Did you know that international policy limits embryo research to the first two weeks of development? It’s known as the 14-day rule. It hasn’t been a problem, as no one has managed to culture an embryo in vitro beyond nine days. That in itself is a rarity as most don’t make it past seven days. Up until recently, culturing human embryos in vitro has been technically difficult.

Earlier this year two groups reported sustaining embryos for 12-13 days. It was a remarkable achievement, but more importantly it gave researches the opportunity to witness nearly a week’s worth of embryonic development that had never been seen before.

The story prompted Insoo Hyun, Amy Wilkerson, and Josephine Johnston to write ‘Embryology policy: Revisit the 14-day rule’ (Nature 533, 169-171 (2016)). I highly recommend reading it, as it gives a great grounding on what the 14-day rule is, and what it was intended to do. It also delves into other areas of research policy that perhaps need to be revisited.

As to why the 14-rule exists and how it came about, Radiolab explored the story in their podcast episode ‘The Primitive Streak’ which you can find at www.radiolab.org/story/primitive-streak/

If you’ve been following Front Line Genomics Magazine, then you’ll be familiar with Radiolab’s work and their high production values. This podcast is all about taking you on a journey. It’s something they do better than anyone else. In this episode they look at the new frontier of developmental biology.

It’s easy to take each bit of policy or research in isolation. The first guest on this episode reminds us that conversations around the 14-day rule need to be framed in the proper context. Leroy Walters (the man largely responsible for drawing the 14-day line in the sand) explains that 1973 saw abortion legalised in the United States of America, genetic engineering was starting to take off, as was the whole field of IVF. Society was faced with difficult questions around what should be protected, and how to define life from a biological and moral perspective.

The 14-day mark was arrived at by some straightforward reasoning. It can still split into twins, or recombine with another embryo. It is not yet an individual. It is also the point at which the primitive streak begins to appear, and gives definition to what will eventual become the spinal cord. There are also some interesting philosophical arguments around the importance of life that is so readily rejected by the body under natural circumstances.

Having set the context, the episode jumps to the work that went into sustaining embryos in vitro. Magdalena Zernicka-Goetz describes the approach her team took to creating just the right environment for embryo growth. This is when we learn the importance of this work. It’s a stage of human development that has essentially been a black box because scientists can’t get to it.

The episode continues with Ali Brivanlou and his team showing presenter Molly Webster images of an embryo at day-8, day-7, day-9, day-10, day-11, and day-12. This is the point at which the episode goes from thoroughly interesting, to truly exciting. You’re witnessing something that very few people have ever seen, despite all of us having gone through the process in our own development.

On a very interesting note, the episode ends with the nature of attachment to the lab grown embryo and how we define life.  As we’ve come to expect, this is another thoroughly exciting and thought provoking look at scientific research from one of the very best podcasts on the planet. Go give it a listen!