Molecular cloning and developmental expression of rat glycogenin in cardiac tissue

Glycogenin is a self-glycosylating protein required to initiate glycogen bi osynthesis. Utilizing the differential display technique to analyze changes in gene expression during early postnatal cardiac development, we have iso lated and cloned a 484 bp cDNA fragment that corresponds to the 3' end of r at glycogenin. Northern blot analysis on neonatal cardiac tissues demonstra ted hybridization to a 1.7-1.8 kb transcript, which was highly expressed at 3 days and at progressively reduced levels at 1, 2, 3 and 4 weeks of age. A 1624 bp fragment of rat glycogenin was cloned by RT-PCR that includes a 1 002 bp open reading frame encoding a 333 amino acid protein. At the nucleot ide level, rat glycogenin exhibited 87.2 and 83.6% identity with human and rabbit glycogenin over the open reading frame. The deduced amino acid seque nce showed 86.7 and 83.4% identity with human and rabbit sequences, respect ively. Given the significance of glycogenin in glycogen biosynthesis, the r esults of this study suggest a possible molecular basis for the regulation of glycogen during early postnatal cardiac development. In addition, the nu cleotide and amino acid sequences of rat glycogenin may be used to investig ate the physiological and pathophysiological roles of glycogenin in rat tis sues.