Promoter-2-derived Cyp19 expression in bovine granulosa cells coincides with gene-specific DNA hypo-methylation.

Cyp19, the key gene of oestrogen biosynthesis, is expressed at very different concentrations and from different promoters in bovine granulosa cells (GCs) and in pregnant corpora lutea (CL), respectively. The present study was aimed to investigate if DNA methylation and thus epigenetic mechanisms might play a potential role in the regulation of Cyp19 expression and promoter-specific activity in GCs of cycling versus CL of pregnant cows. It was demonstrated that GCs express high concentrations of promoter-2-derived Cyp19 transcripts whereas CL samples isolated before and after implantation, and at the end of the first trimester, showed very low Cyp19 transcript concentrations, all of them derived from promoter 1.1. Two genomic regions including promoter 1.1 and promoter 2 were largely unmethylated in GCs but methylated in all CL samples. The data suggest that promoter-2-derived high-level expression but not promoter-1.1-derived low-level expression of Cyp19 might be controlled by cell-type-specific DNA methylation.