Heisenberg C P, Nüsslein-Volhard C
Max-Planck-Institut für Entwicklungsbiologie, Tübingen, Germany.
Dev Biol. 1997 Apr 1;184(1):85-94. doi: 10.1006/dbio.1997.8511.
In zebrafish, as in other vertebrates, an initially singular eye field within the neural plate has to split during morphogenesis to allow the development of two separated eyes. It has been suggested that anterior progression of midline tissue within the neural plate is involved in the bilateralization of the eye field. Mutations in the recently identified silberblick (slb) gene cause an incomplete separation of the eyes. During gastrulation and early somitogenesis, the ventral midline of the central nervous system (CNS) together with the underlying axial mesendoderm is shortened and broadened in slb embryos. While in wild-type embryos the ventral CNS midline extends to the anterior limit of the neural plate at the end of gastrulation, there is a gap between the anterior tip of the ventral CNS midline and the anterior edge of the neural plate in slb. To investigate the cause for the shortening of the ventral CNS midline in slb we determined the fate of labeled ventral CNS midline cells in wild-type and slb embryos at different stages of development. In slb, anterior migration of ventral CNS midline cells is impaired, which indicates that migration of these cells is needed for elongation of the ventral CNS midline. The anterior shortening of the ventral CNS midline in slb leads to medial instead of bilateral induction of optic stalks followed by a partial fusion of the eyes at later developmental stages. The analysis of the slb phenotype indicates that anterior migration of midline cells within the neural plate is required for proper induction and subsequent bilateralization of an initially singular eye field. These findings may therefore provide a starting point in elucidating the role of neural plate morphogenesis in positioning of the eyes.
与其他脊椎动物一样，在斑马鱼中，神经板内最初单一的眼原基在形态发生过程中必须分开，以形成两个分离的眼睛。有人提出，神经板内中线组织向前推进与眼原基的双侧化有关。最近发现的silberblick（slb）基因突变会导致眼睛不完全分离。在原肠胚形成和早期体节发生期间，slb胚胎中中枢神经系统（CNS）的腹侧中线连同其下方的轴旁中胚层会缩短并变宽。在野生型胚胎中，腹侧CNS中线在原肠胚形成结束时延伸至神经板的前端，但在slb胚胎中，腹侧CNS中线的前端与神经板的前缘之间存在间隙。为了研究slb胚胎中腹侧CNS中线缩短的原因，我们确定了野生型和slb胚胎在不同发育阶段标记的腹侧CNS中线细胞的命运。在slb胚胎中，腹侧CNS中线细胞的向前迁移受损，这表明这些细胞的迁移是腹侧CNS中线延长所必需的。slb胚胎中腹侧CNS中线的前端缩短导致视柄向内侧而非双侧诱导，随后在发育后期眼睛部分融合。对slb表型的分析表明，神经板内中线细胞的向前迁移是正确诱导以及随后最初单一的眼原基双侧化所必需的。因此，这些发现可能为阐明神经板形态发生在眼睛定位中的作用提供一个起点。
