Tissue-specific characterisation of DNA methylation in the gonad-specific proto-oncogene, c-mos, in the male laboratory mouse.

The proto-oncogene, c-mos, which is expressed only in the germ cells of both testis and ovary, plays an important role in meiotic maturation of these cells. In this research, the methylation status of several CpG sites, present both upstream and within the coding region of the c-mos gene, has been studied. The HpaII and HhaI sites examined in the 5' half of the coding region were unmethylated in both the c-mos expressing and non-expressing tissues. A HhaI site, h3, present 380bp downstream of the transcription start site, was unmethylated in germ cells, but was partially methylated in the somatic tissues, inversely correlating with the expression status of the gene. In contrast to these tissues, in the mouse fibroblast cell line L929, all the analysed sites were completely methylated.