Estrogen receptors and their genes--potential markers of functional and production traits of farm animals.

Estrogen receptors, similarly as other nuclear receptors, are transcription factors, which after binding to a proper ligand (17beta-estradiol, estron or estriol) are capable of regulating transcription of target genes. Due to the functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered as candidate markers for production and functional traits in farm animals. Known are two isoforms of the estrogen receptor-alpha and beta. They are encoded by separate genes located on different chromosomes. The typical feature of all genes coding for nuclear receptors, including the ER genes, is the complex structure of their 5' regions. In the 5' region of the ERalpha gene of different species are located alternative exons that code for transcripts of different length with different 5'-UTR (untranslated region). The mRNA variants are created by the alternative splicing of the primary transcripts. We sequenced a 2853 bp of the bovine ER gene 5' region, including exons A, B, C and their promoters. Moreover, we found several polymorphic sites, differing by single nucleotide substitutions (SNPs), in the 5' regulatory region and in the coding region of the bovine ERalpha gene.