"Optogenetic, tissue clearing, and viral vector approaches to understand and influence whole-animal physiology and behavior"

Viviana Gradinaru, Ph.D., Assistant Professor, Biology and Biological Engineering Director of the Molecular and Cellular Neuroscience, Center of the Chen Institute California Institute of Technology Our research group at Caltech develops and employs optogenetics, tissue clearing, and viral vectors to gain new insights on circuits underlying locomotion, reward, and sleep. In most recent work the group has delineated novel arousal-promoting dopaminergic circuits that might be at the root of sleep disturbances common to numerous neuropsychiatric disorders. Present-day neuroscience relies on genetically-encoded tools; in both transgenic and non-transgenic animals, current practice for vector delivery is stereotaxic brain surgery—an invasive method that can cause hemorrhages and non-uniform expression over a limited volume. To address this limitation, we have developed viral-vector selection methods to identify engineered capsids capable of reaching target cell-populations across the body and brain after noninvasive systemic delivery. We use whole-body tissue clearing to facilitate transduction maps of systemically delivered genes. With novel AAV capsids, we achieved brain-wide transduction in adult mice after systemic delivery and sparse stochastic Golgi-like genetic labeling that enables morphology tracing for both central and peripheral neurons. Viral vectors that can efficiently and selectively deliver transgenes to target tissues after injection into the bloodstream allow us to genetically modify a high percentage of desired cells with more homogeneous coverage, without the need for either highly invasive direct injections or time-consuming transgenesis. Since CNS disorders are notoriously challenging due to the restrictive nature of the blood brain barrier, the recombinant vectors engineered to overcome this barrier can enable potential future use of exciting advances in gene editing via the CRISPR-Cas, RNA interference and gene replacement strategies to restore diseased CNS circuits.