Fig. 7. sens regulates cell-fate specification in the microchaetae pI progeny. (A-A'') Sc expression is restricted to single cells in a sens clone. Shown is a sens^E2 clone in a 12-hour APF pupal thorax stained for Sc (red). GFP (blue) marks the wild-type tissue. (B,B') A MARCM clone of sens in the thorax 24-30 hours APF stained for Elav (red) and Prospero (green). Note the multiple neurons and an occasional sheath cell in mutant clusters. (C,C') A MARCM clone of sens in the thorax around 28-30 hours APF, stained for Elav (red) and HRP (green). Because of the presence of several neurons in each cluster, some axonal tracts in the mutant tissue are thicker than their wild-type counterparts. (D-D'') Microchaetae pI progeny undergo cell fate transformation in sens clones. A wild-type (left) and a sens^E2 (right) sensory cluster is shown at 24-26 hours APF, stained for Elav (red) and Su(H) (green). Note that the mutant cluster contains multiple neurons but no socket cells. (E) Simplified model of the microchaetae lineages in wild-type and sens^- animals. Note that in addition to the pIIa-to-pIIb transformation, many mutant clusters also exhibit a sheath-to-neuron transformation in the pIIb progeny. so, socket; sf, shaft; st, sheath; n, neuron.