Acetilação das histonas e sua relação com a aquisição da competência em ovócitos bovinos

Abstract

Considering that in cattle many of the oocytes aspirated and used for the in vitro production of embryos (PIVE) have not yet acquired the competence for the development one must look for alternatives that can increase this competence and, consequently, the efficiency of the PIVE. Histone acetylation regulates gene transcription and appears to be related to the acquisition of oocyte competence. However, little is known if altering the status of histone acetylation, it is possible to alter the competence level of oocytes. The aim of this study was to determine the histone acetylation pattern in oocytes of different abilities before, during and after in vitro maturation (IVM), and to evaluate whether the use of scriptaid (HDAC inhibitor) before and after meiosis resumption development competence. In article 1, cumulus-oocyte complex (COCs) were obtained from follicles 1-3mm, considered less competent (IC) and 6-8mm, more competent (CP). Oocytes from both groups were removed from the IVM at 0, 8 and 24h for gene expression evaluations (HAT1, KAT2A, HDAC1, HDAC2, HDAC3) and immunofluorescence. Although the acetylation level was not different in oocytes of different abilities (P> 0.05), the CP group presented transcription of the HAT1 gene from 0 to 8 hours (P <0.05), and higher amount of HDAC1 transcripts at 8 hours in relation to the IC group (P <0.05). In article 2 COCs were submitted to pre-maturation (PIVM) for 6 hours in the presence or absence of scriptaid (HDAC inhibitor). COCs were distributed in 5 groups: T1-MIV for 22h, T2-PIVM for 6h and IVM for 22h, T3-PIVM with scriptaid for 6h and MIV for 22h, T4-PIVM for 6h and MIV with scriptaid for 22h, and T5- PIVM with scriptaid for 6h and MIV with scriptaid for 22h. Nuclear maturation, gene expression, cumulus cell expansion, and embryonic development and quality were analyzed. Only the HAT1 gene showed expression difference in oocytes from different treatments. In relation to the embryonic development in D7, T4 and T5 presented lower rates of blastocysts (P <0.05) in relation to the other treatments. No effect was observed when the scriptaid was used in less competent oocytes (P> 0.05). We conclude that the gene expression pattern of histone acetylation related genes is related to oocyte competence. However, using scriptaid during PIVM and/or IVM does not improve development competence.