By Charles B. Kimmel, Rachel M. Warga*, and Donald A. Kane*
Institute of Neuroscience, University of Oregon, Eugene, OR 97403; * Max-Planck-Institut/Entwicklungsbiologie, Spemannstrabe 35/III, D-7400 Tübingen 1, GERMANY
We examined developing lineages of central nervous system (CNS) progenitor cells during gastrulation and early segmentation in the zebrafish embryo, and observed consistent coupling of specific morphogenetic behaviors with particular cell cycles. The cells divide very synchronously. Their divisions become progressively oriented, and act synergistically with oriented intercalations during the interphases of zygotic cell cycles 15 and 16 to extend a single lineage into a long, discontinuous string of cells aligned with the nascent embryonic axis. Convergence brings the string to the dorsal midline, and once there, the cells enter division 16. This division and following intercalations convert the single string into a bilateral pair of strings, one forming a part of each side of the neural tube. The stereotyped cellular behaviors appear to account for the previously reported clonal restriction in cell fate, and to underlie morphogenesis of a midline organ of proper length and bilateral shape. Regulation of cellular morphogenesis could be cell-cycle dependent.
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