On October 17th, 2016 we learned about

Mice born from skin cells sourced from their mother’s tail

Explaining the birds and the bees just got quite a bit more complicated. What has traditionally just been an awkward explanation of sexual reproduction will likely need to be expanded to include more detail about stem cells, mitosis, and even skin cells, since researchers have now succeeded at giving them all a role in the birth of a family of mice, capable of having pups of their own. It’s not an easy process of course, but it could open of a number significant changes in how we think about sexual reproduction.

Transforming tails

The mice’s conception started with skin cells from their mother’s tail. The normal division and reproductive process of those cells was interrupted and modified, so that instead of creating more skin cells they would grow into stem cells. Unlike other cells that are specialized for their specific roles in the body, stem cells are the blank slate we start with as embryos. They’re the cells that don’t yet have a specialization, and thus can develop in to other types of tissue, from organs to bone. Once researchers had the new stem cells, they could coax those into becoming egg cells, which could then be fertilized like any other mouse egg.

The next steps were much more conventional, at least for a laboratory. The fertilized, skin-sourced eggs were first grown in a petri dish, with the successful embryos then being implanted into a female mouse (although possibly not the donor of the original skin cells?) From that point on, the developing mice have been remarkably unremarkable— they’re apparently healthy and normal in just about every way, including being fertile themselves.

Fertility beyond sex cells

While there are a lot of steps to this process, an important constant was the donor-parent’s DNA. While skin cells were transformed again and again, the nuclear DNA was kept intact, meaning the children of these engineered eggs are as much the offspring of their parent as any other mouse. This isn’t going to be possible in primates, much less humans, for close to a decade, but it might some day benefit people with fertility concerns, since aging or damaged gametes would no longer be necessary to have a baby. Beyond that, same-sex couples could have their cells converted into complementary sperm or eggs to have their own genetic children (although women might be limited to only having girls, unless a Y chromosome can be crafted somehow?)

For now, a lot more work is needed to really understand all the implications of this research. Before humans use this process on themselves, we need to be sure that errors or defects aren’t a problem, and that they might not be turning up generations after the engineered eggs or sperm are made. In lab mice, it’s easier for researchers to monitor and control every step of the process, but once we involve human patients, things need to be ready to run their own course with as little intervention as this whole concept can allow for.

Source: Healthy Baby Mice Produced from Mouse Mom's Skin Cells by Karen Weintraub, Scientific American

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