Imprinting Analysis of RTL1 and DIO3 Genes and Their Association with Carcass Traits in Pigs (Sus scrofa)

Imprinted genes play significant roles in the regulation of fetal growth, development, function of the placenta and postnatal behavior in mammals, but little is known in pigs. In order to investigate the imprinting status of porcine retro-transposon like 1 (RTL1) and type 3 iodothyronine deiodinase (DIO3) genes, DNA or RNA samples of the parents and F-1 animals, generated with reciprocal crosses between Large White and Meishan breeds, were isolated, and analyzed by reverse transcription polymerase chain reaction restriction fragment length polymorphism (RT-PCR-RFLP). The results demonstrated that the RTL1 gene was paternally expressed in 10 tissues, such as the skeletal muscle, heart, spleen, liver, kidney, lung, stomach, fat, small intestine and brain, and DIO3 gene exhibited paternal expression in the skeletal muscle, heart, spleen, lung, stomach, and brain, in 2-month-old pigs. The association of RTL1 and DIO3 with carcass traits was further analyzed in the F-2 population of Large White x Meishan pigs. The statistical results showed that the RTL1 A1101G polymorphism (EU781029) was significantly associated with lean meat percentage (LMP) and fat meat percentage (FMP) (P<0.05), while the DIO3 A744C polymorphism (AY533208) was not significantly associated with any carcass traits. These results indicate that the imprinting status of RTL1 and DIO3 is well kept across the mammalian species, and porcine RTL1 may have important roles in muscle growth and fat deposition.