Translucence Biosystems is honored to present at the Society for Neuroscience's 50th Annual Meeting. Our presentation is entitled, "Brain-wide cellular resolution snapshots of neuronal activity with Npas4 and cFos". Access our presentation materials below.
Abstract:
Recent advances in optical clearing and light sheet imaging have opened an exciting new avenue for brain-wide, cellular resolution immunostaining at the forefront of a dimensional shift from 2D to 3D histology. Providing access to the intricate anatomy of the whole intact brain, new tissue clearing methods can provide neuroscientists with unbiased and complete pictures of brain anatomy and function. With our optimized iDISCO-based clearing methods and our Mesoscale Imaging System for the ZEISS Lightsheet Z.1 microscope, we can image entire mouse brains in ~25 min. Further, our machine learning-enabled 3TK software identifies individual cells throughout the brain and aligns them to the Allen Reference Atlas to produce a regionalized read-out of cellular patterns across 100’s of brain areas. We have applied this technology to generate cellular resolution maps of neuronal activity by measuring the immediate-early gene (IEG) products Npas4 and cFos. Expression of cFos is driven by Ca 2+ - signaling downstream of neuronal activity and is commonly used to mark active neurons. However, cFos expression is also driven by cAMP elevations and signaling pathways engaged by neurotrophins or other paracrine factors. In contrast, Npas4 expression is neuron-specific and tightly tuned to Ca 2+ -dependent signaling pathways. Using our Npas4 recombinant rabbit monoclonal antibody and a commercial cFos antibody, we developed whole-brain co-staining procedures and performed experiments on mice kept in the dark and exposed to light for various periods of time. After 24 hours in the dark, we found a large number of cFos(+) neurons, yet these same neurons did not express Npas4, suggesting that factors other than neuronal activity per se drove cFos expression at baseline. After light exposure, the lower baseline expression of Npas4 supported a much larger fold-change increase in expression than with cFos, where the elevated baseline of cFos(+) cells masked the precise identification of the stimulus-related ‘trace’. The fidelity of the Npas4 response allowed our statistical anatomics tools to identify a large number of brain regions, some expected and some not, that had elevated neuronal activity after light exposure. Similarly, in Contextual Fear Conditioning experiments, home cage mice expressed much less Npas4 than cFos, allowing for more precise monitoring of changes in neuronal activity after context exposure and shock. Our pipeline for brain-wide monitoring of cFos and Npas4 expression allows for high-fidelity monitoring of neuronal activity with Npas4 and also allows for mapping responses to GPCRs or trophic factors by measuring cFos(+)/Npas4(-) neurons.
Access the presentation file here.
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