The new Genome Editor : CRISPR-Cas9

CRISPR-Cas9 is a new acronym  we will soon be encountering more often.   Already it has sent shock waves through scientific circles. MIT technology review ranked  it as the biggest breakthrough of the year. Legal and ethics experts have their antenna picking up every signal.  

CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats and the tag Cas9 short for CRISPR associated proteins represents a class of enzymes. These enzymes are   capable of cleaving DNA at the behest of CRISPR generated RNA fragment.  Together they function as a  very precise and  powerful genome editing tool. This composite tool  was originally discovered in bacterial systems.  Bacteria often keep archival records of viral attacks. These records are in the form of  unique genetic sequences of the viruses. If the virus attacks again, bacteria retrieves archival information and copy paste   it in a newly synthesised fragment of RNA . This RNA fragment then  colludes with  Cas9  enzymes.  RNA fragment locates the target sites on the viral DNA and the Cas9 enzyme nips off the corresponding piece. The   virus  is hit where it hurts most and its DNA can no longer replicate and multiply.  This  is a defence strategy practised and perfected by bacteria. Why should it rake up legal and ethical issues one may wonder.   Well scientists have realised the implications and  potential of CRISPR-Cas9 combination. It could be used  as an editing tool more precise and  powerful than  currently available tools, to snip off genome  sequences that foretell genetic  imperfections in plant and animal kingdom as well.  For example,  scientists have used  this technique  to  successfully treat mice suffering from muscular dystrophy.

Junjiu Huang , a molecular biologist at the Sun Yat-sen University in Guangzhou, China went a step further. Guangzhou team worked with discarded embryos from fertility clinics. Discarded because these were not usable embryos. In their paper published in 2015 April, Huang's team reported the modification of the defective gene that caused  thalassaemia.   Sensing the commercial angle startups too sprang up. Editas Medicine, Caribou, Biosciences, Intellia, CRISPR Therapeutics, Celletics, Precision Biosciences, Sangamo are some such ventures. Editas Medicine located in Cambridge Massachusetts announces  its mission on the  website  : to translate its genome editing technology into a novel class of human therapeutics that enable precise and corrective molecular modification to treat the underlying cause of a broad range of diseases at genetic level.  It is reported that the company's current focus is to set right genetic mutations that cause  vision impairment.

Genome editing naturally brings to the forefront ethical and legal issues. At the International Summit on Human Gene Editing held in December 2015,   scientists, ethicists and legal brains collectively  concluded that the technology is not yet market ready.

REFERENCES:
1. My whirlwind year with CRISPR: Jennifer Doudna, Nature vol.528,2015,   
    pp469-471
2. Gene Edits to order: Nature Vol.528, 2015, pp449
3. Embryo Editor : Nature Vol.528, 2015, pp461