A therapeutic approach

By | Science & Technology
Crystal structure of Cas9 in complex with RNA and its target DNA Credit@Nishimasu

Experts are teaming up to preserve promising gene-editing style approaches to therapeutic research. Specifically, scientists are encouraging a discussion to decide if the modification of DNA in human embryos might be allowed. Edward Lanphier, chairman of the Alliance for Regenerative Medicine in Washington DC, along with four co-authors called for scientists last week to step away from the editing of human embryo DNA, even for research purposes.

Discussion began amid rumours that precision genome modification tools had been used to play with the DNA inside human embryos. Such research might be used for non-therapeutic changes to the genome – for example, cosmetic enhancements like eye colour or the notorious ‘designer babies’.

Genetic modification is a significant area of therapeutic development with the potential to save lives, which is why experts aim to protect the field from public criticism. Many researchers, including Fyodor Urnov, Lanphier’s colleague and gene-editing pioneer, are already using the techniques in order to develop therapeutic approaches that correct genetic mutations that cause disorders in people. Allowing them to continue appears to be central to the field’s medical success.

Man-made DNA. Credit@DuncanHall

Man-made DNA. Credit@DuncanHall

Fundamentally, the practice involves the modification of germline cells – the eggs and sperm of sexually reproducing organisms. Somebody grown from these edited cells may have had their genetic blueprint changed without their consent. Furthermore, these changes are permanent and heritable by future generations of their children. The potential to eradicate inherited conditions, such as HIV and cancer, seems to prove enough reason for scientists to pursue the research and aim for a best practice to support such a powerful approach to treatment.

Lanphier and his team agree that the effect of germline modification on future generations is unpredictable and raises ethical challenges. At this early stage, he urges that researchers reach a consensus to only modify somatic cells (any non-germline cell). Nonetheless, the team aim to remain open to further discussion should a potential therapeutic benefit of germline DNA editing arise.

The latest tool in genome editing is a bacteria-derived system called CRISPR/Cas9. In bacteria, the system provides resistance to foreign genetic material, acting as a form of immunity. Since 2013, scientists have used the CRISPR/Cas system to add to, interrupt and change DNA sequences of a number of living species. With the appropriate cocktail of Cas9 and RNA strands injected into a cell, the organism’s genome may be precisely and accurately changed at any selected location. The goal of Editas Medicine (a company founded in 2013 and now worth more than $43m) is to develop CRISPR/Cas-based treatments. The company aims to harvest blood stem cells from the bone marrow of a patient, correct the genetic mutation, and then transfuse the cells back into the patient’s bone marrow. As a result, the patient may produce healthy blood cells from then on. The therapy aims to be able to treat cystic fibrosis and sickle-cell anaemia.

 

Crystal Structure of Cas9 bound to DNA. Credit@Anders

Crystal structure of Cas9 bound to DNA. Credit@Anders

The CRISPR/Cas9 system has significantly expanded research on genome editing, even past any need to modify human embryos. Besides, “The precise effects of genetic modification to an embryo may be impossible to know until after birth,” Lanphier says.

Many governing bodies have already agreed to preserve the researching of gene-editing for therapeutic applications. The challenges have led to around 40 countries, most notably in Europe, overruling the modification of human embryos. The US National Institute of Health’s Recombinant DNA Advisory Committee has also exclaimed that it refrains from entertaining proposals for germ line alterations. However, many countries are empty of any clear legislation proscribing the genetic engineering of humans.

Only recently has the technology to alter the human germline matched up to the ethical considerations posed a decade ago in a meeting of 80 scientists at the Genetics and Public Policy Center in Washington. As a result, experts are actively encouraging a dialogue within the community to decide how future research might proceed. The goal of this debate is to establish an agreed distinction between genomic editing in somatic cells versus germline cells. Most importantly however, a moratorium on human germline editing must allow the free progress of therapeutic techniques to cure heritable conditions.

What non-therapeutic advancement might be possible with the moratorium on germline DNA editing lifted?

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