Expression patterns and functional roles of protein-coding genes in the Dlk1-Dio3 imprinted domain have been extensively characterized in mammals,but the imprinting status of Retrotransposon-like gene 1 (RTL1) and the type 3 deiodinase (DIO3) is still unknown in pigs.In this study,single nucleotide polymorphisms-based approaches were used to detect the expression patterns of porcine RTL1 and DIO3.Tissue DNA and RNA samples were collected from F1 pigs,generated with reciprocal crosses between the Meishan and Large White breeds.By direct sequencing and restriction fragment length polymorphisms analysis of reverse transcription polymerase chain reaction products,RTL1 was shown to be expressed from the paternal allele in various tissues,while the liver and spleen express much lower levels relative to the skeletal muscle,heart,lung,kidney,small intestine,stomach and brain.DIO3 was also expressed from the paternal allele,but the transcript abundance was greatest in the brain,definitely detectable in the muscle,stomach,lung and spleen,rather low in the heart and undetectable in the liver,kidney and small intestine.These observations suggest that the imprinting status of RTL1 and DIO3 is well kept during development in pigs,and confirm the conservation of genomic imprinting in DLK1-DIO3 cluster across mammals.In addition,porcine RTL1 and DIO3 are expressed in a wide range of tissues during postnatal development.