QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

doi: 10.1242/10.1242/dev.00304

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fanto, M. Articles by McNeill, H. Search for Related Content PubMed PubMed Citation Articles by Fanto, M. Articles by McNeill, H.

The tumor-suppressor and cell adhesion molecule Fat controls planar polarity via physical interactions with Atrophin, a transcriptional co-repressor

¹ Cancer Research UK (ICRF), London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
² Laboratoire de Génétique et Physiologie du Développement, CNRS-INSERM-Université de la Méditerranée-AP de Marseille, Campus de Luminy Case 907, F-13288 Marseille, Cedex 09, France

View larger version (114K): [in a new window]   Fig. 1. ft and ds regulate planar polarity. (A) Wild-type dorsal (D) and ventral (V) ommatidia. At the five-cell stage, preclusters rotate in opposite directions to assume D and V polarity. Outer photoreceptors are recruited into the clusters as pairs and share similar characteristics, indicated by similar colors in the R1/6, R2/5 and R3/4 cells. Dorsal is upwards and anterior is leftwards. (B) Smooth edges of mitotic clones of ftAlbert (arrows). All ft alleles examined had smooth edges, planar polarity defects and enhanced growth in clones. (C-E') Sections (C-E) and schematic diagrams (C'-E') of wild-type, and ft and ds mutant fly eyes. In the wild-type eye (C,C') the trapezoid shapes formed by the photoreceptor rhabdomeres of the D ommatidia point upwards (red arrows), the V ommatidia (blue arrows) point in the opposite direction; D and V fields are separated by a division known as the equator (yellow line). In ftfd/ftchance transheterozygous (D,D') and dsUAO71 homozygous mutants (E,E'), D and V ommatidia are intermixed and no obvious equatorial line can be drawn. (F,G) Sections of ftfd and dsUAO71 mutant clones and (F',G') diagrams of PP. ft- and ds- tissue are marked by the absence of pigment. White arrows indicates wild-type ommatidia on the polar (F) or equatorial (G) sides of the clones, non-autonomously affected by the clones. Red and blue arrows (F',G') indicate ommatidia with D and V polarity, respectively, in these and in all remaining panels.

View larger version (52K): [in a new window]   Fig. 2. Physical and genetic interaction between Atro and ft. (A) Diagram of Ft and Atro structures. Ft is a 560 kDa transmembrane protein with cadherin (green), EGF (red) and Laminin G (yellow) repeats and a novel cytoplasmic domain. Black and green arrows indicate fragments of Ft used in our Y2H. Atro interacts with the fragment indicated by the green arrow. Atro has strong homologies to human atrophins. This homology is especially high in the Atro domain (blue). Atro also contains regions found in transcriptional regulators known as MTA and SANT domain (cyan). (B) FLAG-Ft binds GST-Atro. Western blotting with anti-FLAG antibody reveals the amount of Ft pulled down by GST alone (left, in all panels) and GST-Atro (right, in all panels), respectively. Blotting with -GST indicates the amounts of GST fusion proteins present. GST-Atro is degraded so that most of the protein produced is GST and very little protein is full-length Atro. Probing with -Atro reveals which fragments of the degraded GST-Atro still contain Atro protein. Arrow indicates FLAG-Fat and asterisk marks full-length GST-Atro. (C) Atro dominantly enhances ft mortality rate. w;ftGRV/CyO (control) and w;ft1/CyO females were crossed to w;Atro11/TM6, w;ft1/CyO, w;ftGRV;Atro11/SM6:TM6 and w;ftchance;Atro11/SM6:TM6 males at 29°C. Flies of the correct genotypes were collected every day, kept at 22°C and put in new vials every 48 hours. The results are average of two independent crosses and based on a total number of 50 to 150 flies for each genotype. (D-F) Atro protein expression (green) in the eye imaginal disc. An antibody raised against the last 14 amino acids of the Atro protein reveals ubiquitous staining in all cells of a wild-type eye disc (D,D'), including the neuronal photoreceptors, marked by the Elav protein (red). The staining is partially lost within Atro35 clones (E,E',arrow), both ahead and behind the morphogenetic furrow. (F) Orthogonal reconstruction of a series of confocal sections through the Atro35 clone shown in E' (white arrow). Staining is visible in the cytoplasm and in the nuclei, and both are decreased in the clone.

View larger version (141K): [in a new window]   Fig. 3. Atro, like ft, is required for PP and in the R3 cell. (A) Section of a Atro35 mutant clone and (A') diagram of PP. The clone is marked by the absence of pigment. White arrow indicates a wild-type ommatidium, non-autonomously affected by the clone. The strong photoreceptor specification defects make it impossible to assess the polarity of most ommatidia inside the clone (yellow arrow). (B-B'') Close-ups of three ommatidia from Atro35 clones with mosaic R3/R4 pair and schematic representation of such mosaics (C). The pigment granules (PG; marking the wild type) are always present on the R3 rhabdomere (black arrows) and never on the R4 cell in mosaic ommatidia. (D) Section through the eye of fly expressing Atro under sev control. Several ommatidia appear to have lost their chirality and have adopted a symmetric form of the R3/R3 type (green arrows). (E) Section through the eye of a viable combination of two different Atro mutations (Atro35/Atro11). Several ommatidia appear to have lost their chirality and have adopted a symmetric form of the R4/R4 type (blue arrows). Some ommatidia have extra inner photoreceptors (yellow arrow).

