Tissue specific epigenetic differences in CRH gene expression.

Corticotropin Releasing Hormone (CRH), a 41-amino acid peptide, is a major regulator of hypothalamic-pituitary-adrenal axis function. CRH also has important roles in several processes pertaining to pregnancy and parturition, including being a possible regulator of gestational length and predictor of pre-term birth. Regulation of the CRH promoter exhibits some tissue-specificities, the most well characterized example being glucocorticoids, which can stimulate placental CRH production but suppress hypothalamic CRH. In the last decade there has been growing interest in the role of epigenetic regulation of gene expression. Modification of the structure of chromatin is an example of epigenetic change affecting gene expression. We have found that inhibition of histone deacetylases results in an increase in CRH expression in the AtT20 pituitary cell line, but a decrease in CRH expression in the placenta. In this paper we review tissue specific differences in CRH gene expression, and discuss how epigenetic chromatin modification mechanisms can relate to tissue specific differences in expression of CRH.