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;ft^GRV/CyO (control) and w;ft¹/CyO females were crossed to w;Atro¹¹/TM6, w;ft¹/CyO, w;ft^GRV;Atro¹¹/SM6:TM6 and w;ft^chance;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.

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