Deficiency of glycogenin-1 is detected in the sequence of the glycogenin-1 gene, GYG1, which revealed a non-sense mutation in one allele and a missense mutation, Thr83Met, in the other. The missense mutation resulted in inactivation of the autoglycosylation of glycogenin-1, which is necessary for the priming of glycogen synthesis in muscle.
Autoglycosylation of glycogenin-1 occurs at Tyr195 by a gulose-1-O-tyrosine linkage. An induced missense mutation of this residue results in inactivated autoglycosylation. However, missense mutation affecting some other residues of glycogenin-1 has also been shown to eliminate autoglycosilation.