Genome-wide identification of aberrantly methylated promoters in ovarian tissue of prenatally androgenized rats

Abstract

Objective: To identify aberrantly methylated candidate genes that are involved in the development of polycystic ovary syndrome (PCOS).

Design: Animal model.

Setting: University-affiliated laboratory.

Animal(s): Sprague-Dawley rats.

Intervention(s): The prenatally androgenized (PNA) rat model was established. Pregnant rats were treated with daily SC injections of T propionate during late gestation, and their female offspring were studied as adults.

Main outcome measure(s): Serum glucose and hormone levels, ovary morphology and cell apoptosis, genome-wide CpG methylation, and expression of caspase-3 protein were measured.

Result(s): In the PNA group, the levels of serum glucose, 17-hydroxyprogesterone, and T were significantly higher when compared with the control group. Ovarian morphology showed increased atretic follicles and cystic follicles. Using the MeDIP-chip approach, we identified 528 genes that were hypermethylated in PNA ovaries. Gene ontology analyses revealed that these genes are involved in a variety of reproductive development and biological processes. The methylation enrichments of Bcl2l1 and Scr5a1 observed in the PNA group by MeDIP-quantitative polymerase chain reaction assay were significantly higher than those obtained from the control group. Furthermore, the mRNA level of the Bcl2l1 gene was significantly decreased in the PNA group. The percentage of caspase-3-positive cells in the PNA group was obviously higher compared with the control group, by terminal deoxynucleotidyl transferase dUTP nick end labeling detection as well.

Conclusion(s): DNA methylation alteration may be an important factor affecting the genes involved in the pathophysiological processes that result in the phenotype of PCOS.

Keywords: DNA methylation; Polycystic ovary syndrome; epigenetics; prenatal androgenization.