Kautzmann Steffen, Rey Simone, Krebs Amber, Klämbt Christian
Institut für Neuro- Und Verhaltensbiologie, Universität Münster, Münster, Germany.
Glia. 2025 Jul;73(7):1365-1382. doi: 10.1002/glia.70011. Epub 2025 Mar 17.
In vertebrates, there is a differential interaction between peripheral axons and their associated glial cells. While large-caliber axons are covered by a myelin sheath, small-diameter axons are simply wrapped in Remak fibers. In peripheral nerves of Drosophila larvae, axons are covered by wrapping glial cell processes similar to vertebrate Remak fibers. Whether differences in axonal diameter influence the interaction with glial processes in Drosophila has not yet been analyzed. Likewise, it is not understood whether the modality of the neuron affects the interaction with the wrapping glia. To start to decipher the mechanisms underlying glial wrapping, we employed APEX2 labeling in larval filet preparations. This allowed us to follow individual axons of defined segmental nerves at ultrastructural resolution in the presence or absence of wrapping glia. Using these tools, we first demonstrate that motor axons are larger compared to sensory axons. Sensory axons fasciculate in larger groups than motor axons, suggesting that they do not require direct contact with wrapping glia. However, unlike motor axons, sensory axons show length-dependent degeneration upon ablation of wrapping glia. These data suggest that Drosophila may help to understand peripheral neuropathies caused by defects in Schwann cell function, in which a similar degeneration of sensory axons is observed.
在脊椎动物中，外周轴突与其相关的神经胶质细胞之间存在差异相互作用。大口径轴突被髓鞘覆盖，而小直径轴突则简单地包裹在雷马克纤维中。在果蝇幼虫的外周神经中，轴突被类似于脊椎动物雷马克纤维的包裹性神经胶质细胞突起所覆盖。轴突直径的差异是否会影响果蝇中与神经胶质细胞突起的相互作用尚未得到分析。同样，也不清楚神经元的模式是否会影响与包裹性神经胶质细胞的相互作用。为了开始解读神经胶质细胞包裹的潜在机制，我们在幼虫肉片制备中采用了APEX2标记。这使我们能够在有或没有包裹性神经胶质细胞的情况下，以超微结构分辨率追踪特定节段神经的单个轴突。使用这些工具，我们首先证明运动轴突比感觉轴突更大。感觉轴突比运动轴突更密集地成束，这表明它们不需要与包裹性神经胶质细胞直接接触。然而，与运动轴突不同，感觉轴突在包裹性神经胶质细胞被切除后会出现长度依赖性退化。这些数据表明，果蝇可能有助于理解由施万细胞功能缺陷引起的外周神经病变，在这种病变中观察到感觉轴突有类似的退化。
