QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

doi: 10.1242/10.1242/dev.00166

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Garel, S. Articles by Rubenstein, J. L. R. Search for Related Content PubMed PubMed Citation Articles by Garel, S. Articles by Rubenstein, J. L. R. Social Bookmarking                         What's this?

The early topography of thalamocortical projections is shifted in Ebf1 and Dlx1/2 mutant mice

¹ Nina Ireland Laboratory of Developmental Neurobiology, Department of Psychiatry, University of California San Francisco, San Francisco, CA 94143-0984, USA
² Gene Center and Institute of Biochemistry, University of Munich, Feodor Lynenstrasse 25, 81377 Munich, Germany

^* Author for correspondence (e-mail: jlrr{at}cgl.ucsf.edu)

Accepted 11 September 2002

The prevailing model to explain the formation of topographic projections in the nervous system stipulates that this process is governed by information located within the projecting and targeted structures. In mammals, different thalamic nuclei establish highly ordered projections with specific neocortical domains and the mechanisms controlling the initial topography of these projections remain to be characterized. To address this issue, we examined Ebf1^-/- embryos in which a subset of thalamic axons does not reach the neocortex. We show that the projections that do form between thalamic nuclei and neocortical domains have a shifted topography, in the absence of regionalization defects in the thalamus or neocortex. This shift is first detected inside the basal ganglia, a structure on the path of thalamic axons, and which develops abnormally in Ebf1^-/- embryos. A similar shift in the topography of thalamocortical axons inside the basal ganglia and neocortex was observed in Dlx1/2^-/- embryos, which also have an abnormal basal ganglia development. Furthermore, Dlx1 and Dlx2 are not expressed in the dorsal thalamus or in cortical projections neurons. Thus, our study shows that: (1) different thalamic nuclei do not establish projections independently of each other; (2) a shift in thalamocortical topography can occur in the absence of major regionalization defects in the dorsal thalamus and neocortex; and (3) the basal ganglia may contain decision points for thalamic axons' pathfinding and topographic organization. These observations suggest that the topography of thalamocortical projections is not strictly determined by cues located within the neocortex and may be regulated by the relative positioning of thalamic axons inside the basal ganglia.

Key words: Topography, Thalamocortical axons, Internal capsule, Neocortex, Basal ganglia, Dlx, Ebf1, Mouse

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?