|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Development, Vol 117, Issue 4 1275-1285, Copyright © 1993 by Company of Biologists
JOURNAL ARTICLES |
CA Ettensohn and SW Ruffins
Department of Biological Sciences and Center for Light Microscope Imaging and Biotechnology, Carnegie Mellon University, Pittsburgh, PA 15213.
An interaction between the two principal populations of mesodermal cells in the sea urchin embryo, primary and secondary mesenchyme cells (PMCs and SMCs, respectively), regulates SMC fates and the process of skeletogenesis. In the undisturbed embryo, skeletal elements are produced exclusively by PMCs. Certain SMCs also have the ability to express a skeletogenic phenotype; however, signals transmitted by the PMCs direct these cells into alternative developmental pathways. In this study, a combination of fluorescent cell-labeling methods, embryo microsurgery and cell-specific molecular markers have been used to study the lineage, numbers, normal fate(s) and developmental potential of the skeletogenic SMCs. Previous fate-mapping studies have shown that SMCs are derived from the veg2 layer of blastomeres of the 64-cell-stage embryo and from the small micromeres. By specifically labeling the small micromeres with 5-bromodeoxyuridine, we demonstrate that descendants of these cells do not participate in skeletogenesis in PMC-depleted larvae, even though they are the closest lineal relatives of PMCs. Skeletogenic SMCs are therefore derived exclusively from the veg2 blastomeres. Because the SMCs are a heterogeneous population of cells, we have sought to gain information concerning the normal fate(s) of skeletogenic SMCs by determining whether specific cell types are reduced or absent in PMC(-) larvae. Of the four known SMC derivatives: pigment cells, blastocoelar (basal) cells, muscle cells and coelomic pouch cells, only pigment cells show a major reduction (> 50%) in number following SMC skeletogenesis. We therefore propose that the PMC-derived signal regulates a developmental switch, directing SMCs to adopt a pigment cell phenotype instead of a default (skeletogenic) fate. Ablation of SMCs at the late gastrula stage does not result in the recruitment of any additional skeletogenic cells, demonstrating that, by this stage, the number of SMCs with skeletogenic potential is restricted to 60-70 cells. Previous studies showed that during their switch to a skeletogenic fate, SMCs alter their migratory behavior and cell surface properties. In this study, we demonstrate that during conversion, SMCs become insensitive to the PMC-derived signal, while at the same time they acquire PMC-specific signaling properties.
This article has been cited by other articles:
|
|
 |
|
  C. A. Ettensohn, C. Kitazawa, M. S. Cheers, J. D. Leonard, and T. Sharma Gene regulatory networks and developmental plasticity in the early sea urchin embryo: alternative deployment of the skeletogenic gene regulatory network Development, September 1, 2007; 134(17): 3077 - 3087. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Ettensohn, M. R. Illies, P. Oliveri, and D. L. De Jong Alx1, a member of the Cart1/Alx3/Alx4 subfamily of Paired-class homeodomain proteins, is an essential component of the gene network controlling skeletogenic fate specification in the sea urchin embryo Development, July 1, 2003; 130(13): 2917 - 2928. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Aihara and S. Amemiya Left-right positioning of the adult rudiment in sea urchin larvae is directed by the right side Development, December 15, 2001; 128(24): 4935 - 4948. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Sweet, P. Hodor, and C. Ettensohn The role of micromere signaling in Notch activation and mesoderm specification during sea urchin embryogenesis Development, January 12, 1999; 126(23): 5255 - 5265. [Abstract] [PDF]
|
|
|
|
|
|
D. Sherwood and D. McClay LvNotch signaling mediates secondary mesenchyme specification in the sea urchin embryo Development, January 4, 1999; 126(8): 1703 - 1713. [Abstract] [PDF]
|
|
|
|
|
|
E. Davidson, R. Cameron, and A Ransick Specification of cell fate in the sea urchin embryo: summary and some proposed mechanisms Development, January 9, 1998; 125(17): 3269 - 3290. [Abstract] [PDF]
|
|
|
|
|
|
C. Logan and D. McClay The allocation of early blastomeres to the ectoderm and endoderm is variable in the sea urchin embryo Development, January 6, 1997; 124(11): 2213 - 2223. [Abstract] [PDF]
|
|
|
|
|
|
D. McClay and C. Logan Regulative capacity of the archenteron during gastrulation in the sea urchin Development, January 2, 1996; 122(2): 607 - 616. [Abstract] [PDF]
|
|
|
|
|
|
S. Ruffins and C. Ettensohn A fate map of the vegetal plate of the sea urchin (Lytechinus variegatus) mesenchyme blastula Development, January 1, 1996; 122(1): 253 - 263. [Abstract] [PDF]
|
|
|
|
|
|
C. Ettensohn and K. Malinda Size regulation and morphogenesis: a cellular analysis of skeletogenesis in the sea urchin embryo Development, January 9, 1993; 119(1): 155 - 167. [Abstract] [PDF]
|
|
