Notch1 and T-cell development: insights from conditional knockout mice

Notch proteins influence cell-fate decisions in many developmental systems, Gain-of-function studies have suggested a crucial role for Notch 1 signali ng at several stages during lymphocyte development, including the B/T, alph a beta/gamma delta and CD4/CD8 lineage choices. Here, we critically re-eval uate these conclusions in the light of recent studies that describe inducib le and tissue-specific targeting of the Notch 1 gene.