Monoallelic and biallelic KDM5A variants identified in patients with autism spectrum disorder.

Chromatin regulation is critical for neurodevelopment, and its disruption has emerged as a key pathogenic mechanism in neurodevelopmental disease, including autism spectrum disorder (ASD), a condition known for genetic and phenotypic heterogeneity. We previously identified an ASD gene, KDM5A, encoding a histone H3 lysine 4 demethylase, and reported de novo and inherited variants in nine individuals with severe ASD and other neurodevelopmental phenotypes. Here, we expand the genetic and phenotypic spectrum of KDM5A-related neurodevelopmental disorders and investigate the functional impact of identified variants. Through international collaborations, we assembled a cohort of 24 additional individuals from 21 families with rare, protein-altering KDM5A variants. All individuals presented with severe speech impairment and intellectual disability, often alongside ASD and other neurodevelopmental features. The variants include missense, nonsense, frameshift, and splice site, distributed across nearly all functional domains of the protein. Structural modeling revealed localized conformational disruptions, particularly at conserved residues in enzymatic or chromatin-interacting domains. For a subset of variants, we demonstrated reduced KDM5A protein levels in cell lines derived from affected individuals. Transcriptomic profiling revealed variant-specific gene expression changes, most pronounced in variants affecting the PLU1 chromatin-binding motif and the Jumonji C domain of the enzymatic core. American College of Medical Genetics and Genomics-guided reclassification supported pathogenicity for the majority of variants, including multiple upgrades from uncertain significance to pathogenic or likely pathogenic. Together, these findings implicate diverse KDM5A alleles in a rare but recurrent form of ASD and establish KDM5A as a key regulator of neurodevelopment and chromatin-mediated ASD pathogenesis.