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The Journal of Neuroscience, August 1, 1998, 18(15):5881-5890

Patterns of Chondroitin Sulfate Immunoreactivity in the Developing Tectum Reflect Regional Differences in Glycosaminoglycan Biosynthesis

Diane Hoffman-Kim¹, Arthur D. Lander², and Sonal Jhaveri¹

¹ Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and ² Department of Developmental and Cell Biology and Developmental Biology Center, University of California, Irvine, Irvine, California 92697

The glycosaminoglycan chondroitin sulfate (CS) is expressed in many parts of the developing brain, both in regions where axons preferentially grow and in areas that axons distinctly avoid. Some in vitro studies suggest that CS and proteoglycans (PGs) that carry CS enhance axon growth, whereas others suggest that CS and CSPGs inhibit it. In the developing hamster, there is evidence that midbrain raphe cells act as a barrier to prevent growth of optic axons across the tectal midline. Here we show that in the newborn hamster, CS immunoreactivity is substantially higher in midline than in lateral tectum, raising the possibility that CSPGs play a role in the unilateral containment of optic axons. However, analysis of tectal PGs by anion exchange chromatography and denaturing gel electrophoresis failed to detect substantial differences between midline and lateral tectum in either the types or relative amounts of CSPG and heparan sulfate PG protein cores. In contrast, metabolic labeling of tectal slices in vitro documented that incorporation of ³⁵S-sulfate into macromolecules is significantly increased at the tectal midline, in a pattern resembling chondroitin sulfate immunoreactivity. This difference was evident whether slices were labeled for 1 hr or overnight and was not paralleled by a difference in overall protein synthesis, suggesting that the rate of synthesis of sulfated macromolecules is specifically elevated in midline tectum. We propose that the concentration of CS at the midline of the developing tectum is a reflection of a higher rate of synthesis or sulfation of glycosaminoglycans by midline cells, rather than a higher level of production of any particular CSPG. These results suggest that the distribution of some axon guidance signals in development may be controlled by differential regulation of glycosaminoglycan biosynthetic enzymes.

Key words: axon guidance; chondroitin sulfate; visual system; tectal midline; glia; rodent

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Copyright © 1998 Society for Neuroscience  0270-6474/98/18155881-10$05.00/0

This article has been cited by other articles:

				C. E. Bandtlow and D. R. Zimmermann Proteoglycans in the Developing Brain: New Conceptual Insights for Old Proteins Physiol Rev, October 1, 2000; 80(4): 1267 - 1290. [Abstract] [Full Text] [PDF]

				K. Chung, J. Taylor, D. Shum, and S. Chan Axon routing at the optic chiasm after enzymatic removal of chondroitin sulfate in mouse embryos Development, January 6, 2000; 127(12): 2673 - 2683. [Abstract] [PDF]

				D.-Y. Wu, G. E. Schneider, J. Silver, M. Poston, and S. Jhaveri A Role for Tectal Midline Glia in the Unilateral Containment of Retinocollicular Axons J. Neurosci., October 15, 1998; 18(20): 8344 - 8355. [Abstract] [Full Text] [PDF]

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