Marker for thymic stem cells identified

Scottish researchers, assisted by scientists from the Western Australian Institute for Medical Research, have identified an orphan protein called Plet-1 as a marker for thymic epithelial progenitor cells (TEPC).

The protein might also prove a cell surface marker for pancreatic progenitor cells, as it is highly expressed in by major duct epithelium.

The research, published in the January 22 issue of the US Proceedings of the National Academy of Sciences, was led by Clare Blackburn of the Institute for Stem Cell Research in Edinburgh.

The WAIMR scientists, Professor Grant Morahan and Kathy Davern, produced a new monoclonal antibody for the marker.

The Scottish team said it had previously identified the epithelial progenitor population from which the thymus arises.

The thymus, the organ in which T cells grow and multiply, is active in childhood but becomes non-functional in adulthood.

The same team has demonstrated the cells ability to generate a functional thymus upon transplantation.

The cells were identified by two monoclonal antibodies, MTS20 and MTS24, which also identify skin stem cells.

The new research in mice shows that the two antibodies specifically bind Plet-1 (placenta-expressed transcript 1), whose function is still unknown.

The researchers say Plet-1 is expressed in a number of sites in adult tissues, including mammary and prostate epithelia, and in the pancreas.

"Plet-1 is specifically expressed by the major duct epithelium, providing a specific cell surface marker for this putative reservoir of pancreatic progenitor/stem cells," the researchers write.

Morahan, director of WAIMR's Centre for Diabetes Research, said the marker would help the understanding of a number of human diseases, including diabetes and cancer.

"The thymus is responsible for the creation of disease fighting T-cells and finding this marker of stem cells which gives rise to this organ presents enormous possibilities," he said.

"For example, it may help scientists develop ways to help patients whose immune systems are compromised. Also, we found the same marker in the pancreas so it may define stem cells from which we can create new insulin-producing islet cells for diabetes patients."

See Stem cells, tolerance and rebooting the thymus