O-glycosylation mechanisms of neurological deficits in congenital disorders of glycosylation

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PROJECT SUMMARY/ABSTRACT Glycosylation is an essential, post-translational modification with complex and poorly understood roles in protein function. My 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. The genetic basis of CDG provides an opportunity to identify the neurobiological functions of glycosylation using mouse models and glycoproteomics. Understanding glycosylation in the nervous system will elucidate the pathophysiology of CDGs 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 constitutional knock-out mice recapitulate many of the patient neurological deficits. My central hypothesis is that site-specific loss of O-glycosylation on neural proteins contributes to neurological dysfunction. The specific objective of this project is to identify the cause of neurological dysfunction in GALNT2-CDG. This will be achieved by determining cellular origins of Galnt2 deficiency-mediated neurological deficits using Cre-mediated deletion of Galnt2 in neural cells and by identifying disrupted O-glycosylation in these cells using glycoproteomics. This proposed five-year career development plan focuses on achieving four objectives: develop research skills in mouse models and glycoproteomics, increase my knowledgebase in neuroscience and glycobiology, establish a body of work focusing on the role of glycosylation in the context of neurobiology, and obtain the necessary skills to transition to independence. Mentoring will be provided by Dr. Zhaolan Zhou, a recognized leader in the development and investigation of mouse models of genetic disorders that affect brain development and function, and Dr. Benjamin Garcia, a recognized expert in developing quantitative mass spectrometry techniques to interrogate post-translational modifications. The skill set developed through these investigations and career development plan will make me uniquely poised to uncover glycosylation-mediated mechanisms of CDG and other neurological diseases, as well as to elucidate the critical roles of glycosylation in human neurological function. These studies will generate new tools and a foundation to establish a long-term research program to investigate the pathophysiology of various glycosylation-related disorders in the nervous system and prepare me to become an independent R01-funded physician scientist.