Early in development, cells are multipotent. During development through the action of temporally and spatially controlled signals, cells adopt a specific fate. Umesono et al. studied the role of Notch in regulating neuronal and glial differentiation in Drosophila embryos. In the adult peripheral nervous system, Notch inhibits the expression of glial cells missing (gcm), which inhibits glial cell formation. Umesono et al. showed that in the sensory organ precursors of the dorsal bipolar dendriditic (dbd) and the dorsal dendritic arbor (dda) lineage, Notch was required for gcm expression and glial cell development. Whenever Notch signaling was impaired, fewer glial cells were produced in the dbd and dda, and when Notch signaling was increased, glial cells were produced at the expense of neurons. The expression of the POU-domain-containing transcriptional regulator Nubbin was also temporally regulated in dbd cells. Overexpression of Nubbin and constitutively active Notch resulted in increased glial cells in the dda. These findings suggest that Nubbin may provide contextual information for the effect of Notch--to promote or inhibit gliogenesis.
Y. Umesono, Y. Hiromi, Y. Hotta, Context-dependent utilization of Notch activity in Drosophila glial determination. Development 129, 2391-2399 (2002). [Online Journal]