O-GlcNAcylation Modulates Expression and Abundance of N-Glycosylation Machinery in an Inherited Glycosylation Disorder

Much of the N-glycosylation machinery was identified decades ago, but the regulatory mechanisms influencing normal and disease states are only beginning to be discovered. Recent studies highlight a role for key metabolites and metabolic enzymes in this process, revising the view of the relationship between different metabolic pathways. Using a multi-omic approach in a zebrafish, we discovered a mechanism where O-GlcNAcylation directly influences the expression and abundance of two enzymes essential for the earliest steps of N-linked glycosylation, the nus1-encoded NgBR and Dpagt1. Here we show that phosphomannomutase (pmm2) deficiency is associated with increased levels of UDP-GlcNAc and protein O-GlcNAcylation. Biochemical studies show that O-GlcNAc modification of the NgBR and Dpagt1 increases their abundance in pmm2m/m mutants. Modulating O-GlcNAc levels, NgBR abundance or Dpagt1 activity exacerbated cartilage phenotypes in pmm2 mutants, suggesting that O-GlcNAc mediated increases in the N-glycosylation machinery protects against more severe pathology. These findings highlight nucleotide-sugar donors as metabolic sensors that coordinate two different glycosylation pathways, demonstrating how their interplay is relevant to disease outcome in the most common congenital disorder of glycosylation. We did bulk total RNA-seq with ribo-depletion of whole zebrafish larvae at 2 ages- 5dpf and 8dpf for two genotypes- wildtype WT and Mutant where the mutant is a loss of function of Pmm2. Each sample consisted of 15 larvae and we sequenced 5 biological replicates per genotype and age combination.