Epigenetic setting for long-term expression of estrogen receptor α and androgen receptor in cells

Epigenetic regulation of the nuclear estrogen and androgen receptors, ER and AR, constitutes the molecular basis for the long-lasting effects of sex steroids on gene expression in cells. The effects prevail at hundreds of gene loci in the proximity of estrogen- and androgen-responsive elements and many more such loci through intra- and even inter-chromosomal level regulation. Such a memory system should be active in a flexible manner during the early development of vertebrates, and later replaced to establish more stable marks on genomic DNA. In mammals, DNA methylation is utilized as a very stable mark for silencing of the ER α and AR isoform expression during cancer cell and normal brain development. The factors affecting the DNA methylation of the ER α and AR genes in cells include estrogen and androgen. Since testosterone induces brain masculinization through its aromatization to estradiol in a narrow time window of the perinatal stage in rodents, the autoregulation of estrogen receptors, especially the predominant form of ER α, at the level of DNA methylation to set up the "cell memory" affecting the sexually differentiated status of brain function has been attracting increasing attention. The alternative usage of the androgen-AR system for brain masculinization and estrogenic regulation of AR expression in some species imply that the DNA methylation pattern of the AR gene can be established by closely related but different systems for sex steroid-induced phenomena, including brain masculinization.