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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.

Originally published Mar 8, 2016 and last updated Sept 3, 2020 by Nyla Naim.

Scientists around the world have been making major improvements to CRISPR technology since its initial applications for genome engineering in 2012.  Many of these advances have stemmed from the goal of reducing off-target Cas9 activity. The use of nickases, prime editing, anti-CRISPR proteins, and other techniques all aim to improve targeting specificity or reduce the duration of Cas9 activity. 

The field of optogenetics is renowned for enabling precise temporal and spatial control. Optogenetics uses genetically encoded tools, such as microbial opsins, to control cellular activities using light. In 2015, scientists combined CRISPR and optogenetic techniques to develop a variety of photoactivatable CRISPR tools. These tools allow scientists to use light to externally control the location, timing, and reversibility of the genome editing process. Read on to learn about the various light-controlled CRISPR tools available to researchers - some readily found at Addgene.

Chemogentic and optogenetic technologies have pushed the boundaries in neuroscience by granting targeted control over neuronal activity. While they serve similar purposes, both techniques offer researchers different advantages and limitations. 

The four main factors in which chemogenetics and optogenetics differ are:

• Timing
• Targeted manipulation
• Controlling stimulation
• Invasiveness 

Choosing the best set of tools therefore depends on what you are looking to study.

It’s time to choose your own protein purification adventure. You want to purify your favorite protein (YFP). You have two options: 

Option #1: Affinity tag purification

You tag YFP and use an affinity column for purification. After binding YFP to the column, you wash several times to remove non-specific proteins, and then elute YFP. 

Option #2: Opto-Nanobodies (OptoNBs) purification

You skip adding a tag to YFP and instead use OptoNBs. You fill a column with OptoNB coated beads and wrap the column with blue LED lights. When you switch off the lights, OptoNBs bind YFP and non-specific proteins flow through. To elute YFP, you turn on the blue lights.

Which option do you choose? 

This post was contributed by Alessia Armezzani, scientific communication manager at genOway.

A few decades ago, the brain remained elusive, not from a lack of intellectual curiosity on the part of scientists but, rather, from the limited technologies available. Over the past few years, however, remarkable technological advances have taken researchers to the threshold of a revolution in modern neuroscience, an era in which technologies like FLEx and optogenetics meet, allowing scientists to investigate the fundamental basis of both brain function and dysfunction.

First, let’s start with the basics: What is optogenetics?