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The Journal of Neuroscience, April 23, 2008, 28(17):4322-4330; doi:10.1523/JNEUROSCI.4815-07.2008
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Neurobiology of Disease
Conditional Loss of Dicer Disrupts Cellular and Tissue Morphogenesis in the Cortex and Hippocampus
Tigwa H. Davis,1,2
Trinna L. Cuellar,3
Selina M. Koch,1,2
Allison J. Barker,1,2
Brian D. Harfe,4
Michael T. McManus,3 and
Erik M. Ullian1,2
Departments of 1Ophthalmology and 2Physiology and 3Diabetes Center, University of California, San Francisco, San Francisco, California 94143-0730, and 4Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida 32610-0266
Correspondence should be addressed to Dr. Erik M. Ullian, Department of Ophthalmology and Physiology, Beckman Vision Center, University of California, San Francisco, Room K323, 10 Koret Way, San Francisco, CA 94143-0730. Email: Ulliane{at}vision.ucsf.edu
To investigate the role of Dicer and microRNAs in the mammalian CNS, we used mice in which the second RNase III domain of Dicer was conditionally floxed. Conditional Dicer mice were bred with mice expressing an -calmodulin kinase II Cre to selectively inactivate Dicer in excitatory forebrain neurons in vivo. Inactivation of Dicer results in an array of phenotypes including microcephaly, reduced dendritic branch elaboration, and large increases in dendritic spine length with no concomitant change in spine density. Microcephaly is likely caused by a 5.5-fold increase in early postnatal apoptosis in these animals as determined by active caspase-3 and TUNEL (terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling) staining in the cortex. Loss of Dicer function had no measurable effect on cortical lamination as determined by in situ hybridization, suggesting that microcephaly is not caused by defects in neuronal migration. Together, these results illustrate the in vivo significance of Dicer and miRNAs in the mammalian CNS and provide additional support for previous in vitro studies indicating that misregulation of this pathway may result in gross abnormalities in cell number and function that may contribute to a variety of neurological disorders.
Key words: Dicer; microRNA; CNS; dendritic spine; noncoding RNA; cortex; hippocampus
Received Oct. 24, 2007;
revised Feb. 20, 2008;
accepted March 17, 2008.
Correspondence should be addressed to Dr. Erik M. Ullian, Department of Ophthalmology and Physiology, Beckman Vision Center, University of California, San Francisco, Room K323, 10 Koret Way, San Francisco, CA 94143-0730. Email: Ulliane{at}vision.ucsf.edu
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