|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online 20 July 2005
doi: 10.1242/dev.01929
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Department of Biology, University of Massachusetts, Amherst, MA 01003,
USA
2 Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, UT
84112, USA
Author for correspondence (e-mail:
karlstrom{at}bio.umass.edu)
Accepted 3 June 2005
Three major axon pathways cross the midline of the vertebrate forebrain early in embryonic development: the postoptic commissure (POC), the anterior commissure (AC) and the optic nerve. We show that a small population of Gfap+ astroglia spans the midline of the zebrafish forebrain in the position of, and prior to, commissural and retinal axon crossing. These glial `bridges' form in regions devoid of the guidance molecules slit2 and slit3, although a subset of these glial cells express slit1a. We show that Hh signaling is required for commissure formation, glial bridge formation, and the restricted expression of the guidance molecules slit1a, slit2, slit3 and sema3d, but that Hh does not appear to play a direct role in commissural and retinal axon guidance. Reducing Slit2 and/or Slit3 function expanded the glial bridges and caused defasciculation of the POC, consistent with a `channeling' role for these repellent molecules. By contrast, reducing Slit1a function led to reduced midline axon crossing, suggesting a distinct role for Slit1a in midline axon guidance. Blocking Slit2 and Slit3, but not Slit1a, function in the Hh pathway mutant yot (gli2DR) dramatically rescued POC axon crossing and glial bridge formation at the midline, indicating that expanded Slit2 and Slit3 repellent function is largely responsible for the lack of midline crossing in these mutants. This analysis shows that Hh signaling helps to pattern the expression of Slit guidance molecules that then help to regulate glial cell position and axon guidance across the midline of the forebrain.
Key words: Zebrafish, Cyclopamine, Morpholino, Axon guidance, POC, Chiasm, Gfap, Glia, hedgehog, slit, you-too
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  E. Kastenhuber, U. Kern, J. L. Bonkowsky, C.-B. Chien, W. Driever, and J. Schweitzer Netrin-DCC, Robo-Slit, and Heparan Sulfate Proteoglycans Coordinate Lateral Positioning of Longitudinal Dopaminergic Diencephalospinal Axons J. Neurosci., July 15, 2009; 29(28): 8914 - 8926. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Sanchez-Camacho and P. Bovolenta Autonomous and non-autonomous Shh signalling mediate the in vivo growth and guidance of mouse retinal ganglion cell axons Development, November 1, 2008; 135(21): 3531 - 3541. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Guner, A. T. Ozacar, J. E. Thomas, and R. O. Karlstrom Graded Hedgehog and Fibroblast Growth Factor Signaling Independently Regulate Pituitary Cell Fates and Help Establish the Pars Distalis and Pars Intermedia of the Zebrafish Adenohypophysis Endocrinology, September 1, 2008; 149(9): 4435 - 4451. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Sun, T. Morozova, and M. Sonnenfeld Glial and Neuronal Functions of the Drosophila Homolog of the Human SWI/SNF Gene ATR-X (DATR-X) and the jing Zinc-Finger Gene Specify the Lateral Positioning of Longitudinal Glia and Axons Genetics, July 1, 2006; 173(3): 1397 - 1415. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Sakai and M. C. Halloran Semaphorin 3d guides laterality of retinal ganglion cell projections in zebrafish Development, March 15, 2006; 133(6): 1035 - 1044. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Seth, J. Culverwell, M. Walkowicz, S. Toro, J. M. Rick, S. C. F. Neuhauss, Z. M. Varga, and R. O. Karlstrom belladonna/(lhx2) is required for neural patterning and midline axon guidance in the zebrafish forebrain Development, February 15, 2006; 133(4): 725 - 735. [Abstract] [Full Text] [PDF]
|
|
