Unbiased gene expression analysis implicates the huntingtin polyglutamine tract in extra-mitochondrial energy metabolism

• Published in: PLoS genetics Vol. 3; no. 8; p. e135
• Main Authors: Lee, Jong-Min, Ivanova, Elena V, Seong, Ihn Sik, Cashorali, Tanya, Kohane, Isaac, Gusella, James F, MacDonald, Marcy E
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.08.2007; Public Library of Science (PLoS)
• Subjects: Acids; Analysis; Animals; Cells, Cultured; Cluster Analysis; Energy Metabolism - genetics; Gene expression; Gene Expression Profiling; Gene Expression Regulation; Genetic aspects; Genetics; Genetics and Genomics; Humans; Huntingtin Protein; Huntington's chorea; Huntingtons disease; Hypotheses; Metabolic Networks and Pathways - genetics; Metabolism; Mice; Mice, Transgenic; Mitochondria; Mitochondria - metabolism; Mitochondria - physiology; Mus (Mouse); Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - physiology; Nuclear Proteins - genetics; Nuclear Proteins - physiology; Oligonucleotide Array Sequence Analysis; Peptides - genetics; Peptides - physiology; Properties; United States
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.0030135

The Huntington's disease (HD) CAG repeat, encoding a polymorphic glutamine tract in huntingtin, is inversely correlated with cellular energy level, with alleles over approximately 37 repeats leading to the loss of striatal neurons. This early HD neuronal specificity can be modeled by respiratory chain inhibitor 3-nitropropionic acid (3-NP) and, like 3-NP, mutant huntingtin has been proposed to directly influence the mitochondrion, via interaction or decreased PGC-1alpha expression. We have tested this hypothesis by comparing the gene expression changes due to mutant huntingtin accurately expressed in STHdh(Q111/Q111) cells with the changes produced by 3-NP treatment of wild-type striatal cells. In general, the HD mutation did not mimic 3-NP, although both produced a state of energy collapse that was mildly alleviated by the PGC-1alpha-coregulated nuclear respiratory factor 1 (Nrf-1). Moreover, unlike 3-NP, the HD CAG repeat did not significantly alter mitochondrial pathways in STHdh(Q111/Q111) cells, despite decreased Ppargc1a expression. Instead, the HD mutation enriched for processes linked to huntingtin normal function and Nf-kappaB signaling. Thus, rather than a direct impact on the mitochondrion, the polyglutamine tract may modulate some aspect of huntingtin's activity in extra-mitochondrial energy metabolism. Elucidation of this HD CAG-dependent pathway would spur efforts to achieve energy-based therapeutics in HD.