Goldstein A M, Fishman M C
Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Dev Biol. 1998 Sep 15;201(2):247-52. doi: 10.1006/dbio.1998.8976.
We focus here upon regulation by the notochord of myocardial cell fate in zebrafish. Myocardial precursors, defined by lineage tracing in the living embryo, are in the lateral plate mesoderm adjacent to the notochord-prechordal plate junction. Interestingly, the anterior end of the notochord corresponds to the posterior extent of the heart progenitor field, defined by this lineage analysis. This suggested that the notochord might suppress, or the prechordal plate might enhance, the cardiogenic fate. Nkx2.5 expression is, in the zebrafish embryo, closely correlated with the position of myocardial precursors, which reside adjacent to the notochord-prechordal plate junction. This expression, however, is extinguished in the region posterior to this junction, a region normally not contributing cells to the heart. Laser ablation of the notochord tip between the 4-somite and 12-somite stage causes posterior expansion of the Nkx2. 5-expressing region. The ntl mutation of the notochord is associated with posterior extension of Nkx2.5 expression. Lineage tracking, by laser activation of caged fluoresceinated dextran, confirms that, normally, lateral plate cells next to the notochord do not contribute progeny to the heart. After anterior notochord ablation, these cells are redirected to a heart cell fate. These data suggest that the anterior notochord delimits the posterior extent of the heart field by suppressing the heart cell fate.
我们在此聚焦于斑马鱼中脊索对心肌细胞命运的调控。通过对活胚胎进行谱系追踪所定义的心肌前体细胞，位于与脊索 - 前索板交界处相邻的侧板中胚层。有趣的是，脊索的前端对应于通过该谱系分析所定义的心脏祖细胞区域的后端。这表明脊索可能会抑制，或者前索板可能会增强心脏发生命运。在斑马鱼胚胎中，Nkx2.5的表达与心肌前体细胞的位置密切相关，这些细胞位于脊索 - 前索板交界处附近。然而，在该交界处后方的区域，这种表达会消失，该区域通常不会为心脏提供细胞。在4体节和12体节阶段之间对脊索尖端进行激光消融会导致Nkx2.5表达区域向后扩展。脊索的ntl突变与Nkx2.5表达的向后延伸有关。通过笼锁荧光素化葡聚糖的激光激活进行谱系追踪证实，正常情况下，紧邻脊索的侧板细胞不会为心脏提供后代细胞。在前部脊索消融后，这些细胞会被重定向到心脏细胞命运。这些数据表明，前部脊索通过抑制心脏细胞命运来界定心脏区域的后端范围。