View larger version (158K): [in a new window]   Fig. 4. Ft, Ds and Atro control planar polarity in the eye imaginal disc. In all panels, clones are marked by the absence of GFP (green). Elav (blue) is a marker for all neuronal photoreceptor nuclei. All pictures are vertical projections of several confocal sections. (A,A') Loss of ft alters PP within and outside the clone. Bar (red) highlights the R1/R6 pair of photoreceptors. Black arrows indicates wild-type ommatidia, non-autonomously affected by the clone. (A') Arrows indicate ommatidia with D (blue) and V (red) PP. (B,B') Loss of ds alters PP within and outside the clone. dsUA071 mutant clones and diagram of ommatidial polarity. Bar (red). Black arrows indicate wild-type ommatidia non-autonomously affected by the clone. (C,C') Loss of Atro alters PP within and outside the clone Atro35 mutant clones and diagram of PP. The ß-Gal from m-lacZ, a marker for the R4 cell (red). The endogenous equator is indicated by a yellow line. Black arrows point to wild-type ommatidia, non-autonomously affected by the clone. In several clusters more than one cell expresses ß-Gal (yellow arrows). (D,E') fj transcription is controlled by Atro. Expression of fj-lacZ (red in D and E, white in D' and E') in wild-type (D,D') and in a Atro35 mutant clones (E,E'). ß-Gal is strongly upregulated in Atro mutant tissue. Note that inside Atro clones fj-lacZ maintains its gradient-shape expression, with higher levels on the part of the clone closer to the midline.

View larger version (77K): [in a new window]   Fig. 5. Atro and Ft act separately in some developmental processes and together in others. (A,A',B) Photoreceptor specification defects in Atro35 mutant clones in the eye imaginal disc. The endogenous equator is marked by the yellow line. Bar staining (A) in red. Yellow arrows (A') designate clusters in which only one cells stains for Bar, indicating loss of R1 or R6 cell fate. Staining for the Prospero (Pros; red in B) a nuclear protein (a marker for R7 and the cone cells) reveals that in several clusters more than one cell has adopted the R7 fate (white arrows). Although the cone cells are mostly located above the plane of this section some of their nuclei (identified by their elongated shape) are present in this picture. (C,C') Atro35 mutant clone marked by the absence of GFP (green). Note the round shape of the clone in front of the morphogenetic furrow (white arrows in C and C') compared with the irregular shape of a clone behind the furrow (small arrowhead in C') and of the twinspots, recognizable because of the brighter green staining due to the double amount of GFP (yellow arrows in C') Elav(red). (D,D') ftGRV mutant clone marked by the absence of GFP (green), Elav (red). Note the round shape of all the clones both in front of and behind the morphogenetic furrow (white arrows) compared to the irregular shape of the twinspots (yellow arrow). (E-G) Pictures of wt wings (E) or wings carrying ftGRV (F) or Atro35 (G) mitotic clones. ft and Atro clones (broken yellow lines) generate blisters in which the dorsal and ventral sheet of the wing are separated. (H-J). Dorsal thoraces of a wild-type fly (H) or flies with ftGRV (I) or Atro35 (J) clones (broken yellow lines). Note the cleft in the thorax, indicating incomplete fusion of the left and right imaginal discs.

View larger version (15K): [in a new window]   Fig. 6. Model for ds, ft and Atro in PP establishment. (A) Model for how ft/Atro (green) and ds (red) activity gradients relate to Factor X gradient (black), which is instructive for PP. ds activity is high at the D and V regions of the disc and reaches its minimum at the DV midline. Ft/Atro promote production of Factor X, and Ds inhibits it, probably by inhibiting Ft. As a result, Factor X production will be highest at the midline and lowest at the edges. (B) Effects on Factor X gradient and ommatidial polarity of a ft or Atro clone. The clone (black ellipse) generates a sink in the Factor X gradient. Outside the clone, on the polar side a new maximum of Factor X is created. (C) Effects on Factor X gradient and ommatidial polarity of a ds clone. ds clone is predicted to produce excess Factor X, altering the slope of the gradient, and reorganizing the ommatidia accordingly. (D) Model for Atro function in PP. Initially, Wg (expressed at the D and V poles), N (active at the D/V midline) and Unpaired (Upd) (secreted centrally) set up Fj expression gradient with its peak at the midline. Wg also promotes ds expression. Ft and Atro are responsible for the production of Factor X, the promotion of the R3 versus the R4 cell fate and the repression of fj transcription. In addition to their requirement in PP, Ft and Atro control separate activities (broken gray arrows).