Schwann cell morphology and function in peripheral nerve regeneration

描述（由申请人提供）：周围神经损伤后，许多患者由于神经再生不足而遭受持续疼痛或运动障碍。为了开发新的疗法来促进神经再生，必须了解驱动这一过程的细胞和分子机制。许多研究都集中在神经再生中涉及的神经元内在信号，然而周围细胞类型，如胶质细胞，在促进轴突再生中也起着重要作用。雪旺细胞是周围神经系统的主要胶质细胞，对轴突维持和再生至关重要。损伤后，雪旺细胞退分化为未成熟状态，促进轴突再生和神经修复。雪旺细胞的脱分化过程伴随着剧烈的形态变化和细胞迁移。然而，这些形态变化究竟是如何由细胞内事件驱动的，如细胞骨架重排和通过细胞内运输的膜重塑，仍然未知。除行为改变外，去分化雪旺细胞还为再生的轴突提供生长因子，并提供方向引导，使轴突沿着正确的路径再生。然而，雪旺细胞用来指导轴突再生的具体引导分子尚不清楚。我们实验室最近的数据表明，经典轴突引导受体的突变体，在结肠直肠癌（DCC）中缺失，表现出与缺乏雪旺细胞的突变体相似的轴突再生。这表明DCC可能

DESCRIPTION (provided by applicant): Following damage to peripheral nerves, many patients suffer from persistent pain or motor impairments due to inadequate nerve regeneration. In order to develop new therapies to promote nerve regeneration, it is imperative to understand the cellular and molecular mechanisms that drive this process. Many studies have focused on the neuron-intrinsic cues involved in nerve regeneration, however surrounding cell types, such as glial cells, also play an important role in promoting axonal regrowth. Schwann cells are the main glia of the peripheral nervous system and are critical for axonal maintenance and regeneration. Following injury, Schwann cells dedifferentiate to an immature state that promotes axonal regrowth and nerve repair. The process of Schwann cell dedifferentiation is accompanied by drastic morphological changes as well as cell migration. However, exactly how these morphological changes are driven by intracellular events, such as cytoskeletal rearrangements and membrane remodeling via intracellular transport, remains unknown. In addition to behavioral changes, dedifferentiated Schwann cells provide growth factors to regrowing axons and provide directional guidance, allowing axons to regrow along the proper path. The specific guidance molecules that are used by Schwann cells to direct axonal regrowth, however, are unknown. Recent data from our lab demonstrates that mutants for the classical axon guidance receptor, Deleted in Colorectal Carcinoma (DCC), show misguided axonal regrowth similar to that of mutants lacking Schwann cells. This suggests that DCC may play an important role in guiding axonal regrowth, potentially in a Schwann cell-dependent manner. Here, I propose to define the cellular and molecular mechanisms by which Schwann cells promote axonal regrowth. First, I will use live cell imaging to determine how cytoskeletal structure and intracellular transport change in Schwann cells in response to nerve injury. Additionally, I will determine whether intracellular transport is required in Schwan cells during nerve regeneration using cell-type specific rescue of a dynein mutant, which has significant axonal regeneration defects. Next, I will determine how DCC promotes directional axonal regrowth. Using live cell imaging, I will monitor the behavior of axonal growth cones and Schwann cells simultaneously in wild type and DCC mutants following nerve transection. Additionally, I will determine in which cell type(s) DCC is required to direct axonal regrowth using cell-type specific rescue of DCC mutant regeneration. Combined, the proposed experiments will provide cellular and molecular mechanisms by which Schwann cells promote nerve regeneration in vivo.