Department of Biology, University of Washington, Seattle, WA
Department of Biology, University of Washington, Seattle, WA.
eNeuro. 2022 Sep 14;9(5). doi: 10.1523/ENEURO.0100-22.2022. Print 2022 Sep-Oct.
Birds are exceptionally adept at controlling their body position. For example, they can coordinate rapid movements of their body while stabilizing their head. Intriguingly, this ability may rely in part on a mechanosensory organ in the avian lower spinal cord called the lumbosacral organ (LSO). However, molecular mechanotransduction mechanisms have not been identified in the avian spinal cord. Here, we report the presence of glycinergic neurons in the LSO that exhibit immunoreactivity for myosin7a and espin, molecules essential for function and maintenance of hair cells in the inner ear. Specifically, we find glycinergic cell bodies near the central canal and processes that extend laterally to the accessory lobes and spinal ligaments. These LSO neurons are reminiscent of glycinergic neurons in a recently-described lateral spinal proprioceptive organ in zebrafish that detects spinal bending. The avian LSO, however, is located inside a series of fused vertebrae called the synsacrum, which constrains spinal bending. We suggest the LSO may be a modification and elaboration of a preexisting mechanosensory spinal network in vertebrates. A mechanistic understanding of its function may be an important clue to understanding the evolution and development of avian locomotion.
鸟类在控制身体姿势方面非常出色。例如，它们可以协调身体的快速运动，同时稳定头部。有趣的是，这种能力可能部分依赖于鸟类脊髓下部的一个机械感觉器官，称为腰骶器官（LSO）。然而，鸟类脊髓中的分子机械转导机制尚未确定。在这里，我们报告了 LSO 中存在表达肌球蛋白 7a 和 espin 的甘氨酸能神经元，这两种分子对于内耳毛细胞的功能和维持至关重要。具体来说，我们发现甘氨酸能细胞体靠近中央管，并且其过程向侧面延伸到附属叶和脊柱韧带。这些 LSO 神经元类似于斑马鱼中最近描述的一个侧向脊髓本体感受器官中的甘氨酸能神经元，该器官可以检测到脊柱弯曲。然而，鸟类的 LSO 位于一系列称为 synsacrum 的融合椎骨内部，这限制了脊柱弯曲。我们认为 LSO 可能是脊椎动物中一个预先存在的机械感觉性脊髓网络的修改和扩展。对其功能的机械理解可能是理解鸟类运动进化和发展的重要线索。
