Motile cilia modulate neuronal and astroglial activity in the zebrafish larval brain

The brain uses a specialized system to transport cerebrospinal fluid (CSF), consisting of interconnected ventricles lined by motile ciliated ependymal cells. These cells act jointly with CSF secretion and cardiac pressure gradients to regulate CSF dynamics. To date, the link between cilia-mediated CSF flow and brain function is poorly understood. Using zebrafish larvae as a model system, we identify that loss of ciliary motility does not alter progenitor proliferation, brain morphology, or spontaneous neural activity despite leading to an enlarged telencephalic ventricle. We observe altered neuronal responses to photic stimulations in the optic tectum and hindbrain and brain asymmetry defects in the habenula. Finally, we investigate astroglia since they contact CSF and regulate neuronal activity. Our analyses reveal a reduction in astroglial calcium signals during both spontaneous and light-evoked activity. Our findings highlight a role of motile cilia in regulating brain physiology through the modulation of neural and astroglial networks. To analyze the impact of cilia paralysis on gene expression, we performed RNA sequencing analysis of 4 days old smh mutant and sibling control zebrafish larvae. We extracted total RNA from mutant (selected based on their curly tail down phenotype) and sibling controls (mixture of heterozygous and wild-type). RNAsequencing was performed on 4 different clutches.

大脑拥有一套专门的脑脊液（cerebrospinal fluid, CSF）运输系统，该系统由相互连通的脑室构成，脑室内壁衬有运动性纤毛室管膜细胞（motile ciliated ependymal cells）。此类细胞与脑脊液分泌过程及心脏压力梯度协同作用，共同调控脑脊液动力学。迄今为止，纤毛介导的脑脊液流动与大脑功能之间的关联仍鲜为人知。本研究以斑马鱼幼鱼（zebrafish larvae）为模型系统，研究发现：尽管纤毛运动丧失会导致端脑室（telencephalic ventricle）扩大，但并不会改变祖细胞增殖、大脑形态或自发神经活动。我们观察到，中脑顶盖（optic tectum）与后脑（hindbrain）区域的神经元对光刺激（photic stimulations）的反应出现异常，同时缰核（habenula）存在大脑不对称性缺陷。鉴于星形胶质细胞（astroglia）可接触脑脊液并调控神经元活动，我们对其展开了后续研究。分析结果显示，在自发活动与光诱发活动过程中，星形胶质细胞钙信号（astroglial calcium signals）均出现显著降低。本研究结果表明，运动纤毛可通过调控神经与星形胶质细胞网络，进而发挥调节大脑生理功能的作用。为分析纤毛麻痹对基因表达的影响，我们对4日龄的smh突变体（smh mutant）斑马鱼幼鱼及其同胞对照幼鱼开展了RNA测序（RNA sequencing）分析。我们从依据卷尾下垂表型（curly tail down phenotype）筛选得到的突变体，以及由杂合子与野生型个体混合组成的同胞对照样本中提取总RNA。本测序实验共使用4个独立的繁育批次（clutches）完成。