Figure 14-19. Formation of sensory organ precursors (SOPs) in the wing imaginal disc of Drosophila.

Figure 14-19Formation of sensory organ precursors (SOPs) in the wing imaginal disc of Drosophila

A set of extracellular signaling molecules and transcription factors, encoded by so-called patterning genes, control the precise spatiotemporal pattern of expression of proneural bHLH proteins such as Achaete and Scute (green) and related proteins that antagonize their function (e.g., Emc). Most cells within the disc express Emc (light red), but only small groups of cells, the proneural clusters, express proneural bHLH proteins. The region of the proneural cluster from which an SOP will form expresses lower levels of Emc, giving these cells a bias towards SOP formation. Interactions between these cells, leading to accumulation of E(spl) repressor proteins in neighboring cells (orange), then restrict SOP formation to a single cell (see Figure 14-20). The activity of Achaete in the SOP promotes expression of Asense (blue), which is required for further differentiation.

From: Section 14.2, Cell-Type Specification in Animals

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.