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First published online 17 November 2004
doi: 10.1242/dev.01550

Development 131, 6175-6184 (2004)
Published by The Company of Biologists 2004
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Planar cell polarity in the Drosophila eye is directed by graded Four-jointed and Dachsous expression

Michael A. Simon

Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA



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  		Fig. 1. Planar polarity in the Drosophila eye. All images are oriented anterior to the left and dorsal down. (A) An SEM of a Drosophila compound eye. The blue and magenta boxes indicate the regions of the eye examined in equatorial and polar sections, respectively, throughout the paper. (B) Dorsal (green arrows) and ventral (red arrows) ommatidia shown in apical (left) and basal sections of the eye. The gray structures are the rhabdomeres of the indicated photoreceptor cells. In apical sections, the central rhabdomere belongs to the R7 cell, whereas in basal sections, the R8 rhabdomere is visible instead. (C) A tangential section of the eye showing that the eye is divided into dorsal and ventral fields. The equator is indicated by the blue line. (D) A schematic of the section shown in C. In this, and all subsequent figures, the orientation of ommatidia is indicated by arrows drawn from the rhabdomere of R1 to that of R3. Green arrows indicate ommatidia of dorsal chirality and orientation, whereas red arrows designate ventral type ommatidia. (E) A diagram of the process of R3/R4 cell fate specification and ommatidial rotation. When clusters first emerge behind the morphogenetic furrow (1), the R3/R4 precursors (beige) are not in contact. Following cell-cell contact between the R3 and the R4 precursors (2), the two cells adopt distinct fates, with the cell located closer to the equator becoming R3 (red), while the other becomes R4 (green). The clusters then rotate 90° (3 and 4) to establish the final pattern of polarity. R1, R6, and R7 are not included in the diagram for simplicity. (F) A diagram of the proposed model for the control of Fz signaling and R3/R4 cell fate specification by Fj, Ds and Ft. Diffusible signaling proteins drive graded transcription of Fj and Ds. The resulting Ds and Fj protein gradients then regulate the action of Ft, which is uniformly expressed, to generate graded Ft function across the eye. The resulting difference in Ft between the neighboring R3 and R4 cells biases their Fz competition, and ensures that the equatorial cell assumes the elevated Fz signaling state and thus becomes R3.

 


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  		Fig. 2. Graded Fj and Ds expression provide partially redundant directional cues. Schematics of representative equatorial sections of adult eyes. Yellow circles represent either incorrectly constructed ommatidia or ommatidia exhibiting severe misrotation (greater than 90° from normal). Relevant changes from wild type with regard to Fj and Ds function or expression are indicated at the bottom of each panel. Precise genotypes are listed below. Quantitative results are summarized in Table 1. The schematics along with the sections on which they are based are presented in Fig S1 in supplementary material. (A) w1118. (B) w1118; ds38k/dsUA071, fjd1. (C) w1118; fjN7/dsUA071, fjd1. (D) w1118; ds38k, fjN7/dsUA071, fjd1. (E) w1118; fjN7/dsUA071, fjd1; TubP-Gal4/UAS-Fj. (F) w1118; ds38k/dsUA071, fjd1; TubP-Gal4/UAS-Ds. (G) w1118; ds38k, fjN7/dsUA071, fjd1; TubP-Gal4, UAS-Ds/UAS-Fj. (H) w1118; ds38k, fjN7/dsUA071, fjd1; TubP-Gal4/UAS-Ds. (I) w1118; ds38k, fjN7/dsUA071, fjd1; TubP-Gal4/UAS-Fj.

 


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  		Fig. 3. Reversals in the pattern of Fj and Ds expression can redirect ommatidial polarity. Schematics of representative sections of adult eyes. Relevant changes from wild type with regard to Fj and Ds function or expression are indicated at the bottom of each panel. Yellow circles indicate ommatidia that were either incorrectly formed or severely misrotated. The schematics along with the sections on which they are based are presented in Fig. S2 in supplementary material. (A,B,E,G-I) Equatorial sections; (C,D,F) polar sections. (A) w1118; TubP-Gal4/UAS-Fj. (B) w1118; fjVg1-Gal4/+; UAS-Fj/+. (C) w1118, Omb3-Gal4/w1118; UAS-Fj/+. (D) w1118, Omb3-Gal4/w1118; fjN7/dsUA071, fjd1; UAS-Fj/+. (E) w1118; TubP-Gal4/UAS-Ds. (F) w1118, Omb3-Gal4/w1118; UAS-Ds/+. (G) w1118; fjVg1-Gal4/+; UAS-Ds/+. (H) w1118; dsUA071, fjVg1-Gal4/ds38k; UAS-Ds/+. (I) w1118; dsUA071, fjVg1-Gal4/ds38k fjN7; UAS-Ds/+.

 


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  		Fig. 4. Graded Ft expression can direct ommatidial polarity. (A) Anti-Ft antibody staining of a wild-type eye imaginal disc. Anterior is left, dorsal up. Ft is expressed in a uniform pattern along the dorsoventral axis at the morphogenetic furrow (arrowheads). (B) Anti-Ft antibody staining of a w1118; fjVg1-Gal4/+; UAS-Ft/+ eye imaginal disc. Ft expression is elevated in the equator region and drops in a graded fashion towards the poles of the disc. (C) Anti-Ft antibody staining of a w1118, Omb3-Gal4/w1118; UAS-Ft/+ eye imaginal disc. Ft expression is slightly elevated near the poles (yellow arrow) and drops rapidly towards the equator. The inset is a magnified view of the arrowed region. (D-I) Schematics of representative sections of adult eyes. Relevant changes from wild type with regard to Ft and Fj function or expression are indicated at the bottom of each panel. The schematics along with the sections on which they are based are presented in Fig. S3 in supplementary material. (D-F) Equatorial sections; (G-I) polar sections. (D) w1118; ftG-rv/ftl(2)fd; TubP-Gal4/UAS-Ft. (E) w1118; TubP-Gal4/UAS-Ft. (F) w1118; fjVg1-Gal4/+; UAS-Ft/+. (G) w1118, Omb3-Gal4/w1118; UAS-Ft/+. (H) w1118, Omb3-Gal4/w1118; fjN7/dsUA071, fjd1; UAS-Ft/+. (I) w1118; fjN7/dsUA071, fjd1.

 


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  		Fig. 5. The Ds and Fj gradients do not provide essential directional cues in the wing. (A-D) Schematics showing the orientation of wing hairs in adult flies. Relevant changes from wild type with regard to Fj and Ds function or expression are indicated at the bottom of each panel. Images are drawn to scale. (E-H) Micrographs showing the region between veins 3 and 4, and just distal to the anterior crossvein. The genotypes shown are: (A,E) w1118; (B,F) w1118; ds38k, fjN7/dsUA071, fjd1; (C,G) w1118; ds38k, fjN7/dsUA071, fjd1; TubP-Gal4, UAS-Ds/UAS-Fj; (D,H) w1118; ds38k, fjN7/dsUA071, fjd1; TubP-Gal4/UAS-Ds.

 

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© The Company of Biologists Ltd 2004