Journal of Neuroscience, Vol 1, 271-284, Copyright © 1981 by Society for Neuroscience
Clonal organization of the central nervous system of the frog. II. Clones stemming from individual blastomeres of the 32- and 64-cell stages
M Jacobson and G Hirose
Horseradish peroxidase injected into individual blastomeres of 32- and
64-cell embryos of Xenopus laevis was identified in cells of the central
nervous system (CNS) at larval stages 31 to 39. The CNS received
contributions from 24 blastomeres of the 32-cell stage and 38 blastomeres
of the 64-cell stage. The region of CNS in which all of the labeled
descendants of a single blastomere were dispersed is called a clonal
domain. Mingling of labeled and unlabeled cells always occurred in a clonal
domain, but boundaries were seen between such a labeled region and
completely unlabeled regions. These boundaries occurred at various places
in the CNS but were most frequently seen in the transverse plane at the
level of the isthmus between mesencephalon and rhombencephalon and in the
horizontal plane between dorsal and ventral regions of the CNS. When the
maternal clonal domain was partitioned between the descendants of the
daughter cells, the partitioning occurred only at one or both of those
boundaries. The constant relationship between the position of each of the
initially labeled blastomeres and the final spatial distribution of the
labeled descendants in the CNS provided a detailed fate map of the main
regions of the CNS in the 32- and 64-cell embryo.
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