Browsing by Author "Land, Michelle A."

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    Sustained deep-tissue voltage recording using a fast indicator evolved for two-photon microscopy
    (Elsevier, 2022) Liu, Zhuohe; Lu, Xiaoyu; Villette, Vincent; Gou, Yueyang; Colbert, Kevin L.; Lai, Shujuan; Guan, Sihui; Land, Michelle A.; Lee, Jihwan; Assefa, Tensae; Zollinger, Daniel R.; Korympidou, Maria M.; Vlasits, Anna L.; Pang, Michelle M.; Su, Sharon; Cai, Changjia; Froudarakis, Emmanouil; Zhou, Na; Patel, Saumil S.; Smith, Cameron L.; Ayon, Annick; Bizouard, Pierre; Bradley, Jonathan; Franke, Katrin; Clandinin, Thomas R.; Giovannucci, Andrea; Tolias, Andreas S.; Reimer, Jacob; Dieudonné, Stéphane; St-Pierre, François
    Genetically encoded voltage indicators are emerging tools for monitoring voltage dynamics with cell-type specificity. However, current indicators enable a narrow range of applications due to poor performance under two-photon microscopy, a method of choice for deep-tissue recording. To improve indicators, we developed a multiparameter high-throughput platform to optimize voltage indicators for two-photon microscopy. Using this system, we identified JEDI-2P, an indicator that is faster, brighter, and more sensitive and photostable than its predecessors. We demonstrate that JEDI-2P can report light-evoked responses in axonal termini of Drosophila interneurons and the dendrites and somata of amacrine cells of isolated mouse retina. JEDI-2P can also optically record the voltage dynamics of individual cortical neurons in awake behaving mice for more than 30 min using both resonant-scanning and ULoVE random-access microscopy. Finally, ULoVE recording of JEDI-2P can robustly detect spikes at depths exceeding 400 μm and report voltage correlations in pairs of neurons.
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    A synthetic circuit for buffering gene dosage variation between individual mammalian cells
    (Springer Nature, 2021) Yang, Jin; Lee, Jihwan; Land, Michelle A.; Lai, Shujuan; Igoshin, Oleg A.; St-Pierre, François; Bioengineering; Biosciences; Chemistry; Systems, Synthetic, and Physical Biology
    Precise control of gene expression is critical for biological research and biotechnology. However, transient plasmid transfections in mammalian cells produce a wide distribution of copy numbers per cell, and consequently, high expression heterogeneity. Here, we report plasmid-based synthetic circuits – Equalizers – that buffer copy-number variation at the single-cell level. Equalizers couple a transcriptional negative feedback loop with post-transcriptional incoherent feedforward control. Computational modeling suggests that the combination of these two topologies enables Equalizers to operate over a wide range of plasmid copy numbers. We demonstrate experimentally that Equalizers outperform other gene dosage compensation topologies and produce as low cell-to-cell variation as chromosomally integrated genes. We also show that episome-encoded Equalizers enable the rapid generation of extrachromosomal cell lines with stable and uniform expression. Overall, Equalizers are simple and versatile devices for homogeneous gene expression and can facilitate the engineering of synthetic circuits that function reliably in every cell.