Genetic Mechanisms in Formation and Specification of Founder Cells

Genetic Mechanisms in Formation and Specification of Founder Cells Segregation and Specification of Muscle Founders 

The Roles of Lineage Cenes in Asymmetric Cell Divisions of Muscle Progenitors 

How does numb determine the identities of these founder cells Apparently, it does so, at least in part, by regulating the maintenance of Kr and S59 expression in the founder cell of muscle 27 that inherits Numb protein. By contrast, its sibling lacks Numb protein, which results in the downregulation of Kr and S59, and consequently this cell assumes the identity as a founder cell of muscle 26. Kr seems to act upstream of S59 in this maintenance process. Thus, in ifr mutants, S59 is not maintained in either of the two founder cells and both develop into muscle 26, while upon ectopic Kr expression in all myoblasts, both maintain S59 expression and develop into muscle 27 (Ruiz Gomez and Bate, 1997). 

It is not known how numb maintains Kr expression in the muscle 27 founder. In neuronal specification, numb has been shown to act through the inhibition of Notch signaling, and this seems also to be the case for some other muscle founders that have been examined (Ruiz Gomez and Bate, 1997 Carmena et al., 1998). Thus, it 

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