Investigating Post-translational Changes of Histones, DNA Methylation Level, and ERβ Protein Level in the Cumulus Cell Genome of Infertile Women with Endometriosis

Among the important factors affecting female infertility, endometriosis (with a prevalence rate of up to 50% in infertile women) has a special place. Endometriosis, which is known as the presence of endometrial glands and stroma outside the uterine tissue, causes a wide range of functional disorders in the process of follicular development and changes in the follicular microenvironment, which ultimately leads to the creation of an egg that is of suitable quality for the formation of The fetus does not have Therefore, the aim of the present study was to determine and investigate post-translational changes of histones, DNA methylation level and ERβ protein level in the genome of cumulus cells of infertile women with endometriosis.

The present case-control study was conducted at the infertility treatment clinic of Royan Research Institute in 2014. Twenty-four patients were divided into two equal groups. Cumulus cells were obtained from 12 infertile patients with endometriosis and 12 women with male factor infertility (as a control group) under ovulation stimulation protocols for intracytoplasmic sperm injection. Extraction of chromatin from cumulus cells was done after stabilization of DNA binding proteins and then cell lysis and preparation of soluble chromatin. The binding and incorporation levels of MeCP2 protein (as DNA methylation marker), two epigenetic markers related to histone modifications (H3K9me2 and H3K9ac), and ERβ protein to chromatin of cumulus cells were evaluated using the corresponding primary antibodies, secondary antibodies conjugated and Nucleosome-ELISA technique. Data were analyzed using independent t-test t and Levene's test.

MeCP2 protein incorporation into DNA was significantly higher in the endometriosis group than in the control group. The level of two epigenetic marks H3K9ac and H3K9me2 in the chromatin of cumulus cells of the patient group showed a significant increase compared to the control group (P<0.05). In addition, an increased level of binding of ERβ protein to the genome was observed compared to the control group.

Epigenetic changes, including histone hyperacetylation and hypermethylation, and DNA hypermethylation of the whole genome of cumulus cells of patients with endometriosis had occurred, accompanied by an increase in the level of ERβ protein binding.