Fame Ryann M, Chang Jessica T, Hong Alex, Aponte-Santiago Nicole A, Sive Hazel
Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA, 02142, USA.
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307, USA.
Fluids Barriers CNS. 2016 Jun 21;13(1):11. doi: 10.1186/s12987-016-0036-z.
Cerebrospinal fluid (CSF) contained within the brain ventricles contacts neuroepithelial progenitor cells during brain development. Dynamic properties of CSF movement may limit locally produced factors to specific regions of the developing brain. However, there is no study of in vivo CSF dynamics between ventricles in the embryonic brain. We address CSF movement using the zebrafish larva, during the major period of developmental neurogenesis.
CSF movement was monitored at two stages of zebrafish development: early larva [pharyngula stage; 27-30 h post-fertilization (hpf)] and late larva (hatching period; 51-54 hpf) using photoactivatable Kaede protein to calculate average maximum CSF velocity between ventricles. Potential roles for heartbeat in early CSF movement were investigated using tnnt2a mutant fish (tnnt2a (-/-)) and chemical [2,3 butanedione monoxime (BDM)] treatment. Cilia motility was monitored at these stages using the Tg(βact:Arl13b-GFP) transgenic fish line.
In wild-type early larva there is net CSF movement from the telencephalon to the combined diencephalic/mesencephalic superventricle. This movement directionality reverses at late larval stage. CSF moves directionally from diencephalic to rhombencephalic ventricles at both stages examined, with minimal movement from rhombencephalon to diencephalon. Directional movement is partially dependent on heartbeat, as indicated in assays of tnnt2a (-/-) fish and after BDM treatment. Brain cilia are immotile at the early larval stage.
These data demonstrate directional movement of the embryonic CSF in the zebrafish model during the major period of developmental neurogenesis. A key conclusion is that CSF moves preferentially from the diencephalic into the rhombencephalic ventricle. In addition, the direction of CSF movement between telencephalic and diencephalic ventricles reverses between the early and late larval stages. CSF movement is partially dependent on heartbeat. At early larval stage, the absence of motile cilia indicates that cilia likely do not direct CSF movement. These data suggest that CSF components may be compartmentalized and could contribute to specialization of the early brain. In addition, CSF movement may also provide directional mechanical signaling.
在脑发育过程中，脑室中的脑脊液（CSF）与神经上皮祖细胞接触。脑脊液流动的动态特性可能会将局部产生的因子限制在发育中脑的特定区域。然而，目前尚无关于胚胎脑室内脑脊液动力学的体内研究。我们利用斑马鱼幼体，在发育性神经发生的主要时期研究脑脊液的流动。
在斑马鱼发育的两个阶段监测脑脊液流动：早期幼体[咽胚期；受精后27 - 30小时（hpf）]和晚期幼体（孵化期；51 - 54 hpf），使用光激活的Kaede蛋白来计算脑室之间的平均最大脑脊液流速。利用tnnt2a突变鱼（tnnt2a（-/-））和化学物质[2,3 - 丁二酮一肟（BDM）]处理来研究心跳在早期脑脊液流动中的潜在作用。在这些阶段使用Tg（βact：Arl13b - GFP）转基因鱼系监测纤毛运动。
在野生型早期幼体中，脑脊液有从端脑向间脑/中脑联合脑室的净流动。这种流动方向在晚期幼体阶段发生逆转。在两个检测阶段，脑脊液都从间脑向菱脑脑室定向流动，从菱脑向间脑的流动极少。定向流动部分依赖于心跳，如在tnnt2a（-/-）鱼的检测以及BDM处理后所示。脑纤毛在早期幼体阶段是不动的。
这些数据证明了在发育性神经发生的主要时期，斑马鱼模型中胚胎脑脊液的定向流动。一个关键结论是脑脊液优先从间脑流入菱脑脑室。此外，端脑和间脑脑室之间脑脊液流动的方向在早期和晚期幼体阶段之间发生逆转。脑脊液流动部分依赖于心跳。在早期幼体阶段，不存在活动的纤毛表明纤毛可能不引导脑脊液流动。这些数据表明脑脊液成分可能被分隔，并可能有助于早期脑的特化。此外，脑脊液流动也可能提供定向机械信号。
