Isolation and characterisation of mRNA encoding the salmon- and XXXX -II type gonadotrophin-releasing hormones in the teleost fish Rutilus rutilus (Cyprinidae).

@entity535 @entity377 @entity1573 @entity1176 @entity2083
The complementary DNAs (cDNA) encoding the [Trp7,Leu8]-gonadotrophin-releasing hormone (salmon-type @entity1176 ; sGnRH:GeneBank accession no. u60667) and the [His5,Trp7,Tyr8]- @entity1176 ( @entity1573 -II-type @entity1176 ; cGnRH-II: GeneBank accession no. u60668) precursor in the roach (Rutilus rutilus) were isolated and sequenced following reverse transcription and rapid amplification of cDNA ends (RACE). The s @entity1176 and cGnRH-II precursor cDNAs consisted of 439 and 628 bp, and included open reading frames of 282 and 255 bp respectively. The structures of the encoded peptides were the same as GnRHs previously identified in other vertebrates. The s @entity1176 and cGnRH-II precursor cDNAs, including the non-coding regions, had 88.6 and 79.9% identity respectively, to those identified in @entity2083 ( @entity2083 ). However, significant similarity was not observed between the non-coding regions of the @entity1176 cDNAs of Cyprinidae and other fish. The presumed third exon, encoding partial sGnRH associated peptide (GAP) of roach, demonstrated significant @entity377 and @entity535 similarity with the appropriate regions in the @entity2083 , but not with other species, and this may indicate functional differences of GAP between different families of fish. cGnRH-II precursor cDNAs from roach had relatively high @entity377 similarity across this @entity1176 variant. Cladistic analysis classified the sGnRH and cGnRH-II precursor cDNAs into three and two groups respectively. However, the divergence between @entity377 sequences within the sGnRH variant was greater than those encoding the cGnRH-II precursors. Consistent with the consensus developed from previous studies, Northern blot analysis demonstrated that expression of sGnRH and cGnRH-II was restricted to the olfactory bulbs and midbrain of roach respectively. This work forms the basis for further study on the mechanisms by which the tapeworm, Ligula intestinalis, interacts with the pituitary-gonadal axis of its fish host.
