PhD Student: Séverine Maire

abstract

Huntington’s disease (HD) is an autosomal dominant genetic disorder caused by the expansion of a CAG repeat encoding a polyglutamine tract in the first exon of the Huntingtin gene (HTT). This gene encode a ubiquitous protein in which mutation lead to severe motor, psychiatric and cognitive deficits and causes degeneration of specific neuronal populations, in particular the GABAergic medium spiny neurons of the striatum. We propose to use trans-splicing to develop a gene therapy vector that will significantly reduce or eliminate the expression of the mutant protein while restoring a physiological level of normal HTT in cells affected by the HD mutation. This technology is based on replacement of the mutated exon by a normal version during the mRNA maturation process. HTT mutation being dominant, therapeutic benefits necessitates a highly efficient trans-splicing reaction that would convert a significant proportion of mutant-HTT pre-mRNA into normal HTT mRNA. For this purpose, we developed a fluorescent reporter system enabling the detection of trans-splicing events in high content screening in order to identify the most potent trans-splicing sequences among hundreds of molecules. We validated our fluorescent screening strategy and implement trans-splicing screening on 3 HTT introns (3, 9 and 20), in which we demonstrated the presence of hotspot promoting trans-splicing reactions. A direct and absolute quantification method was also validated to accurately assess the correction rate. Overall, this work generated additional evidences of trans-splicing feasibility in HD.