Cell lineage restrictions in the chick embryo hindbrain.

During development of the chick embryo, early neuronal differentiation and axonogenesis in the hindbrain follow a segmented pattern in register with the segmented morphology of this region. Cell marking experiments have shown that the segments, or rhombomeres, are lineage-restriction units each constructing a defined piece of the hindbrain. This raises the interesting possibility that, as in the developing fly, metamerism is used to generate level-specific anatomical structures with great and reliable precision. In the hindbrain, as for many invertebrates, lineage ancestry may be important in the determination of cell fate. The segmentation seen in this body region could therefore reflect a similar condition once present in the ancestor common to vertebrates and invertebrates.