Friocourt François, Kozulin Peter, Belle Morgane, Suárez Rodrigo, Di-Poï Nicolas, Richards Linda J, Giacobini Paolo, Chédotal Alain
Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France.
The Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia.
J Comp Neurol. 2019 Aug 15;527(12):2009-2029. doi: 10.1002/cne.24648. Epub 2019 Mar 4.
In Bilaterians, commissural neurons project their axons across the midline of the nervous system to target neurons on the opposite side. In mammals, midline crossing at the level of the hindbrain and spinal cord requires the Robo3 receptor which is transiently expressed by all commissural neurons. Unlike other Robo receptors, mammalian Robo3 receptors do not bind Slit ligands and promote midline crossing. Surprisingly, not much is known about Robo3 distribution and mechanism of action in other vertebrate species. Here, we have used whole-mount immunostaining, tissue clearing and light-sheet fluorescent microscopy to study Robo3 expression pattern in embryonic tissue from diverse representatives of amniotes at distinct stages, including squamate (African house snake), birds (chicken, duck, pigeon, ostrich, emu and zebra finch), early postnatal marsupial mammals (fat-tailed dunnart), and eutherian mammals (mouse and human). The analysis of this rich and unique repertoire of amniote specimens reveals conserved features of Robo3 expression in midbrain, hindbrain and spinal cord commissural circuits, which together with subtle but meaningful modifications could account for species-specific evolution of sensory-motor and cognitive capacities. Our results also highlight important differences of precerebellar nuclei development across amniotes.
在两侧对称动物中，连合神经元将其轴突投射穿过神经系统的中线，以靶向另一侧的神经元。在哺乳动物中，后脑和脊髓水平的中线交叉需要Robo3受体，所有连合神经元都会短暂表达该受体。与其他Robo受体不同，哺乳动物的Robo3受体不结合Slit配体，而是促进中线交叉。令人惊讶的是，对于Robo3在其他脊椎动物物种中的分布和作用机制了解甚少。在这里，我们使用了全组织免疫染色、组织透明化和光片荧光显微镜技术，来研究不同羊膜动物代表在不同发育阶段的胚胎组织中Robo3的表达模式，这些动物包括有鳞目动物（非洲家蛇）、鸟类（鸡、鸭、鸽、鸵鸟、鸸鹋和斑胸草雀）、产后早期的有袋类哺乳动物（肥尾袋鼬）以及真兽类哺乳动物（小鼠和人类）。对这一丰富且独特的羊膜动物标本库的分析揭示了中脑、后脑和脊髓连合回路中Robo3表达的保守特征，这些特征连同细微但有意义的修饰，可能解释了感觉运动和认知能力的物种特异性进化。我们的研究结果还突出了羊膜动物间小脑前核发育的重要差异。
