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Drosophila retinal pigment cell death is regulated in a position-dependent manner by a cell memory gene
Nicolas Dos-Santos1, Thomas Rubin, Fabienne Chalvet
1CNRS - UMR 8159, LGBC, Université de Versailles St Quentin, Versailles, France.
Abstract:
The stereotyped organization of the Drosophila compound eye depends on the elimination by apoptosis of about 25% of the inter-ommatidial pigment cell precursors (IOCs) during metamorphosis. This program of cell death is under antagonistic effects of the Notch and the EGFR pathways. In addition, uncharacterized positional cues may underlie death versus survival choices among IOCs. Our results provide new genetic evidences that cell death is regulated in a position- dependent manner in the eye. We show that mutations in Trithorax-like (Trl) and lola-like/batman specifically block IOC death during eye morphogenesis. These genes share characteristics of both Polycomb-Group and trithorax-Group genes, in that they are required for chromatin-mediated repression and activation of Hox genes. However, Trl function in triggering IOC death is independent from a function in repressing Hox gene expression during eye development. Analysis of mosaic ommatidiae containing Trl mutant cells revealed that Trl function for IOC death is required in cone cells. Strikingly, cell death suppression in Trl mutants depends on the position of IOCs. Our results further support a model whereby death of IOCs on the oblique sides of ommatidiae requires Trl-dependent reduction of a survival signal, or an increase of a death signal, emanating from cone cells. Trl does not have the same effect on horizontal IOCs whose survival seems to involve additional topological constraints.
Insights
In Drosophila eyes, Trithorax-like (Trl) regulates programmed cell death of pigment cell precursors. This cell death is position-dependent, with Trl controlling survival signals from cone cells.
Area of Science:
- Developmental Biology
- Genetics
- Cell Biology
Background:
- The precise structure of the Drosophila compound eye requires the apoptosis of inter-ommatidial pigment cell precursors (IOCs).
- Notch and EGFR signaling pathways antagonistically regulate this cell death program.
- Positional cues are suspected to influence IOC survival decisions.
Purpose of the Study:
- To investigate the genetic basis of position-dependent cell death in Drosophila eye development.
- To identify genes involved in regulating IOC survival and death.
- To elucidate the role of Trithorax-like (Trl) in IOC apoptosis.
Main Methods:
- Genetic screens using Drosophila eye development models.
- Analysis of mutations in Trithorax-like (Trl) and lola-like/batman.
- Mosaic analysis of Trl mutant cells in cone cells.
- Investigating the positional dependence of IOC death.
Main Results:
- Mutations in Trithorax-like (Trl) and lola-like/batman block IOC death during eye morphogenesis.
- Trl's role in IOC death is independent of its function in Hox gene regulation.
- Trl function for IOC death is required in cone cells and is position-dependent.
- Cell death suppression in Trl mutants is linked to IOC position, particularly on oblique sides of ommatidia.
Conclusions:
- Trithorax-like (Trl) plays a crucial role in regulating the position-dependent apoptosis of inter-ommatidial pigment cell precursors in Drosophila.
- Trl likely functions by modulating survival or death signals from cone cells.
- The survival of horizontal IOCs may involve additional topological factors beyond Trl regulation.
