XIST, a long non-coding RNA, plays an important role in triggering X chromosome 
inactivation in eutherians, and is used extensively for qualifying stem cells 
and cloned embryos. However, a porcine XIST has not yet been thoroughly 
identified despite its biological importance in a wide variety of research 
fields. Here, we present a full-length porcine XIST sequence assembled using 
known sequences (GenBank), RNA-Seq data (NCBI SRA), and PCR/sequencing. The 
proposed porcine XIST gene model encodes a 25,215-bp transcript consisting of 7 
exons, including two conserved and two porcine-specific repeat regions. 
Transcription covering the entire XIST region was observed specifically in 
female cells, but not in male cells. We also identified eight transcription 
starting sites (TSSs) and evaluated CpG methylation patterns in the upstream 
(+2.0 kb) and downstream (-2.0 kb) regions. Sixty-seven CG di-nucleotides 
identified in the target region were considered to be candidate CpG sites, and 
were enriched in the following two regions: -284 to +53 bp (13 sites) and +285 
to +1,727 bp (54 sites) from the selected TSS. Male 5` region of XIST (64.5 
sites, 96.26%) had a higher level of CpG methylation than female DNA (33.4 
sites, 49.85%). Taken together, our results revealed that the porcine XIST gene 
is expressed exclusively in female cells, which is influenced by the lower level 
of CpG methylation in the putative promoter region compared with male cells. The 
porcine XIST presented in this study represents a useful tool for related 
research areas such as porcine embryology and stem cell biology.