ASD-ASSOCIATED CNTNAP2 VARIANTS DISRUPT NEURONAL ARBORIZATION THROUGH IMPAIRED REGULATION BY ECTODOMAIN SHEDDING

Ectodomain shedding (ES) is a process by which a protease cleave the extracellular portion of membrane-bound proteins, releasing soluble fragments that influence diverse cellular functions. ES is critical for neurodevelopment, synaptic plasticity, and neurodegenerative disorders, including Alzheimer’s disease, and has recently been implicated in neurodevelopmental conditions such as autism spectrum disorders (ASD). Contactin-associated protein-like 2 (CNTNAP2 or Caspr2) is an adhesion molecule regulated by ES, releasing a soluble ectodomain (sCNTNAP2) that enhances neuronal synchrony. CNTNAP2 is implicated in ASD, schizophrenia, and cortical dysplasia focal epilepsy syndrome (CDFE) and regulates neuronal connectivity by modulating dendritic arborization and dendritic spine development. However, the impact of CNTNAP2 ES on dendritic architecture and neuroplasticity remains poorly understood.
Here, we show that the brain sheddome is enriched in shed ectodomains involved in neuronal projection regulation and that its composition is modulated by sensory deprivation in a sex-dependent manner, with reduced sCNTNAP2 levels observed specifically in male mice. Furthermore, we demonstrate that sCNTNAP2 promotes dendritic arborization, while ASD-associated CNTNAP2 variants exhibit decreased sCNTNAP2 levels due to endoplasmic reticulum retention or altered processing by the metalloprotease MMP9. These mutations are associated with impaired dendritic branching in neuronal cultures.
Together, our findings highlight ES as a key mechanism regulating neuroplasticity and reveal how CNTNAP2 genetic variation disrupts this process, leading to altered neuronal connectivity. These results provide mechanistic insight into CNTNAP2-related neurodevelopmental disorders and suggest potential therapeutic strategies targeting CNTNAP2 shedding to restore neuronal connectivity.