Viral vector-based RNAi therapy for Alexander Disease

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DESCRIPTION (provided by applicant): Alexander Disease (AlxD) is an autosomal dominantly inherited neurologically devastating disorder of white matter that affects children. AlxD has no specific therapy, but its pathogenesis makes it an ideal candidate for gene therapy utilizing RNA interference. The goal of this project is to develop an effective gene therapy for AlxD. AlxD is caused by a mutation of glial fibrillary acidic protein (GFAP), a protein expressed exclusively in astrocytes within the brain. The pathologic hallmark of AlxD is the Rosenthal fiber, an inclusion body composed of aggregates of GFAP and several other proteins. Rosenthal fibers are present in large numbers in AlxD and found exclusively in astrocytes. The disease is caused by a toxic gain of function in which the mutated GFAP induces formation of abnormal filamentous assemblies, which are the Rosenthal fibers. Our collaborator has generated an animal model of AlxD in which mice express mutated GFAP genes. The abnormal genes contain point mutations inducing amino acid substitutions at the same sites as those causing AlxD in humans. Astrocytes from the mutant mice develop Rosenthal fibers in vitro and in vivo. RNA interference (RNAi) is a powerful tool for selectively suppressing specific genes. We will utilize RNAi to suppress expression of the mutant GFAP gene, thus blocking and perhaps reversing the neuropathology of AlxD. To deliver the RNAi to astrocytes, we will engineer a lentivirus pseudotyped with lymphocytic choriomeningitis virus (LCMV), a virus that selectively targets astrocytes within the developing brain. This viral gene therapy vector containing short hairpin RNA (shRNA) against mutant GFAP will selectively suppress expression of mutant GFAP in astrocytes. In Aim One, small interfering RNA (siRNA) corresponding to the mutated genes will be used in Cos cells transfected with wild type and mutant GFAP to achieve allele-specific suppression. In Aim Two, the lentiviral vector, carrying corresponding shRNA, will be used to achieve selective RNA interference in astrocyte cultures derived from AlxD mice. In Aim Three, the viral vector will be injected into the brains of neonatal AlxD mice, to selectively inhibit expression of mutant GFAP mRNA and protein and block the formation of Rosenthal fibers. This research is highly relevant to public health because it may lead to development of a specific and effective treatment for AlxD, a fatal degenerative disease of childhood for which there is currently no specific treatment. Alexander Disease is a progressive and devastating pediatric brain disease. The disease is due to an abnormal gene. This research aims to develop a form of gene therapy to prevent and reverse the brain dysfunction of Alexander Disease.