Identification of Ovis aries Gelsolin isoform b, a candidate gene for milk quality

In this report, we describe the identification of the complete ovine gelsolin (GSN) isoform b cDNA. We sequenced exons 12 and 13 and parts of introns 11, 12 and 13 in 263 sheep of three breeds. We found 11 novel SNPs, of which 2 were missense mutations. GSN is a Ca2+-dependent actin-regulatory protein that modulates actin assembly and disassembly. Because actin is involved in the regulation of intracellular lipid metabolism, particularly in the formation of cytoplasmic fat droplets and in the transport of lipid constituents, we tested the hypothesis that different GSN genotypes might influence actin activity and, consequently, milk yield and quality. An association analysis was performed between each SNP and the following traits, which were evaluated in 464 recorded lactations of the same sheep: milk yield, fat and protein content, as well as somatic cell score. Significant associations (P = 0.02) were found between three SNPs in intron 12 and fat content in the Altamurana breed. For two of the SNPs, the effect was also noted in the Gentile breed (P = 0.09). Suggestive associations were also found between the SNPs and other traits, albeit not in all of the breeds. The three SNPs that affected fat content were located in the consensus sequences of binding sites for the following transcription factors: Tal-1 alpha, Evi-1 and Egr-3. Therefore, we hypothesised that the incorrect modulation of actin assembly occurs in one of the GSN genotypes, with a particularly evident effect on fat content.