MUTANT HTT MRNA AS THERAPEUTIC TARGET IN ALLELE-SELECTIVE CAG REPEAT-DIRECTED RNAI APPROACH AND PUTATIVE PATHOGENIC AGENT IN HD

In development of therapeutic strategy for Huntington’s disease (HD) targeting mutation site directly to inhibit selectively the expression of mutant gene is an attractive option. We have previously described CAG repeat-targeting siRNAs with specific substitutions resulting in one or more base mismatches with the target sequence. Interestingly, miRNA-like activity of these siRNAs resulting in allele-selectivity in downregulation of mutant protein in cellular models of HD, SCA3, SCA7 and DRPLA were reported by us and others. Currently, we investigate activity and mechanism of allele-selective CAG repeat-targeting siRNAs in inducible Flp-In 293 T-REx cell lines expressing HTT fragment and iPSC-derived human neural HD progenitors. Furthermore, we have generated new mouse models to investigate the extent of toxic RNA contribution to HD pathogenesis as well as range of cellular processes and pathways altered by mutant HTT transcript. These models allow to distinguish events in the pathogenesis that are triggered by toxic RNA from those initiated by mutant protein. We achieved those two HD transgenic mouse models by using knock-in strategy into Rosa26 locus. Upon Cre-lox crossing they express human mutated cDNA HTT fragment (in translated or non-translated version) with additional sequences for protein and transcript visualization. Currently, we perform experiments to characterize these models at molecular and behavioral level.