Epigenética do desenvolvimento inicial em bovinos e as técnicas de reprodução assistida

Abstract

Epigenetics is an area of genetics that studies the heritable modifications in gene expression and phenotype that are not controlled by the primary sequence of DNA. The main epigenetic mechanisms are DNA methylation, post-translational covalent modifications in histone tails, and non-coding RNAs. During the early mammalian development, two global waves of epigenetic reprogramming occur. The first one occurs during the prenatal phase of gametogenesis and the second one begins immediately after fertilization. Environmental factors such as exposure to chemicals, nutrition, behavioral factors, stress, in vitro culture conditions, can influence the epigenetic reprogramming during early development. In this review, we describe the main epigenetic marks and the epigenetic events such as the genomic imprinting and X chromosome inactivation that occur during the early mammalian developmet. Moreover, we discuss the detrimental effects of cloning procedure on the establishment of the epigenetic patterns and some molecular alternatives to minimize these negative impacts.