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Channelrhodopsins with improved light sensitivity for minimally-invasive optogenetics

Posted by Beth Kenkel on Nov 3, 2020 9:15:00 AM

Optogenetics is a neuroscience method that lets you fire neurons with the flick of a light switch. Neurons are not typically persuaded to fire when light is shined on them, but the expression of light-gated ion channels such as channelrhodopsins (ChRs) makes them light-responsive. When light shines on excitatory channelrhodopsin-expressing neurons, the channelrhodopsins respond by opening and allowing an influx of ions into the neuron which generates an action potential (Figure 1). This light-induced excitation can take place in a tissue culture dish but can also happen in real-time inside a mouse’s brain. 

But the brain is a tricky organ to access, which often forces scientists to use invasive measures to perform in vivo optogenetic experiments. Intracranial injections of AAV are commonly used to deliver channelrhodopsins to the brain. This delivery route concentrates lots of channelrhodopsins in one region of the brain, which is needed since current channelrhodopsins tools have low conductance, but also confines channelrhodopsin activation to a small volume of brain tissue (~1 mm3). Current channelrhodopsins also need high-intensity light for activation which requires implantation of fiber-optic cables into the brain.

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Topics: Optogenetics, Viral Vectors, Neuroscience

Deciphering the Mysteries of Behavior with Viral Vectors

Posted by Klaus Wanisch on Sep 17, 2019 8:40:54 AM

Over the past decades, neuroscientists have made great strides to map brain regions and allocate specific functions to them. Electrical recordings and lesioning studies have been essential for this task. However, most lesioning methods destroy areas larger than intended and may unintentionally remove connecting pathways between other distant regions. They also don’t give any clues about the types of neurons involved or whether their involvement is activating, inhibiting, or modulating. Viral vectors, in contrast, are considerably more versatile and specific in how they manipulate neuronal function, with far fewer side effects compared to lesioning methods -  they may be the key to further unraveling the mysteries of behavior.

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Topics: Viral Vectors, Neuroscience

Getting Started with Behavioral Neuroscience: Standardizing Experiments and Using Viral Vectors

Posted by Klaus Wanisch on Aug 20, 2019 8:31:11 AM

The aim of behavioral neuroscience is to define brain areas that are linked to a certain behavior. It is a very old branch of science, dating back several hundred years, with historical ties to psychology and philosophy (the mind-body problem). Because of the availability of tools for genetic manipulations, mice have become the model of choice for many behavioral studies, though other organisms such as rats or zebrafish are also used. With the development of viral vectors, behavioral neuroscientists can now precisely control where and when certain genes are expressed to investigate their role in a specific behavior. This blog post will give an introduction to behavioral neuroscience, and address experimental design considerations used in all behavioral studies.

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Topics: Viral Vectors, Neuroscience

New Tools Enable CRISPRa for Neuroscience Applications

Posted by Guest Blogger on Jul 2, 2019 8:51:40 AM

This post was contributed by Patrick Miller-Rhodes, a Ruth L. Kirschstein NRSA Predoctoral Fellow at University of Rochester Medical Center.

During development, complex genetic programs specify and assemble diverse arrays of neurons, forming the neuronal circuits that will later be refined through experience. However, studying the genetic underpinnings of these processes has been complicated by the lack of precise genetic tools for modulating gene expression in the central nervous system (CNS). To address this technological gap, a trio of recent papers describe the development of CRISPR activation (CRISPRa) tools for neuroscience, including transgenic mice, neuron-optimized viral vectors, and high-throughput screening approaches. Here, we’ll highlight these recent advancements and offer commentary on their application to neuroscience research.

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Topics: CRISPR, Other CRISPR Tools, Neuroscience

Multicolor Animals: Using Fluorescent Proteins to Understand Single Cell Behavior

Posted by Aliyah Weinstein on Mar 5, 2019 8:08:52 AM

Stochastic multicolor labeling is a popular technique in neuroscience and developmental biology. This type of cell labeling technique involves the introduction of a transgene construct containing fluorescent proteins (XFP) of different colors to label an organ or entire organism. Because each cell can have multiple copies of the transgene that will recombine independently, cells may acquire one of a variety of colors when a combination of XFP are expressed. Each cell remains the same color for its entire lifetime and daughter cells retain the same color, allowing for the fate mapping of cell populations over time. The ability to track single cell dynamics at the organism level has been made possible by tools that allow cells to become persistently fluorescent during development. Stochastic multicolor labeling systems, many based on Brainbow, now exist for a variety of species, cell types, and research applications.

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Topics: Fluorescent Proteins, Cell Tracing, Neuroscience

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