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Cell fate control in the Drosophila retina by the orphan receptor seven-up: its role in the decisions mediated by the ras signaling pathway

Authors :
Kramer, Susanne
West, Steven R.
Hiromi, Yasushi
Source :
Development; May 1995, Vol. 121 Issue: 5 p1361-1372, 12p
Publication Year :
1995

Abstract

Drosophila seven-up is an orphan receptor of the steroid receptor family that is required to specify photoreceptor neuron subtypes in the developing compound eye. Expression of seven-up is confined to four of the eight photoreceptor precursors, R3/R4/R1/R6. We show that misexpression of seven-up in any of the other cell types within the developing ommatidium interferes with their differentiation. Each cell type responds differently to seven-up misexpression. For example, ectopic expression in the non-neuronal cone cells using the sevenless promoter/enhancer (sev-svp) causes the cone cells to take on a neuronal identity. Ectopic expression of seven-up in R2/R5 using the rough enhancer (ro-svp) causes these neurons to lose aspects of their photoreceptor subtype identity while remaining neuronal. Each cell type appears to have a different developmental time window that is sensitive to misexpressed seven-up. The temporal order of responsiveness of each cell type to misexpressed seven-up is similar but not identical to the order of neuronal differentiation. This suggests that there are processes of specification that are distinct from the specification to become a photoreceptor neuron. We have identified members of the ras signaling pathway as suppressors of the cone cell to R7 neuron transformation caused by sev-svp. Suppression of the sev-svp phenotype can be achieved by decreasing the gene-dosage of any of the members of the ras-pathway. This suggests that the function of seven-up in the cone cells requires ras signaling. However, a decrease in ras signaling results in enhancement of the phenotype caused by the rosvp transgene. We discuss the relationship between decisions controlled by seven-up and those controlled by ras signaling.

Details

Language :
English
ISSN :
09501991 and 14779129
Volume :
121
Issue :
5
Database :
Supplemental Index
Journal :
Development
Publication Type :
Periodical
Accession number :
ejs59001611
Full Text :
https://doi.org/10.1242/dev.121.5.1361