Expression of the Myogenin-LacZ Reporter Gene Introduced into Embryonic Stem (ES) Cells In Vitro

The mouse myogenin gene regulatory region carrying the β-galactosidase (LacZ) gene was fused to a neomycin resistant gene, and introduced into ESD3 embryonic stem (ES) cells by electroporation. Transfected cells were expanded, and Southern hybridization was performed using the LacZ DNA sequence as a probe. The sublines of transformed cells were selected by karyotype analysis and by their ability to form embryoid bodies (EBs); some sublines were used for analysis of the transgene expression. The transgene was not expressed by the transformed cells in an undifferentiated state. In suspended EBs produced in hanging drops, the transgene was expressed within certain limited parts of the EBs. In some EBs, the transgene was expressed as patches in the edge of simple embryoid bodies (SEBs) and in the inner wall of cystic embryoid bodies (CEBs). In the differentiation culture system, the transgene was expressed at a cellular level, and polarization of the cells which expressed LacZ was observed. The results suggest that our sublines could be useful as skeletal muscle-specific cell markers for analysis of mouse myogenesis.