Allele-Selective Suppression of Mutant Huntingtin in Primary Human Blood Cells

Sci Rep. 2017 Apr 24;7:46740. doi: 10.1038/srep46740.

Abstract

Post-transcriptional gene silencing is a promising therapy for the monogenic, autosomal dominant, Huntington's disease (HD). However, wild-type huntingtin (HTT) has important cellular functions, so the ideal strategy would selectively lower mutant HTT while sparing wild-type. HD patients were genotyped for heterozygosity at three SNP sites, before phasing each SNP allele to wild-type or mutant HTT. Primary ex vivo myeloid cells were isolated from heterozygous patients and transfected with SNP-targeted siRNA, using glucan particles taken up by phagocytosis. Highly selective mRNA knockdown was achieved when targeting each allele of rs362331 in exon 50 of the HTT transcript; this selectivity was also present on protein studies. However, similar selectivity was not observed when targeting rs362273 or rs362307. Furthermore, HD myeloid cells are hyper-reactive compared to control. Allele-selective suppression of either wild-type or mutant HTT produced a significant, equivalent reduction in the cytokine response of HD myeloid cells to LPS, suggesting that wild-type HTT has a novel immune function. We demonstrate a sequential therapeutic process comprising genotyping and mutant HTT-linkage of SNPs, followed by personalised allele-selective suppression in a small patient cohort. We further show that allele-selectivity in ex vivo patient cells is highly SNP-dependent, with implications for clinical trial target selection.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Alleles
  • Cells, Cultured
  • Cohort Studies
  • Genotype
  • Humans
  • Huntingtin Protein / genetics*
  • Huntington Disease / blood
  • Huntington Disease / genetics*
  • Middle Aged
  • Mutant Proteins / genetics*
  • Myeloid Cells / metabolism
  • Polymorphism, Single Nucleotide*
  • RNA Interference

Substances

  • HTT protein, human
  • Huntingtin Protein
  • Mutant Proteins