Role of Transforming Growth Factor Beta Superfamily (TGFβ) on Steroidogenic Enzyme Expression in Rainbow Trout (Oncorhynchus mykiss) Oocyte Somatic Layer Isolates
Parrott, Hannah R.
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Increasing the knowledge on the regulation of steroid synthesis in teleost fish is key to optimizing the production of competent follicles (fecundity), which will assist the aquaculture industry in meeting the ever-increasing demand for consumable fish. The objectives of this project are to compare the steroidogenic enzyme activity of steroidogenic acute regulatory protein (StAR), 3β-hydroxysteroid dehydrogenase (3β-HSD), and aromatase (cyp19a1) enzymes expressed by the somatic follicular layers of both immature and mature oocytes when treated with BMP4/7 and Activin A. We also investigated the role of a new receptor blocker, DMH-1, to see if it is an effective regulator in steroidogenesis and final oocyte maturation. The enzyme StAR and 3β-HSD are required for both estradiol (E2) and maturation inducing hormones (MIH) production, whereas cyp19a1 is only required for E2. As all steroids are synthesized from a common precursor, it is the alteration of these enzyme’s expression profiles that dictates the steroid being synthesized. Quantitative Real-Time PCR (qPCR) was preformed to measure steroidogenic enzyme mRNA levels. Quantification of the gene expression were determined by the [delta][delta]-CT method normalized to the standard housekeeping gene EF1 alpha. A 2-way Analysis of Variance (ANOVA) demonstrated a significant difference in steroidogenic enzyme expression based on maturity level. In contrast, independent treatments with ActA, BMP4/7, and DMH-1 showed no significant effect in regulating steroidogenesis.