GCaMP6m

GCaMP6m is a genetically encoded calcium indicator (GECI) widely used in neuroscience and biological research to monitor intracellular calcium levels in real time. Developed as an improved variant of earlier GCaMP (Green Fluorescent Calcium Indicator) series, GCaMP6m was introduced to enhance sensitivity, dynamic range, and signal-to-noise ratio compared to its predecessors. It belongs to the family of circularly permuted yellow fluorescent proteins (cpYFPs) fused with calmodulin and a calmodulin-binding peptide, allowing fluorescence changes upon calcium binding.

The design of GCaMP6m incorporates several key modifications, including optimized fluorophore sequences, enhanced calmodulin affinity, and improved linker regions to ensure robust and reliable calcium sensing. This variant exhibits a high fluorescence response to calcium ions, making it suitable for high-resolution imaging of neuronal activity, synaptic transmission, and other calcium-dependent processes. Its spectral properties, including excitation and emission peaks, are well-suited for two-photon microscopy and other advanced imaging techniques.

GCaMP6m is often expressed in target cells via viral vectors, such as adeno-associated viruses (AAVs), enabling targeted delivery to specific brain regions or cell types in model organisms like mice and rats. Its widespread adoption stems from its ability to provide high spatiotemporal resolution of calcium dynamics, facilitating the study of neural circuits and cellular signaling pathways. However, like other GEICIs, GCaMP6m may exhibit limitations such as photobleaching, background fluorescence, and potential artifacts due to overexpression or calcium buffering effects.

Researchers continue to refine and explore variants of GCaMP6m, including further optimized versions like GCaMP7, to address these challenges and expand its applications in diverse biological contexts. Its continued use underscores its importance as a versatile tool in modern neuroscience and cellular biology.