The maturation-inducing hormone 17alpha,20beta-dihydroxy-4-pregnen-3-one regulates gene expression of inhibin betaA and bambi (bone morphogenetic protein and activin-membrane-bound inhibitor) in the rainbow trout ovary

Molecular characterization and expression pattern of inhibin α and βb in Chinese tongue sole (Cynoglossus semilaevis)

Inhibin plays important roles in vertebrate reproduction and development. In this study, we have cloned two genes encoding inhibin subunits, inhα and ihnβb, in Chinese tongue sole. inhα consists of 1032 bp, encoding a 343 amino-acid protein. inhβb is composed of 1275 bp, encoding a 424 amino-acid protein. Phylogenetic tree analysis indicated that INHα and INHβB were independently evolved. qPCR showed that inhα expression of in male testis was higher than that in ovary and pseudomale testis, while the expression of inhβb in ovary was higher than that in male and pseudomale testis. During gonadal developmental stages, inhα expression reached highest at 120 days post hatching (dph) both in ovary and testis, then showed decline in ovary but it was first decreased and then increased in the testis. Similarly, inhβb expression in ovary was low at 50-80 dph. At 120 dph, its expression was significantly increased to the peak level, and then gradually decreased. inhβb expression in testis maintained at a low level. During the embryonic developmental stages, inhα displayed the highest expression at 32-cell stage, whereas inhβb reached the highest expression at blastula stages. In situ hybridization data showed that both of inhα and inhβb were detected in oocytes of all stages. In male testis, inhα and inhβb was localized in spermatogonia, spermatocytes, spermatozoa, sertoli and leydig cells. In pseudomale testis, inhα showed the similar pattern in male testis, while the inhβb was detected in spermatocytes and spermatozoa. These data suggested that inhα may participate the spermatogenesis and oogenesis of Chinese tongue sole, while inhβb might predominantly function in oogenesis.

Effects of sex steroids on expression of genes regulating growth-related mechanisms in rainbow trout (Oncorhynchus mykiss)

Effects of a single injection of 17β-estradiol (E2), testosterone (T), or 5β-dihydrotestosterone (DHT) on expression of genes central to the growth hormone (GH)/insulin-like growth factor (IGF) axis, muscle-regulatory factors, transforming growth factor-beta (TGFβ) superfamily signaling cascade, and estrogen receptors were determined in rainbow trout (Oncorhynchus mykiss) liver and white muscle tissue. In liver in addition to regulating GH sensitivity and IGF production, sex steroids also affected expression of IGF binding proteins, as E2, T, and DHT increased expression of igfbp2b and E2 also increased expression of igfbp2 and igfbp4. Regulation of this system also occurred in white muscle in which E2 increased expression of igf1, igf2, and igfbp5b1, suggesting anabolic capacity may be maintained in white muscle in the presence of E2. In contrast, DHT decreased expression of igfbp5b1. DHT and T decreased expression of myogenin, while other muscle regulatory factors were either not affected or responded similarly for all steroid treatments. Genes within the TGFβ superfamily signaling cascade responded to steroid treatment in both liver and muscle, suggesting a regulatory role for sex steroids in the ability to transmit signals initiated by TGFβ superfamily ligands, with a greater number of genes responding in liver than in muscle. Estrogen receptors were also regulated by sex steroids, with era1 expression increasing for all treatments in muscle, but only E2- and T-treatment in liver. E2 reduced expression of erb2 in liver. Collectively, these data identify how physiological mechanisms are regulated by sex steroids in a manner that promotes the disparate effects of androgens and estrogens on growth in salmonids.

Reference genes to quantify gene expression during oogenesis in a teleost fish

Understanding the molecular events involved in the acquisition of competence during oogenesis is a key step to determine the secret of 'high quality' eggs for aquaculture. Quantitative real time polymerase chain reaction (qPCR) is the technique of election to determine changes in transcript abundance in such studies, but choosing reference genes for normalization, in particular during oogenesis, remains a challenge. In the present study, transcription of 6 functionally distinct genes, β actin (ACTB), cathepsin D (CTSD), cathepsin Z (CTSZ), elongation factor 1 α (EEF1A), TATA binding protein (TBP) and tubulin A (TUBA1A) was assessed as normalizers of bone morphogenetic protein (BMP) and activin membrane-bound inhibitor (BAMBI) gene expression in mRNA from Mozambique tilapia oocytes during oogenesis. Reverse transcription was equally efficient and varies little in all samples. Most of the genes considered for reference were stable during early stages of oogenesis but variations were observed during vitellogenesis. A single gene and up to 3 genes were shown to be insufficient for reliable normalization throughout the whole oogenesis. The combination of the genes ACTB, CTSD, EEF1A and CTSZ as reference was found to minimize variation and has the most stable expression pattern between maturation stages.