@article {46647,
	title = {Dorsoventral patterning in the Drosophila retina by wingless.},
	journal = {Development},
	volume = {125},
	year = {1998},
	month = {1998 Feb},
	pages = {567-77},
	abstract = {<p>The eye imaginal disc displays dorsal-ventral (D-V) and anterior-posterior polarity prior to the onset of differentiation, which initiates at the intersection of the D-V midline with the posterior margin. As the wave of differentiation progresses anteriorly, additional asymmetry develops as ommatidial clusters rotate coordinately in opposite directions in the dorsal and ventral halves of the disc; this forms a line of mirror-image symmetry, the equator, which coincides with the D-V midline of the disc. How D-V pattern is established and how it relates to ommatidial rotation are unknown. Here we address this question by assaying the expression of various asymmetric markers under conditions that lead to ectopic differentiation, such as removal of patched or wingless function. We find that D-V patterning develops gradually and that wingless plays an important role in setting up this pattern. We show that wingless is necessary and sufficient to induce dorsal expression of the gene mirror prior to the start of differentiation and also to restrict the expression of the WR122 marker to differentiating photoreceptors near the equator. In addition, we find that manipulations in wingless expression shift the D-V axis of the disc as evidenced by changes in the expression domains of asymmetric markers, the position of the site of initiation and the equator, and the pattern of epithelial growth. Thus, Wg appears to coordinately regulate multiple events related to D-V patterning in the developing retina.</p>
},
	keywords = {Animals, Animals, Genetically Modified, Crosses, Genetic, Drosophila, Drosophila Proteins, Eye Proteins, Female, Gene Expression Regulation, Developmental, Genes, Insect, Genetic Markers, Homeodomain Proteins, Lac Operon, Larva, Male, Proto-Oncogene Proteins, Retina, Transcription Factors, Wnt1 Protein},
	issn = {0950-1991},
	author = {Heberlein, U and Borod, E R and Chanut, F A}
}
@article {46646,
	title = {Mutual regulation of decapentaplegic and hedgehog during the initiation of differentiation in the Drosophila retina.},
	journal = {Devopemental Biology},
	volume = {197},
	year = {1998},
	month = {1998 May 15},
	pages = {187-97},
	abstract = {<p>Neuronal differentiation in the Drosophila retinal primordium, the eye imaginal disc, begins at the posterior tip of the disc and progresses anteriorly as a wave. The morphogenetic furrow (MF) marks the boundary between undifferentiated anterior cells and differentiating posterior cells. Anterior progression of differentiation is driven by Hedgehog, synthesized by cells located posterior to the MF. We report here that hedgehog (hh), which is expressed prior to the start of differentiation along the disc{\textquoteright}s posterior margin, also plays a crucial role in the initiation of differentiation. Using a temperature-sensitive allele we show that hh is normally required at the posterior margin to maintain the expression of decapentaplegic (dpp) and of the proneural gene atonal. In addition, we find that ectopic differentiation driven by ectopic dpp expression or loss of wingless function requires hh. Consistent with this is our observation that ectopic dpp induces the expression of hh along the anterior margin even in the absence of differentiation. Taken together, these data reveal a novel positive regulatory loop between dpp and hh that is essential for the initiation of differentiation in the eye disc.</p>
},
	keywords = {Animals, Animals, Genetically Modified, Basic Helix-Loop-Helix Transcription Factors, Cell Differentiation, DNA-Binding Proteins, Drosophila, Drosophila Proteins, Female, Gene Expression Regulation, Developmental, Genes, Insect, Hedgehog Proteins, Immunohistochemistry, Insect Proteins, Larva, Male, Nerve Tissue Proteins, Neurons, Retina},
	issn = {0012-1606},
	doi = {10.1006/dbio.1998.8888},
	author = {Borod, E R and Heberlein, U}
}
