Researchers have successfully identified over 5,000 proteins that are present in embryonic stem cells, tripling the size of previous results and in the process creating the largest quantified protein map to date.

Stem cells hold great potential in biology and medicine, but a host of questions lingers about how they operate and convert into other cells. To help answer these questions, researchers have begun taking a 'big picture' approach, identifying all the proteins that are expressed in stem cells.

Currently, around 1700 proteins have been identified in stem cells. Now, using mass spectrometry and special "heavy" amino acids (made with carbon-13), Matthias Mann and colleagues quantified 5111 distinct mouse stem cell proteins. As expected, a good portion of these proteins are involved in rapid cell growth, but overall the proteome encompassed a broad range of cell functions.

While this study may help uncover new clues to stem cell biology, it does raise the bar on the complexity of these important cells, considering they express at least 25% of all known mouse proteins.

Journal reference: "SILAC-labeling and proteome quantitation of mouse embryonic stem cells to a depth of 5111 proteins" by Johannes Graumann, Nina Hubner, Jeong Beom Kim, Kinarm Ko, Markus Moser, Chanchal Kumar, Jürgen Cox, Hans Schöler and Matthias Mann. Molecular & Cellular Proteomics. April 2008.