engrailed controls glial/neuronal cell fate decisions at the midline of the central nervous system
The molecular mechanisms involved in glial/neuronal fate decisions during embryonic development are largely unknown. Here we show that the segment-polarity gene engrailed, which encodes a homeodomain protein, controls these decisions within an insect CNS lineage. The grasshopper median neuroblast (MNB) generates both neurons and midline glia in distinct temporal phases. engrailed expression in MNB progeny can be inhibited by injection of antisense oligodeoxynucleotides into the MNB nucleus. This produces a phenotype in which the midline glia do not develop and extra midline neurons are generated. In the absence of engrailed function, midline glial precursors are apparently converted into neuronal precursors. Thus, engrailed is required for execution of the decision between the glial and neuronal fates.
© 1994 Elsevier. Received June 28, 1994. We thank Scott Fraser for helpful discussions and for the use of injection equipment, Gilles Laurent for the use of his grasshopper colony, and David Anderson and Sarah Fashena for comments on the manuscript. This work was supported by National Institutes of Health grants #NS28182 to K. Z. and #GM47268 to N. H. P., by McKnight Scholars Awards to K. Z. and N. H. P, and by a Pew Scholars Award to K. Z. B. G. C. was supported by a Del Webb postdoctoral fellowship. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC Section 1734 solely to indicate this fact.