Drs Nicolas Renier and Zhuhao Wu are post-doctoral fellows in the laboratory of Marc Tessier-Lavigne, Carson Family Professor and head of the Laboratory of Brain Development and Repair and President of Rockefeller University in New York. Over recent years, they have co-developed methodologies for new imaging techniques applying light sheet microscopy. Their latest work shows the study of neuronal activity in intact brains.
The work has been published online in Cell.1 Entitled "Mapping of brain activity by automated volume analysis of immediate early genes," the paper introduces a new methodology called ClearMap, a pipeline for automated activity mapping in intact samples. This goes through a number of steps: the high-speed acquisition of brain activity at cellular resolution through profiling immediate early gene expression using immunostaining and light-sheet fluorescence imaging, followed by automated mapping and analysis of activity by an open-source software program (ClearMap).
Image: Dr Nicolas Renier from the Rockefeller University, NY, with results from his LaVision BioTec UltraMicroscope light sheet microscope.
Describing the process, Dr Renier says "We wanted to develop a technique that would show you the level of activity at the precision of a single neuron, but at the scale of the whole brain. In our method, we validate the pipeline first by analysis of brain regions activated in response to haloperidol. Next, we report new cortical regions downstream of whisker-evoked sensory processing during active exploration. Last, we combine activity mapping with axon tracing to uncover new brain regions differentially activated during parenting behavior. This pipeline is widely applicable to different experimental paradigms, including animal species for which transgenic activity reporters are not readily available."
The technique also has broader implications than simply looking at what areas of the mouse brain are active in different situations, he adds. It could be used to map brain activity in response to any biological change, such as the spread of a drug or disease, or even to explore how the brain makes decisions. "You can use the same strategy to map anything you want in the mouse brain," says Renier.
For light sheet imaging, the group has chosen the LaVision BioTec UltraMicroscope providing high speed and large fields of view. In neuroanatomy, users mostly want to look at large regions, up to 1 cm wide. Combining this with the need to image a large number of samples to get statistical significance, a very high acquisition speed is required. To date, the researchers feel that the UltraMicroscope is the only microscope on the market that can perform to their stringent requirements. In comparison to confocal microscopy where bleaching is an issue, light sheet microscopy is 20 x faster. The UltraMicroscope is the only commercial light sheet microscope that allows the handling of organic solvents.
Talking about his use of the light sheet microscopy, Dr Renier says "We are now using the iDISCO2 technique routinely in the lab for most of our projects. This preserves morphology and size of cleared samples for automated registration. The technique has upgraded most of our histology assays and we now rarely section tissues anymore. We use the technique to study the trajectory of nerves in whole embryos, to count cell number in whole organs, to trace single axons in the brain. We also have further work being published soon about the mapping of features of neurodegenerative disorders in mouse and human brains using light sheet microscopy and iDISCO."
1. Renier N et al., Mapping of Brain Activity by Automated Volume Analysis of Immediate Early Genes, Cell (2016), http://dx.doi.org/10.1016/j.cell.2016.05.007
2. Renier N, Wu ZH, Simon DJ, Yang J, Ariel P, Tessier-Lavigne M iDISCO: A Simple, Rapid Method to Immunolabel Large Tissue Samples for Volume Imaging CELL 2014 NOV 6; 159(4):896-910 Full Text | PMID/PMCID.
LaVision BioTec GmbH in profile
LaVision BioTec was founded in 2000 to develop and manufacture advanced microscopy solutions for the life sciences. There are currently two product lines:
TriM Scope II is a modular multi-photon/confocal microscopy platform that combines single- and multi-beam operation in one microscope. This allows for deep in-vivo imaging with Ti:Sapphire, OPO and visible lasers simultaneously with frame rates up to 60 Hz. PMTs, TCSPC and CCD detectors, multicolour imaging, spectral discrimination, FLIM/FRET capabilities and adaptive optics provide customization of the TriM Scope.
UltraMicroscope II utilizes six thin light sheets to excite samples with fluorescence light which is detected with a sCMOS-equipped microscope mounted perpendicular to the plane of illumination. Moving the sample through the light sheets generates 3D image stacks at cellular resolution.
For information about LaVision BioTec's TriM Scope 2-photon Microscope II and the UltraMicroscope II,view website: www.lavisionbiotec.com Refer to page 331