Mammalian embryos are unlike those of any other organism as they must grow within the mother's body. While other animal embryos grow outside the mother, their embryonic cells can get right to work accepting assignments, such as head, tail or vital organ. By contrast, mammalian embryos must first choose between forming the placenta or creating the baby.
New research published in eLife today has pinpointed two proteins that are the keys to this decision making. The process of assigning cells to placenta or baby is important because that is when pluripotent cells are made. These adaptable pluripotent cells are critical to stem cell research, and these two proteins could be the key to deciphering how pluripotent cells are born, said Amy Ralston, Michigan State University’s inaugural James K. Billman Jr., M.D. endowed professor and the study's senior author.
"Pluripotent cells are the progenitors of embryonic stem cells, and they are famous because they can become any part of the body," she said. "We have discovered a process that regulates the balance between pluripotent and placenta, and it works by changing the physical location of cells within the embryo's ball of cells."
To form this wondrous ball, the mother packages two closely related proteins into her eggs, which help oversee this decision-making process. The scientific team used genetic tools to eliminate the proteins YAP1 and WWTR1 from mouse eggs and embryos. The team discovered that these two proteins first position these cells into distinct inside and outside locations, which then decides their fate: placenta or pluripotent.
Each phase of Ralston's research peels back a layer into the creation of stem cells, a process that nature performs with 100 percent efficiency. On the other end of the spectrum, lab-created stem cells are created with 1 percent efficiency.
"Obviously, our understanding of how nature creates stem cells is incomplete," said Tristan Frum, MSU biochemist and molecular biologist, who performed the study along with Tayler Murphy, MSU genetics graduate student. "We've suspected these proteins were involved in creating stem cells, but our work reveals that they do so in a surprising way."
Image: New research has pinpointed two proteins that are the keys to stem cell creation. Image courtesy of MSU.