Haplotype analysis within quantitative trait locus affecting intramuscular fat content on porcine chromosome 7

Previous results of fine mapping for quantitative trait loci affecting intramuscular fat content identified a 3.0-Mb chromosome interval on porcine chromosome 7, which contains at least 9 genes, based on the pig genome assembly. Therefore, we proposed these nine genes (LOC100154481, LOC100155711, LOC100155276, SPATA7, PTPN21, ZCH14, EML5, TTC8, and FOXN3) as positional candidate genes. The coding exons of the nine genes were characterized, and 45 polymorphisms were detected in F-2 Duroc x Meishan population. Within the nine genes, 10 non-synonymous substitutions and 1 insertion were genotyped among three European breeds (Landrace, Large White, and Duroc) and 1 Chinese breed (Meishan). Genotyping data was used to perform the haplotype analysis. Polymorphisms were found in all the studied genes, except ZCH14. We surveyed the frequency of 33 haplotypes that formed non-synonymous substitutions in four breeds. One of them was distributed widely in the Landrace, Large White, and Meishan breeds, but not in Duroc. Each breed had different major haplotypes.