Subcellular localization, expression patterns, SNPs and association analyses of the porcine HUMMLC2B gene

Myosin regulatory light chain (MLC) regulates myofilament activation via phosphorylation by Ca²⁺ dependant myosin light chain kinase. In order to further understand the functions of the porcine fast myosin regulatory light chain gene (HUMMLC2B) in muscle, the subcellular localization, the temporal and spatial distributions of its gene product were analyzed, and the association between the presence of specific polymorphisms and commercial meat traits in pig was also examined. HUMMLC2B was demonstrated to localize both in the cytoplasm and the nucleus by confocal fluorescence microscopy. Real-time PCR further revealed HUMMLC2B expression variation in a waveform manner in the skeletal muscle of both Chinese Tongcheng and Western Landrace pig breeds at days 33, 65 and 90 post coitum (pc). After birth, the expression levels of HUMMLC2B were also found to decrease gradually with age. Our spatial expression analysis showed that HUMMLC2B was highly expressed in the semitendinosus, gastrocnemius, biceps femoris and longissimus dorsi muscles. In contrast, only low levels of expression of this gene were evident in fat, and no expression was detectable in brain, heart, kidney, lung, liver, lymph node, spleen, stomach, or in either large or small intestine. A total of 23 potential polymorphisms, comprising 3 exonic and 20 intronic, were detectable in the porcine HUMMLC2B gene and the G1094A, T1513C, G1876A and T2005G polymorphisms were further analyzed. The significant associations between the T1513C, G1876A and T2005G polymorphisms with marbling score, dressing percent and meat color, respectively, were identified (P < 0.05). Associations with the percentage of leaf fat could also be demonstrated by analysis of haplotypes harboring these three polymorphisms. Our current results thus shed further light on the roles and functions of the HUMMLC2B gene in muscle.