High-Throughput Optical Controlling and Recording Calcium Signal in iPSC-Derived Cardiomyocytes for Toxicity Testing and Phenotypic Drug Screening.

Understanding how excitable cells work in health and disease and how that behavior can be altered by small molecules or genetic manipulation is important. Genetically encoded calcium indicators (GECIs) with multiple emission windows can be combined (e.g., for simultaneous observation of distinct subcellular events) or used in extended applications with other light-dependent actuators in excitable cells (e.g., combining genetically encoded optogenetic control with spectrally compatible calcium indicators). Such approaches have been used in primary or stem cell-derived neurons, cardiomyocytes, and pancreatic beta-cells. However, it has been challenging to increase the throughput, or duration of observation, of such approaches due to limitations of the instruments, analysis software, indicator performance, and gene delivery efficiency. Here, a high-performance green GECI, mNeonGreen-GECO (mNG-GECO), and red-shifted GECI, K-GECO, is combined with optogenetic control to achieve all-optical control and visualization of cellular activity in a high-throughput imaging format using a High-Content Imaging System. Applications demonstrating cardiotoxicity testing and phenotypic drug screening with healthy and patient-derived iPSC-CMs are shown. In addition, multi-parametric assessments using combinations of spectral and calcium affinity indicator variants (NIR-GECO, LAR-GECO, and mtGCEPIA or Orai1-G-GECO) are restricted to different cellular compartments are also demonstrated in the iPSC-CM model.

Improved genetically encoded near-infrared fluorescent calcium ion indicators for in vivo imaging.

Near-infrared (NIR) genetically encoded calcium ion (Ca2+) indicators (GECIs) can provide advantages over visible wavelength fluorescent GECIs in terms of reduced phototoxicity, minimal spectral cross talk with visible light excitable optogenetic tools and fluorescent probes, and decreased scattering and absorption in mammalian tissues. Our previously reported NIR GECI, NIR-GECO1, has these advantages but also has several disadvantages including lower brightness and limited fluorescence response compared to state-of-the-art visible wavelength GECIs, when used for imaging of neuronal activity. Here, we report 2 improved NIR GECI variants, designated NIR-GECO2 and NIR-GECO2G, derived from NIR-GECO1. We characterized the performance of the new NIR GECIs in cultured cells, acute mouse brain slices, and Caenorhabditis elegans and Xenopus laevis in vivo. Our results demonstrate that NIR-GECO2 and NIR-GECO2G provide substantial improvements over NIR-GECO1 for imaging of neuronal Ca2+ dynamics.

Autocrine and paracrine unpaired signaling regulate intestinal stem cell maintenance and division.

The Janus kinase (JAK) signal transducer and activator of transcription (STAT) pathway is involved in the regulation of intestinal stem cell (ISC) activity to ensure a continuous renewal of the adult Drosophila midgut. Three ligands, Unpaired 1, Unpaired 2 and Unpaired 3 (Upd1, Upd2 and Upd3, respectively) are known to activate the JAK/STAT pathway in Drosophila. Using newly generated upd mutants and cell-specific RNAi, we showed that Upd1 is required throughout the fly life to maintain basal turnover of the midgut epithelium by controlling ISC maintenance in an autocrine manner. A role of Upd2 and Upd3 in basal conditions is discernible only in old gut, where they contribute to increased ISC abnormal division. Finally, upon an acute stress such as oral bacterial infection, we showed that Upd3 is released from enterocytes and has an additive effect with Upd2 to promote rapid epithelial regeneration. Taken together, our results show that Upd ligands are required to maintain the midgut homeostasis under both normal and pathological states.