CHPT1, also known as AAPT1-like protein and Diacylglycerol cholinephosphotransferase 1, is a 406 amino acid multi-pass membrane protein that is localized to the golgi apparatus. By catalyzing the phosphatidylcholine biosynthesis from CDP-choline, it plays an essential role in the formation and maintenance of vesicular membranes. CHPT1 is most abundant in testis, as well as small intestine, heart, colon, spleen and prostate. Expression of CHPT1 is increased in cancerous breast cells as compared to normal breast cell lines and it has been determined that the CHPT1 gene exhibits mutations within the cancerous cells. Interestingly, exposure to mustard gas significantly decreases CHPT1 gene expression and activity, an event that may play an important role in the development of acute respiratory distress syndrome (ARDS). There are two isoforms of CHPT1 that are produced as a result of alternative splicing events.