Article

Gene expression profiling of R6/2 transgenic mice with different CAG repeat lengths reveals genes associated with disease onset and progression in Huntington's disease.

Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA.
Neurobiology of Disease (Impact Factor: 5.62). 02/2011; 42(3):459-67. DOI: 10.1016/j.nbd.2011.02.008
Source: PubMed

ABSTRACT R6/2 transgenic mice with expanded CAG repeats (>300) have a surprisingly prolonged disease progression and longer lifespan than prototypical parent R6/2 mice (carrying 150 CAGs); however, the mechanism of this phenotype amelioration is unknown. We compared gene expression profiles in the striatum of R6/2 transgenic mice carrying ~300 CAG repeats (R6/2(Q300) transgenic mice) to those carrying ~150 CAG repeats (R6/2(Q150) transgenic mice) and littermate wildtype controls in order to identify genes that may play determinant roles in the time course of phenotypic expression in these mice. Of the top genes showing concordant expression changes in the striatum of both R6/2 lines, 85% were decreased in expression, while discordant expression changes were observed mostly for genes upregulated in R6/2(Q300) transgenic mice. Upregulated genes in the R6/2(Q300) mice were associated with the ubiquitin ligase complex, cell adhesion, protein folding, and establishment of protein localization. We qPCR-validated increases in expression of genes related to the latter category, including Lrsam1, Erp29, Nasp, Tap1, Rab9b, and Pfdn5 in R6/2(Q300) mice, changes that were not observed in R6/2 mice with shorter CAG repeats, even in late stages (i.e., 12 weeks of age). We further tested Lrsam1 and Erp29, the two genes showing the greatest upregulation in R6/2(Q300) transgenic mice, for potential neuroprotective effects in primary striatal cultures overexpressing a mutated human huntingtin (htt) fragment. Overexpression of Lrsam1 prevented the loss of NeuN-positive cell bodies in htt171-82Q cultures, concomitant with a reduction of nuclear htt aggregates. Erp29 showed no significant effects in this model. This is consistent with the distinct pattern of htt inclusion localization observed in R6/2(Q300) transgenic mice, in which smaller cytoplasmic inclusions represent the major form of insoluble htt in the cell, as opposed to large nuclear inclusions observed in R6/2(Q150) transgenic mice. We suggest that the prolonged onset and disease course observed in R6/2 mice with greatly expanded CAG repeats might result from differential upregulation of genes related to protein localization and clearance. Such genes may represent novel therapeutic avenues to decrease htt aggregate toxicity and cell death in HD patients, with Lrsam1 being a promising, novel candidate disease modifier.

0 Bookmarks
 · 
74 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Misfolding of proteins containing abnormal expansions of polyQ repeats is associated with cytotoxicity in several neurodegenerative disorders, including Huntington's disease. Recently, the eukaryotic chaperonin TRiC hetero-oligomeric complex has been shown to play an important role in protecting cells against the accumulation of misfolded polyQ protein aggregates. It is essential to elucidate how TRiC function is regulated to better understand the pathological mechanism of polyQ aggregation. Here, we propose that vaccinia-related kinase 2 (VRK2) is a critical enzyme that negatively regulates TRiC. In mammalian cells, overexpression of wild-type VRK2 decreased endogenous TRiC protein levels by promoting its ubiquitination, but VRK2 kinase dead mutant did not. Interestingly, VRK2-mediated down-regulation of TRiC increased aggregate formation of polyQ-expanded huntingtin fragment. This effect was ameliorated by rescue of TRiC protein levels. Notably, siRNA-mediated knockdown of VRK2 enhanced TRiC protein stability and decreased polyQ aggregation. The VRK2-mediated reduction of TRiC protein levels was subsequent to the recruitment of COP1 E3 ligase. Among the COP1 E3 ligase complex, VRK2 interacted with RBX1 and increased E3 ligase activity on TRiC in vitro. Taken together, these results demonstrate that VRK2 is crucial to regulate the ubiquitination-proteosomal degradation of TRiC which controls folding of polyglutamine proteins involved in Huntington's disease.
    Molecular and cellular biology 12/2013; · 6.06 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Transcriptional dysregulation in Huntington's disease (HD) is an early event that shapes the brain transcriptome by both the depletion and ectopic activation of gene products that eventually affect survival and neuronal functions. Disruption in the activity of gene expression regulators, such as transcription factors, chromatin-remodeling proteins, and noncoding RNAs, accounts for the expression changes observed in multiple animal and cellular models of HD and in samples from patients. Here, I review the recent advances in the study of HD transcriptional dysregulation and its causes to finally discuss the possible implications in ameliorative strategies from a genome-wide perspective. To date, the use of genome-wide approaches, predominantly based on microarray platforms, has been successful in providing an extensive catalog of differentially regulated genes, including biomarkers aimed at monitoring the progress of the pathology. Although still incipient, the introduction of combined next-generation sequencing techniques is enhancing our comprehension of the mechanisms underlying altered transcriptional dysregulation in HD by providing the first genomic landscapes associated with epigenetics and the occupancy of transcription factors. In addition, the use of genome-wide approaches is becoming more and more necessary to evaluate the efficacy and safety of ameliorative strategies and to identify novel mechanisms of amelioration that may help in the improvement of current preclinical therapeutics. Finally, the major conclusions obtained from HD transcriptomics studies have the potential to be extrapolated to other neurodegenerative disorders.
    Molecular Neurobiology 05/2014; · 5.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Following spinal cord injury (SCI), limit spontaneous functional recovery often emerged. However, the neuronal mechanisms associated with this phenomenon still remains obscure. By using proteomics analysis, endoplasmic reticulum protein 29 (ERp29) was discovered to increase in the motor cortexes of spinal cord transection (SCT) rats for 28 days post-operation (dpo) compared with in 14dpo. Then, the change in the expression of ERp29 was confirmed by using reverse transcription polymerase chain reaction (RT-PCR) and Western blot. To determine the role of ERp29 in the recovery of locomotor functions following SCT, lentiviral vectors were used to up- and downregulate the expression level of ERp29. Here, we found that cortical neurons in vitro with high level of ERp29 expression exhibited a significant proliferation, characterized by smaller size of soma and more extensive axon outgrowth, compared with neurons used as control, while ERp29 silence got the opposite results. In vivo, Lentivirus was inject into the cerebral cortex following SCT at thoracic level 10, which resulted in an increase number of neuronal nuclei(NeuN)-positive cells and less apoptotic cells. Moreover, increased PKC-γ immunoreactivity density was also found in the spinal cord T9 level compared with control rats. This was associated with a great functional improvement, indicated by Basso, Beattie, Bresnahan (BBB) locomotor rating scale. Lastly, we verified that ERp29 acts as a regulator by regulating a group of genes related with cell survival and apoptosis, involving in caspase and Erk, but not PI3K. Our findings showed that ERp29 can improve locomotor function by promoting neuronal survival and axonal regeneration in SCT rats via caspase and Erk signal pathway.
    Molecular Neurobiology 05/2014; · 5.47 Impact Factor

Full-text

View
0 Downloads
Available from