Tag Archives: GECI

A photoconvertible genetically-encoded calcium indicator

One of the primary goal of neuroscience research is to dissect the role of different cell-types in neuronal circuits. Thanks to the development of optogenetic reporters and control tools in recent years, researchers can now optically control and monitor the activity of genetically defined neuronal populations. Going deeper into the understanding of neuronal circuit requires to follow and control the activity of individual cells within these genetically-defined populations. Imaging the activity of individual neurons in vitro and in vivo can be achieved with classical microscopy techniques but labelling and following the activity of arbitrarily defined subsets of cells in a given population remains hard to implement. Optical highlighters which can be photoactivated or photoconverted are routinely used to label cell subpopulations but have only been used so far for anatomical tracing or cell migration studies. In a recent study published in JACS, Campbell and coworkers introduce a photoconvertible genetically-encoded calcium indicator, providing the possibility to easily monitor the activity of subsets of cells of a given cell type.

This dual-function Ca2+ indicator was made by combining two of the most powerful implementations of fluorescent protein (FP) technology: the “highlighters” that can be converted from non-fluorescent to fluorescent or from one … Continue reading

Posted in Journal Club, News | Tagged , , | Leave a comment

R-CaMP1.07, an improved genetically encoded red fluorescent Ca2+ indicator

In a recent paper published in PLoS One, Ohkura et al. introduce R-CaMP1.07, an improved variant of a recently developed red fluorescent Ca2+ indicator protein called R-GECO1. While the sensitivity of R-CaMP1.07 is similar to that of R-GECO1 (Kd for Ca2+ is around 200 nM), R-CaMP1.07 shows 1.5–2-fold greater signals than R-GECO1 due to its enhanced dynamic range (Fmax/Fmin is near 30). The greatest advantage of R-CaMP1.07 is that its excitation wavelength ranges from 500 to 580 nm, which rarely overlaps with the photo-stimulation range of channelrhodopsin-2 (ChR2). Taking this merit of R-CaMP1.07, the authors demonstrate an application example of this indicator in hippocampal pyramidal neurons expressing ChR2: the successful detection of Ca2+ signals in response to action potentials evoked by the photo-stimulation of ChR2. Needless to say, this red fluorescent R-CaMP1.07 can be used for Ca2+ imaging of cells expressing blue, cyan or green fluorescent proteins.

Posted in Journal Club | Tagged , | Leave a comment