Among the about 20,000 genes giving rise to the human proteome there are still many rather unknown but potentially interesting genes that deserve some extra attention. Here we will focus on TMEM213, a gene with little evidence and specific expression in the kidney and salivary gland.

There are only eight genes in the Human Protein Atlas classified as group enriched in kidney and salivary gland. Two of them are subunits of the well-known multisubunit enzyme V-ATPase that is responsible for acidifying and maintaining the pH of intracellular compartments and also mediates secretion of protons from renal intercalated cells into the urine to ensure correct urinary acidification.

TMEM213 on the other hand lacks protein and transcript evidence in UniProt and has no suggested function. That this protein also deserves more attention is however strongly suggested when looking into the data in the Human Protein Atlas. The expression profiles in both bulk and single cell RNA seq show specific expression in kidney and salivary gland and more specifically in distal tubular cells, salivary duct cells, collecting duct cells and serous glandular cells.

Expression clustering and correlation of tissue and single cell RNA seq data further show TMEM213 to cluster together with other genes known to be related to transmembrane transport in kidney and salivary secretion. These findings have been confirmed on the protein level using immunohistochemistry that show staining of the protein exclusively in salivary gland and tubular cells of the kidney. A more detailed analysis of the expression in the salivary gland using multiplex immunofluorescence shows the protein located in ionocytes and in the large ducts. This might be a starting point to further understand the function of this interesting protein.