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Development, Vol 126, Issue 23 5255-5265, Copyright © 1999 by Company of Biologists
JOURNAL ARTICLES |
HC Sweet, PG Hodor and CA Ettensohn
Department of Biological Sciences and Science and Technology Center for Light Microscope Imaging and Biotechnology, Carnegie Mellon University, Pittsburgh, PA 15213, USA. hsweet+@andrew.cmu.edu
In the sea urchin embryo, the micromeres act as a vegetal signaling center. These cells have been shown to induce endoderm; however, their role in mesoderm development has been less clear. We demonstrate that the micromeres play an important role in the induction of secondary mesenchyme cells (SMCs), possibly by activating the Notch signaling pathway. After removing the micromeres, we observed a significant delay in the formation of all mesodermal cell types examined. In addition, there was a marked reduction in the numbers of pigment cells, blastocoelar cells and cells expressing the SMC1 antigen, a marker for prospective SMCs. The development of skeletogenic cells and muscle cells, however, was not severely affected. Transplantation of micromeres to animal cells resulted in the induction of SMC1-positive cells, pigment cells, blastocoelar cells and muscle cells. The numbers of these cell types were less than those found in sham transplantation control embryos, suggesting that animal cells are less responsive to the micromere-derived signal than vegetal cells. Previous studies have demonstrated a role for Notch signaling in the development of SMCs. We show that the micromere-derived signal is necessary for the downregulation of the Notch protein, which is correlated with its activation, in prospective SMCs. We propose that the micromeres induce adjacent cells to form SMCs, possibly by presenting a ligand for the Notch receptor.
This article has been cited by other articles:
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M. Levine and E. H. Davidson From the Cover@;DELIM@;Gene Regulatory Networks Special Feature: Gene regulatory networks for development PNAS, April 5, 2005; 102(14): 4936 - 4942. [Abstract] [Full Text] [PDF]
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L. M. Angerer, L. A. Newman, and R. C. Angerer SoxB1 downregulation in vegetal lineages of sea urchin embryos is achieved by both transcriptional repression and selective protein turnover Development, March 1, 2005; 132(5): 999 - 1008. [Abstract] [Full Text] [PDF]
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