Split-intein mediated re-assembly of genetically encoded Ca2+ indicators

While genetically encoded Ca2+ indicators (GECIs) allow Ca2+ imaging in model organisms, the gene expression is often under the control of a single promoter that may drive expression beyond, the cell types of interest. To enable more cell-type specific targeting, GECIs can be brought under the, control of the intersecting expression from two promoters. Here, we present the splitting and, reassembly of two representative GECIs (TN-XL and GCaMP2) mediated by the split intein from Nostoc, punctiforme (NpuDnaE). While the split TN-XL biosensor offered ratiometric Ca2+ imaging, it had a, diminished Ca2+ response relative to the native TN-XL biosensor. In contrast, the split GCaMP2, biosensor retained similar Ca2+ response to the native GCaMP2. The split GCaMP2 biosensor was, further targeted to the pharyngeal muscles of Caenorhabditis elegans where Ca2+ signals from feeding C. elegans, were imaged. Thus, we envision that increased cell-type targetability of GECIs is feasible with two, complementary promoters.