Cloning and cortical expression of rat Emx2 and adenovirus-mediated overexpression to assess its regulation of area-specific targeting of thalamocortical axons

Leingartner, A, Richards, LJ, Dyck, RH, Akazawa, C and O'Leary, DDM (2003) Cloning and cortical expression of rat Emx2 and adenovirus-mediated overexpression to assess its regulation of area-specific targeting of thalamocortical axons. Cerebral Cortex, 13 6: 648-660. doi:10.1093/cercor/13.6.648


Author Leingartner, A
Richards, LJ
Dyck, RH
Akazawa, C
O'Leary, DDM
Title Cloning and cortical expression of rat Emx2 and adenovirus-mediated overexpression to assess its regulation of area-specific targeting of thalamocortical axons
Journal name Cerebral Cortex   Check publisher's open access policy
ISSN 1047-3211
Publication date 2003-01-01
Sub-type Article (original research)
DOI 10.1093/cercor/13.6.648
Volume 13
Issue 6
Start page 648
End page 660
Total pages 13
Place of publication Cary
Publisher Oxford Univ Press Inc
Language eng
Abstract A goal of this study was to use recombinant adenovirus (AdV) to ectopically express Emx2 in the embryonic neocortex as a gain-of-function approach to study its role in the area-specific targeting of thalamocortical axons (TCAs), using the rat as a model. First, we cloned the cDNA for the full-length coding region of rat Emx2, a homologue of Drosophila empty spiracles. We also used this sequence to define the full-length coding region of mouse Emx2 from genomic DNA. Our analysis of Emx2 expression shows that in rat, as reported in mouse, Emx2 is expressed in high caudal to low rostral, and high medial to low lateral, gradients across the cortex throughout cortical neurogenesis, and expression is primarily restricted to progenitors in the neuroepithelium. We also carried out an analysis of the distribution of cells infected with a replication defective recombinant type 5 adenovirus (AdV) containing a CAG/LacZ expression construct, following an injection into the lateral ventricle of the cerebral hemisphere at different stages of embryonic cortical neurogenesis. AdV-infected cells are broadly distributed tangentially, but their laminar distribution is differentially restricted and reflects the temporal sequence of generation of cortical neurons. This finding indicates that the AdV predominantly infects progenitors in the ventricular zone, which leads to a preferential labeling of their immediate progeny, and infects cells that have recently become postmitotic and have yet to move far from the ventricular surface. We then show that AdV-mediated ectopic Emx2 expression results in aberrant intracortical pathfinding and areal targeting of TCAs from the dorsal lateral geniculate nucleus. These findings indicate that EMX2 imparts positional information normally associated with caudal cortical areas, such as the primary visual area, that influences the area-specific targeting of TCAs. These results are consistent with a role for EMX2 in areal specification of the neocortex as suggested by recent analyses of Emx2 null mutants.
Keyword Neurosciences
Developing Cerebral-cortex
Developing Mouse-brain
Subplate Neurons
Gene-expression
Optic Tectum
Mutant Mice
Thalamic Axons
Nervous-system
Homeobox Genes
Retinal Axons
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biomedical Sciences Publications
 
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Created: Wed, 17 Oct 2007, 22:03:26 EST