Meeting Abstract

56.1  Tuesday, Jan. 5  Gene Expression Changes during Early Secondary Oocyte Growth and Onset of Atresia in Coho Salmon YAMAMOTO, Y*; LUCKENBACH , JA; GOETZ, FW; YOUNG , G; SWANSON, P; Univ. of Washington, Seattle; Northwest Fisheries Science Center, Seattle; Univ. of Wisconsin, Milwaukee ; Univ. of Washington, Seattle; Northwest Fisheries Science Center, Seattle yojifish@u.washington.edu

Mechanisms regulating the normal progression of oocyte growth versus onset of ovarian atresia are poorly understood. To gain a better understanding of these processes, we exposed previtellogenic, two-year old coho salmon to prolonged fasting to induce ovarian atresia, while maintaining control fish on a normal diet that would promote continued development of the ovary. Fasted salmon showed significantly lower gonad weights, oocyte diameters, and plasma estradiol-17β levels relative to normally fed animals by week 14. A higher proportion of atretic oocytes was observed in ovaries of fasted fish at week 14 and numbers further increased by week 17. Suppression subtractive hybridization (SSH) cDNA libraries using ovaries from fed and fasted animals at week 14 were generated. The library composed of genes up-regulated in the fed ovary included steroidogenesis-related genes and TGFβ superfamily members, such as 3β-hydroxysteroid dehydrogenase (hsd3b), P450-aromatase (cyp19a1a), and anti-Mullerian hormone (amh). The library composed of genes up-regulated in the fasted ovary included genes associated with apoptosis, such as programmed cell death protein 4 (pdcd4) and lipopolysaccharide-induced TNF factor (litaf). The differential expression of genes identified by SSH was confirmed with quantitative PCR over the time course of the study (0-17 wks). Interestingly, ovarian mRNA levels for hsd3b, amh, and pdcd4 were significantly different between fed and fasted fish by week 9, before endocrinological and histological differences were observed. This study has identified ovarian genes involved in normal early secondary oocyte growth and potential markers of atresia onset.