Research NewsDevelopmental Biology

Embryo's Organizational Chart Redrawn

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Science  19 Jun 1998:
Vol. 280, Issue 5371, pp. 1838-1839
DOI: 10.1126/science.280.5371.1838

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Early in development, the notochord, a rodlike group of cells running from the embryonic head to the tail, sends out a command to tissue destined to be part of the spinal cord, ordering it to differentiate into a specialized sheet of cells called the floor plate, which in turn sends out signals that trigger the formation of motor neurons, which transmit signals between muscles and the spinal cord. But now both developmental and genetic evidence suggests that the floor plate is not ordered into existence by the notochord but rather that it is another member of the executive committee, forming at the same time and from the same group of precursor cells as the notochord itself. This and genetic studies in the zebrafish are forcing embryologists to reconsider some of their basic assumptions.