{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nPTCHD1 is a gene that has emerged as an important contributor to neurodevelopmental disorders, with rare copy number variants, microdeletions, truncating mutations, and missense variants being repeatedly identified in individuals with autism spectrum disorder (ASD) and intellectual disability (ID). These genetic alterations have been detected in multiple studies, where disruptions at the Xp22.11 locus that includes PTCHD1 (often together with nearby genes such as DDX53 and adjacent regulatory noncoding RNAs) were associated with phenotypes ranging from subtle dysmorphic features and developmental delays to prominent behavioral issues and autistic traits."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAt the molecular level, PTCHD1 encodes a transmembrane protein containing a patched-related domain that suggests its involvement in signaling pathways, potentially including the sonic hedgehog pathway. Expression studies indicate that PTCHD1 is predominantly present in brain regions such as the cortex and cerebellum, consistent with its proposed role in neural development and synaptic function. Functional analyses of PTCHD1 missense variants have revealed that some substitutions can impair protein stability, post-translational processing, and folding – although in certain cases the mutant proteins still localize to dendritic regions and retain interactions with postsynaptic scaffolding proteins, such as SAP102."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "7"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nMoreover, neural disease modeling, including studies with induced pluripotent stem cell (iPSC)-derived neural progenitors, has provided further support that both regulatory variants and coding missense changes in PTCHD1 contribute to the pathophysiology of ASD and ID by altering gene expression patterns related to synaptic transmission and neuronal signaling. Together, these findings indicate that although the precise biochemical functions of PTCHD1 remain to be fully delineated, its normal activity is critical for proper synaptic organization and neurodevelopment, and its disruption may be a key risk factor in a subset of neurodevelopmental disorders."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Dalila Pinto, Alistair T Pagnamenta, Lambertus Klei, et al. 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