Dysregulation of Human Juvenile Huntington's Disease Brain Proteomes in Cortex and Putamen Involves Mitochondrial and Neuropeptide Systems.

BACKGROUND: Huntington's disease (HD) is a genetic neurodegenerative disease caused by trinucleotide repeat CAG expansions in the human HTT gene. Early onset juvenile HD (JHD) in children is the most severe form of the disease caused by high CAG repeat numbers of the HTT gene. OBJECTIVE: To gain understanding of human HD mechanisms hypothesized to involve dysregulated proteomes of brain regions that regulate motor and cognitive functions, this study analyzed the proteomes of human JHD cortex and putamen brain regions compared to age-matched controls. METHODS: JHD and age-matched control brain tissues were assessed for CAG repeat numbers of HTT by PCR. Human brain JHD brain cortex regions of BA4 and BA6 with the putamen region (n = 5) were analyzed by global proteomics, compared to age-matched controls (n = 7). Protein interaction pathways were assessed by gene ontology (GO), STRING-db, and KEGG bioinformatics. RESULTS: JHD brain tissues were heterozygous for one mutant HTT allele containing 60 to 120 CAG repeats, and one normal HTT allele with 10 to 19 CAG repeats. Proteomics data for JHD brain regions showed dysregulated mitochondrial energy pathways and changes in synaptic systems including peptide neurotransmitters. JHD compared to control proteomes of cortex and putamen displayed (a) proteins present only in JHD, (b) proteins absent in JHD, and (c) proteins that were downregulated or upregulated. CONCLUSIONS: Human JHD brain cortex and putamen regions display significant dysregulation of proteomes representing deficits in mitochondrial and synaptic neurotransmission functions. These findings advance understanding of JHD brain molecular mechanisms associated with HD disabilities.

Mutant Huntingtin Protein Interaction Map Implicates Dysregulation of Multiple Cellular Pathways in Neurodegeneration of Huntington's Disease.

BACKGROUND: Huntington's disease (HD) is a genetic neurodegenerative disease caused by trinucleotide repeat (CAG) expansions in the human HTT gene encoding the huntingtin protein (Htt) with an expanded polyglutamine tract. OBJECTIVE: HD models from yeast to transgenic mice have investigated proteins interacting with mutant Htt that may initiate molecular pathways of cell death. There is a paucity of datasets of published Htt protein interactions that include the criteria of 1) defining fragments or full-length Htt forms, 2) indicating the number of poly-glutamines of the mutant and wild-type Htt forms, and 3) evaluating native Htt interaction complexes. This research evaluated such interactor data to gain understanding of Htt dysregulation of cellular pathways. METHODS: Htt interacting proteins were compiled from the literature that meet our criteria and were subjected to network analysis via clustering, gene ontology, and KEGG pathways using rigorous statistical methods. RESULTS: The compiled data of Htt interactors found that both mutant and wild-type Htt interact with more than 2,971 proteins. Application of a community detection algorithm to all known Htt interactors identified significant signal transduction, membrane trafficking, chromatin, and mitochondrial clusters, among others. Binomial analyses of a subset of reported protein interactor information determined that chromatin organization, signal transduction and endocytosis were diminished, while mitochondria, translation and membrane trafficking had enriched overall edge effects. CONCLUSION: The data support the hypothesis that mutant Htt disrupts multiple cellular processes causing toxicity. This dataset is an open resource to aid researchers in formulating hypotheses of HD mechanisms of pathogenesis.