The pre-ovulatory luteinizing hormone surge is followed by down-regulation of CYP19A1, HSD3B1, and CYP17A1 and chromatin condensation of the corresponding promoters in bovine follicles.
The pre-ovulatory luteinizing hormone (LH) surge induces an extensive molecular, physiological, and morphological reorganization of the bovine follicle. This study was designed to elucidate if chromatin modulation is involved in the LH-induced gene regulation. Granulosa and theca of well-characterized large bovine follicles were isolated before and after the LH surge. CYP19A1, HSD3B1, and CYP17A1 transcripts, which encode key enzymes of steroid hormone biosynthesis, were quantified by real-time PCR (qPCR) and the degree of chromatin condensation was determined by DNase I protection assays. After LH, granulosa-specific CYP19A1 and theca-specific CYP17A1 transcripts were almost completely down-regulated. Also, the abundance of HSD3B1 transcripts was reduced. The promoter chromatin of HSD3B1 and particularly of CYP19A1 was significantly less accessible to DNAse I in both cell types after LH, whereas the chromatin accessibility of the CYP17A1 promoter changed only in the theca. Correlation analysis revealed partly, highly significant negative correlations between transcript abundance and protection from DNase I digestion of the corresponding chromatin. The data strongly suggest that LH induces cell type- and gene-specific chromatin condensation in the pre-ovulatory bovine follicle. This epigenetic mechanism might be involved in the pre-ovulatory down-regulation of genes.
Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
Marika
M
Nimz
Marion
M
Spitschak
Rainer
R
Fürbass
Jens
J
Vanselow
D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D007986:Luteinizing Hormone / Q000378:metabolism*; D006080:Ovarian Follicle / Q000254:growth & development / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*
D002843:Chromatin; D007986:Luteinizing Hormone; D015096:3-Hydroxysteroid Dehydrogenases; D019363:Cytochrome P-450 CYP1A1; D013254:Steroid 17-alpha-Hydroxylase