CRISPR
Tags: #🌲evergreen
Links: Biotech | Innovation
A technique capable of editing DNA of animals and plants.
Bacteria can be infected by viruses (bacteriophage) that inject DNA to make copies of themselves. They have only a few minutes to fight against it otherwise they die [1]. Their immune system is called CRISPR. They defend themselves by creating certain proteins that cut and eventually degrade viral DNA.
Stands for Clustered Interspaced Short Palindromic Repeats. A CRISPR sequence is made of spacer and repeats. A spacer is a history of old infections so that they can be recognized by the cell defense system.
CAS
CAS genes are "CRISPR ASsociated" genes. They create CAS proteins that can unwind and cut DNA.
When an infection happens, the bacteria creates crRNA (CRISPR RNA) that takes a spacer and is able to destroy the viral DNA.
If there's no spacer for that new virus, it creates a special CAS protein that can cut the viran DNA and create a spacer that will become part of the bacteria.
Cas9 complex is made of gRNA (guide RNA) and the Cas9 protein.
Cas9 (an enzyme) is the "scissors" that can cut DNA .
Gene editing
Instead of using spacers we can substitute that for arbitrary DNA.
We can use the CRISPR system to:
- inactivate gene sequences
- insert DNA sequences
Using CAS9 we can cut DNA strands in arbitrary locations. A cell will try to repair that by mending the break with some code that will most of the time inactivate the sequence. Another way the cell will try to repair that is by adding a new sequence.
CRISPR 2.0 (CRISPR-on/off)
A technique developed in 2021 lead by MIT and UCSF that can activate and unactivate genes. [2]
It changes gene expression in a heritable way without damaging the DNA [3]. It uses a process called Epigenetics, specifically adding or removing methylation markers. It has the advantage of being reversible. The technology can even reverse itself naturally within a few weeks [2:1].
Has a direct implecation for Alzheimer's by inhibiting the expression of the "tau" gene [3:1].
The catch is that there's no solution currently available to deliver that to a human adult.
Designer Humans
Right now we don't know enough about our genetic code to reprogram certain characteristics like IQ, strength, etc. [1:1]
Usage
They have been used to change genes in mice and human embryos [1:2].