Expression of contractile protein-encoding genes TPM2 and TNNT3 during ontogenesis in pigs raised in Poland

Troponin is a regulatory proteins complex composed of subunits TnC, TnI, and TnT encoded by separate genes - TNNT1, TNNT2 and TNNT3. It is a component of thin filaments (along with actin and tropomyosin), to which calcium binds to accomplish this regulation. The TPM2 gene encodes beta-tropomyosin. An imprinted QTL for muscle mass deposition has been detected near the TNNT3 gene and several significant linkages between TPM2 and QTLs on chromosome 1 have been identified. However, no significant correlation was found between polymorphism in both genes and economically important pig traits. The study aimed at analysing the level of expression of TNNT3 and TPM2 in the developing muscle (day 60-210 of life) and determining the expression differences among Polish Large White, Polish Landrace, Pulawska, Duroc and Pietrain pigs. Within the mentioned period the expression level of both genes in question did not change significantly. No developmental pattern characteristic for all breeds was revealed. In PL gilts a highly significant correlation was found among the level of expression in both white muscles (longissimus dorsi and semimembranosus) and the animals' maternal origin. The above results suggest that an unknown polymorphism, probably located in regulatory part of the gene has an effect on the level of TNNT3 expression. Expression of the TPM2 did not change during ontogenesis and was not correlated with maternal origin. However, significant differences among gilts of different breeds were identified.