CRISPR revolution: Gene editing and the power to control evolution

CRISPR

Imagine a world where genetic diseases, or even HIV or cancer, could be cured by simply editing them out of your DNA. At first, it seems unrealistic, but it might not even be that far away. We may be lucky enough to see a time when gene editing becomes standard medical practice. However, as with almost everything incredibly powerful, gene editing comes with its dark sides. Why stop at curing diseases if we could create designer babies? – Choosing from a catalogue of improved genes, such as increased muscle strength or intelligence. There are of course, many ethical issues that would have to be addressed before proceeding with caution.

Biological Diversity: Genetic modification occurs naturally

For billions of years, life on earth has evolved through randomly occurring genetic modifications and therefore, improved by variation. This phenomenon is widely known as Darwin’s law of evolution; perhaps modifying the genetic code is not as new and unnatural as it might sound.

Cases of natural gene editing indeed occur. Since 1960 researchers at the National Institute for Health (NIH) have been studying a rare disease called WHIM, a painful immunodeficiency disorder brought on by a single letter mutation in the DNA. One of the patients, known as the WHIM-9 patient to NIH researchers, was diagnosed in the1960s with WHIM, but when she was observed again in 2013, she seemed to be cured due to a phenomena called chromothripsis.

Chromothripsis is when a chromosome suddenly shatters and is repaired, resulting in a massive rearrangement of genes (1, 2). This chain of events must have erased the misspelling in the patient’s genetic code, which was causing the illness and symptoms. We could say that nature spontaneously and unintentionally edited the patient’s genome to the great benefit of her health.

What if science could reverse the often devastating effects of genetic misspellings and correct them to cure genetic disorders?

Gene editing’s breakthrough

Gene editing made its first breakthrough in the 1980s, where researchers first succeeded in overwriting defective genes with healthy ones in mice through a process known as homologous recombination (3,4). So far, this technique has had no therapeutic viability. Many other techniques have come since, but they all came with huge complexity and impracticality in clinical applications. This all changed when a region of bacterial DNA with an exactly repeating sequence over certain intervals was discovered – CRISPR or Clustered Regularly Interspaced Short Palindromic Repeats. This discovery gave researchers the chance to develop a technique which was simple and effective enough to be used in gene therapy (5, 6). CRISPR DNA is an important key to the bacterial immune system and is responsible for fighting off viruses, enabling bacteria to recognize and destroy viruses during future infections – But how?

CRISPRs as cutting machines

CRISPR relys on three essential components to cleave and destroy viral DNA – the CRISPR-associated CAS genes, the CRISPR RNA (crRNAs) and tracrRNA (trans-activating crRNA). While the CAS9 gene codes for an endonuclease which cuts the DNA, the crRNA serves as a messenger which guides the endonuclease to the location were a cut is needed. There are several pathways of CRISPR activation, one requires a tracrRNA to play a role in the maturation of crRNA (7,8,9).

CRISPR 2
Figure 1: CRISPR-Cas9 system: Complex association with CRISPR-associated protein-9 nuclease (Cas9) and single stranded Guide RNA (crRNA) on target DNA.

Gene engineering: A wide new world of opportunities

The CRISPR gene editing methods broke all limits of imagination in gene engineering and opens up a wide new world of opportunities. Such gene editing tools not only change the way we look for cures for genetic disorders, but also impact other practical applications in many areas.

It’s clear that gene editing has much to offer, but being in control of our genes and therefore having some control over evolution is not simple – foremost there are serious ethical questions. We have reached a point in medical science where major genetic interventions are possible, and we must carefully consider the implications of this ability.

See how QIAGEN can support you in your own CRISPR/CAS9 Gene Editing and discover how our Ingenuity Pathway Analysis (IPA) software supports modeling, analyzing and understanding complex genomic data. As always, count on QIAGEN for the most reliable start to your genomics research, with our QIAquick PCR Purification Kit and HotStar HiFidelity Polymerase Kit.

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References:

  1. 1. Jennifer Doudna and Samuel Sternberg A Crack in Creation: The New Power to Control Evolution (link)
    2. McDermott DH, Gao J-L, Liu Q, et al. Chromothriptic Cure of WHIM Syndrome (link)
    3. Szostak JW et al. The double-strand-break repair model for recombination (link)
    4. Doetschman et al. Targeted correction of a mutant HPRT gene in mouse embryonic stem cells (link)5. Y. Wang et al. The CRISPR/Cas System mediates efficient genome engineering in Bombyx mori(link)
  2. 6. T. R. Sampson, D. S. Weiss: Exploiting CRISPR/Cas systems for biotechnology (link)
  3. 7. Martin Jinek et al. A Programmable Dual-RNA–Guided DNA Endonuclease in Adaptive Bacterial Immunity (link)
  4. 8. Elitza Deltcheva et al. CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III (link)
  5. 9. Stan J. J. Brouns et al. A Swiss Army Knife of Immunity (link)
Laura Alina Mohr, M.Sc.

Laura Alina Mohr joined QIAGEN in 2015. She received her Master’s Degree in Chemical Biology at the Technical University Dortmund in Germany. During this time, she was involved in Systemic Cell Biology research at the prestigious Max Planck Institute. Before joining QIAGEN, Laura Alina worked at the Scripps Research Institute, San Diego, where she first focused on DNA damage/repair pathways and telomere biology. Later, she joined the Muscle Development, Aging and Regeneration program at the Sanford Burnham Prebys Medical Discovery Institute. At QIAGEN she is interested in gene expression profiling focusing on various biological pathways, e.g. cancer research and neurodegeneration.

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