Effect of mouse genotype on DNA methylation and developmental competence of oocytes exposed to in vivo heat stress

Abstract

In mammals, the growth and maturation of the oocyte require a series of coordinated events that allows fertilization and embryonic development. Exposure of oocytes to adverse environmental conditions compromises cellular and molecular events during oogenesis, reducing oocyte competence. Although the cellular effects caused by heat stress on mammalian gametes have been well studied, little is known about the heat-induced changes in the epigenetic profile of the oocyte. Therefore, the objective of this project is to determine the effect of genotype on the response of mice oocytes exposed to in vivo heat stress. It has been demonstrated that the strains of mice show differences in reproductive performance and susceptibility to environmental factors. Thus, the model of heat stress using an environmental chamber will be established using C57BL / 6 and CD1-Swiss mice strain to determine the effect of heat stress on the DNA methylation pattern and oocyte competence. Six mice couples of each strain will be mated and on day 10th postnatal, the mothers and their litters will be placed in environmental chambers with controlled temperature: control (21°C / 24h) and heat stress (35°C / 12h during the light period and 21°C / 12h during the dark period) for 11 days. This window from the 10th to the 21st day postnatal represents a major wave of DNA methylation during mice oogenesis. After the 21st, the litter will be weaned and kept at the control temperature until puberty. On a postnatal day 35, females will be superovulated with intraperitoneal administration of 10 IU ECG and 10 IU hCG with an interval of 48 hours. On postnatal day 38 (P38), the oocytes will be collected to determine DNA methylation profile by immunofluorescence and subjected to parthenogenetic activation to determine oocyte competence. (AU)