GENE EDITING

 Chinese researcher He Jiankui set off a storm when he claimed that he had created the world’s first babies, a pair of twin girls, genetically edited with CRISPR-cas9. He said that the twins had genes now that protected them from HIV. 

CRISPR-Cas9, a gene-editing technology that is being explored by scientists worldwide as a way of removing and replacing gene defects  CRISPR- Cas9 - Clustered Regularly Interspaced Short Palindromic Repeats -discovered by Francisco Mojica (University of Alicante in Spain) -proposed that CRISPRs serve as part of the bacterial immune system, defending against invading viruses. 

 CRISPRs consist of repeating sequences of genetic code, interrupted by “spacer” sequences – remnants of genetic code from past invaders. 

This system serves as a genetic memory that helps the cell detect and destroy invaders Since the CRISPR-Cas9 system itself is capable of cutting DNA strands, CRISPRs do not need to be paired with separate cleaving enzymes as other tools do. They can also easily be matched with tailor-made “guide” RNA (gRNA) sequences 

CRISPR genome editing allows scientists to quickly create cell and animal models, which researchers can use to accelerate research into diseases such as cancer and mental illness.

CRISPR is now being developed as a rapid diagnostic.

Ethical concerns arise when genome editing, using technologies such as CRISPR-Cas9, is used to alter human genomes. Mostly genome editing are limited to somatic cells, means not on the egg and sperm cells. These changes affect only certain tissues and are not passed from one generation to the next. Cpf1 system provides new flexibility in choosing target sites. Like Cas9, the Cpf1 complex must first attach to a short sequence known as a PAM (Proto-Spacer Adjacent Motif) & targets must be chosen that are adjacent to naturally occurring PAM sequences.

(CRISPR-Cas9) system has revolutionised genetic manipulations and made gene editing simpler, faster and easily accessible to most laboratories.

Based on this, multiple clinical trials have been initiated in the U.S. and China (using the CRISPR-Cas9 system) to produce gene-edited cells for cancer and HIV-1 therapy 

Two studies, one from the Karolinska Institute, Sweden, and the other from the biopharmaceutical company Novartis, have highlighted that CRISPR-Cas9-edited cells might trigger cancer.

According to karolinska experiment CRISPR-Cas9 system induced activation of P 53 protein , which prevents cells from turning cancerous.  

CRISPR “spacer” sequences are transcribed into short RNA sequences capable of guiding the system to matching sequences of DNA. When the target DNA is found, Cas9 – one of the enzymes produced by the CRISPR system – binds to the DNA and cuts it, shutting the targeted gene off. Using modified versions of Cas9, researchers can activate gene expression instead of cutting the DNA.