Brave New Genome

The discovery of recombinant DNA, a defensive mechanism within bacteria, breathed life into the developing field of Biotechnology.  Occurring 50 years later, the discovery of another regulatory immune system within bacteria may not only prove hugely disruptive the field of biotechnology, but to our future genomes.  The discovery is that of the CRISPR-Cas9 system.  This innate prokaryotic system uses a programmable nuclease directing mechanism labelled Cas9, which operates on targeted DNA’s as identified by clustered regularly interspaced short palindromic repeats (CRISPR).  When adapted, this mechanism allows deliberate removal of unwanted genetic sequences, and insertion of more favored ones.  The next significant adaptation or discovery in terms of this mechanism was allowing it to become effective in mammalian cells. Allowing this system to be efficacious in human cells allows scientists and the medical community to explore the practical applications ethical considerations of such a development.  The foremost of the possible implications of such a technology may be the elimination of genetic disorders such as huntingtons disease, and other recessive diseases. Upon further consideration, the benefitting populations must be relatively large for the procedure to be effective. As it turns out the populations affected by such disorders are 1 per 10,000 or 1 million. Unless all individuals in the larger populations are screened, pre conception and then conception occurs in vitro, then the process will be ineffective. This barrier may provide excessive cost relative to the reward of eliminating these disorders and may therefore become exceedingly ineffective due to inefficiency.

More generally acquired diseases are the next alternative, such as heart disease, diabetes and Multiple Sclerosis. When determining efficacy of CRISPR-Cas9 for being a viable medical intervention, one cannot overlook the polygenic influences encompassed by these conditions, where altering one gene may influence a very small percentage of the condition, or worse, exhibit unwanted effects such as cancer promoting alterations.  The most realistic genetic altering candidate for such technology, would alter a gene that promotes Alzheimer’s and cardiovascular disease.  Even this candidate is riddled with problems as the gene is linked to increased episodic memory and working memory in young adults.

Currently, there are coordinated efforts on an international level that recognize the implications of such a gene editing technology and pay fair warning to all considering its utility. As its effects are largely unknown, and the alterations of the genes would be permanent to all future offspring, it is urged that the science community progress with great caution and sensitivity to the issue.

N Engl J Med 2015; 373:5-8

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