Region-specific cell clones in the developing spinal cord of the zebrafish

To analyse the proliferative abilities of cells within particular regions o f the zebrafish neural plate, injections of fluorescein-dextran were made i nto single cells at either medial or intermediary positions in the neural p late region of two-somite stage embryos. The resulting cell clones were ana lysed in 3.5-day-old embryos. Clones with similar compositions were found a mong those derived from injections in both regions, and these were grouped into classes. 78 clones 29 obtained following injections in the medial regi on, and 22 of 59 cell clones derived from injections in the intermediary re gion, were classifiable into 9 and 10 different classes, respectively, each comprising a variable number of clones. Several identified cell types, as well as each of the clone classes themselves, were specific for the regions of the neural plate from which they derived, i.e. they were not represente d among the clones derived from the other region. These results suggest tha t the composition of the lineages derived from particular cells is constant in different animals.