HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article 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 Schwarz, J. Articles by Lester, H. A. Search for Related Content PubMed PubMed Citation Articles by Schwarz, J. Articles by Lester, H. A.

Enhanced expression of hypersensitive 4* nAChR in adult mice increases the loss of midbrain dopaminergic neurons

Johannes Schwarz^*,,1, Sigrid C. Schwarz^*,,1, Oliver Dorigo, Alexandra Stützer^*, Florian Wegner^*, Cesar Labarca, Purnima Deshpande, Jose S. Gil, Arnold J. Berk and Henry A. Lester²

^* Department of Neurology, University of Leipzig, Leipzig, Germany;

Division of Biology 156–29, California Institute of Technology, Pasadena, California, USA; and

Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California, USA

²Correspondence: 156–29 Caltech, Pasadena CA 91125, USA. E-mail: lester{at}caltech.edu

We describe an inducible genetic model for degeneration of midbrain dopaminergic neurons in adults. In previous studies, knock-in mice expressing hypersensitive M2 domain Leu9’Ser (L9’S) 4 nicotinic receptors (nAChR) at near-normal levels displayed dominant neonatal lethality and dopaminergic deficits in embryonic midbrain, because the hypersensitive nAChR is excitotoxic. However, heterozygous L9’S mice that retain the neomycin resistance cassette (neo) in a neighboring intron express low levels of the mutant allele (25% of normal levels), and these neo-intact mice are therefore viable and fertile. The neo cassette is flanked by loxP sites. In adult animals, we locally injected helper-dependent adenovirus (HDA) expressing cre recombinase. Local excision of the neo cassette, via cre-mediated recombination, was verified by genomic analysis. In L9’S HDA-cre injected animals, locomotion was reduced both under baseline conditions and after amphetamine application. There was no effect in L9’S HDA-control treated animals or in wild-type (WT) littermates injected with either virus. Immunocytochemical analyses revealed marked losses (> 70%) of dopaminergic neurons in L9’S HDA-cre injected mice compared to controls. At 20–33 days postinjection in control animals, the coexpressed marker gene, yellow fluorescent protein (YFP), was expressed in many neurons and few glial cells near the injection, emphasizing the neurotropic utility of the HDA. Thus, HDA-mediated gene transfer into adult midbrain induced sufficient functional expression of cre in dopaminergic neurons to allow for postnatal deletion of neo. This produced increased L9’S mutant nAChR expression, which in turn led to nicotinic cholinergic excitotoxicity in dopaminergic neurons.—Schwarz, J., Schwarz, S. C., Dorigo, O., Stützer, A., Wegner, F., Labarca, C., Deshpande, P., Gil, J. S., Berk, A. J., Lester, H. A. Enhanced expression of hypersensitive 4* nAChR in adult mice increases the loss of midbrain dopaminergic neurons.

Key Words: nicotinic receptor • substantia nigra • cholinergic excitotoxicity • knock-in mouse • helper-dependent adenovirus • Parkinson’s disease