Genomic Regulation through RNA in Oocyte Maturation of Large Mammals
Pp. 71-79 (9)
The oocyte is a unique cell amongst the 212 cell types that makes an individual. This cell does not
divide until it resumes meiosis and remains in a special chromatin status during the dictiate stage of the prophase
from oocyte formation in the gonad in the female fetus until it dies through apoptosis or proceeds to ovulation.
This status requires unique features to allow transcription to be active during oocyte growth and an automatic
pilot system to drive the transition from tetraploidy to haploidy during maturation and fertilization and back to
diploidy, all this in a few days in large mammals. Therefore, the regulatory program for all the transformations
required for chromosome separation, cell cycle progression, response to sperm entry, and embryonic genome
activation must be stored in the oocyte prior to ovarian release or even prior to final chromatin condensation as it
inhibits further transcription. The data related to gene regulation during this period is limited for two main
reasons: limited amount of material to study in mammals and differences with somatic tissues where gene
pathways are much better characterized. Nevertheless, using the genomic amplification approaches and the
increasing amount of information in somatic tissues and in oocytes from lower species, it is becoming possible to
study this automatic pilot system that drives the mammalian oocyte through maturation-fertilization and
embryonic genome activation. This chapter will focus on the progression of our understanding of the oocyte using
proteomic and transcriptomic tools.
Centre de recherche en biologie de la reproduction, Université Laval, Québec, Canada.