First published online June 20, 2008
Development 135, 1403e (2008)
© The Company of Biologists Limited
Notch not numbed by Numb
The membrane-localized intracellular protein Numb is known to antagonize
Notch signalling in several developmental contexts, such as during mesodermal
development in Drosophila. But now, surprisingly, Range and
co-workers report that the sea urchin homologue of Numb (LvNumb) regulates
Notch signalling positively during the specification of non-skeletal mesoderm
(NSM) cells in sea urchin embryos (see
p. 2445). The
researchers show that LvNumb protein localizes to the presumptive NSM cells in
early embryos. By injecting LvNumb RNA and antisense morpholinos, they
demonstrate that LvNumb is needed for the specification of all the NSM cell
types. The authors also show that LvNumb acts synergistically with Notch
during NSM specification and that, unlike in other systems, LvNumb does not
need to interact with the endocytic machinery to regulate Notch signalling.
Numb might, the researchers speculate, regulate Notch positively by binding to
other unknown factors, the identification of which could provide new insights
into Notch and Numb signalling and shed light on the changing role of Numb
during evolution.

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Related articles in Development:
- LvNumb works synergistically with Notch signaling to specify non-skeletal mesoderm cells in the sea urchin embryo
- Ryan C. Range, Thomas D. Glenn, Esther Miranda, and David R. McClay
Development 2008 135: 2445-2454.
[Abstract]
[Full Text]