POMGNT1 and muscle-eye-brain disease: Defects in protein O-mannosylation due to loss-of-function (LoF) POMGNT1 variants also produce disturbances in assembling and organizing the basal membrane in the neuroretinal system [1], as seen in typical characteristics of muscle–eye–brain disease (MEB), which is mainly characterized by the co-occurrence of myopathy, structural brain abnormalities, and retinal dystrophy.