XIST has been known to long-non coding RNA which regulate X-chromosome inactivation in female mammal and the gene has been suggested to having important role in early embryo development and embryonic stem cell. However, its coding region has been unclear in pig. To determine the coding region of XIST in pig, we have examined candidate site of XIST coding region in pig by BLAST, PCR, and sequencing. By comparing pig whole genome sequence (Sus scrofa 10.2) with human, murine, and bovine XIST transcript sequence using BLAST, we selected candidate coding region of XIST in pig. The result showed XIST is coded on the minus strand of NW_003612825 contig and its length was nearly 32kb which was similar to the length of human and bovine XIST gene. With the candidate model, we performed RT-PCR to confirm the coding region of XIST with 24 primer pairs and they were expressed only female porcine embryonic fibroblast (PEF) but not in male PEF. By designing candidate intron spaning primer we could confirmed candidate intron is present between first and last exon (distance, 9.2kb vs product size, 2kb). The seqeucne of amplicon was analyzed and we could confirmed there were 5 small exons (less than 400 bp) like XIST coding region of other species which have 4 to 5 small exon between first and last exon. To confirm coding strand in pig, we conducted strand specific reverse transcription. We confirmed candidate XIST was coded on the negative strand of contig on X-chromosome as the result of homology analysis by BLAST. With the candidate pig XIST sequence, we aligned the sequence with XIST sequences of 3 species, human, mouse, and bull by clustalW. These result showed candidate sequence of pig XIST is most similar to that of bovine and the homology between pig and human was higher than result between mouse and human. These results could support for X chromosome inactivation analysis and the function of XIST in pig preimplantation embryos. * This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012006276)

• Jae-Yeon Hwang(Department of Agricultural Biotechnology, Anumal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University)
• Eunbae Kim(Interested in Lactic Acid Bacteria, Gut Health and Bacterial Bioinformatics Marco Laboratory at University of California, Davis)
• Dong-Chan Son(Department of Agricultural Biotechnology, Anumal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University)
• Chang-Kyu Lee(Department of Agricultural Biotechnology, Anumal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University)