Mitchell K J, Doyle J L, Serafini T, Kennedy T E, Tessier-Lavigne M, Goodman C S, Dickson B J
Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley California 94720, USA.
Neuron. 1996 Aug;17(2):203-15. doi: 10.1016/s0896-6273(00)80153-1.
Two tandem Netrin genes in Drosophila are expressed at the midline of the developing CNS and in different subsets of neurons, muscles, and epidermal patches. In embryos carrying a small deficiency that deletes both genes, CNS axon commissures are partially missing or thinner. This phenotype is rescued by expressing either Netrin gene at the midline. Pan-neural expression of either gene causes disruption of commissural and longitudinal tracts, indicating that the pattern of Netrin expression is crucial and that Netrins function as instructive cues. The double mutant also shows defects in motor axon projections. Expression of either Netrin gene in all muscles also results in aberrant motor projections. Thus, Drosophila Netrins are required for the guidance of commissural axons at the midline, and of motor axons to their target muscles.
果蝇中的两个串联的Netrin基因在发育中的中枢神经系统中线以及不同的神经元、肌肉和表皮斑亚群中表达。在携带缺失这两个基因的小缺失突变体胚胎中，中枢神经系统轴突连合部分缺失或变细。通过在中线表达任一Netrin基因可挽救此表型。任一基因的泛神经表达都会导致连合束和纵束的破坏，这表明Netrin的表达模式至关重要，并且Netrins起着指导性信号的作用。双突变体在运动轴突投射方面也表现出缺陷。在所有肌肉中表达任一Netrin基因也会导致异常的运动投射。因此，果蝇Netrins对于中线处连合轴突以及运动轴突向其靶肌肉的导向是必需的。
