Nine inherited neurodegenerative disorders, including Huntington's disease (HD), are caused by the expansion of a polyglutamine (polyQ) domain in their associated disease proteins. A common pathological feature of these diseases is selective neurodegeneration in distinct brain regions associated with each disease, despite the widespread expression of mutant proteins throughout the brain and body. Understanding the mechanism by which expanded polyQ-containing proteins mediate selective neurodegeneration is critical for developing effective therapeutic strategies to treat these polyQ diseases. In HD patients, the selective neurodegeneration occurs first to the medium spiny neurons, which account for >90% of neurons in the striatum. In HD mice that express full-length mutant huntingtin (htt), there is a preferential accumulation of mutant htt in the nuclei of medium spiny neurons in the striatum. Since mutant htt in the nucleus interacts with transcription factors and affects gene expression, this preferential nuclear accumulation is believed to account for the selective neurodegeneration in the striatum. Understanding the mechanism for this nuclear localization will not only help elucidate the pathogenesis of HD, but also other polyQ diseases that feature nuclear accumulation and inclusions of polyQ proteins. We hypothesize that the nuclear localization of mutant htt stems from multiple factors. First, the full- length mutant htt must be degraded to generate small N-terminal htt fragments that can passively enter the nucleus to affect gene transcription. Second, cell type-specific factors can regulate the nuclear localization of mutant htt. To test these hypotheses, we will compare the subcellular distribution of full-length and N- terminal mutant htt in HD knock-in mice that express mutant htt at the endogenous level. The relationship between the nuclear accumulation of N-terminal mutant htt and neurological phenotypes or changes in gene expression will be evaluated. We will also investigate the cell type-specific toxicity of N-terminal mutant htt via the Cre-loxP system. These studies aim to test whether N-terminal mutant htt, when expressed at the endogenous level, accumulates more rapidly in the nucleus and causes more severe phenotypes than full-length mutant htt. We will also examine whether striatal neurons have specific molecules or factors that regulate N-terminal phosphorylation of mutant htt to promote its nuclear accumulation. These studies will help us develop therapies that alter htt phosphorylation to reduce the nuclear accumulation of mutant htt and its associated neuropathology.

Public Health Relevance

Huntington disease (HD) is the most common form of polyglutamine diseases that are featured by abnormal gene expression caused by mutant proteins in the nucleus. In this application, we will use genetic mouse models of HD to investigate the mechanism by which the HD protein accumulates in neuronal nucleus. Elucidating this mechanism will help find therapeutic intervention to reduce HD neuropathology.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS041669-11
Application #
8225291
Study Section
Cell Death in Neurodegeneration Study Section (CDIN)
Program Officer
Sutherland, Margaret L
Project Start
2001-05-01
Project End
2016-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
11
Fiscal Year
2012
Total Cost
$335,453
Indirect Cost
$116,703
Name
Emory University
Department
Genetics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Yan, Sen; Wang, Chuan-En; Wei, Wenjie et al. (2014) TDP-43 causes differential pathology in neuronal versus glial cells in the mouse brain. Hum Mol Genet 23:2678-93
Yang, Su; Huang, Shanshan; Gaertig, Marta A et al. (2014) Age-dependent decrease in chaperone activity impairs MANF expression, leading to Purkinje cell degeneration in inducible SCA17 mice. Neuron 81:349-65
Xiang, Jianxing; Yang, Hao; Zhao, Ting et al. (2014) Huntingtin-associated protein 1 regulates postnatal neurogenesis and neurotrophin receptor sorting. J Clin Invest 124:85-98
Yang, Huaqiang; Wang, Guohao; Sun, Haitao et al. (2014) Species-dependent neuropathology in transgenic SOD1 pigs. Cell Res 24:464-81
Wade, Brandy E; Wang, Chuan-En; Yan, Sen et al. (2014) Ubiquitin-activating enzyme activity contributes to differential accumulation of mutant huntingtin in brain and peripheral tissues. J Neurosci 34:8411-22
Weng, Ling; Lin, Yung-Feng; Li, Alina L et al. (2013) Loss of Ahi1 affects early development by impairing BM88/Cend1-mediated neuronal differentiation. J Neurosci 33:8172-84
Huang, Shanshan; Ling, Joseph J; Yang, Su et al. (2011) Neuronal expression of TATA box-binding protein containing expanded polyglutamine in knock-in mice reduces chaperone protein response by impairing the function of nuclear factor-Y transcription factor. Brain 134:1943-58
Li, Xiao-Jiang; Li, Shihua (2011) Proteasomal dysfunction in aging and Huntington disease. Neurobiol Dis 43:4-8
Havel, Lauren S; Wang, Chuan-En; Wade, Brandy et al. (2011) Preferential accumulation of N-terminal mutant huntingtin in the nuclei of striatal neurons is regulated by phosphorylation. Hum Mol Genet 20:1424-37
Li, Xiang; Wang, Chuan-En; Huang, Shanshan et al. (2010) Inhibiting the ubiquitin-proteasome system leads to preferential accumulation of toxic N-terminal mutant huntingtin fragments. Hum Mol Genet 19:2445-55

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