The future of reproduction and its influence across biology.
anghai Jiao Tong provided a new step forward in same-sex reproduction technologies. Achieved in 2018 with two female parents, researchers have now reported that for the first time, mice from the genetic material of two male parents were born and survived to healthy adulthood.
This has been a long time coming and represents an exciting time in this field. But why has it taken so long to get to this point, and does this actually mean anything for same sex couples?
When an egg and sperm fuse, the DNA inside them combines in the egg, and fertilization occurs. Modern reproduction technologies like IVF allow this to occur in the lab, and so it is natural to wonder why it’s not so simple as just visiting the lab and injecting two sets of paternal DNA into an egg.
Since two males can create both the male and female combination of sex-determining chromosomes, XX for females, XY for males, this wasn’t such a problem for the researchers performing this in male mice. The main reason that creating these mice was difficult is because of something called epigenetics. Our DNA, the instructions for building a working human, are neatly folded away into chromosomes. But it’s about more than just the DNA instructions. It turns out that the way DNA is folded into chromosomes are vitally important to how these instructions are read. Imagine some parts of the chromosome are covered in labels that say, ‘Read me!’, while other parts huddle together and make themselves difficult to read.
Remarkably, all the chromosomes your mother passed on to you are folded differently from the chromosomes your father passed on. While they may have roughly the same DNA information, the way they are annotated is completely different, and therefore they work to build a human in very different ways. Therefore, when attempting to combine two sets of chromosomes from parents of the same sex, there’s just not the right balance of instructions, or mix of ‘ingredients’ to grow a baby.
This is the key difficulty Wei’s team managed to overcome: rewiring a male set of chromosomes to be folded the “female” way. This involved intricate genetic manipulation on one of the male sets of chromosomes, resulting in the two sets of male chromosomes combining inside an empty egg and healthy mice being born for the first time.
So back to the question of what this means for same sex couples – could we see this happening within our lifetimes? This is the first time bi-paternal mice have been created, and the methods are still highly investigative – to do this just once required a massive effort, lots of money, and many failed attempts. By the time this technology is refined, feasible, and safe enough to be used in humans, unfortunately it’s unlikely this will still be within our lifetimes despite a promising future ahead.
With that said, some argue that the development of this technology is unnecessary. Particularly since same-sex couples are already able to raise families, whether that means adoption or being genetically related to one parent. This technology isn’t going to save any lives – is it really worth the massive costs to develop it?
To scientists, the answer is yes. Same-sex reproduction technology is much bigger than just allowing same-sex couples to have genetic children. This research has already contributed to the development of vastly useful techniques for efficient chromosome rewriting. Chromosome folding is essential to biological function across the majority of living organisms. Having access to efficient chromosome refolding techniques could immeasurably increase our understanding of developmental biology, regenerative medicine, and human disease – it could fundamentally change how we are able to study and understand biology as a whole.
So, while this technology may not directly impact people’s lives just yet, there is a network of scientific advancements that will underpin our lives in ways that we probably will not notice. As for our new ability to create mice with two dads, it’s a very exciting step forward…and definitely a good way to start a heated debate at family dinner.
Illustration credit: Eva Casey
