title: Wingless mediated apoptosis: How cone cells direct the death of peripheral ommatidia in the developing Drosophila eye.
abstract: Morphogen gradients play pervasive roles in development, and understanding how they are established and decoded is a major goal of contemporary developmental biology. Here we examine how a Wingless (Wg) morphogen gradient patterns the peripheral specialization of the fly eye. The outermost specialization is the pigment rim; a thick band of pigment cells that circumscribes the eye and optically insulates the sides of the retina. It results from the coalescence of pigment cells that survive the death of the outermost row of developing ommatidia. We investigate here how the Wg target genes expressed in the moribund ommatidia direct the intercellular signaling, the morphogenetic movements, and ultimately the ommatidial death. A salient feature of this process is the secondary expression of the Wg morphogen elicited in the ommatidia by the primary Wg signal. We find that neither the primary nor secondary sources of Wg alone are able to promote ommatidial death, but together they suffice to drive the apoptosis. This represents an unusual gradient read-out process in which a morphogen induces its own expression in its target cells to generate a concentration spike required to push the local cellular responses to the next threshold response.
authors.affiliation: Department of Genetics and Development College of Physicians and Surgeons Columbia University, United States.
authors.forename: Sudha R
authors.initials: SR
authors.lastname: Kumar
authors.affiliation: Department of Genetics and Development College of Physicians and Surgeons Columbia University, United States.
authors.forename: Hina
authors.initials: H
authors.lastname: Patel
authors.affiliation: Department of Genetics and Development College of Physicians and Surgeons Columbia University, United States. Electronic address: at41@columbia.edu.
authors.forename: Andrew
authors.initials: A
authors.lastname: Tomlinson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D019521:Body Patterning; D054910:Compound Eye, Arthropod / Q000166:cytology* / Q000254:growth & development* / Q000648:ultrastructure; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D011679:Pupa / Q000378:metabolism; D034622:RNA Interference; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D051155:Wnt1 Protein; C000604451:sna protein, Drosophila; C074622:wg protein, Drosophila