Gene
The numb gene protein product controls binary cell fate decisions in the peripheral and central nervous systems of both invertebrates and mammals during neurogenesis. During cell division, Numb is asymmetrically localized to one end of the progenitor cell and subsequently segregates to only one daughter cell where it intrinsically determines cell fate. Numb protein signaling plays a key role in binary cell fate decisions following asymmetric cell divisions. One daughter cell, generally that receiving the Numb, is able to adopt a neuronal fate and innervate the developing nervous system. The other daughter cell becomes a progenitor cell to fill the lost role of the parent cell and maintain proliferation. In addition to its role in proliferation and differentiation, Numb has also been shown to play a role in tumorigenesis and the chemotactic migration of neural progenitors during migration.
In mammals, there are four alternatively spliced forms of the Numb protein. In addition, there is a Numb homolog called “Numb-like,” or NUMBL. Numb proteins in mammals are not as well understood as their fly counterparts. The various forms of Numb have differential progenitor-promoting and differentiation-promoting functions. More research is necessary to understand the complex relationships between these forms of Numb and their functions.
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