RT Journal Article SR Electronic T1 A bright and high-performance genetically encoded Ca2+ indicator based on mNeonGreen fluorescent protein JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.01.16.909291 DO 10.1101/2020.01.16.909291 A1 Landon Zarowny A1 Abhi Aggarwal A1 Virginia M.S. Rutten A1 Ilya Kolb A1 The GENIE Project A1 Ronak Patel A1 Hsin-Yi Huang A1 Yu-Fen Chang A1 Tiffany Phan A1 Richard Kanyo A1 Misha Ahrens A1 W. Ted Allison A1 Kaspar Podgorski A1 Robert E. Campbell YR 2020 UL http://biorxiv.org/content/early/2020/01/21/2020.01.16.909291.abstract AB Genetically encodable calcium ion (Ca2+) indicators (GECIs) based on green fluorescent proteins (GFP) are powerful tools for imaging of cell signaling and neural activity in model organisms. Following almost two decades of steady improvements in the Aequorea victoria GFP (avGFP)-based GCaMP series of GECIs, the performance of the most recent generation (i.e., GCaMP7) may have reached its practical limit due to the inherent properties of GFP. In an effort to sustain the steady progression towards ever-improved GECIs, we undertook the development of a new GECI based on the bright monomeric GFP, mNeonGreen (mNG). The resulting indicator, mNG-GECO1, is 60% brighter than GCaMP6s in vitro and provides comparable performance as demonstrated by imaging Ca2+ dynamics in cultured cells, primary neurons, and in vivo in larval zebrafish. These results suggest that mNG-GECO1 is a promising next-generation GECI that could inherit the mantle of GCaMP and allow the steady improvement of GECIs to continue for generations to come.