Effects of oocyte vitrification on histone modifications

Abstract

Vitrification has been widely used as an assisted reproductive technology in animals and humans, yet the impact of oocyte vitrification and warming on survival and histone modifications has to be evaluated. In the present study, the survival of mouse MII oocytes was assessed after freezing, as were changes in histone 3 lysine 9 (H3K9) dimethylation, histone 4 lysine 5 (H4K5) acetylation and histone 3 lysine 14 (H3K14) acetylation. The results show that, in oocytes subjected to vitrification, H3K9 methylation and H4K5 acetylation were increased. H3K14 acetylation could not be detected in either non-vitrified or vitrified oocytes. Oocytes are very sensitive to changes in H3K9 and H4K5 following vitrification. Both these histone modifications could be useful markers to monitor epigenetic perturbations induced by various experimental vitrification protocols and eventually for optimising the cryopreservation of human oocytes.

Cryopreservation of mammalian oocytes and embryos: current problems and future perspectives

“…In contrast, vitrification has been found to reduce gene methylation in mouse oocytes [113], embryos [112], and fetuses [117]. However, other studies have demonstrated that vitrification significantly increases gene methylation in mouse oocytes [116] as well as bovine two cell embryos and the resulting in vitro-derived blastocysts [111]. Regarding the effects of vitrification on acetylation patterns, several studies have indicated that vitrification significantly alters acetylation patterns in oocytes [92,114,116,118,120].…”

“…However, other studies have demonstrated that vitrification significantly increases gene methylation in mouse oocytes [116] as well as bovine two cell embryos and the resulting in vitro-derived blastocysts [111]. Regarding the effects of vitrification on acetylation patterns, several studies have indicated that vitrification significantly alters acetylation patterns in oocytes [92,114,116,118,120]. The conclusions of these studies are somewhat contradictory, suggesting that the effects of vitrification on gene methylation patterns vary in a manner dependent on species, developmental stage, and genes, and may also depend on the size of the analyzed genomic regions [110].…”

Insufficient histone-3 lysine-9 deacetylation in human oocytes matured in vitro is associated with aberrant meiosis

“…Environmental factors can also alter the pattern of histone modification in oocytes. For example, vitrification followed by thawing of oocytes has been show to increase dimethylation of lysine-9 of histone-3 (H3K9) as well as acetylation of lysine-5 of histone-4 (H4K5) (17).…”

Effect of 5-aza-2′-deoxycytidine on methylation of the putative imprinted control region of H19 during the in vitro development of vitrified bovine two-cell embryos

“…Vitrification significantly increased the putative ICR methylation level of H19 in bovine two-cell embryos (71.4% AE 5.7% vs. 60.7% AE 3.5%), which was similar to the H3K9 methylation level found in vitrified mouse oocytes (18). These experiments demonstrated that vitrification significantly increased the methylation level in vitrified embryos or oocytes after immediate warming.…”

“…Researchers have investigated the effect of cryopreservation on DNA methylation in mammalian oocytes (7,(18)(19)(20), embryos (6), and oocytes from cryopreserved ovaries (21), and obtained conflicting results. In addition, no effective methods to positively regulate DNA methylation changes that occur during vitrification have been reported.…”