MOLECULAR AND FUNCTIONAL CHARACTERIZATION OF <EM>CCDC32</EM>: A TDARK GENE ASSOCIATED WITH A RARE SYNDROMIC INTELLECTUAL DISABILITY

Coiled-coil domain-containing protein 32 (CCDC32), also known as C15orf57, is a small 185 amino acid protein whose molecular function is still unknown. Homozygous loss-of-function mutations cause a severe congenital cardio-facial-neurodevelopmental syndrome (CFNDS) characterized by intellectual disability and developmental abnormalities that resembles ciliopathy-like syndromes. Genome wide co-essentiality and mass spectrometry analyses in non-neuronal cells have linked CCDC32 to the Adaptor Protein complex 2 (AP2), suggesting a role in clathrin-mediated endocytosis and vesicular trafficking. Thus, CCDC32 may serve as an interface between primary cilium-related pathways and the endocytic processes that influence neuronal morphology and connectivity.
Our preliminary data support its neuronal role: quantitative RT-qPCR in rats shows that CCDC32 is strongly enriched in cortex and hippocampus compared to other organs. High-resolution imaging show protein localization at the base of dendritic spines, along axons, within dendrites, and in the soma, thus the specific localization and role of CCDC32 in neurons remains to be elucidated.
We are currently developing a CRISPR-Cas9-mediated knockout strategy to investigate how the loss of this protein may affect neuronal organization and function, by combining functional readouts of endocytic pathways with analyses of synapse morphology, number, and nanoarchitecture. In parallel, we will define the molecular interactome of CCDC32 through IP-MS, to identify partners and pathways that may link CCDC32 to endocytic control.
In addition to advancing our understanding of a rare genetic disorder, this project may have the potential to reveal fundamental neurobiological mechanisms with broader implications for brain health and disease.