Pig fatness in relation to FASN and INSIG2 genes polymorphism and their transcript level

Fat content and fatty acid (FA) profile influence meat quality in pigs. These parameters are important for consumers due to their preferences for healthy, high quality meat. The aim of this study was searching for polymorphisms and transcript levels of two positional and functional candidate genes, FASN and INSIG2, encoding proteins which take part in lipid metabolism. The molecular findings were analyzed in relation to fatness traits. Pigs of four commercial breeds were included: Polish Landrace (PL), Polish Large White (PLW), Duroc and Pietrain. DNA sequencing, 5'RACE technique and real time PCR and association analysis were applied. In total, 20 polymorphisms in 5'-flanking, 5'UTR and 3'UTR regions of FASN (12 novel polymorphisms) and INSIG2 (seven novel ones and one known) genes were found. Association study with fatness traits (PL n = 225, PLW n = 179) revealed that four polymorphisms (c.-2908G > A, c.-2335C > T, c.*42_43insCCCCA and c.*264A > G) of the FASN gene were associated with back fat thickness in PL and PLW. Since the polymorphisms were identified in regulatory sequences of the both genes also their transcript levels were studied in PLW (n = 23), PL (n = 22), Pietrain (n = 17) and Duroc (n = 23). The INSIG2 transcript level was positively correlated with monounsaturated FA contents in the longissimus thoracis et lumborum muscle. Several correlations were also found between three polymorphisms (c.*264A > G and c.-2335C > T in FASN, and c.-5527C > G in INSIG2) and the FA content. Our study showed that the FASN gene is a promising marker for subcutaneous fat tissue accumulation, while INSIG2 is a promising marker for FA composition.