A theory for the arrangement of sensory organs in Drosophila.
We study the arrangements of recurved bristles on the anterior wing margin of wild-type and mutant Drosophila. The epidermal or neural fate of a proneural cell depends on the concentrations of proteins of the achaete-scute complex. At puparium formation, concentrations of proteins are nearly identical in all cells of the anterior wing and each cell has the potential for neural fate. In wild-type flies, the action of regulatory networks drives the initial state to one where a bristle grows out of every fifth cell. Recent experiments have shown that the frequency of recurved bristles can be made to change by adjusting the mean concentrations of the zinc-finger transcription factor Senseless and the micro-RNA miR-9a. Specifically, mutant flies with reduced levels of miR-9a exhibit ectopic bristles, and those with lower levels of both miR-9a and Senseless show regular organization of recurved bristles, but with a lower periodicity of 4. We argue that these characteristics can be explained assuming an underlying Turing-type bifurcation whereby a periodic pattern spontaneously emerges from a uniform background. However, bristle patterns occur in a discrete array of cells, and are not mediated by diffusion. We argue that intracellular actions of transmembrane proteins such as Delta and Notch can play a role of diffusion in destabilizing the homogeneous state. In contrast to diffusion, intercellular actions can be activating or inhibiting; further, there can be lateral cross-species interactions. We introduce a phenomenological model to study bristle arrangements and make several model-independent predictions that can be tested in experiments. In our theory, miRNA-9a is one of the components of the underlying network and has no special regulatory role. The loss of periodicity in its absence is due to the transfer of the system to a bistable state.
Zhu
Huifeng
H
Department of Physics, University of Houston, Houston, Texas 77204, USA.
Gunaratne
Preethi H
PH
Roman
Gregg W
GW
Gunaratne
Gemunu H
GH
D000465:Algorithms; D000818:Animals; D001703:Biophysics / Q000379:methods; D015509:Developmental Biology / Q000379:methods; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D053263:Gene Regulatory Networks; D017344:Genes, Insect; D008957:Models, Genetic; D015233:Models, Statistical; D008962:Models, Theoretical; D012679:Sense Organs / Q000502:physiology*; D013269:Stochastic Processes; D013696:Temperature; D014921:Wings, Animal / Q000378:metabolism
D029721:Drosophila Proteins