Generation of region-specific neural cells from Embryonic Stem Cells

近年来，非洲爪蟾和果蝇神经诱导的分子机制研究取得了重要进展。相比之下，对哺乳动物神经诱导和产生不同神经元的分子机制知之甚少。本研究开始，我们建立了一个体外诱导小鼠和灵长类动物胚胎干细胞向神经细胞分化的实验体系。利用共培养系统，我们鉴定了ES细胞在某些基质细胞中的神经诱导活性，并将这种活性命名为基质细胞衍生的诱导活性（SDIA）。特别是PA6细胞（来自颅骨骨髓的基质细胞）有效地（>90%）诱导ES细胞的神经分化。SD1A处理的ES细胞表达前脑、中脑和后脑标志物，但不表达脊髓标志物。他们表达了各种背腹神经标记的背腹ax.Finally，我们研究了SDIA处理的ES细胞产生各种神经细胞类型的能力。视黄酸修饰SDIA处理的ES细胞向尾部方向。Shh抑制背侧神经标记物，诱导腹侧中枢神经系统组织，如运动神经元和底板细胞。BMP 4抑制腹侧神经标记物，诱导背侧和神经嵴标记物。因此，SDIA处理的ES细胞具有响应图案化因子（例如视黄酸、Shh和BMP 4）的能力，并且可以被修饰为区域特异性神经细胞。

Recently significant progress has been made in the molecular understanding of neural induction in Xenopus and Drosophila. By contrast, relatively little is known about molecular mechanisms of mammalian neural induction and generation of diverse neurons. Using mammalian Embryonic Stem (ES) cells, we are studying these issues.To begin with, we established an in vitro experimental system that induces neural differentiation of mouse and primate ES cells. Using co-culture system, we have identified neural inducing activity of ES cells in some stromal cells and named this activity Stromal Cell-Derived Inducing Activity (SDIA). Especially PA6 cells (stromal cells derived from skull bone marrow)efficiently (>90%) induce neural differentiation of ES cells.We next analyzed regional identities of SDIA-induced neural cells. SDlA-treated ES cells express forebrain, midbrain and hindbrain markers but not spinal cord markers. They express a variety of dorsal-ventral neural markers in terms of dorsal-ventral axis.Finally, we examined the capacity of SDIA-treated ES cells to generate a wide variety of neural cell types. Retinoic Acid modified SDIA-treated ES cells into the caudal direction. Shh suppressed dorsal neural markers and induce ventral Central Nervous System tissues, such as motor neurons and floor plate cells. BMP4 suppressed ventral neural markers and induced dorsal and neural crest markers. Thus SDIA-treated ES cells have the competence to respond to patterning factors, such as Retinoic Acid, Shh and BMP4, and can be modified to region-specific neural cells.