Treating infertility, editing genes and gene therapy

Dr Derrick Aarons

Saturday, February 06, 2016

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DURING this past week, the United Kingdom Human Fertilisation and Embryology Authority (HFEA), who are the UK regulators on fertility matters, granted permission to scientists in London to edit the genomes (an organism’s complete set of genetic instructions, that is, DNA, which includes all the genes) of human embryos for research purposes.


This represents the world’s first endorsement of such research by a national regulatory authority. The HFEA approved an application by a developmental biologist to use the gene-editing technique CRISPR-Cas9 in healthy embryos to alter genes that are active in the first few days after fertilisation. The researcher will stop the experiments after seven days, after which the researched embryos will be destroyed.


This research into the modifications of genes reportedly could help researchers develop treatments for infertility, although the embryos will not comprise the basis of treatment themselves.


GENE EDITING IN THE HUMAN EMBRYO


The approval in the UK will also likely embolden other scientists who are interested in pursuing embryo-editing techniques to apply for permission to proceed with their own research.


However, in countries that have no such national regulatory authority, such research may proceed without delay. The research may proceed using the healthy human embryos that have been left over from in vitro fertilisation procedures performed in fertility clinics. The UK scientist receiving the approval plans to block the activity of a ‘master regulator’ gene that is active in cells that go on to form the human foetus.


The researchers aim to discover how a healthy human develops by examining the very earliest stages of human development, thereby improving their understanding of in vitro fertilisation success rates. However, in approving the research application, the HFEA stipulated that a local research ethics committee in the UK will need to evaluate and approve the research proposed by the researchers before such research could begin.


INTERNATIONAL IMPACT


This development in the UK is likely to have a reverberating effect around the world, particularly in countries that were considering regulating this technology. What is needed, however, is a well-regulated system across countries that is able to clearly distinguish between research in this area and reproduction.


In the UK, it still remains illegal to alter the genomes of embryos that are used to conceive a child. However, many countries have not yet considered legislation that addresses this new and emerging field.


The decision to allow embryo-editing research could further inform the debate over whether the gene-editing technique should be used for treatment purposes only, or also in germ-line editing (editing genes that will be passed on to children).


Some countries do not explicitly prohibit using gene editing for reproductive purposes. Consequently, the research that was approved last week may further serve to teach us the potential risks involved in editing genes to be passed on to children to prevent certain hereditary diseases.


GENE THERAPY


Gene therapy involves a different process from gene editing. Gene editing uses a technique that cuts out the bad or undesired gene from the DNA and replaces it with a healthy gene. Gene therapy (treatment) does not involve any splicing out the ‘bad’ gene, but rather the addition of new genes to the patient’s cells in the hope that they will be taken up and replace missing or malfunctioning genes. To do this researchers typically use a virus to carry the genetic material into cells, since viruses customarily enter our cells to live and survive there.


So if a gene has mutated and as a result causes a protein that is vital to our normal functioning to be damaged or absent, gene therapy may be able to introduce a normal copy of the gene into the cell in order to restore the function of the protein.


Lately, good results have occurred in the treatment of certain inherited blood disorders, such as beta-thalassemia — a blood disorder involving greatly reduced amounts of haemoglobin (the substance inside red blood cells that binds oxygen for it to be transported around our bodies). Research in this area is ongoing, but the results so far indicate that gene therapy is a promising option for eliminating the need for blood transfusions in patients with beta-thalassemia.


POSSIBLE BENEFITS


Gene therapy, however, is more likely to be successful with diseases caused by defects in a single gene, while the new gene-editing technique is able to splice and address abnormalities in several genes. The latter’s potential use includes hereditary diseases such as Duchenne muscular dystrophy (progressive weakness and loss of muscle function, which first begins in the lower limbs of young boys and worsens quickly), and cystic fibrosis (in which an afflicted young person may die in their early 30s due to lungs that are blocked by very thick mucous).


Let us begin to discuss these issues.





Derrick Aarons MD, PhD is a consultant bioethicist/family physician, a specialist in ethical issues in medicine, the life sciences and research, and is the ethicist at the Caribbean Public Health Agency – CARPHA. (The views expressed here are not written on behalf of CARPHA)


 


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