title: An evaluation of oligonucleotide-based therapeutic strategies for polyQ diseases.
abstract: BACKGROUND
  RNA interference (RNAi) and antisense strategies provide experimental therapeutic agents for numerous diseases, including polyglutamine (polyQ) disorders caused by CAG repeat expansion. We compared the potential of different oligonucleotide-based strategies for silencing the genes responsible for several polyQ diseases, including Huntington's disease and two spinocerebellar ataxias, type 1 and type 3. The strategies included nonallele-selective gene silencing, gene replacement, allele-selective SNP targeting and CAG repeat targeting.
  
  
  RESULTS
  Using the patient-derived cell culture models of polyQ diseases, we tested various siRNAs, and antisense reagents and assessed their silencing efficiency and allele selectivity. We showed considerable allele discrimination by several SNP targeting siRNAs based on a weak G-G or G-U pairing with normal allele and strong G-C pairing with mutant allele at the site of RISC-induced cleavage. Among the CAG repeat targeting reagents the strongest allele discrimination is achieved by miRNA-like functioning reagents that bind to their targets and inhibit their translation without substantial target cleavage. Also, morpholino analog performs well in mutant and normal allele discrimination but its efficient delivery to cells at low effective concentration still remains a challenge.
  
  
  CONCLUSIONS
  Using three cellular models of polyQ diseases and the same experimental setup we directly compared the performance of different oligonucleotide-based treatment strategies that are currently under development. Based on the results obtained by us and others we discussed the advantages and drawbacks of these strategies considering them from several different perspectives. The strategy aimed at nonallele-selective inhibiting of causative gene expression by targeting specific sequence of the implicated gene is the easiest to implement but relevant benefits are still uncertain. The gene replacement strategy that combines the nonallele-selective gene silencing with the expression of the exogenous normal allele is a logical extension of the former and it deserves to be explored further. Both allele-selective RNAi approaches challenge cellular RNA interference machinery to show its ability to discriminate between similar sequences differing in either single base substitutions or repeated sequence length. Although both approaches perform well in allele discrimination most of our efforts are focused on repeat targeting due to its potentially higher universality.
authors.affiliation: Laboratory of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Fiszer
authors.forename: Marta
authors.initials: M
authors.lastname: Olejniczak
authors.forename: Pawel M
authors.initials: PM
authors.lastname: Switonski
authors.forename: Joanna P
authors.initials: JP
authors.lastname: Wroblewska
authors.forename: Joanna
authors.initials: J
authors.lastname: Wisniewska-Kruk
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Mykowska
authors.forename: Wlodzimierz J
authors.initials: WJ
authors.lastname: Krzyzosiak
mesh_terms: D000483:Alleles; D000067699:Ataxin-3; D002460:Cell Line; D004353:Drug Evaluation, Preclinical; D020868:Gene Silencing; D015316:Genetic Therapy; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000628:therapy; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020754:Spinocerebellar Ataxias / Q000235:genetics* / Q000628:therapy
chemical_list: C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D009841:Oligonucleotides; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C092341:ATXN3 protein, human; D000067699:Ataxin-3