Abstract: 【Objective】 In order to find more novel candidate imprinted genes in pigs and assess their conservation among mammalian species and provide the basic molecular biology information and molecular markers for procine molecular genetics and breeding, comparative biology method was used to study porcine COPG2 and MEST genes. 【Method】 The porcine COPG2 and MEST genes from the one-month-old F1 hybrid pigs, between Rongchang and Landrace were cloned and sequenced, and then its molecular features were analyzed. Mapping of the porcine COPG2 and MEST genes to porcine chromosome were made with the IMpRH panel. Through the direct sequencing of the RT-PCR products, the imprinting status of both genes in 11 different tissues of one-month-old F1 heterozygotes were analyzed. The mRNA distribution of the porcine COPG2 and MEST genes in 11 different tissues (heart, stomach, skeletal muscle, kidney, lung, liver, small intestine, bladder, tongue, spleen and fat) were examined by real-time PCR. 【Result】 Two sequences with the full-length of 2 817 bp for COPG2 gene and 2 219 bp for MEST gene were cloned. COPG2 and MEST contain coding sequence of 2 616 bp and 981 bp, encoding proteins of 871 and 326 amino acid residues, respectively. By the IMpRH panel, porcine COPG2 and MEST genes were assigned to porcine chromosome 18, and closely linked with CL365941 with the LOD of 14.32 and 8.5, respectively. Imprinting analysis demonstrated that COPG2 was biallelically expressed in 11 tissues examined and MEST was paternally expressed in heart, stomach, skeletal muscle, kidney, lung, bladder, tongue and fat, while biallelically expressed in liver, small intestine and spleen. Real-time PCR results showed that the expression level of porcine COPG2 and MEST were significantly different among tissues of one-month-old pig (P＜0.01). Both the COPG2 and MEST genes showed the highest expression levels in the kidney than all of the other tissues. 【Conclusion】 The sequence of COPG2 is conservative, but the imprinting status is not conservative among mammalian species. For MEST, both the sequence and imprinting status are conservative, and MEST has tissue specific expression in pigs. In addition, the results of mapping and imprinting status of MEST and COPG2 confirm the novel imprinted domain on porcine chromosome 18.

Key words: pig, COPG2, MEST, cloning, mapping, tissue expression