Posttranslational palmitoylation in brain development and disease

Two percent of all patients with X-linked intellectual disability (XLID) exhibit loss-of-function mutations in the palmitoylating enzyme, ZDHHC9. One of the main anatomical deficits observed in these patients is a decrease in corpus callosum volume and a disruption of white matter integrity. We demonstrated that ablation of Zdhhc9 in mice substantially impairs the maturation of oligodendrocytes and a concomitant decrease in the density of myelinated axons. Ultrastructural analysis of the remaining myelinated axons in the corpus callosum revealed further disruptions in myelin integrity. RNA sequencing and proteomic analyses revealed a concomitant decrease in the expression of genes and proteins involved in lipid metabolism, cholesterol synthesis and myelin compaction. These results reveal a previously underappreciated and fundamental role for ZDHHC9 and protein palmitoylation in regulating oligodendrocyte maturation and myelinogenesis and provide mechanistic insights into the deficits observed in white matter volume in patients with mutations in ZDHHC9.