Tearle R, Tomlinson A, Saint R
Department of Biochemistry, Adelaide University, Australia.
Mol Gen Genet. 1994 Aug 15;244(4):426-34. doi: 10.1007/BF00286695.
The three existing dominant gain-of-function Drop alleles, Dr1, DrMio and DrWe, previously assumed to define a single locus, severely disrupt eye development. Genetic analysis of ethylmethanesulphonate (EMS) and irradiation-induced revertants revealed that the Drop mutations define two loci: the Drop locus, which is defined by the Dr1 and DrMio mutants, and a separate locus defined by the DrWe mutation, which has been renamed Wedge. The majority of the Dr1 and DrMio revertants are embryonic lethal in trans, mutant embryos exhibiting trachea that fail to join the Filzkörper, thus revealing a role for the Drop gene in embryogenesis. Clonal analysis of lethal revertant alleles suggests a role for both genes in eye development. In the Drop homozygous mutant clones, the outer photoreceptor cells R1-R6 develop aberrantly. Wedge, however, is not required by the developing photoreceptor cells but its absence does disrupt normal ommatidial alignment. Although the Drop and nearby string loci were shown to be genetically distinct, both Dr1 and DrMio were found to interact in trans with lesions at the string locus, causing loss and derangement of bristles and loss of neuromuscular coordination.
现有的三个主要功能获得性Drop等位基因，即Dr1、DrMio和DrWe，以前被认为定义了一个单一基因座，它们严重破坏眼睛发育。对甲磺酸乙酯（EMS）和辐射诱导的回复突变体进行的遗传分析表明，Drop突变定义了两个基因座：由Dr1和DrMio突变体定义的Drop基因座，以及由DrWe突变定义的一个单独基因座，该基因座已重新命名为Wedge。大多数Dr1和DrMio回复突变体在反式中是胚胎致死的，突变胚胎表现出气管无法与Filzkörper相连，从而揭示了Drop基因在胚胎发生中的作用。对致死性回复突变等位基因的克隆分析表明这两个基因在眼睛发育中都起作用。在Drop纯合突变克隆中，外部光感受器细胞R1-R6发育异常。然而，发育中的光感受器细胞不需要Wedge，但其缺失确实会破坏正常的小眼排列。尽管Drop和附近的string基因座在遗传上是不同的，但发现Dr1和DrMio都能与string基因座的损伤进行反式相互作用，导致刚毛缺失和紊乱以及神经肌肉协调丧失。
