Do rodents have a gene encoding glycogenin-2, the liver isoform of the self-glucosylating initiator of glycogen synthesis?

The discovery of a second human gene, GYG2, encoding a liver-specific isofo rm of glycogenin, the self-glucosylating initiator of glycogen biosynthesis , raised the possibility for differential controls of this protein in liver and muscle. The new protein, glycogenin-2, had several properties similar biochemically to the muscle isoform, glycogenin-1, but unlike glycogenin-1, stable expression in fibroblasts led to a significant overaccumulation of glycogen. Ensuing attempts to generate reagents suitable for use with roden ts, to examine the physiological regulation of glycogenin-2 by nutritional and hormonal factors, have been unsuccessful. Proof of a negative is diffic ult but the weight of the evidence is beginning to mitigate against the exi stence of a second glycogenin gene in rodents leading us to hypothesize tha t the presence of the GYG2 gene is limited to primates.