Biomedical subjects
R Cagan
Publications and source records attributed to R Cagan.
Cell fate specification in the developing Drosophila retina.
The developing Drosophila retina provides an excellent experimental system in which to address questions of cell fate choice and patterning. By focusing first on a detailed morphological description of eye development and more recently on the genes required for its development, the first steps have been taken toward understanding how these two aspects combine to direct cell fate in the retinal neuroepithelium. In addition, developing cell types emerge within the ommatidium in stereotyped patterns; these patterns may provide further clues regarding the mechanisms involved in cell fate choice. Previous reviews have focused on the detailed morphological description of, and molecules involved with, retinal development. This review focuses on current progress in understanding the role of several genes that play critical roles in retinal development, with special emphasis on how they define symmetric groups of cells within each ommatidium. In addition, the role of local cell interactions in directing cell fate is assessed.
Neuronal development in the Drosophila retina: the sextra gene defines an inhibitory component in the developmental pathway of R7 photoreceptor cells.
Mutations in a gene called sextra (sxt) have been isolated. Loss of one copy of sxt promotes R7 photoreceptor cell development in a genetically sensitized background, while loss of both copies results in precursors of non-neuronal cone cells transforming into R7 cells. The requirement for sxt function is cell-autonomous. The transformation of cone-cell precursors into R7 cells occurs independently of the sevenless signal. However, the R7 precursor becomes neuronal in an sxt/sxt mutant only in a wild-type sevenless background. The genetic analysis of sxt suggests that it plays an inhibitory role, preventing cone cells from becoming neuronal. Additionally, sxt functions in R7 precursors, but the sevenless signal is essential for specification of this fate, since loss of sextra alone is unable to impart a neural fate to this cell.
Induction of the R7 neuron in the Drosophila compound eye: the bride of sevenless and sevenless interaction.
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Pharmaceutical agents for preventing caries--a review. II. Topical application procedures.
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