An association analysis between a missense polymorphism at the pig PCSK9 gene and serum lipid and meat quality traits in Duroc pigs

• The PCSK9 gene maps to a QTL for lipid traits on pig chromosome 6.
• We have typed a missense PCSK9 polymorphism (E408K) in 271 Duroc pigs
• PCSK9 genotype was nominally associated with gluteus medius palmitelaidic content.

A genome-wide association analysis in a Duroc pig population allowed us detecting a genomic region on pig chromosome 6 (141–147 Mb) that was associated with serum cholesterol (CHOL), triglyceride (TRIG) and low-density lipoprotein (LDL) concentrations. This region contains the proprotein convertase subtilisin-like kexin type 9 (PCSK9) gene (SSC6, 145 Mb), which has a key role in the regulation of CD36, LDL receptor and very low density lipoprotein (VLDL) receptor levels. In the current work, we have genotyped by pyrosequencing a missense PCSK9 c.1222G>A mutation (E408K) in 273 Duroc pigs. The performance of an association analysis with the GEMMA software did not reveal any association between PCSK9 genotype and serum lipid concentrations, evidencing that this polymorphism is not the causal mutation of the CHOL, TRIG, and LDL SSC6 QTL. However, we detected an association, that was highly significant at the nominal level, between PCSK9 genotype and palmitelaidic content at the gluteus medius muscle (P-value = 0.008). There is evidence that PCSK9 induces the degradation of CD36, a key long-chain fatty acid transporter, and that it may decrease the uptake of palmitate. However, the E408K polymorphism analysed in the current work is not predicted to be deleterious, suggesting that the associations found are probably due to the linkage of this polymorphism with a causal mutation yet to be found.