Publication Date:
2008-03-28
Description:
The retinotectal projection has long been studied experimentally and theoretically, as a model for the formation of topographic brain maps. Neighbouring retinal ganglion cells (RGCs) project their axons to neighbouring positions in the optic tectum, thus re-establishing a continuous neural representation of visual space. Mapping along this axis requires chemorepellent signalling from tectal cells, expressing ephrin-A ligands, to retinal growth cones, expressing EphA receptors. High concentrations of ephrin A, increasing from anterior to posterior, prevent temporal axons from invading the posterior tectum. However, the force that drives nasal axons to extend past the anterior tectum and terminate in posterior regions remains to be identified. We tested whether axon-axon interactions, such as competition, are required for posterior tectum innervation. By transplanting blastomeres from a wild-type (WT) zebrafish into a lakritz (lak) mutant, which lacks all RGCs, we created chimaeras with eyes that contained single RGCs. These solitary RGCs often extended axons into the tectum, where they branched to form a terminal arbor. Here we show that the distal tips of these arbors were positioned at retinotopically appropriate positions, ruling out an essential role for competition in innervation of the ephrin-A-rich posterior tectum. However, solitary arbors were larger and more complex than under normal, crowded conditions, owing to a lack of pruning of proximal branches during refinement of the retinotectal projection. We conclude that dense innervation is not required for targeting of retinal axons within the zebrafish tectum but serves to restrict arbor size and shape.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885002/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885002/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gosse, Nathan J -- Nevin, Linda M -- Baier, Herwig -- R01 EY012406/EY/NEI NIH HHS/ -- R01 EY012406-06A2/EY/NEI NIH HHS/ -- R01 EY012406-07/EY/NEI NIH HHS/ -- R01 EY012406-08/EY/NEI NIH HHS/ -- R01 EY012406-09/EY/NEI NIH HHS/ -- R01 EY013855/EY/NEI NIH HHS/ -- R01 EY013855-01A1/EY/NEI NIH HHS/ -- R01 EY013855-02/EY/NEI NIH HHS/ -- R01 EY013855-03/EY/NEI NIH HHS/ -- R01 EY013855-04/EY/NEI NIH HHS/ -- R01 EY013855-05/EY/NEI NIH HHS/ -- R01 EY013855-06/EY/NEI NIH HHS/ -- R01 EY013855-07/EY/NEI NIH HHS/ -- R01 EY013855-08/EY/NEI NIH HHS/ -- England -- Nature. 2008 Apr 17;452(7189):892-5. doi: 10.1038/nature06816. Epub 2008 Mar 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Program in Developmental Biology, University of California, San Francisco, Department of Physiology, 1550 Fourth Street, San Francisco, California 94158-2324, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18368050" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Axons/*physiology
;
DNA-Binding Proteins/genetics/metabolism
;
Models, Neurological
;
Retinal Ganglion Cells/*cytology/*physiology
;
Superior Colliculi/*cytology/*physiology
;
Zebrafish/*physiology
;
Zebrafish Proteins/genetics/metabolism
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
Permalink
