sDarken: Next generation genetically encoded fluorescent sensors for serotonin

Abstract

We developed a new family of genetically encoded serotonin (5-HT) sensors (sDarken) on the basis of the native 5-HT1A receptor and circularly permuted GFP. sDarken 5-HT sensors are bright in the unbound state and diminish their fluorescence upon binding of 5-HT. Sensor variants with different affinities for serotonin were engineered to increase the versatility in imaging of serotonin dynamics. Experiments in vitro and in vivo showed the feasibility of imaging serotonin dynamics with high temporal and spatial resolution. As demonstrated here, the designed sensors showed excellent membrane expression, have high specificity, a superior signal-to-noise ratio, detect the endogenous release of serotonin and are suitable for two-photon in vivo imaging.

Techniques for in vivo serotonin detection in the brain: State of the art

“…Recently, genetically encoded serotonin indicators (GESIs) have been developed for direct recurrent 5‐HT measurement in vivo, such as iSeroSnFR (Unger et al, 2020), GRAB 5‐HT (Wan et al, 2021), psychLight (Dong et al, 2021), and sDarkern (Kubitschke et al, 2022). They can provide release dynamics at a subsecond resolution, with submicromolar affinity and high molecular specificity.…”

“…Recently, a new family of GESIs (sDarken) was developed based on the 5‐HT 1A receptor (Kubitschke et al, 2022). In contrast to all other GESIs, sDarken 5‐HT biosensors are a set of turn‐off sensors that exhibit bright baseline fluorescence when 5‐HT is absent and diminish their fluorescence upon binding.…”