Ruffins S W, Ettensohn C A
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213.
Dev Biol. 1993 Nov;160(1):285-8. doi: 10.1006/dbio.1993.1306.
The secondary mesenchyme cells (SMCs) give rise to most of the mesoderm of the sea urchin embryo. Although the early embryonic lineage of these cells has been described, the mechanisms that cause SMCs to become restricted to a particular mesodermal cell fate are unknown. To begin to address this question, we performed a clonal analysis of the fates of SMC precursors in the vegetal plate by labeling single cells with the fluorescent dye DiI (C18). Our data show that some presumptive SMCs remain pluripotent at the late blastula stage, since some cells labeled at this stage gave rise to more than one mesodermal cell type. Surprisingly, however, most labeled cells gave rise to homogeneous clones composed of a single cell type. This observation indicates that either many SMC precursors are restricted in their fate before the start of gastrulation or that all the progeny of a single vegetal plate cell are influenced by the same instructional signals during gastrulation, despite the cell divisions and extensive cell movements that occur during this time. The percentage of clones composed of a single cell type increased during the blastula stage, supporting the view that the process of SMC fate specification begins before the onset of gastrulation.
次级间充质细胞（SMCs）产生海胆胚胎的大部分中胚层。尽管已经描述了这些细胞的早期胚胎谱系，但导致SMCs局限于特定中胚层细胞命运的机制尚不清楚。为了开始解决这个问题，我们通过用荧光染料DiI（C18）标记单个细胞，对植物极板中SMC前体的命运进行了克隆分析。我们的数据表明，一些推定的SMCs在囊胚后期仍保持多能性，因为在这个阶段标记的一些细胞产生了不止一种中胚层细胞类型。然而，令人惊讶的是，大多数标记细胞产生了由单一细胞类型组成的同质克隆。这一观察结果表明，要么许多SMC前体在原肠胚形成开始之前就已受到命运限制，要么单个植物极板细胞的所有后代在原肠胚形成期间都受到相同的指令信号影响，尽管在此期间会发生细胞分裂和广泛的细胞运动。由单一细胞类型组成的克隆百分比在囊胚期增加了，这支持了SMC命运特化过程在原肠胚形成开始之前就已开始的观点。
