Cloning, expression, and polymorphism of the ECI1 gene in various pig breeds

The enzyme Δ3,Δ2-dienoyl-CoA isomerase (ECI1) plays a crucial role in the mitochondrial β-oxidation of fatty acids with a double-bond in odd and even positions. The ECI1 gene might be a qualified candidate for studies pertaining to lipid deposition and meat quality in swine. In the present study, ECI1 cDNA of the Tibetan pig was obtained by in silico cloning and verified by PCR analysis. Single-nucleotide polymorphisms (SNPs) of ECI1 were screened by PCR-sequencing and genotypes of those SNPs were tested by PCR-restriction fragment length polymorphism (PCR-RFLP) in Diannan small-ear pigs (DSP, n=40), Tibetan pigs (TP, n=60) and Yorkshire pigs (YP, n=30). The expression levels of ECI1 were analyzed by real-time quantitative PCR and Western blotting in tissues of the liver, backfat, and longissimus dorsi (LD) muscle of DSP (n=8), TP (n=8) and YP (n=8). Single factor linear correlation analysis was applied separately for each breed to evaluate correlations between ECI1 gene expression in the LD muscle and intramuscular fat (IMF) content. We obtained an ECI1 gene length of 1 401 bp from the cDNA that contained a full coding region of 909 bp. Three novel SNPs (g.42425337G>A; g.42424666A>G; and g.42422755A>G) were detected, and only g.42424666A>G exhibited three genotypes among the three breeds. The ECI1 expression levels in the LD muscle of DSP and TP were significantly higher than that of YP (P<0.05). Moreover, TP had the highest ECI1 expression in backfat (P<0.01), and a positive correlation was observed between gene expression and IMF content. The results suggest that differences in ECI1 gene expression might be related to lipid deposition and meat quality in pig.