The klarMW allele supports nuclear migration in photoreceptors. Eye discs from third-instar larvae were fixed, stained with anti-Elav to reveal photoreceptor nuclei and examined by confocal microscopy. In klarZ discs, the photoreceptor nuclei are present in apical positions; a few nuclei are visible in the basal section because the disc curves at the edges. Nuclei are absent from the optical nerve (ON). This is the pattern observed in wild-type discs [22, 24]. In klarYG3 discs, many nuclei are found basally and in the optical nerve because apical migration of nuclei has failed. KlarMW discs display the wild-type pattern.