Growth hormone gene polymorphisms in tench, Tinca tinca L.

Studies of the growth hormone (GH) gene have both fundamental and practical significance, but no data on intra-specific polymorphisms of the tench, Tinca tinca, GH gene has been available. In the present study, the complete GH gene was cloned from 17 tench individuals chosen from 10 European and two Asian populations, cultured as well as wild and sequenced from 28 recombinant plasmids (at least one per individual). The tench GH gene was found to be 1758–1763 bp in length. Altogether 14 polymorphic sites were observed, 12 located in introns (SNPs and very short indels) and two in exons (SNPs only). In non-coding regions, the highest polymorphism was found in intron 2 (five SNPs and two indels). Intron 4 was short (137 bp) and monomorphic. In coding regions, one polymorphic site was observed in exon 3 and one in exon 5. The detected SNPs in exons were synonymous, having no effect on the amino acid composition of the GH protein. Thirteen GH gene haplotypes were observed. The tench GH gene haplotypes clustered into two major classes with a mean genetic distance of 0.0037 ± 0.0014 and coefficient of GH gene differentiation of 0.67 ± 0.129 (mean ± S.E.). The two classes corresponded, based on phylogroup-specific PCR-RFLP, with previously determined two phylogroups, western and eastern. Although the described tench GH gene haplotypes might not include all the existing ones, all common polymorphic sites were identified. Polymorphisms in the tench GH gene, a representative of the five-exon type, are not as extensive as in fishes with the six-exon GH gene. However, GH gene polymorphisms in tench can still serve as suitable markers for population studies and conservation purposes. Investigation of growth performance differences in fish of different GH gene classes and/or haplotypes may be valuable.