Padrão de metilação do gene XIST e da ICR/H19 em ovócitos imaturos e maturados in vitro de porcas cíclicas e marrãs pré-púberes

Abstract

The reproductive age of the female is one of the factors that affects the in vitro embryo production. It is known that oocytes from prepubertal females compared to cycling females have lower developmental competence. Therefore, it is important to better understand the aspects causing this lesse competence to achieve better efficiency of the IVP. In this research, the methylation pattern of the XIST gene and the ICR/H19 of oocytes obtained from prepubertal gilts (g) and cycling sows (s) were compared. Regarding the ICR/H19, there were no differences for methylation levels among the groups. The methylation percentage were: gGV (36.15 ± 8.6%), sGV (30.14 ± 7.2%), gMII (17.35 ± 6.7%) and sMII (19.96 ± 6,9%). However, when compared to the control (spermatozoa - 94.3 ± 1.04%), gMIII and sMII were less methylated (p=0.0001). These data confirm the imprinted pattern of the gene, with spermatozoa highly methylated and MII oocytes hypomethylated. The XIST gene showed different methylation pattern when comparing gGV (17.29 ± 5.8%) and sGV (48.81 ± 9.6%) groups (p=0.0305), gGV and gMII (0.28 ± 0.2%) (p=0.0342) and gMIII and sMII (82.35%) (p=0.0001). However, to the spermatozoa (0.42 ± 0.42%), sMII oocytes comparing were different (p = 0.0001). These data confirm that this region of the XIST also exhibits an imprinted pattern, with spermatozoa demethylated and the oocytes highly methylated. In addition, results showed that less competent oocytes, from gilts, were unable to correctly reprogram the methylation pattern of this region of XIST after in vitro maturation. Thus, it is suggested that this region of XIST has potential to be used as an epigenetic molecular marker for oocyte competence, since the less competent oocytes exhibit an altered methylation pattern than that what is expected for a matured competent oocyte.