Effetto del polimorfismo del gene GH ovino sulla produzione di latte

The aim of this work was to analyze the growth hormone GH1/GH2-N and GH2-Z gene copies in ovine species and to assess their possible association with milk traits. Two hundred muliparous lactating ewes were monitored. The two gene copies were amplified separately and each one was used as template for a nested PCR, to investigate single strand conformation polymorphism (SSCP) of seven fragments of the gene (5'UTR, exon-1, exon-2, exon-3, exon-4, exon-5 and 3'UTR). SSCP analysis revealed marked differences: fragment II was monomorphic at GH2-Z, but showed 4 profiles at GH1/GH2-N; fragment III was monomorphic at GH1/GH2-N and showed 6 patterns at GH2-Z, fragment V monomorphic at GH1/GH2-N and showed 3 patterns at GH2-Z, fragment VII had 3 patterns at GH2-Z vs 5 at GH1/GH2-N. Sequencing revealed six polymorphic base changes at GH1/GH2-N, three in the 5'UTR, one in exon-3 and two in the 3'UTR. Nine nucleotide changes occurred at GH2-Z: two at the 5'UTR, two in exon-2, one in exon-3, one in exon-4, one in exon-5 and two at the 3'UTR; the nucleotide change in exon-5 (c.556G>A), resulting in a putative amino acid substitution G179S. The nucleotide change c.*30delT was common to both GH1/GH2-N and GH2-Z. The variability of the promoter regions within each gene might have consequences on the expression level, due to the involvement in potential transcription factor binding sites. Both gene copies influenced milk traits, as some genotypes produced higher yields of milk, with higher fat content. A correlation with milk protein and casein content was also evidenced. These results may have implications that make them useful for future breeding strategies in dairy sheep breeding.