Neural Ectoderm Cells Remain Competent to Form Muscle Fibers in X. laevis Embryos

As the embryo develops, cells become committed to specific fates that will eventually form all the tissues found in the adult. An important stage of early development is gastrulation when the three embryonic germ layers form; the endoderm, mesoderm, and ectoderm. Previous studies have shown that cells in the gastrula remain pluripotent (Domingo and Keller, 2000). However, the extent to which specific regions of the embryo remain pluripotent after gastrulation remains unclear. To determine the range of plasticity specifically within the neural ectoderm region, we have transplanted fluorescently-labeled neural ectoderm cells into the prospective dorsal mesoderm region of host embryos to determine whether prospective neural ectoderm cells can change their fate and differentiate in muscle cells. By varying the developmental stage of the donor cells, we were able to show that anterior neural ectoderm cells remain competent to form muscle during gastrulation, but that this plasticity is lost by the onset of neurulation. In contrast, cells from the posterior neural ectoderm appear to remain competent to form muscle for a longer period of time. These results offer new insights into the ability of embryonic cells to regulate pluripotency during development.