title: Levels of mutant huntingtin influence the phenotypic severity of Huntington disease in YAC128 mouse models.
abstract: Huntington disease (HD) is a devastating neuropsychiatric disease caused by expansion of a trinucleotide repeat (CAG) in the HD gene. Neuropathological changes include the appearance of N-terminal huntingtin fragments, decreased brain weight and apoptotic neuronal loss in a select subset of neurons located in the striatum. There is still controversy over whether homozygosity for the mutation in HD is associated with a more severe phenotype. In humans, resolution of this issue has been complicated by the small number of homozygous patients and difficulty in the definition of reliable phenotypic endpoints. In order to definitively determine whether there is a correlation between phenotypic severity and expression levels of mutant huntingtin, we undertook a behavioral and neuropathological assessment of YAC128 mice with varying levels of mutant huntingtin. The results reveal a clear relationship between levels of mutant huntingtin and phenotype defined by earlier age of onset, more rapid progression, enhanced striatal volume loss, acceleration of nuclear huntingtin fragment accumulation and increased sensitivity to NMDAR-mediated excitotoxicity. These results provide clear evidence in vivo supporting a more severe phenotype associated with increased levels of mutant huntingtin as seen in homozygotes for HD.
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, 980 West 28th Avenue, Vancouver, BC, Canada V5Z 4H4.
authors.forename: Rona K
authors.initials: RK
authors.lastname: Graham
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Slow
authors.forename: Yu
authors.initials: Y
authors.lastname: Deng
authors.forename: Nagat
authors.initials: N
authors.lastname: Bissada
authors.forename: Ge
authors.initials: G
authors.lastname: Lu
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Pearson
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Shehadeh
authors.forename: Blair R
authors.initials: BR
authors.lastname: Leavitt
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Raymond
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hayden
mesh_terms: D017668:Age of Onset; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism / Q000473:pathology; D018244:Chromosomes, Artificial, Yeast; D004195:Disease Models, Animal; D018450:Disease Progression; D006720:Homozygote; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019680:Trinucleotide Repeat Expansion
chemical_list: C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate