Recent insights into the implications of UGDH mutations for human developmental disease

Congenital disorders of glycosylation are a significant underlying cause of developmental and epileptic encephalopathy (DEE). A subset of these DEE cases results from biallelic variants in the unique, essential gene encoding UDP-glucose dehydrogenase (UGDH). The UGDH enzyme catalyzes two successive NAD+- dependent oxidation reactions to convert the C6 hydroxyl of UDP-glucose to a carboxylate, generating the UDP-glucuronate product. This product is required for three critical reactions that generate: (1) hyaluronan, (2) secreted and cell surface proteoglycans, and (3) glucuronide conjugates for cellular detoxification. UGDH polymorphisms are not frequently observed as they are largely deleterious. However, a number of UGDH variants have been reported and characterized as causative agents of congenital defects in cardiac valve and brain development, and most recently of dystroglycanopathy. The effects of these mutations, clinically and at the molecular level, are summarized and discussed in this review.