Neuronal development in the Drosophila compound eye: rap gene function is required in photoreceptor cell R8 for ommatidial pattern formation.

Abstract

In the compound eye of Drosopbila, cell-cell interactions are thought to play an important role in the determination of neuronal cell fate and pattern morphogenesis. Recent work on the bride of sevenless {boss) gene has demonstrated an inductive role for photoreceptor R8 in the differentiation of photoreceptor R7. These studies have shown that while R8 differentiates early in the scheme of ommatidial assembly, it continues to play an active role in subsequent patterning events. We describe studies on a new genetic locus rap {retina aberrant in pattern), whose functions are critical for normal pattern formation in the developing eye. Mutations in the rap gene perturb the early stages of pattern formation and lead to a variable number of photoreceptor cells (R cells) in each ommatidium. Experiments with a temperature-sensitive allele have shown that rap gene function is required during the period of development when pattern formation occurs. In addition, a somatic mosaic analysis of rap has shown that its function is required only in photoreceptor cell R8 for normal ommatidial patterning. These studies suggest an important role for rap in the initial events leading to pattern formation and are consistent with R8 playing a central role in directing ommatidial pattern formation.

Regulation of Glia Number in Drosophila by Rap/Fzr, an Activator of the Anaphase-Promoting Complex, and Loco, an RGS Protein

“…The following mutant flies were used: w,rap3 and rap E6 have been previously described (Karpilow et al 1989;Jacobs et al 2002), as has loco P452 (Yu et al 2005). Enhancer trap lines, P{lacZ-un1}loco rC56 w 67c23 , P{lacW}rap G0326 /FM7c, and repo-GAL4/TM6;Tb, were obtained from the Bloomington Stock Center.…”

“…rap/fzr mutants have a rough-eye phenotype (Karpilow et al 1989). Here we show that in the developing larval nervous system loss of Rap/Fzr leads to an increase in glia and, moreover, targeted overexpression of Rap/Fzr leads to a dramatic decrease in glia number.…”

Genetical analysis ofvisual system disorganizer (vid), a new gene involved in normal development of eye and optic lobe of the brain inDrosophila melanogaster

“…Mutations in a large number of genes have been isolated that affect development and/or function of the eye (Banerjee et al, 1987;Reinke & Zipursky, 1988;Karpilow et al, 1989;Duus et al, 1992;Kramer et al, 1995) and the optic lobe (Heisenberg & B6hl, 1978;Fischbach & Heisenberg, 1981;Ramos et al, 1993;Schneider et al, 1995). Most of these mutations perturb both the normal adult axon organization in the optic lobe and the normal ommatidial organization in the eye (Meyerowitz & Kankel, 1978;Fischbach & Technau, 1984;Stelter et al, 1987;Cheyette et al, 1994;Serikaku & O'Tousa, 1994;Xiong & Montell, 1995;Martin et al, 1995).…”

Positive and negative signaling mechanisms in the regulation of photoreceptor induction in the developingDrosophila retina

“…It is inferred that Sca acts as a diffusible lateral inhibitor which prohibits induction of R8 in an inappropriate position, thus enabling proper spacing of the precluster. Another gene called rhabdomere aberrant in pattern (rap) is also required in R8 for ommatidial pattern formation (Karpilow et al, 1989).…”