TMEM27 is a membrane protein. It has been proposed as a beta cell mass biomarker since it is cleaved and shed by pancreatic beta cells. Overexpression of TMEM27 leads to increased thymidine incorporation, whereas silencing of Tmem27 using RNAi results in a reduction of cell replication. Furthermore, transgenic mice with increased expression of Tmem27 in pancreatic beta cells exhibit increased beta cell mass. TMEM27 is also important for trafficking amino acid transporters to the apical brush border of proximal tubules.