Yu H H, Araj H H, Ralls S A, Kolodkin A L
Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Neuron. 1998 Feb;20(2):207-20. doi: 10.1016/s0896-6273(00)80450-x.
The semaphorins comprise a large family of conserved glycoproteins, several members of which have been shown to function in repulsive neuronal growth cone guidance. We show here that Drosophila Semaphorin I (Sema I), a transmembrane semaphorin expressed on embryonic motor and CNS axons, is required for correct guidance of motor axons and for the formation of CNS pathways. In mutant embryos lacking Sema I, motor axons stall and fail to defasciculate at specific choice points where normally they would project to their muscle targets. In addition, a specific CNS fascicle fails to form correctly in these embryos. Rescue and ectopic expression experiments show that Sema I is required in neurons to mediate axon guidance decisions. These studies further suggest that like secreted semaphorins, transmembrane semaphorins can function as repulsive guidance cues for specific axon guidance events during neurodevelopment.
信号素构成了一个保守的糖蛋白大家族，其中几个成员已被证明在排斥性神经元生长锥导向中发挥作用。我们在此表明，果蝇信号素I（Sema I）是一种在胚胎运动神经元和中枢神经系统轴突上表达的跨膜信号素，对于运动轴突的正确导向和中枢神经系统通路的形成是必需的。在缺乏Sema I的突变胚胎中，运动轴突停滞不前，无法在特定的选择点解束，而在正常情况下它们会投射到其肌肉靶标。此外，在这些胚胎中，一个特定的中枢神经系统束未能正确形成。拯救和异位表达实验表明，Sema I在神经元中是介导轴突导向决策所必需的。这些研究进一步表明，与分泌型信号素一样，跨膜信号素在神经发育过程中可作为特定轴突导向事件的排斥性导向线索。
