Reprogrammable cell type depends on a single gene to keep it...( Scientists at St. Jude Children's Re...)

Scientists at St. Jude Children's Research Hospital have discovered that a certain differentiated cell type is so ready to change its identity that it requires the constant expression of a gene called Prox1 to dissuade it.

The researchers showed that Prox1 acts as a two-way switch whose inactivity is sufficient to reprogram a specialized type of cell, called a lymphatic endothelial cell (LEC). In the absence of active Prox1, the LEC actually loses its identity and assumes characteristics of a blood endothelial cell (BEC), which plays a different role in the body. Endothelial cells line the inside of blood and lymphatic vessels. The results of the study appear in the Dec. 1, 2008, issue of the journal Genes & Development.

The new finding is important because it helps to explain how during embryogenesis a critical set of vessels called the lymphatic vasculature arises from veins; and how lymphatic vessels can eventually lose their characteristics and acquire features typical of blood vessels and transport blooda trick that might, for example, let the body quickly build up a supply of additional blood vessels when there is an emergency need for more nourishment in a certain area. A switch from lymphatic to blood vessels might also be triggered by certain tumors trying to nourish their own growth.

The lymphatic vasculature is a vital network of vessels that performs important housekeeping functions in the body. Specifically, it drains fluids that normally escape from capillaries, which provide nutrients to the body's cells. The lymphatic vasculature is also part of the immune system that traps and attacks invading organisms and is a primary route for malignant tumor dissemination to the regional lymph nodes.

"The new finding adds to a growing body of evidence showing that some fully differentiated cell types can exhibit great plasticity and upon reprogramming revert back to their previous identity," said Guillermo Olive
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