Study On The Developmental Expression Of Pax7, MyoD And MyoG Genes In Longissimus Dorsi Of Pigs

The growth and development of skeletal muscle was regulated critically by a series of myogenic decide factor in time and space. Whereby, the MRFs family and Pax family were two important myogenic factor families. Pax7 is a member of Pax family, the main control factor in the upstream of the myogenic process, and plays an important role during skeletal muscle development. MyoD and MyoG are two main members of MRFs family. MyoG can promte cell differentiation, and transform many types of cells into myogenic cell. MyoD plays a role in the regulation of the fusion process from muscle cells to muscle fiber, which is regarded as key factor of differentiation of final muscle cells. The aim of this study was to investigate the expression profile of Pax7gene in different tissues and the developmental expressions of MyoD, MyoG, and Pax7 genes in longissimus dorsi of pigs. The expression profiles of Pax7 gene at the levels of mKNA and protein in 12 different tissues including heart, liver, spleen, lung, kidney, stomach, small intestine, hypothalamus, cerebellum, longissimus dorsi, biceeps femoris, psoas major of Mashen pigs at birth and the developmental expression patterns of MyoD, MyoG, and Pax7 at the levels of mRNA and protein in longissimus dorsi at seven stages (1,30,60,90,120,150, and 180-day old) in Mashen and Large White pigs were studied by quantitative real-time PCR and western-blot. The main results were showed as follows:(1) The Pax7 mRNA was expressed in longissimus dorsi, biceeps femoris, psoas major, hypothalamus, and cerebellum, while the Pax7 protein was only expressed in skeletal muscles of longissimus dorsi, biceeps femoris, and psoas major. The developmental expression patterns of Pax7 mRNA and protein in Mashen pig was basically in accordance with those in Large White pig. The greatest mRNA expression of Pax7 gene in longissimus dorsi was at 30-day old (P<0.01), significantly higher than at other days, followed by the expression at 1-day old, and kept lower stable levels at other stages both in Mashen and Large White pigs. The Pax7 protein expression at 1-day old was the greatest, followed by it at 30-day old, which were significantly greater than those at other stages, and the Pax7 expression was in lower stable levels.at other days. The Pax7 protein expression from one-day old to 180-day old in Mashen pig was significantly greater than those in Large White (P<0.05, P<0.01).(2) The developmental expression patterns of MyoD mRNA and protein in longissimus dorsi of Mashen pig were basically in accordance with those in Large White pig. From one-day old to 180-day old, with the time increasing, the mRNA expression showed the trend of rising first and declining then and the lowest at 180-day (except 60-day of Mashen). However, the MyoD mRNA expression from 30-day old to 180-day old in Mashen pig was significantly greater than those in Large White (P<0.01) and the difference of mRNA expression was not significant at 1-day old. The MyoD protein expression only at 150-day old and 180 day in Mashen pig was significantly greater than those in Large White (P<0.05, P<0.01).(3) The deveopmental expression patterns of MyoG mRNA and protein expression in Mashen were not basically in accordance with those in Large White. The greatest mRNA expression of MyoG gene in longissimus dorsi in Mashen pig was at 30-day old and 60-day old, respectively, which was significantly greater than those at other stages (P<0.01), and the difference was not significant in the other days; The greatest protein expression of MyoG in longissimus dorsi was at 30-day old and 90-day old and the lowest was at 60-day old and 180-day old. The greatest mRNA expression of Large Whie pig was at 180-day old, and significantly higher than the other days, the difference was not significant in other days. At the of protein level, the greatest protein expression of MyoG was at 1-day old and 60-day old, respectively, which was significantly greater than those at other stages(P<0.01), and the lowest expression was at 150-day old and 180-day old. The expression of MyoG showed no significant difference from 1-day old to 180-day old.