Regulação epigenética no desenvolvimento embrionário inicial e reprogramação celular na clonagem por transferência nuclear

Abstract

Recent studies highlight the role of epigenetic changes during reproductive events, from the formation of gametes to fertilization and early embryo development. In these processes, a dynamic epigenetic regulation is observed and is thought to be determinant for the subsequent development. Recent studies have identified several molecules and genes that catalyze the addition and removal of epigenetic modifications in an active way. Therefore, in the first study, several genes coding for histone demethylases were characterized during initial embryo development in bovine and porcine species. Embryos produced by in vitro fertilization and somatic cell nuclear transfer were used. A significant increase in the expression of several demethylases during embryo genome activation period was observed in both species. In addition, the expression of such genes was altered in embryos produced by nuclear transfer. The obtained results have identified that histone demethylase enzymes may have an important role during early embryo development. Moreover, the aberrant expression of such genes may be related to an incomplete cellular reprogramming in cloned embryos. In a second study, the effect of the association between a deacetylase inhibitor, a molecule that promotes histone acetylation, and an inhibitor of transcriptional activity on embryonic development in cloned embryos was evaluated. The treatment was able to improve embryo development. In addition, the expression of several histone demethylases previously characterized in the first study was assessed. The treatments were able to modulate the expression of some histone demethylases, showing a pattern of expression similar to fertilized embryos. In the final study, a functional assessment was performed with a lysine demethylase that was previously showed to have a peak of expression during genome activation in bovine and porcine species. Knockdown of KDM7A gene expression was performed by interference RNA microinjection. The knockdown effect resulted in impaired embryo development, altered levels of histone methylation and affected the expression of key pluripotency genes. Altogether, data presented in these studies provided evidence that epigenetic modulators, such as, lysine demethylases play important roles on embryo development and cell reprogramming in cloned embryos.