Identification of mutations in the porcine cathepsin L (CTSL) and cathepsin S (CTSS) genes and association study between meat quality and production traits in Italian Large White pigs.

Cathepsins are lysosomal proteinases involved in a large number of biological processes that could be directly or indirectly linked to the physiological mechanisms that might affect different production traits in farm animals. Furthermore, in pigs, an elevated cathepsin activity in fresh ham muscles and throughout the processing period has been shown to be a factor contributing to the excessive softness defect of dry cured hams. We recently showed that several cathepsin and lysosomal proteinase inhibitor genes are associated with meat production and carcass traits in Italian heavy pig populations but none of the investigated loci was associated with cathepsin activity. Here we studied two additional genes of the cathepsin family, cathepsin L (CTSL) and cathepsin S (CTSS), with the aim to identify DNA markers associated with meat production and quality traits in pigs. Single nucleotide polymorphisms in these genes were identified mining porcine expressed sequence tags and confirmed by sequencing. PCR-RFLP tests were used to genotype pigs of seven different breeds to obtain allele frequencies information for these polymorphisms. Estimated breeding values for average daily gain (ADG), back fat thickness (BFT), lean cuts (LC), ham weight (HW) and feed:gain ratio (FGR) as well as cathepsin B activity, pH1, pH2, and glycolytic potential of semimembranosus muscle were determined for 265 sib-tested Italian Large White pigs that were genotyped for the CTSL and CTSS markers. Significant associations were observed for ADG (CTSL, P<0.01; CTSS, P<0.05), BFT, LC and HW (CTSL, P<0.05) and FGR (CTSS, P<0.05) but not for any meat quality trait.