Shih, John and Fraser, Scott E. (1996) Characterizing the zebrafish organizer: microsurgical analysis at the early-shield stage. Development, 122 (4). pp. 1313-1322. ISSN 0950-1991 http://resolver.caltech.edu/CaltechAUTHORS:20120208-153016233
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The appearance of the embryonic shield, a slight thickening at the leading edge of the blastoderm during the formation of the germ ring, is one of the first signs of dorsoventral polarity in the zebrafish embryo. It has been proposed that the shield plays a role in fish embryo patterning similar to that attributed to the amphibian dorsal lip. In a recent study, we fate mapped many of the cells in the region of the forming embryonic shield, and found that neural and mesodermal progenitors are intermingled (Shih, J. and Fraser, S.E. (1995) Development 121, 2755–2765), in contrast to the coherent region of mesodermal progenitors found at the amphibian dorsal lip. Here, we examine the fate and the inductive potential of the embryonic shield to determine if the intermingling reflects a different mode of embryonic patterning than that found in amphibians. Using the microsurgical techniques commonly used in amphibian and avian experimental embryology, we either grafted or deleted the region of the embryonic shield. Homotopic grafting experiments confirmed the fates of cells within the embryonic shield region, showing descendants in the hatching gland, head mesoderm, notochord, somitic mesoderm, endoderm and ventral aspect of the neuraxis. Heterotopic grafting experiments demonstrated that the embryonic shield can organize a second embryonic axis; however, contrary to our expectations based on amphibian research, the graft contributes extensively to the ectopic neuraxis. Microsurgical deletion of the embryonic shield region at the onset of germ ring formation has little effect on neural development: embryos with a well-formed and well-patterned neuraxis develop in the complete absence of notochord cells. While these results show that the embryonic shield is sufficient for ectopic axis formation, they also raise questions concerning the necessity of the shield region for neural induction and embryonic patterning after the formation of the germ ring.
|Additional Information:||© 1996 The Company of Biologists Limited. Accepted 27 January 1996. The authors express heart-felt appreciation to all those who supported our research through its difficult early years. We would like to especially thank Drs J. P. Trinkaus, Ray Keller, Eric Davidson, Jane Oppenheimer and William Ballard for their encouragement and insights. Moreover, we thank Dr Katherine Woo for her critical reading of the manuscript and many valuable discussions. We wish to express our gratitude to Woods Hole Marine Biology Laboratory, where these experiments were first performed in the summer of 1992, in the middle of the great Swoopenella outbreak. Finally, we would also like to express our thanks to Dian De Sha for her help in editing and re-editing the manuscript. This research was supported by the NIH and a NIH Post-Doctoral Training Fellowship #5T32 HD07257.|
|Subject Keywords:||zebrafish, induction, shield, microsurgery, homology, organizer, dorsal lip, gastrulation|
|Official Citation:||J. Shih and S.E. Fraser Characterizing the zebrafish organizer: microsurgical analysis at the early-shield stage Development 1996 122:1313-1322|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||08 Feb 2012 23:46|
|Last Modified:||26 Dec 2012 14:49|
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