Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8614
Title: Alterations in gene expression during fasting-induced atresia of early secondary growth ovarian follicles of coho salmon, Oncorhynchus kisutch
Author: Yoji Yamamoto, J. Adam Luckenbach, Graham Young, Penny Swanson
Publication Year: 2016
Journal: Comparative Biochemistry and Physiology, Part A: Molecular and Integrative Physiology
Volume: 201
Pages: 1-11
Keywords: follicular atresia,Gene expression,fasting,genomics,Ovarian follicle,salmon

Molecular processes that either regulate ovarian atresia or are consequences of atresia are poorly understood in teleost fishes. We hypothesized that feed restriction that perturbs normal ovarian growth and induces follicular atresia would alter ovarian gene expression patterns. Previtellogenic, two-year old coho salmon (Oncorhynchus kisutch) were subjected to prolonged fasting to induce atresia or maintained on a normal feeding schedule that would promote continued ovarian development. To identify genes that were specifically up- or down-regulated during oocyte growth in healthy, growing fish compared to fasted fish, reciprocal suppression subtractive hybridization (SSH) cDNA libraries were generated using ovaries from fed and fasted animals. Differential expression of genes identified by SSH was confirmed with quantitative PCR. The SSH library representing genes elevated in ovaries of fed fish relative to those of fasted fish contained steroidogenesis-related genes (e.g., hydroxy-delta-5-steroid dehydrogenase), Tgf-beta superfamily members (e.g., anti-Mullerian hormone) and cytoskeletal intermediate filament proteins (e.g., type I keratin s8). Overall, these genes were associated with steroid production, cell proliferation and differentiation, and ovarian epithelialization. The library representing genes elevated in ovaries of fasted fish relative to fed fish contained genes associated with apoptosis (e.g., programmed cell death protein 4), cortical alveoli (e.g., alveolin), the zona pellucida (e.g., zona pellucida protein c), and microtubules (e.g., microtubule associated protein tau). Elevated expression of this suite of genes was likely associated with the initiation of atresia and/or a reduced rate of follicle development in response to fasting. This study revealed ovarian genes involved in normal early secondary oocyte growth and potential early markers of atresia.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Develop methods to use physiological, biological and behavioral information to predict population-level processes.
Characterize the population biology of species, and develop and improve methods for predicting the status of populations.