Androgens and growth of previtellogenic oocytes in Atlantic cod: Identification and pattern of differentially expressed genes and proteins

The overall objective of the proposed project is to study the role and effect of androgens (e.g. 11-ketotestosterone; 11-KT) on the growth of previtellogenic oocytes through the characterization of androgen-responsive ovarian genes and proteins. Thus incr easing our understanding on the hormonal control of previtellogenic oocyte growth in teleosts. To assess the utility of suppression subtractive hybridization (SSH) as a method of gene discovery in the previtellogenic ovarian oocytes of teleosts, we will s equence subtracted clones from two cDNA libraries constructed from the mRNA of previtellogenic ovarian oocytes, before and after exposure to 11-KT. Inter- and intra-species differences in fecundity (number of eggs spawned) exist in teleosts. Despite the c oncept of life-history strategies, the internal (within the body) signals that regulate fecundity are not known. Prior to vitellogenesis (previtellogenesis), androgens may play an integral role in the regulation of oocytes (immature eggs) growth. Prelimin ary evidence supporting these assumptions are derived from the induction of oocyte growth in in vitro androgen exposed immature female eels, probably by gene regulation mechanisms (genomics) or by protein modification mechanisms (proteomics). In this stud y we will use the analytical power of SSH to open a possible revealing window of understanding into the functional aspects of oocyte development in organisms that control fecundity. By explaining how fecundity is controlled in teleosts, these results will have some positive implications in the aquaculture industry (particularly for new species and especially for declining fish stocks such as the Atlantic cod, Gadus morhua).