The transcription factor Otx2 regulates choroid plexus development and function

The choroid plexuses (ChPs) are the main regulators of cerebrospinal fluid (CSF) composition and thereby also control the composition of a principal source of signaling molecules that is in direct contact with neural stem cells in the developing brain. The regulators of ChP development mediating the acquisition of a fate that differs from the neighboring neuroepithelial cells are poorly understood. Here, we demonstrate in mice a crucial role for the transcription factor Otx2 in the development and maintenance of ChP cells. Deletion of Otx2 by the Otx2-CreERT2 driver line at E9 resulted in a lack of all ChPs, whereas deletion by the Gdf7-Cre driver line affected predominately the hindbrain ChP, which was reduced in size, primarily owing to an increase in apoptosis upon Otx2 deletion. Strikingly, Otx2 was still required for the maintenance of hindbrain ChP cells at later stages when Otx2 deletion was induced at E15, demonstrating a central role of Otx2 in ChP development and maintenance. Moreover, the predominant defects in the hindbrain ChP mediated by Gdf7-Cre deletion of Otx2 revealed its key role in regulating early CSF composition, which was altered in protein content, including the levels of Wnt4 and the Wnt modulator Tgm2. Accordingly, proliferation and Wnt signaling levels were increased in the distant cerebral cortex, suggesting a role of the hindbrain ChP in regulating CSF composition, including key signaling molecules. Thus, Otx2 acts as a master regulator of ChP development, thereby influencing one of the principal sources of signaling in the developing brain, the CSF. We performed gene expression microarray analysis of fourth ventricular choroid plexus tissue from Otx2 k.o. mice compared to wildtype mice from the same litters.脉络丛（choroid plexuses, ChPs）是脑脊液（cerebrospinal fluid, CSF）成分的主要调控因子，进而可调控与发育中大脑内神经干细胞直接接触的主要信号分子源的组成。目前，介导脉络丛获得区别于邻近神经上皮细胞命运的发育调控因子仍知之甚少。本研究在小鼠模型中证实，转录因子Otx2在脉络丛细胞的发育与维持过程中发挥关键作用。通过Otx2-CreERT2驱动株在胚胎第9天（E9）条件性敲除Otx2，会导致所有脉络丛完全缺失；而通过Gdf7-Cre驱动株敲除Otx2，则主要影响后脑脉络丛，使其体积缩小，这一缺陷主要源于Otx2缺失后细胞凋亡水平的升高。值得注意的是，当在胚胎第15天（E15）诱导Otx2缺失时，仍需要Otx2来维持后脑脉络丛细胞，这表明Otx2在脉络丛的发育与维持中处于核心地位。此外，由Gdf7-Cre介导的Otx2敲除所引发的后脑脉络丛主要缺陷，揭示了其在调控早期脑脊液成分中的关键作用：脑脊液的蛋白质组成发生改变，包括Wnt4及Wnt调控因子Tgm2的水平异常。相应地，远端大脑皮层的细胞增殖水平与Wnt信号通路活性均有所升高，这提示后脑脉络丛在调控包括关键信号分子在内的脑脊液成分中发挥重要功能。综上，Otx2作为脉络丛发育的核心调控因子，可影响发育中大脑内主要信号源之一的脑脊液成分。本研究对同窝Otx2基因敲除小鼠与野生型小鼠的第四脑室脉络丛组织开展了基因表达微阵列分析。