Gm7325 is MyoD-dependently expressed in activated muscle satellite cells.

The Gm7325 gene, bioinformatically identified in the mouse genome, encodes a small protein but has not been characterized until recently. Our gene expression analysis revealed that Gm7325 transcription is remarkably upregulated in injured skeletal muscle tissues. Activated satellite cells and immature myotubes were densely decorated with positive signals for Gm7325 mRNA in in situ hybridization analysis, while no obvious signals were observed in quiescent satellite cells and mature myofibers. In the 5'-flanking regions of mouse Gm7325 and its human homologue, conserved E-box motifs for helix-loop-helix transcription factors are repeatedly arranged around the putative promoter regions. Reporter gene assays suggested that MyoD, a master transcription factor for myogenesis, binds to the conserved E-box motifs to activate Gm7325 expression. Therefore, Gm7325, as a novel MyoD-target gene, is specifically induced in activated satellite cells, and may have an important role in skeletal myogenesis.