Revolutionary method to map brains at single-neuron resolution successfully demonstrated | Neuroscientist News
http://www.neuroscientistnews.com/...d-map-brains-single-neuron-resolution-successfully-demonstrated
Already in progress are experiments in which the entire cortex is being "tiled" with injections. It is hoped this will yield the first connectome of the entire cortex at single-neuron resolution.
"We are very keen on being able to do these kind of studies in a single animal, which will eliminate the past problem of injecting multiple animals to trace multiple neurons, a method that requires one to make a single map based on many brains, each of which is somewhat different."
Zador's next goal with MAPseq is to map the brains of animals that model various neurodevelopmental and neuropsychiatric illnesses, to see how gene mutations strongly associated with causality alter the structure of brain circuits, and thus, presumably, brain function.
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a technology that enables them to assign unique barcode-like identifiers to large numbers of individual neurons via a single injection in any brain region of interest. Each injection consists of a deactivated virus that has been engineered to contain massive pools of individually unique RNA molecules, each of whose sequence - consisting of 30 "letters," or nucleotides - is taken up by single neurons. Thirty letters yields many, many times more barcode sequences (1018) than there are neurons in either the mouse or human brain, so this method is especially well suited to the massive complexity problem that brain mapping presents.
An injection into a "source" region of the brain contains a viral library encoding a diverse collection of barcode sequences, which are hitched to an engineered protein that is designed to carry the barcode along axonal pathways. The barcode RNA is expressed at high levels and transported into the terminals of axons in the source region where the injection is made. In each neuron, it travels to the point where the axon forms a synapse with a projection from another neuron. Tests show that the technology works - the barcodes travel reliably and evenly throughout the brain, along the "trunklines" that are the axons, and out to the "branch points" where synapses form.
About two days after one or more injections are made in a region of interest, the brain is dissected and RNA is collected and sequenced. RNA barcodes in the "source" area are now matched with the same barcodes collected in distant parts of the brain.