Three new studies have found large unwanted changes in embryonic chromosomes after cutting and sewing the Crispr-Cas9 editing tool, confirming how little is still known about the DNA repair mechanisms in different cell types
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After the questionable experiment that led to the birth of genetically modified Chinese twins with Crispr-Cas9 to be resistant to hiv, the scientific community continues to question the security of this genome editing tool for editing human cells, embryos in particular.
While on one hand this technology seems to offer extraordinary opportunities (for example the correction of serious genetic defects hereditary), from the the other still feed many doubts on its feasibility at present.
Doubts that seem to be confirmed by three new studies which to only research purpose (there has never been the intention to establish a pregnancy) they have modified human embryos with Crispr, but then verified the presence of important unwanted changes at the chromosomal level.
These evidences, for experts, are not the result of chance but are a clue to how little is known still on mechanisms of DNA repair in embryos and how far we are from the conscious application of certain experimental methods. We cannot underestimate the risks .
Although the three new studies have not yet undergone peer-review (are available in preprint on bioRxiv ), the observations that report I am I agree , and it is this that causes concern and to suggest that are not random events unlucky.
In research by Kathy Niakan’s team from the Francis Crick Institute in London, scientists used Crispr to modify the gene POU5F1 , which plays a key role in embryonic development. On 18 modified human embryos, the 22% has reported important unwanted changes (rearrangements, deletions) that concerned large portions of the DNA adjacent to the target gene.
Dieter Egli’s team from Columbia University in New York City has achieved similar results. In the experiments, the researchers attempted to correct an inherited mutation in the EYS gene that causes blindness , but half of the embryos subjected to the procedure has lost large portions of the chromosome (sometimes the entire chromosome) on which EYS is located.
Experts from Oregon Health & Science University of Portland, led by Shoukhrat Mitalipov, have also noted similar unwanted changes on the chromosome which hosts their target gene when they used Crispr to correct a mutation that causes heart disease .
Where is Crispr wrong?
There are no official comments from the authors of the research at the moment, reports Nature News . Researchers prefer to wait until the peer review process is complete and the articles officially published. However, from what can be read in the manuscripts, their hypotheses on the reasons for which such undesirable effects of Crispr fall back on the action of embryonic DNA repair systems after the cut and sew of the editing tool.
Perhaps the embryonic mechanisms are different from those of other cell types, and perhaps the damage to the DNA is repaired differently depending on the position where they occur on the chromosome.
All of these perhaps , the various theories that exist, do nothing but tell us that we still don’t know enough : before think we can fix an error, we should be reasonably sure not to cause others , especially when they might have permanent consequences on the life and health of a future human being and his descendants.
Originally published at NJ MMA NEWS