Latimer Andrew J, Dong Xinhong, Markov Youlia, Appel Bruce
Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA.
Development. 2002 Jun;129(11):2555-63. doi: 10.1242/dev.129.11.2555.
Different cell types that occupy the midline of vertebrate embryos originate within the Spemann-Mangold or gastrula organizer. One such cell type is hypochord, which lies ventral to notochord in anamniote embryos. We show that hypochord precursors arise from the lateral edges of the organizer in zebrafish. During gastrulation, hypochord precursors are closely associated with no tail-expressing midline precursors and paraxial mesoderm, which expresses deltaC and deltaD. Loss-of-function experiments revealed that deltaC and deltaD were required for her4 expression in presumptive hypochord precursors and for hypochord development. Conversely, ectopic, unregulated Notch activity blocked no tail expression and promoted her4 expression. We propose that Delta signaling from paraxial mesoderm diversifies midline cell fate by inducing a subset of neighboring midline precursors to develop as hypochord, rather than as notochord.
占据脊椎动物胚胎中线的不同细胞类型起源于施佩曼-曼戈尔德组织者或原肠胚组织者。其中一种细胞类型是脊索下板，在无羊膜动物胚胎中位于脊索下方。我们发现，在斑马鱼中，脊索下板前体起源于组织者的外侧边缘。在原肠胚形成过程中，脊索下板前体与表达no tail的中线前体以及表达deltaC和deltaD的近轴中胚层紧密相连。功能丧失实验表明，deltaC和deltaD是假定的脊索下板前体中her4表达以及脊索下板发育所必需的。相反，异位的、不受调控的Notch活性会阻断no tail表达并促进her4表达。我们提出，来自近轴中胚层的Delta信号通过诱导一部分相邻的中线前体发育为脊索下板而非脊索，从而使中线细胞命运多样化。
