Investigation of Neural Pathogenic Mechanisms Associated with Congenital Disorders of Glycosylation

Icahn School Of Medicine At Mount Sinai, New York NY

Investigators

Abstract

PROJECT SUMMARY / ABSTRACT Congenital disorders of glycosylation (CDG) are rare inherited metabolic diseases that disrupt protein glycosylation, leading to severe neurological impairments such as developmental delay, seizures, and motor dysfunction. Despite their impact on the central nervous system, few treatments target these neurological issues. Using human cortical organoids (hCOs) derived from patient-specific induced pluripotent stem cells (iPSCs), we aim to mechanistically explore glycosylation defects, metabolic dysregulation, and neuronal dysfunction in two key CDG types: PMM2-CDG and ALG13- CDG. The proposed project synergistically builds on findings from zebrafish and fruit fly models of CDG. By integrating data from three complementary disease models, we seek to uncover novel mechanisms and identify therapeutic targets to address these debilitating conditions. In Specific Aim 1, we focus on PMM2-CDG, the most common subtype, where our preliminary studies identified significant disruptions in sugar and glycogen metabolism in patient-derived cortical organoids. We will investigate whether inhibition of GSK3β, a regulator of glycogen metabolism, can restore glycogen homeostasis and improve neurogenesis and neuronal network function in PMM2-CDG organoids. We will also test the role of Glut1 glycosylation in PMM2-CDG by knocking out endogenous Glut1 and replacing it with a non-glycosylatable Glut1 variant to assess the impact on neuronal and metabolic function. In Specific Aim 2, we focus on ALG13-CDG, characterized by severe neurological symptoms, including frequent seizures. We hypothesize that glycosylation defects in ALG13-CDG disrupt excitatory/inhibitory synaptic balance, contributing to seizure development. Using patient-derived cortical organoids, we will perform multi-omic analyses, including glycoproteomics and transcriptomics, to identify key dysregulated pathways in neuronal signaling and synapse formation. In addition, we will test the therapeutic potential of Topiramate, an anti- epileptic drug, which may restore neuronal function by enhancing glycosylation through Golgi and ER acidification. The impact of this research will be substantial in identifying molecular mechanisms driving neuronal dysfunction in PMM2-CDG and ALG13-CDG, with a focus on GSK3β signaling, Glut1 glycosylation, and glycosylation defects in synaptic balance. These findings may lead to the development of novel therapies, including GSK3β inhibitors and topiramate, to improve neuronal function and reduce seizures in CDG patients.