Kretzschmar D, Brunner A, Wiersdorff V, Pflugfelder G O, Heisenberg M, Schneuwly S
Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl Genetik, Würzburg, FRG.
EMBO J. 1992 Jul;11(7):2531-9. doi: 10.1002/j.1460-2075.1992.tb05318.x.
Mutations in the Drosophila gene giant lens (gil) affect ommatidial development, photoreceptor axon guidance and optic lobe development. We have cloned the gene using an enhancer trap line. Molecular analysis of gil suggests that it encodes a secreted protein with an epidermal-growth-factor-like motif. We have generated mutations at the gil locus by imprecise excision of the enhancer trap P-element. In the absence of gil, additional photoreceptors develop at the expense of pigment cells, suggesting an involvement of gil in cell determination during eye development. In addition, gil mutants show drastic effects on photoreceptor axon guidance and optic lobe development. In wildtype flies, photoreceptor axons grow from the eye disc through the optic stalk into the larval brain hemisphere, where retinal innervation is required for the normal development of the lamina and distal medulla. The projection pattern of these axons in the developing lamina and medulla is highly regular and reproducible. In gil, photoreceptor axons enter the larval brain but fail to establish proper connections in the lamina or medulla. We propose that gil encodes a new type of signalling molecule involved in the process of axon pathfinding and cell determination in the visual system of Drosophila.
果蝇巨眼晶状体（gil）基因的突变会影响小眼发育、光感受器轴突导向和视叶发育。我们利用一个增强子捕获系克隆了该基因。对gil的分子分析表明，它编码一种具有表皮生长因子样基序的分泌蛋白。我们通过增强子捕获P元件的不精确切除在gil基因座产生了突变。在没有gil的情况下，额外的光感受器得以发育，代价是色素细胞，这表明gil参与了眼睛发育过程中的细胞决定。此外，gil突变体在光感受器轴突导向和视叶发育方面表现出显著影响。在野生型果蝇中，光感受器轴突从眼盘通过视柄生长到幼虫脑半球，在那里视网膜神经支配是神经层和远端髓质正常发育所必需的。这些轴突在发育中的神经层和髓质中的投射模式高度规则且可重复。在gil突变体中，光感受器轴突进入幼虫脑，但未能在神经层或髓质中建立正确的连接。我们提出，gil编码一种新型信号分子，参与果蝇视觉系统中轴突寻路和细胞决定过程。
