Three gonadotropin-releasing hormone genes in one organism suggest novel roles for an ancient peptide.
AUTOR(ES)
White, S A
RESUMO
Gonadotropin-releasing hormone (GnRH) is known and named for its essential role in vertebrate reproduction. Release of this decapeptide from neurons in the hypothalamus controls pituitary gonadotropin levels which, in turn, regulate gonadal state. The importance of GnRH is underscored by its widespread expression and conservation across vertebrate taxa: five amino acids are invariant in all nine known forms, whereas two others show only conservative changes. In most eutherian mammals, only one form, expressed in the hypothalamus, is thought to exist, although in a recent report, antibody staining in developing primates suggests an additional form. In contrast, multiple GnRH forms and expression loci have been reported in many non-mammalian vertebrates. However, evidence based on immunological discrimination does not always agree with analysis of gene expression, since GnRH forms encoded by different genes may not be reliably distinguished by antibodies. Here we report the expression of three distinct GnRH genes in a teleost fish brain, including the sequence encoding a novel GnRH preprohormone. Using in situ hybridization, we show that this form is found only in neurons that project to the pituitary and exhibit changes in soma size depending on social and reproductive state. The other two GnRH genes are expressed in other, distinct cell populations. All three genes share the motif of encoding a polypeptide consisting of GnRH and a GnRH-associated peptide. Whereas the GnRH moiety is highly conserved, the GnRH-associated peptides are not, reflecting differential selective pressure on different parts of the gene. GnRH forms expressed in nonhypothalamic regions may serve to coordinate reproductive activities of the animal.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=41157Documentos Relacionados
- Three forms of gonadotropin-releasing hormone characterized from brains of one species.
- Second gene for gonadotropin-releasing hormone in humans
- Direct inhibition of testicular function by gonadotropin-releasing hormone: mediation by specific gonadotropin-releasing hormone receptors in interstitial cells.
- Regulation of pituitary gonadotropin-releasing hormone receptors by pulsatile gonadotropin-releasing hormone injections in male rats. Modulation by testosterone.
- Prepubertal increases in gonadotropin-releasing hormone mRNA, gonadotropin-releasing hormone precursor, and subsequent maturation of precursor processing in male rats.