Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Echinobase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
Development 2008 Aug 01;13514:2445-54. doi: 10.1242/dev.018101.
Show Gene links Show Anatomy links

LvNumb works synergistically with Notch signaling to specify non-skeletal mesoderm cells in the sea urchin embryo.

Range RC , Glenn TD , Miranda E , McClay DR .

Activation of the Notch signaling pathway segregates the non-skeletogenic mesoderm (NSM) from the endomesoderm during sea urchin embryo development. Subsequently, Notch signaling helps specify the four subpopulations of NSM, and influences endoderm specification. To gain further insight into how the Notch signaling pathway is regulated during these cell specification events, we identified a sea urchin homologue of Numb (LvNumb). Previous work in other model systems showed that Numb functions as a Notch signaling pathway antagonist, possibly by mediating the endocytosis of other key Notch interacting proteins. In this study, we show that the vegetal endomesoderm expresses lvnumb during the blastula and gastrula stages, and that the protein is localized to the presumptive NSM. Injections of lvnumb mRNA and antisense morpholinos demonstrate that LvNumb is necessary for the specification of mesodermal cell types, including pigment cells, blastocoelar cells and muscle cells. Functional analysis of the N-terminal PTB domain and the C-terminal PRR domain of LvNumb shows that the PTB domain, but not the PRR domain, is sufficient to recapitulate the demonstrable function of full-length LvNumb. Experiments show that LvNumb requires an active Notch signal to function during NSM specification and that LvNumb functions in the cells responding to Delta and not in the cells presenting the Delta ligand. Furthermore, injection of mRNA encoding the intracellular domain of Notch rescues the LvNumb morpholino phenotype, suggesting that the constitutive intracellular Notch signal overcomes, or bypasses, the absence of Numb during NSM specification.

PubMed ID: 18550713
PMC ID: PMC3794459
Article link: Development
Grant support: [+]

Genes referenced: LOC100887844 LOC115919910 LOC115921237 LOC574897 LOC579389 LOC764088
Morpholinos: LOC764088 MO1 LOC764088 MO2

References [+] :
Artavanis-Tsakonas, Notch signaling: cell fate control and signal integration in development. 1999, Pubmed