The jumonji domain containing 1C protein (JMJD1C) was initially discovered in silico, and later suggested to be a candidate gene for autism. Like the related proteins JMJD1A and JMJD1B, JMJD1C is a histone H3K9 demethylase implicated in the nuclear hormone receptor-based transcriptional regulation. JMJD1C mRNA is highly expressed in undifferentiated embryonic stem (ES) cells as well as pancreatic islet, diffuse-type gastric cancer, and other tissues and tumors. The JMJD1C gene promoter contain bHLH-, AP-1-, and POU5F1-binding sites, and as preferential expression of POU5F1 has been reported in ES cells, pancreatic islet, and diffuse-type gastric cancer, it has been suggested that POU5F1-mediated expression of JMJD1C reactivates previously silenced genes in ES cells and diffuse-type gastric cancer. At least three isoforms of JMJD1C are known to exist.