![]() AAV capsids have also been engineered to deliver specific transgenes in many tissues ( Tervo et al., 2016 Deverman et al., 2016 Chan et al., 2017 Greig et al., 2018 Song et al., 2019), and specific promoters and enhancers can be used to control transgene expression from recombinant AAVs ( Nord et al., 2013 Visel et al., 2013 Silberberg et al., 2016 Dimidschstein et al., 2016 Xiong et al., 2019 Jüttner et al., 2019 Nair et al., 2020 Markenscoff-Papadimitriou et al., 2020 Vormstein-Schneider et al., 2020). Adeno-associated viruses (AAVs) are ubiquitous nonpathogenic viruses that allow transduction of adult post-mitotic neurons and could be leveraged to build tools for genetic access to specific brain cell subclasses. Viral vectors have recently been shown to allow transgene delivery and genetic marking of neurons from mouse to humans ( Dimidschstein et al., 2016 Andersson et al., 2016 Ting et al., 2018 Schwarz et al., 2019 Vormstein-Schneider et al., 2020). New somatic genetic tools to label orthologous neuronal subclasses across species will be highly impactful to directly target and compare conserved and divergent properties of orthologous subclasses. ![]() However, direct cross-species correspondences between the most granular divisions in the cell type taxonomy (i.e., cell types) can be challenging due to cross-species variation, with the exception of a handful of highly distinctive cell types ( Hodge et al., 2019). Comparison of gene expression between mouse and human shows strong conservation of molecular features across brain cell classes (e.g., inhibitory, excitatory, and glial classes) and subclasses (e.g., Parvalbumin, Somatostatin, and Vasoactive intestinal polypeptide subclasses). Most basic research in neuroscience and neurological diseases occurs in rodents, although it is often not known if the functional roles of cell populations are conserved. These results demonstrate how genome-wide open chromatin data mining and cross-species AAV validation can be used to create the next generation of non-species-restricted viral genetic tools.Ī major goal in neuroscience is to establish the distinct role of each cell population in brain circuitry, how they give rise to complex function, and how their dysfunction can cause disease. Five vectors maintain PVALB-enriched expression in primate neocortex. We present a collection of Parvalbumin (PVALB) enhancer-AAVs that show highly enriched expression not only in cortical PVALB cells but also in some subcortical PVALB populations. Over 30% of enhancer-AAVs produce specific expression in the targeted subclass, including both excitatory and inhibitory subclasses. The cellular specificity of reporter expression from enhancer-AAVs is established by molecular profiling after systemic AAV delivery in mouse. Here, we use comparative open chromatin analysis to identify thousands of human-neocortical-sub-class-specific putative enhancers from across the genome to control gene expression in adeno-associated virus (AAV) vectors. Viral genetic tools that target specific brain cell types could transform basic neuroscience and targeted gene therapy. provided program and budgetary management. wrote the manuscript and prepared figures with assistance from B.B.G., B.P.L., and J.T.T. processed NHP brain tissue from in vivo virus testing with assistance from V.O. performed NHP in vivo virus injection surgery with assistance from J.T.T. carried out NHP ex vivo slice culture experiments with assistance from G.D.H., N.W., and X.O.-A. scRNA-seq was conducted by J.K.M., D.B., and K.A.S. performed human ex vivo brain slice culture and viral labeling experiments with assistance from P.C. procured human surgical tissue for research. tested AAV vectors with assistance from P.C. performed AAV vector design and molecular biology. analyzed ATAC-seq data using techniques developed by L.T.G., with assistance from S.S., J.A.M., L.T.G., J.G., and Y.D. performed ATAC-seq with assistance from D.B. performed tissue processing and flow cytometry. AUTHOR CONTRIBUTIONSJ.T.T., N.S., E.E.H., T.C., N.D., and J.K.M.
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