GESTIÓN EN SALUD PÚBLICA: BioEdge: Landmark stem cell paper questioned

sábado, 2 de septiembre de 2017

BioEdge: Landmark stem cell paper questioned

Landmark stem cell paper questioned

by Michael Cook | 2 Sep 2017 |

Oh no! Not again! Such must be the sentiments of stem cell scientists after a paper to be published in Nature cast cold water on landmark research about editing the genome of a human embryo.

On August 2, a team led by Shoukhrat Mitalipov, of Oregon Health and Science University, announced in Nature that they had successfully deleted a disease-causing faulty gene and replaced it with a healthy copy using the CRISPR-Cas9 technique. Their innovative experiment introduced the CRISPR machinery earlier. When they examined the embryos, they found that they did not contain the faulty sequence.

This discovery was greeted around the world as a first step towards freeing mankind from genetic disorders – or towards a eugenicist society, depending on your attitude towards modifying the human genome. Technically, it was a tour de force, as it was relatively easy and accurate and did not result in mosaic embryos.

With 10,000 harmful single-gene mutations known, there is a lot at stake.

However, a closer examination of the exciting paper has sparked a lot of debate amongst stem cell scientists. In a preprint release of a paper in Nature on bioRxiv, Dieter Egli, of Columbia University, and Maria Jasin, of Memorial Sloan Kettering Cancer Center, along with Harvard geneticist George Church, have questioned whether Mitalipov’s team has actually succeeded, as the new technique contradicts the conventional wisdom about how fertilisation occurs. They point out that although the disease-causing gene had disappeared, there was no proof that the correct sequence had been inserted.

Furthermore, the DNA from the sperm and the egg are probably not close enough in the brief interval after fertilisation to interact or share genes. Mitalipov and his team had speculated that the embryos used the DNA of the egg as a guide to repair the mutation carried by the sperm.

“In my view Egli et al. convincingly provided a series of compelling arguments explaining that the correction of the deleterious mutation by self repair is unlikely to have occurred,” Gaétan Burgio, a geneticist at the Australian National University told Nature News.

Mitalipov has responded, promising to answer the “critiques point by point in the form of a formal peer-reviewed response in a matter of weeks.”

Inevitably, this latest “breakthrough” recalls a string of too-good-to-be true-and too-amazing-to-reject articles about stem cell research. They were published in leading journals, hyped in the media and then crashed and burned. Time will tell whether Mitalipov’s paper will be vindicated.

“Fatherhood” is what the guys in the business of policing the language call an “essentially contested concept” – no matter how much palaver you invest in it, you won’t make any progress. At least nowadays.

Below we feature a story from the Netherlands about two men who have each sired over a hundred children, one through sperm donation to IVF clinics, the other mostly through more conventional channels. Are they fathers?

Another story comes from Australia, which is girding its loins for a campaign on same-sex marriage. A group promoting closer links between fathers and their children, Dads4Kids, has been running a public service TV advertisement for 15 years. This year, a 30-second spot of a dad crooning to his wee sprog was rejected because it was “too political”.

A spokesman for the foundation complained:

“It is extraordinary that this is where we have come to as a country; we can no longer celebrate Father’s Day without being forced to look at it through the lens of the same-sex marriage debate. It’s a tragedy that a political motive is now implied in any mention of fatherhood. Not everything is about same-sex marriage.”

The history of this simple advertisement tracks the evolving concept. In a span of 15 years, fatherhood, or rather “fatherhood”, has shifted from a universally admired status to a politically suspect notion. Are we the better for it?

Happy Father’s Day to our Australian readers.