ABSTRACT:The normal differentiation of follicles from the preantral to the antral stage is regulated by the synthesis and secretion of several important growth factors. Moreover, the proper growth and development of the oocyte and its surrounding somatic granulosa-cumulus cells is accomplished through the activation of paracrine pathways that form a specific cross-talk between the gamete and somatic cells. It has been shown that several growth factors produced by the ovary are responsible for the proper growth and development of follicles. The developmental competence of mammalian oocytes (also termed developmental potency) is defined as the ability of female gametes to reach maturation (the MII stage) and achieve successful monospermic fertilisation. Proper oocyte development during folliculo-and oogenesis also plays a critical role in normal zygote and blastocyst formation, as well as implantation and the birth of healthy offspring. Several molecular markers have been used to determine the developmental potency both of oocytes and follicles. The most important markers include transforming growth factor beta superfamily genes (TGFB), and the genes in this family have been found to play a crucial role in oocyte differentiation during oogenesis and folliculogenesis. In the present review, we summarise several molecular aspects concerning the assessment of mammalian oocyte developmental competence. In addition, we present the molecular mechanisms which activate important growth factors within the TGFB superfamily that have been shown to regulate not only follicle development but also oocyte maturation.

ABSTRACT:The main role of sperm is the delivery of the paternal genome into the oocyte during fertilisation. However, several lines of evidence have indicated that mammalian spermatozoa contribute more than just their DNA, namely, they also deliver a large range of RNA molecules. Microarray analysis has revealed a complex population of 3000 different kinds of messenger RNA that are delivered to oocytes by sperm and ejaculated spermatozoa are estimated to contain about 0.015 pg of total RNA. Some of the transcripts encode proteins crucial for early embryo development. Messenger RNAs from sperm also help to protect the paternal genes, which have an integral role soon after fertilisation. The molecular participation of the oocyte during fertilisation is well understood but the function of the sperm in this process remains unclear. During spermatogenesis the structure of the male haploid genome is permanently modified. Transition proteins (TNPs), protamines (PRMs) and histones (HILS-spermatid specific linker histone) play a unique role in spermatid chromatin compaction. In this review, the structure and role of sperm RNA as well as chromatin organisation during spermatogenesis are discussed.