Nobel Prize in Chemistry - 2020

This year the Nobel Prize in Chemistry is being shared between two notable scientists - French microbiologist Emmanuelle Charpentier and American biochemist Jennifer Doudna - for their breakthrough work on CRISPR. This is also the first time in history that the Nobel Prize in chemistry is exclusively shared by two women. In this blog post I plan to understand and elucidate their research after reading articles from various sources.

To begin with, what does CRISPR stand for? Clustered Regularly Interspaced Short Palindromic Repeats is a method of gene editing that allows precise editing of an organisms genome and is the sequence of genes found in archaea and bacteria. It is the microbial immune system present in these kingdoms that help them prevent infection from bacteriophages (virus that affect bacteria) and hence play an important role in the antiviral system of the bacteria. The sequence is derived in them from those phages that have earlier affected the organism.

How does the bacteria protect itself from an infection? CRISPR helps bacteria identify genetic sequences that match phages or similar infectious organisms which are targeted with the help of specific enzymes. Earlier research showed that these enzymes were CRISPR Associated proteins or Cas proteins. Charpentier also discovered another essential component to the CRISPR system, a molecule of RNA used to recognize the phage sequence found in Streptococcus pyogenes, a disease causing bacterium in humans. This happened in 2011. From 2012 Charpentier and Doudna started working together.

The breakthrough with CRISPR came when these two scientists came together and showed how the defense system of the bacterium could be used as a 'cut and paste' tool to edit genome. They isolated the components of CRISPR, adapted it to live in a test-tube and proved that it could be programmed to cut DNA at specific sites hence acting as genetic scissors. Naturally these scissors can recognize sequences from a virus but the duo proved that this concept could be extended to cut any DNA sequence at a specific site.

Though there are other gene editing tools, the Charpentier - Doudna tool seems to be more adaptable and easier to use. Their tool also helps users achieve high precision, thereby allowing scientists to make precise single base pair insertions. This tool has also allowed scientists in the past few years to gain a better understanding of mutations causing diseases, treatment for such diseases and so on.

Another major contribution of this tool is the curing of chromosomal/genetic disorders. Sickle cell disease/thalassemia affected individuals are usually treated by periodical transfusion of bone marrow cells. This is a repetitive process as marrow cells are mortal. But with CRISPR techniques, the genome of the bone marrow can be corrected and hence the individual can be cured. CRISPR based therapy has been first administered to a person affected with hereditary blindness earlier this year.

To summarize, I understand that Charpentier and Doudna have expanded the use of the CRISPR technique (that organisms under Archaea and Bacteria use as an anti viral defense) to other organisms, thereby improving the fields of gene editing and the ability to cure genetic disorders.

References:

1. https://en.wikipedia.org/wiki/CRISPR
2. https://www.sciencefocus.com/science/who-really-discovered-crispr-emmanuelle-charpentier-and-jennifer-doudna-or-the-broad-institute/
3. https://www.nature.com/articles/d41586-020-02765-9
4. The Hindu, dated October 11, 2020

Image References :

1. https://www.nationalheraldindia.com/international/nobel-prize-for-chemistry-awarded-to-emmanuelle-charpentier-and-jennifer-doudna
2. https://blog.gao.gov/2020/04/23/crispr-a-technology-that-could-help-in-the-fight-against-covid-19/
3. https://www.genengnews.com/insights/for-confidence-in-crispr-outcomes-results-must-be-fully-validated/