Development

Turning On and Staying On

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Science  12 Dec 2008:
Vol. 322, Issue 5908, pp. 1610
DOI: 10.1126/science.322.5908.1610c

During metazoan development, cells generally progress inexorably to a terminally differentiated fate. However, recent in vitro manipulations have enabled the conversion of one differentiated cell type either to a pluripotent state (as occurs with somatic cell nuclear transfer and induced pluripotent cells) or to another differentiated cell type (for example, reprogramming of mature B cells into T cells). Although quite a bit is known about the factors necessary to specify particular cell types, relatively little is known about the factors required to maintain the terminally differentiated phenotype. For specification of lymphatic endothelial cells (LECs), Prox1 expression is crucial, and Johnson et al. extend this finding to show an additional role of Prox1 in maintaining the lymphatic fate. Down-regulation of mouse Prox1 results in mispatterned lymphatic vessels that fill with blood; LECs are effectively reprogrammed into blood endothelial cells (BECs). Hence, Prox1 acts as a binary switch participating in the known roles of suppressing BEC fate and promoting LEC fate; furthermore, sustained Prox1 expression is necessary to maintain the lymphatic cell phenotype. — BAP.

Genes Dev. 22, 10.1101/gad.1727208 (2008).

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