Division of Neurogenetics, Tohoku University Graduate School of Life Sciences, Sendai 980-8577, Japan.
Curr Biol. 2010 May 11;20(9):836-40. doi: 10.1016/j.cub.2010.02.064. Epub 2010 Apr 15.
Synapses mediate inductive interactions for the proper development of pre- and postsynaptic cells: presynaptic electrical activities and synaptic transmission ensure the organization of postsynaptic structures, whereas neurotrophins produced in postsynaptic cells support the survival and enlargement of presynaptic partners. In Drosophila, a motor nerve has been implicated in the induction of the muscle of Lawrence (MOL), the formation of which is male specific and depends on the neural expression of fruitless (fru), a neural sex-determinant gene. Here we report the identification of a single motoneuron essential for inducing the MOL, which we call the MOL-inducing (Mind) motoneuron. The MOL is restored in fru mutant males, which otherwise lack the MOL, if the fru(+) transgene is selectively expressed in the Mind motoneuron by mosaic analysis with a repressible cell marker. We further demonstrate that synaptic outputs from the Mind motoneuron are indispensable to MOL induction, because the blockage of synaptic transmission by shibire(ts) (shi(ts)) during the critical period in development abolished the MOL formation in males. Our finding that sex-specific neurons instruct sexually dimorphic development of their innervating targets through synaptic interactions points to the novel mechanism whereby the pre- and postsynaptic partners coordinately establish their sexual identity.
突触介导诱导相互作用，以确保前突触和后突触细胞的正常发育：前突触的电活动和突触传递确保后突触结构的组织，而在后突触细胞中产生的神经营养因子则支持前突触伙伴的存活和扩大。在果蝇中，运动神经元参与诱导劳伦斯肌（MOL）的形成，其形成是雄性特异性的，并且依赖于神经性别决定基因 fru 的神经表达。在这里，我们报告了一个单一的运动神经元对于诱导 MOL 是必不可少的，我们称之为 MOL 诱导（Mind）运动神经元。如果 fru(+)转基因通过可抑制细胞标记的嵌合体分析选择性地在 Mind 运动神经元中表达，则 fru 突变体雄性中恢复了 MOL，否则它们缺乏 MOL。我们进一步证明，Mind 运动神经元的突触输出对于 MOL 诱导是必不可少的，因为在发育的关键时期，通过 shibire(ts)（shi(ts)）阻断突触传递会使雄性中的 MOL 形成消失。我们的发现表明，性别特异性神经元通过突触相互作用指导其支配的靶器官的性别二态发育，这指出了前突触和后突触伙伴协调建立其性别身份的新机制。
