Genetic Barcodes Trace Cells Back to Single Cell Origin

Genetic Barcodes to Trace Single Cell parentage

A mystery in biology that every scientist has tried to solve is determining the history of cells. All life begins with a single cell and then that cell divides into two, then four until finally it reaches 26 billion or there about cells, which is found in newborn babies. Looking at how that one zygote resulted to form a newborn is what biologists are interested in. At present, biologists are only able to capture snippets of the process rather than a detailed continuous account of how cells form. This was until now. Biologists have discovered a system of genetic barcodes that could aid in determining the history of cells.

Scientists at Wyss Institute together with Harvard Medical School have discovered this novel way of using evolving genetic barcodes to determine the history of cells. Using this method of genetic barcodes every cell in the body can be traced back to its lineage until one comes to its single cell origin.

The current practice of determining a Cell’s history: 

At present before the discovery of genetic barcodes, cell history could be looked at only in the form of snapshots. What scientists have to do in order to view these snapshots is to physically stop the development process. It is described as looking at frames of a motion picture rather than a continuous picture.

On the other hand using the genetic barcodes method, scientists are able to determine the history of all mature cells right up to their single cell parent. It is like looking at a motion picture backwards.
How are these Genetic Barcodes made?

The genetic barcodes system is created using a special type of DNA sequence which encodes a modified RNA molecule which is come to be called a homing guide RNA or hgRNA. This homing guide RNA is made in such a way that they guide an enzyme known as Cas9 which is present in the cell, to its own hgRNA sequence in the genome which the enzyme then proceeds to cut.

The next process in genetic barcodes is the healing process. When the cell then proceeds to heal that cut, it introduces genetic mutations in the hgRNA sequence. This collects over time to create a unique barcode that is called a genetic barcode.

The test subject to the Genetic Barcodes system: 

The genetic barcodes system was tested out in mice with a founder mouse being chosen. This founder mouse had 60 different hgRNA sequences scattered throughout its genome.

Scientist then took this founder mouse and crossed bred it with other mice with the Cas9 protein, the resulting zygotes had their hgRNA sequences cut and which mutated.

The progeny from the zygote too had hgRNA cells that mutated. Each generation of the mice had their own unique mutation or barcode as well as the barcode that they inherited from their parent.
By comparing the cells with mutation, scientists are able to determine which cells are more closely related than others.

This can be especially useful in determining how diseases like cancer become active in the human body.