Neurological pathophysiology of disrupted O-glycosylation in congenital disorders of glycosylation - PROJECT SUMMARY/ABSTRACT Glycosylation is an essential, post-translational modification with complex and poorly understood roles in protein function. My lab’s long-term objective is to elucidate the neurobiological functions of glycosylation, including identifying the roles of critical glycosylation sites in neuronal protein function. The importance of glycosylation is emphasized by the congenital disorders of glycosylation (CDG), a group of genetic disorders that disrupt cellular glycosylation machinery. Affected patients exhibit severe neurological deficits, including epilepsy and developmental delay. The genetic basis of CDG provides an opportunity to identify the neurobiological functions of glycosylation using mouse models and human cells and organoids to identify and manipulate glycosylation events to determine the roles of individual glycans on specific glycoproteins. Understanding glycosylation in the nervous system will elucidate the pathophysiology of CDG and other neurological diseases, enable therapeutic advances targeting glycosylation pathways, and inform normal function of glycosylation. GALNT2-CDG is a new CDG type caused by biallelic mutations in GALNT2, which encodes a critical glycosyltransferase initiating the first step in mucin-type O-glycosylation. GALNT2-CDG patients suffer from epilepsy and global developmental delay. Galnt2 whole body knock-out and conditional pan-neuronal knock- out mice recapitulate many of the patient neurological deficits. My central hypothesis is that loss of site-specific O-glycosylation in neurons impairs protein function contributing to the neurological deficits observed in Galnt2 KO mice and GALNT2-CDG patients. The specific objective of this proposal is to identify the roles of GALNT2- mediated O-glycosylation in neurological function and disease. This will be achieved by genetically dissecting the neurological circuit dysfunction in GALNT2-CDG cKO mice, using state-of-the-art glycoproteomics advances in instrumentation, experimental methodologies, and computational approaches to identify O- glycoproteome disruption, and determining the pathogenic impacts of disrupted O-glycosylation events using human induced neurons (iNeurons) and brain organoids. Successful completion of these aims will establish critical normal functions of GALNT2-mediated O- glycosylation and elucidate glycosylation-related pathophysiology of human neurological diseases, potentially enabling therapeutic advances.
