Novel AAV Capsids and Gene Regulatory Elements for GeneExpression in Microglia

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Project Summary: Microglia, the resident macrophages of the brain, assume a multitude of functions during brain development and disease. Long known to react to changes in brains affected by Alzheimer’s disease (AD), genetic studies of late- onset AD indicate that AD risk variants are commonly found in or near genes that are specifically expressed in microglia, suggesting that microglia play an active role in driving AD. In addition, microglia exhibit various functions during brain development, including synapse pruning. Genes coding for components of the complement system, which mediates synapse pruning by microglia, have been linked to schizophrenia. However, a major bottleneck in studying the roles of microglia in normal and diseased brains is the lack of viral tools for rapidly manipulating their gene expression. Viral vectors would also benefit studies where transgenic animals are not available. Finally, viral vectors would enable studies on the potential of gene therapy for AD and rare diseases that affect microglia. However, while microglia show modest and localized transduction by lentiviruses in vivo, they are resistant to transduction by adeno-associated viruses (AAVs), the preferred viral vectors used in neuroscience research and gene therapy due to their superior spread and excellent safety profile. Here we propose to elucidate the barriers to microglia transduction by AAVs, engineer AAV capsid variants that are able to overcome these barriers and transduce microglia in vivo, and develop novel gene regulatory elements that will enable microglia-specific transgene expression from viral vectors. This will be a collaborative project between the Stevens and Deverman labs, combining their expertise in studying microglia (Stevens) and in developing novel AAV vectors (Deverman).