A relationship between the PCR-RFLP polymorphism in porcine MYOG, MYOD1 and MYF5 genes and microstructural characteristics of m. longissimus lumborum in Pietrain × (Polish Large White × Polish Landrace) crosses

Abstract

Muscle fibre formation takes place during embryonic development and is regulated by the MyoD gene family, which consists of four genes, MYOD1, myogenin, MYF5 and MRF4. A relationship was studied between MYOD1, myogenin and MYF5 genotypes and microstructural characteristics of the m. longissimus lumborum in pigs – crosses: Pietrain × (Polish Large White × Polish Landrace). The data included 115 unrelated animals slaughtered at about 105 kg live body weight. Within 45 min after exsanguination, samples were taken from the m. longissimus lumborum, frozen in liquid nitrogen and later analysed for the diameter of slow-twitch oxidative, fast-twitch oxidative and fast-twitch low-oxidative fibres, their proportion in a bundle, the proportion of pathological changes and number of fibres per unit area. The RYR1 and MyoD genotypes were determined using the PCR-RFLP technique. A significant or highly significant relation was observed between the diameter of all types of muscle fibres and genotype RYR1 – the highest values were recorded for homozygotes TT (genetically stress-sensitive). A relation between MyoD genotypes and microstructural characteristics of the m. longissimus lumborum was analysed on a group of 93 animals of the genotype CC or CT at locus RYR1. Sex appeared to have no significant effect on the muscle microstructural traits in this group of animals. The content of fast-twitch oxidative fibres (FTO) was significantly related to the MYF5 genotype, whereas that of fast-twitch low-oxidative fibres (FT) was affected by the MYOD1 and MYF5/DdeI genotypes. The proportion of angular fibres in a bundle was related to MYF5/HinfI genotype. The results showed that MyoD genes could be considered as candidate genes for some microstructural characteristics of m. longissimus lumborum in pigs.