Gene Editing And Predictive Diagnostics

Current global health care systems were developed in the post world war II Era and it’s a sick care system. i.e. The system waits for one to become sick before it kicks into reactive action. For the most part, the system was not developed to help prevent the onset of disease but instead to diagnose and treat illness.

Some of the highlights of the system:

1. Patients are passive recipients of treatments or other interventions mandated by professionals.

2. Clinical visits/encounters are symptomatic/treatment focused as opposed to holistic /root cause and patient centered .

Concept of molecular genetic testing for predictive diagnostics:

Recent advances in medical science particularly in bio-molecular technologies has made  possible the use of DNA and molecular genetic testing for effective predictive health screening.

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The new techniques involve extracting the DNA from the patient`s blood sample. The DNA material would be the processed and analyzed for diagnosis and prognosis of his/her disease. Since its discovery molecular genetic testing has revolutionized health screening. Doctors could now rely on molecular genetic analysis to provide highly accurate diagnosis not only of the patient`s current disease but also the diseases he/she is genetically predisposed to as well. Our genome is made up of nitrogenous bases A,T,C and G and they play a role in the way they affect our different traits.

The reason we differ from one another in appearance, the likelihood of disease and even personality is because we have inherited from our ancestors single letter changes in our DNA---for instance, G instead of C. Single letter differences are called SNPS(single nucleotide polymorphisms),pronounced as SNIPS. There are some rare gene diseases that are caused by changes in a single gene (like cystic fibrosis/muscular dystrophy) but most human diseases are called multi-factorial because multiple factors are involved like genetic and family history predispositions, environmental influences and lifestyle, behavior (diet, exercise, smoking, etc) contribute to a risk factor which health care providers use to inform medical decisions. We are beginning to unravel the genetic component of such multi-factorial diseases such as breast cancer, crohns disease, diabetes, macular degeneration, prostate cancer and many others.

Since 2006 more than 100 gene relationships have been discovered between SNPS and many common disease. The effect of single SNP/gene may be small but when combined with other genes/SNPs/environmental factors, the overall effect may become significant.

DNA editing is another area where researchers are showing interest in the hope of editing genomes/target regions to remove faulty genes but how far this will be successful, only time will tell. CRISPR-Cas gene editing is the newest craze. It is a prokaryotic derived immune system from which researchers have designed an artificial system which can be targeted to cleave any target DNA sequence. CRISPRs are much easier to design because the process requires making only a short RNA sequence when compared to TALENS and zinc finger nucleases. The applications of CRISPR CAS looks promising especially when one says mosquitoes can be engineered using this not to transmit diseases like malaria, dengue etc. The second good point about CRISPR Cas is the low cost associated with it. CRISPR can be utilized to create human cellular models of disease. For instance, applied to human pluripotent stem cells CRISPR introduced targeted mutations in genes relevant to polycystic kidney disease (PKD) and focal segmental glomerulosclerosis (FSG).

Researchers have been trying unsuccessfully to use CRISPR in embryonic medicine. Altering of gametocytes and embryos to generate inheritable changes in humans is defined to be irresponsible. It was thus agreed upon only to support basic and clinical research under appropriate legal and ethical guidelines in the December 2015, Summit on Human Gene Editing in Washington.

References:

Niewoehner O, Jinek M, Doudna JA (January 2014).” Evolution of CRISPR RNA recognition and processing by Cas6 endonucleases”  Nucleic Acids Research. 42 (2): 1341–53

Ledford H (March 2016). "CRISPR: gene editing is just the beginning". Nature. 531 (7593): 156–9.

Hsu PD, Lander ES, Zhang F (June 2014).”Development and applications of CRISPR_Cas9 for genome engineering” Cell. 157 (6): 1262–78

Barrangou R, van der Oost J (2013). CRISPR-Cas Systems : RNA-mediated Adaptive Immunity in Bacteria and Archaea. Heidelberg: Springer. p. 6.

Rho M, Wu YW, Tang H, Doak TG, Ye Y (2012).”Diverse CRISPRs evolving in human microbiomes”  PLoS Genetics. 8 (6): e1002441.