Rose D, Zhu X, Kose H, Hoang B, Cho J, Chiba A
Department of Cell and Structural Biology, University of Illinois, Urbana 61801, USA.
Development. 1997 Apr;124(8):1561-71. doi: 10.1242/dev.124.8.1561.
Toll, a transmembrane molecule with extracellular leucine-rich repeats, is dynamically expressed by the Drosophila embryonic musculature. Growth cones of RP3 and other motoneurons normally grow past Toll-positive muscle cells and innervate more distal muscle cells, which have down-regulated their Toll expression. In this study, we show that reciprocal genetic manipulations of Toll proteins can produce reciprocal RP3 phenotypes. In Toll null mutants, the RP3 growth cone sometimes innervates incorrect muscle cells, including those that are normally Toll-positive. In contrast, heterochronic misexpression of Toll in the musculature leads to the same growth cone reaching its correct target region but delaying synaptic initiation. We propose that Toll acts locally to inhibit synaptogenesis of specific motoneuron growth cones and that both temporal and spatial control of Toll expression is crucial for its role in development.
Toll是一种具有细胞外富含亮氨酸重复序列的跨膜分子，由果蝇胚胎肌肉组织动态表达。RP3和其他运动神经元的生长锥通常会越过Toll阳性的肌肉细胞，支配更远端的肌肉细胞，这些远端肌肉细胞的Toll表达已下调。在本研究中，我们表明对Toll蛋白进行相互的基因操作可产生相互的RP3表型。在Toll基因敲除突变体中，RP3生长锥有时会支配错误的肌肉细胞，包括那些通常为Toll阳性的细胞。相反，在肌肉组织中异时性错误表达Toll会导致同一个生长锥到达其正确的靶区域，但会延迟突触起始。我们提出，Toll在局部起作用以抑制特定运动神经元生长锥的突触形成，并且Toll表达的时间和空间控制对其在发育中的作用至关重要。
