Ammonium accumulation and use of mineral oil overlay do not alter imprinting establishment at three key imprinted genes in mouse oocytes grown and matured in a long-term follicle culture.

Imprinted genes are differentially methylated during gametogenesis to allow parent-of-origin specific monoallelic expression. Follicle culture under oil overlay has been associated with altered imprinting establishment in mouse oocytes. We previously demonstrated normal imprinting establishment at four key imprinted genes in mouse oocytes grown and matured in a long-term in vitro follicle culture system without oil overlay. Ammonium (300 microM) has been linked with aberrant imprinting in in vitro preimplantation embryo culture. Compared to culture without oil, mineral oil overlay during follicle culture led to a dramatic increase in ammonia levels in culture medium: mean ammonia levels were respectively 39 and 290 microM at Day 4 of culture, 73 and 465 microM at Day 8, and 101 and 725 microM at Day 12 (p

Publication year:2009

Keywords:ammonium, mineral oil, oocytes, follicle culture