TSIX, Official Symbol TSIXprovided by HGNC Official Full Name TSIX transcript, XIST antisense RNAprovided by HGNC Primary source HGNC:HGNC:12377 See related Ensembl:ENSG00000270641 MIM:300181; AllianceGenome:HGNC:12377 Gene type ncRNA RefSeq status REVIEWED Organism Homo sapiens Lineage Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae; Homo Also known as XISTAS; XIST-AS; XIST-AS1; LINC00013; NCRNA00013 Summary In mammals, dosage compensation of genes on the X chromosome occurs by X inactivation, which is regulated in cis by the X-inactivation center (XIC) and expression of the XIST non-coding RNA. This gene expresses a non-coding antisense transcript across the 3' end of the XIST locus, and is coexpressed with XIST only from the inactive X chromosome. The mouse ortholog of this locus is required for imprinted X inactivation in extraembryonic tissues and silences Xist through modification of the chromatin structure in the Xist promoter region. In contrast, imprinted X inactivation does not occur in human extraembryonic tissues and transcripts from this locus do not repress XIST expression or affect random X chromosome inactivation in embryonic cells. This transcript is thought to be unspliced and extend over more than 30 kb, but its exact nature has not been determined. [provided by RefSeq, Jul 2008]