Identification of transcripts involved in meiosis and follicle formation during ovine ovary development
- Equal contributors
1 INRA, ENVA, UMR 1198 Biologie du Développement et Reproduction, F-78350 Jouy en Josas, France
2 CNRS, FRE 2857, F-78350 Jouy en Josas, France
3 INRA, SIGENAE, UR83 Unité de Recherches Avicoles, 37380 Nouzilly, France
BMC Genomics 2008, 9:436 doi:10.1186/1471-2164-9-436Published: 23 September 2008
The key steps in germ cell survival during ovarian development are the entry into meiosis of oogonies and the formation of primordial follicles, which then determine the reproductive lifespan of the ovary. In sheep, these steps occur during fetal life, between 55 and 80 days of gestation, respectively. The aim of this study was to identify differentially expressed ovarian genes during prophase I meiosis and early folliculogenesis in sheep.
In order to elucidate the molecular events associated with early ovarian differentiation, we generated two ovary stage-specific subtracted cDNA libraries using SSH. Large-scale sequencing of these SSH libraries identified 6,080 ESTs representing 2,535 contigs. Clustering and assembly of these ESTs resulted in a total of 2,101 unique sequences depicted in 1,305 singleton (62.11%) and 796 contigs (37.9%) ESTs (clusters). BLASTX evaluation indicated that 99% of the ESTs were homologous to various known genes/proteins in a broad range of organisms, especially ovine, bovine and human species. The remaining 1% which exhibited any homology to known gene sequences was considered as novel. Detailed study of the expression patterns of some of these genes using RT-PCR revealed new promising candidates for ovary differentiation genes in sheep.
We showed that the SSH approach was relevant to determining new mammalian genes which might be involved in oogenesis and early follicle development, and enabled the discovery of new potential oocyte and granulosa cell markers for future studies. These genes may have significant implications regarding our understanding of ovarian function in molecular terms, and for the development of innovative strategies to both promote and control fertility.