Saldivar, Jose R. and Krull, Catherine E. and Krumlauf, Robb and Ariza-McNaughton, Linda and Bronner, Marianne E. (1996) Rhombomere of origin determines autonomous versus environmentally regulated expression of Hoxa3 in the avian embryo. Development, 122 (3). pp. 895-904. ISSN 0950-1991 http://resolver.caltech.edu/CaltechAUTHORS:20120208-115800543
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We have investigated the pattern and regulation of Hoxa3 expression in the hindbrain and associated neural crest cells in the chick embryo, using whole mount in situ hybridization in conjunction with DiI labeling of neural crest cells and microsurgical manipulations. Hoxa3 is expressed in the neural plate and later in the neural tube with a rostral border of expression corresponding to the boundary between rhombomeres (r) 4 and 5. Initial expression is diffuse and becomes sharp after boundary formation. Hoxa3 exhibits uniform expression within r5 after formation of rhombomeric borders. Cell marking experiments reveal that neural crest cells migrating caudally, but not rostrally, from r5 and caudally from r6 express Hoxa3 in normal embryo. Results from transposition experiments demonstrate that expression of Hoxa3 in r5 neural crest cells is not strictly cell-autonomous. When r5 is transposed with r4 by rostrocaudal rotation of the rhomobomeres, Hoxa3 is expressed in cells migrating lateral to transposed r5 and for a short time, in condensing ganglia, but not by neural crest within the second branchial arch. Since DiI-labeled cells from transposed r5 are present in the second arch, Hoxa3-expressing neural crest cells from r5 appear to down-regulate their Hoxa3 expression in their new environment. In contrast, when r6 is transposed to the position of r4 after boundary formation, Hoxa3 is maintained in both migrating neural crest cells and those positioned within the second branchial arch and associated ganglia. These results suggest that Hoxa3 expression is cell-autonomous in r6 and its associated neural crest. Our results suggest that neural crest cells expressing the same Hox gene are not eqivalent; they respond differently to environmental signals and exhibit distinct degrees of cell autonomy depending upon their rhombomere of origin.
|Additional Information:||© 1996 Company of Biologists Limited. Accepted 23 November 1995. The first two authors contributed equally to this work. We thank Phoebe Villanueva and Roham Zamanian for excellent technical support and Drs John Sechrist and Scott Fraser for helpful suggestions and critical reading of the manuscript. This work was supported by USPHS grants DE10066 and HD15527 to M. B. F.|
|Subject Keywords:||neural crest; hindbrain; Hox gene; chick; rhombomere|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||08 Feb 2012 20:26|
|Last Modified:||26 Dec 2012 14:48|
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