Nature's new RNA editing tools illuminate brain circuitry and alter specific cells

Labeling and illuminating inhibitory "brake" cells (green) in human brain tissue is just one of
many features of Duke University's new CellREADR tool.

The editing technique is precise and widely applicable to all tissues and species
.

Scientists at Duke University have developed a DNA-based editing tool that targets individual cells, not genes
.
It is capable of precisely targeting any type of cell and selectively adding any protein
of interest.
The researchers say the tool can manage disease
by modifying very specific cells and cellular functions.

Neurobiologist Z.
Using RNA-based probes, led by Dr.
Josh Huang and postdoctoral researcher Yongjun Qian, Ph.
D.
, demonstrated that they can introduce fluorescent markers into cells to label specific types of brain tissue; A light-sensitive on/off switch that silences or activates neurons of their choice; There is even a self-destructing enzyme that precisely clears some cells without clearing others
.
The study was published in the October 5 issue of Nature

Their selective cell monitoring and control system relies on the ADAR enzyme, which is present in every animal's cell
.
While CellREADR (Endogenous ADAR Sensing Cellular Access via RNA) is still in its early stages, its application prospects seem limitless, and its potential for use in the
animal kingdom is also limitless.

CellREADR is a customizable RNA string that consists of three main parts: a sensor, a stop flag, and a set of cryptographic blueprints
.

First, the research team decides on the specific cell type they want to study and identifies the only RNA
of interest produced by that cell type.
The tool's significant tissue specificity relies on each cell type producing iconic RNAs
that are not seen in other cell types.
A sensor sequence is then designed as a complementary strand
of the RNA of interest.
Just as strands of DNA are made up of complementary molecules that attract each other, if the RNA has a matching molecule, it has the same magnetic properties to connect
with another segment of RNA.

When a sensor enters a cell and finds its target RNA sequence, the two fragments combine to form a double-stranded RNA fragment
.
This new RNA mashup triggers the ADAR enzyme to examine the newly generated RNA and then change the one nucleotide it codes for
.

ADAR enzymes, a cellular defense mechanism designed to edit double-stranded RNA, are thought to be present in all animal cells
.

Knowing this, Qian designed the stop symbol
for CellREADR with the same specific nucleotide ADAR edit in double-stranded RNA.
Stop signs that prevent protein blueprint construction are removed only when CellREADR's sensor docks on the RNA sequence of interest, making it highly specific to a specific cell type
.
Once the ADAR removes the stop marker, the blueprint can be read
by the cellular mechanisms that generate new proteins within the target cell.

In their paper, Huang and his team tested
CellREADR.
"I remember two years ago, Yongjun made the first generation of CellREADR and tested
it in mouse brains," Huang said.
To my surprise, he achieved amazing results
on his first try.
”

The team's meticulous planning and design paid off as they were then able to demonstrate that CellREADR accurately labels specific brain cell populations in live mice and effectively adds activity monitors and control switches at designated locations
.
It is also effective
in mice and human brain tissue collected from epilepsy surgery.

"With CellREADR, we can pick the study population and really start investigating all the cell types that exist in the human brain," said
Derek Southwell, a neurosurgeon, assistant professor, MD, Ph.
D.
, and co-author at Duke University.

Southwell hopes that CellREADR will improve his and others' understanding of human brain circuits and the wiring diagrams of the cells in them, and in the process help advance new therapies for neurological disorders, such as a promising new treatment
for drug-resistant epilepsy that he is experimenting.

The team was particularly bullish on the potential of CellREADR as a "programmable RNA drug" with the potential to cure disease — because that's why
the two of them first went to science.
They have patented the technology
.

Programmable RNA Sensing for Cell Monitoring and Manipulation," Yongjun Qian, Jiayun Li, Shengli Zhao, Elizabeth A.
Matthews, Michael Adoff, Weixin Zhong, Xu An, Michele Yeo, Christine Park, Xiaolu Yang, Bor-Shuen Wang, Derek G.
Southwell and Z.
Josh Huang, 5 October 2022 Nature.