Nuclear receptor peroxisomal proliferators activated receptors-gamma ligands decrease histone acetylation and attenuate CYP19 gene expression by chromatin remodeling in buffalo (Bubalis bubalis) granulosa cells

Abstract

Objective

Role of peroxisomal proliferator activated receptors-gamma (PPARγ) in regulating fertility establishes it as novel signal for the integration of energy balance and reproduction. PPARγ ligands are known to down regulate CYP19 gene expression, a candidate gene encoding rate-limiting enzyme aromatase involved in estradiol-17β biosynthesis. It has been well established that CYP19 gene is regulated epigenetically during folliculogenesis and luteinization. In the present study, we investigated if PPARγ ligands epigenetically regulate CYP19 gene.

Methods

The total acetylation of histone H3 (K9/14) and difference in enrichment of acetylated histone H3 (K9/14) on CYP19 gene promoter were analyzed by western analysis and ChIP assay, respectively.

Results

Result showed that acetylated histone H3 (K9/14) is down-regulated in granulosa cells treated with PPARγ ligands, whereas its expression was reversed when cells were treated with PPARγ antagonist. To validate further, analysis of histone modification under basal and treated conditions using a ChIP assay revealed that the CYP19 gene proximal promoter (PII, known to be ovary-specific promoter) was 450 and 550 fold more enriched with acetylated histone H3 (K9/14) in control and antagonist (GW9662) treated cells, respectively, than the ligand treated cells. The present study demonstrated that CYP19 gene proximal promoter (PII) was more accessible to transcription in control than treated cells.

Conclusion

In conclusion, the present findings provide a novel mechanistic insight into nuclear receptor PPARγ mediated decrease in acetylated histone H3 (K9/14) which in turn remodel chromatin through histone modification and regulate key steroidogenic gene in buffalo granulosa cells.