SYVN1 and cerebellar ataxia: Mutations in SYVN1 and SEL1, the genes encoding HMG-CoA reductase degradation 1 homolog (HRD1), an ubiquitin ligase, and SEL1, an HDR1 interactor, can cause NDDs such as ID, ataxia, and facial dysmorphisms by distinct mechanisms, including deficient substrate recruitment, SEL1L-HRD1 complex formation, and HRD1 activity [28].