Patterned Anchorage to the Apical Extracellular Matrix Defines Tissue Shape in the Developing Appendages of Drosophila.
Bottom Line: Here, we describe a genetic pathway that shapes appendages in Drosophila by defining the pattern of global tensile forces in the tissue.Altering Dp expression in the developing wing results in predictable changes in wing shape that can be simulated by a computational model that incorporates only tissue contraction and localized anchorage.Three other wing shape genes, narrow, tapered, and lanceolate, encode components of a pathway that modulates Dp distribution in the wing to refine the global force pattern and thus wing shape.
Affiliation: School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK; The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. Electronic address: firstname.lastname@example.org.Show MeSH
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Mentions: We sought to identify genes involved in defining the pattern of tensile forces in the pupal wing. We reasoned that hinge contraction could only result in anisotropic tension if the wing epithelium is anchored distally to provide the mechanical resistance necessary to give rise to the tension. Mutants that disrupt this anchoring should have the normal pattern of veins and interveins, but show a retraction of the wing blade toward the hinge. Such a phenotype is associated with alleles of the dumpy (dp) locus. Classical genetic studies on dp mutants revealed three phenotypic states for the locus: an oblique truncation of the wing (“o”), pits on the thorax known as vortices (“v”), and homozygous lethality (“l”). While the phenotype of the locus is lethality, dpo alleles as homozygotes or in combination with other alleles produce a continuous spectrum of wing phenotypes ranging from a mild flattening of the distal tip of the wing (the “oblique” phenotype), to a collapse of the distal tip (the eponymous “dumpy” phenotype), and, in the most extreme case, to a complete retraction of the wing blade (the “truncate” phenotype) (Figures 1A–1D) (Carlson, 1959). RNAi silencing of dp throughout the wing blade recapitulates the truncate phenotype with 100% penetrance (Figure 1E) and the same phenotype is produced with the Dll-Gal4 driver, which is expressed at high levels only at the margin (Figure 1F). Dll-Gal4 is also expressed in legs and antennae, and depleting dp in these tissues results in retraction of the distal segments of both appendages (Figures 1G and 1H), indicating that dp plays a general role in determining appendage shape.
Affiliation: School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK; The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. Electronic address: email@example.com.