04 August, 2017
A team of researchers has successfully corrected a disease-causing gene mutation in human embryos by using a gene-editing tool, stopping it from passing to future generations, according to a study published Wednesday in the journal Nature. The genetic defect corrected in the study is the leading cause of sudden heart attack in young people, carried by about 1 in 500.
Proponents of gene-editing research see the potential to one day eradicate a string of inheritable diseases because a person born with edited DNA would pass these alterations on to their offspring without any treatment. "Consent is particularly important when dealing with very vulnerable research subjects, and human embryos are among the most vulnerable of God's creatures".
"We need much more basic studies like this to answer the question of whether this is a feasible approach", said Salk staff scientist Jun Wu, who contributed to the study along with Salk researchers Juan Carlos Izpisua Belmonte and Keiichiro Suzuki.
The team programmed a gene-editing tool, named CRISPR-Cas9, that acts like a pair of molecular scissors to find that mutation - a missing piece of genetic material.
The experiments were privately funded; USA tax dollars aren't allowed for embryo research.
Critics of the study were quick to allege that the research team - whose work can not be taken much further in the United States given legal limitations - had already pushed the boundaries too far.More news: SKorea to deploy more THAAD units after North Korea missile launch
In February, the National Academy of Sciences released a 261-page report that gave a cautious go-ahead to human gene-editing, endorsing the practice for purposes of curing disease and for basic research but determining that uses such as creating designer babies are unethical.
Forty two out of 58 embryos (72.4%) were correctly fixed and were found to no longer carry the heart failure mutation, which normally has a 50% chance of being passed on. In this study, the researchers injected sperm and CRISPR-Cas9 into the egg at the same time to improve the accuracy of the gene correction. "So, for me, this is the big take home for everyone else in this area - that the DNA fix mechanism works much better in an early embryo, after the egg and sperm come together".
CRISPR allows scientists to make extremely targeted edits to the genome of humans, animals and other organisms. "Moreover, if such embryos were to grow up, as will doubtless occur in the future, there are likely to be unintended effects from modifying their genes", Fr. Pacholczyk continued.
In the US, Congress has blocked any clinical trials with the aim of turning an edited IVF embryo into a baby.
The technique could be used through in vitro fertilization to cure thousands of diseases caused by mutations in single genes.
But these embryos weren't actually allowed to develop beyond a few days. Think of it as a biological cut-and-paste program. The phenomenon of "mosaicism" (simultaneous presence of genes in healthy and defective in embryo) could not be avoided, the researchers of the new study have been able to do. Carrying just one mutant copy of the gene causes an inherited heart problem called hypertrophic cardiomyopathy (SN: 9/17/16, p. 8).
In fact, Mitalipov said the research should offer critics some reassurance: If embryos prefer self-repair, it would be extremely hard to add traits for "designer babies" rather than just eliminate disease.