Neuroscience 2005 Abstract
| Presentation Number: | 710.17 |
|---|---|
| Abstract Title: | Retinoic acid, a possible regulator of axon growth into chick hindlimb. |
| Authors: |
Wang, G.*1
; Scott, S. A.1
1Dept Neurobiol & Anatomy, Univ. of Utah School of Medicine, Salt Lake City, UT |
| Primary Theme and Topics |
Development - Axonal and Dendritic Development -- Axon growth and guidance: Biological effects |
| Secondary Theme and Topics | Development<br />- Axonal and Dendritic Development<br />-- Axon growth and guidance: Other |
| Session: |
710. Axon Growth and Guidance V Poster |
| Presentation Time: | Tuesday, November 15, 2005 1:00 PM-2:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # B30 |
| Keywords: | RALDH2, MOTOR NEURON, SENSORY NEURONS, LIMB INNERVATION |
During embryonic development, motor and sensory axons innervate the chick hindlimb precisely. Axons from different segmental levels converge in a plexus region at the base of the limb, pause for 24 hr, and then enter the limb in distinct dorsal and ventral pathways around St. 24.5 (E4.5). We previously showed that axons wait in the plexus region for maturational changes in the limb, but the molecular mechanisms responsible are unknown. Recently, we found that Raldh2, an enzyme required for synthesis of retinoic acid (RA), is first expressed in both dorsal and ventral regions of the hindlimb around St. 24, just before axons leave the plexus region and grow into the limb. The timing and pattern of Raldh2 expression suggest that RA could potentially regulate the waiting period. To investigate this possibility, we prematurely increased RA in the limb by implanting beads soaked in all-trans-RA just distal to the plexus region in St. 22-23 (E4) embryos. Both motor and sensory axons exited the plexus region and grew into the limb precociously prior to St. 24 in the presence of early exogenous RA, but did not fasciculate into distinct dorsal and ventral pathways. The effects of exogenous RA appeared to be confined to the limb; Lim1/Islet1 and EphA4 staining were unchanged in RA-treated embryos, suggesting that motor neurons differentiated normally. Importantly, axons appear to require RA in the limb in order to leave the plexus region. Following implantation of beads soaked in Citral, which inhibits RA synthesis, axons remained confined to the plexus region as late as St. 26, well after the time they normally enter the limb. Together, our results suggest that (1) RA plays a critical role in regulating the time that motor and sensory axons wait in and exit from the plexus region, and (2) RA from the limb acts locally to regulate axon ingrowth, rather than acting on the motor neurons themselves. We are currently investigating whether RA influences the expression of molecules in the limb that contribute to the waiting period or directly attracts axons into the limb.
Supported by NS16067 to SAS
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
Copyright © 2005-2025 Society for Neuroscience; all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
