Abstract
Unlike specific expression in the skin of wild mice, the agouti signaling protein (ASIP) is expressed widely in the tissue of cattle, including adipose and muscle tissue. Hence, it has been suggested that ASIP plays a role in bovine fat metabolism. An inserted L1-BT element was recently identified upstream of the ASIP locus which led to an ectopic expression of ASIP mRNA in cattle. In this study, we detected the indel of the L1-BT element at g. nt and three SNPs in introns of the ASIP gene (g. A G, g. A T, and g. 4805A T) in a Chinese Simmental steer population. The association analysis between variants of ASIP and economic traits showed that the homozygous genotype of L1-BT element insertion, AA genotype of g. A G, and AT genotype of g. 4805A T were significantly correlated with carcass and fat-related traits, such as live weight and back fat thickness. Moreover, three haplotypes (H1: AT; H2: AA; H3: GT) were identified by linkage disequilibrium analysis and formed six combined genotypes. Results indicated that Chinese Simmental steers with an H1H2 combined genotype had a higher measured value of fat-deposition-related traits (), including thickness of back fat and percentage of carcass fat coverage, but a lower content of linoleic acid and -linolenic acid (). Individuals of an H3H3 combination had a lower marbling score, perirenal fat weight, and carcass weight (). This suggests that these three SNPs and two combined haplotypes might be molecular markers for beef cattle breeding selection.
Highlights
The Agouti signaling protein (ASIP) has been described as a secreted protein expressed mainly in the skin and regulated pigmentation in wild mice (Bultman et al, 1992; Voisey and van Daal, 2002)
ASIP mRNA could be detected in human adipose tissue, skin, heart, testis, ovary, liver, and kidney (Wilson et al, 1995)
We found that a heterozygous insertion of L1-BT led to an ectopic expression of ASIP mRNA but not protein (Liu et al, 2018)
Summary
The Agouti signaling protein (ASIP) has been described as a secreted protein expressed mainly in the skin and regulated pigmentation in wild mice (Bultman et al, 1992; Voisey and van Daal, 2002). The ectopic ASIP expression in mice caused yellow fur and obesity (Klebig et al, 1995). Another biological function of ASIP was suggested in the regulation of obesity in mice. ASIP mRNA could be detected in human adipose tissue, skin, heart, testis, ovary, liver, and kidney (Wilson et al, 1995). Norris and Whan (2008) detected ASIP mRNA in the liver, kidney, skin, heart, and spleen of sheep. Several bovine studies had reported on ASIP mRNA expression in adipose tissue, M. longissimus, skin, heart, testis, ovary, and kidney (Girardot et al, 2005; Albrecht et al, 2012; Liu et al, 2018).
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