A series of N-terminal epitope tagged Hdh knock-in alleles expressing normal and mutant huntingtin: Their application to understanding the effect of increasing the length of normal huntingtins polyglutamine stretch on CAG140 mouse model pathogenesis

Shuqiu Zheng, Nima Ghitani, Jessica S. Blackburn, Jeh Ping Liu, Scott O. Zeitlin

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Background: Huntingtons disease (HD) is an autosomal dominant neurodegenerative disease that is caused by the expansion of a polyglutamine (polyQ) stretch within Huntingtin (htt), the protein product of the HD gene. Although studies in vitro have suggested that the mutant htt can act in a potentially dominant negative fashion by sequestering wild-type htt into insoluble protein aggregates, the role of the length of the normal htt polyQ stretch, and the adjacent proline-rich region (PRR) in modulating HD mouse model pathogenesis is currently unknown. Results: We describe the generation and characterization of a series of knock-in HD mouse models that express versions of the mouse HD gene (Hdh) encoding N-terminal hemaglutinin (HA) or 3xFlag epitope tagged full-length htt with different polyQ lengths (HA7Q-, 3xFlag7Q-, 3xFlag20Q-, and 3xFlag140Q-htt) and substitution of the adjacent mouse PRR with the human PRR (3xFlag20Q- and 3xFlag140Q-htt). Using co-immunoprecipitation and immunohistochemistry analyses, we detect no significant interaction between soluble full-length normal 7Q- htt and mutant (140Q) htt, but we do observe N-terminal fragments of epitope-tagged normal htt in mutant htt aggregates. When the sequences encoding normal mouse htts polyQ stretch and PRR are replaced with non-pathogenic human sequence in mice also expressing 140Q-htt, aggregation foci within the striatum, and the mean size of htt inclusions are increased, along with an increase in striatal lipofuscin and gliosis. Conclusion: In mice, soluble full-length normal and mutant htt are predominantly monomeric. In heterozygous knock-in HD mouse models, substituting the normal mouse polyQ and PRR with normal human sequence can exacerbate some neuropathological phenotypes.

Original languageEnglish
Article number28
JournalMolecular Brain
Volume5
Issue number1
DOIs
StatePublished - 2012

Bibliographical note

Funding Information:
This work was supported by NIH NS043466.

Keywords

  • Epitope tag
  • Huntingtin
  • Huntingtons disease
  • Knock-in
  • Polyglutamine
  • Proline-rich region
  • Sequestration

ASJC Scopus subject areas

  • Molecular Biology
  • Cellular and Molecular Neuroscience

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