title: An enhanced Q175 knock-in mouse model of Huntington disease with higher mutant huntingtin levels and accelerated disease phenotypes.
abstract: Huntington disease (HD) model mice with heterozygous knock-in (KI) of an expanded CAG tract in exon 1 of the mouse huntingtin (Htt) gene homolog genetically recapitulate the mutation that causes HD, and might be favoured for preclinical studies. However, historically these mice have failed to phenotypically recapitulate the human disease. Thus, homozygous KI mice, which lack wildtype Htt, and are much less relevant to human HD, have been used. The zQ175 model was the first KI mouse to exhibit significant HD-like phenotypes when heterozygous. In an effort to exacerbate HD-like phenotypes and enhance preclinical utility, we have backcrossed zQ175 mice to FVB/N, a strain highly susceptible to neurodegeneration. These Q175F mice display significant HD-like phenotypes along with sudden early death from fatal seizures. The zQ175 KI allele retains a floxed neomycin resistance cassette upstream of the Htt gene locus and produces dramatically reduced mutant Htt as compared to the endogenous wildtype Htt allele. By intercrossing with mice expressing cre in germ line cells, we have excised the neo cassette from Q175F mice generating a new line, Q175FΔneo (Q175FDN). Removal of the neo cassette resulted in a ∼2 fold increase in mutant Htt and rescue of fatal seizures, indicating that the early death phenotype of Q175F mice is caused by Htt deficiency rather than by mutant Htt. Additionally, Q175FDN mice exhibit earlier onset and a greater variety and severity of HD-like phenotypes than Q175F mice or any previously reported KI HD mouse model, making them valuable for preclinical studies.
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute asouthwell@cmmt.ubc.ca mrh@cmmt.ubc.ca.
authors.forename: Amber L
authors.initials: AL
authors.lastname: Southwell
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Smith-Dijak
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Chris
authors.initials: C
authors.lastname: Kay
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Marja
authors.initials: M
authors.lastname: Sepers
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Erika B
authors.initials: EB
authors.lastname: Villanueva
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Parsons
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Yuanyun
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Lisa
authors.initials: L
authors.lastname: Anderson
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Boguslaw
authors.initials: B
authors.lastname: Felczak
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Sabine
authors.initials: S
authors.lastname: Waltl
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Seunghyun
authors.initials: S
authors.lastname: Ko
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Daphne
authors.initials: D
authors.lastname: Cheung
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Louisa
authors.initials: L
authors.lastname: Dal Cengio
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Ramy
authors.initials: R
authors.lastname: Slama
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Petoukhov
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Raymond
authors.affiliation: Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute asouthwell@cmmt.ubc.ca mrh@cmmt.ubc.ca.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hayden
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D055879:Gene Knock-In Techniques / Q000379:methods*; D006579:Heterozygote; D006801:Humans; D000071058:Huntingtin Protein / Q000235:genetics*; D006816:Huntington Disease / Q000235:genetics* / Q000473:pathology; D051379:Mice; D009154:Mutation; D010641:Phenotype
chemical_list: C506812:Htt protein, mouse; D000071058:Huntingtin Protein