing and Hippo-YAP/TAZ signaling pathway. Finally, proteomics analysis corroborated that VPA alters the microenvironment of the human dorsal forebrain organoids by disrupting the secretion of extracellular matrix (ECM) proteins. Altogether, our study suggests VPA-treated dorsal forebrain organoids serve as a model to investigate the role of extracellular processes in brain development and to understand how their disruptions might contribute to neurodevelopmental disorders.