"We've always thought of embryos as living or dying, but in reality we find that each cell in the embryo is making decisions autonomously," said Reijo Pera. "No one has ever looked at this before." She and her colleagues found that embryos in which individual cells varied significantly in their cell-division schedules or gene-expression profiles were less likely to become successful blastocysts.
Together the research indicates that the maternal RNA transcripts that is, the molecules that carry instructions from the mother's DNA to the embryo's protein-making factories must be actively degraded in each cell of the embryo, and that this degradation is necessary for the cells to begin to express embryonic genes. Cells that fail to execute some part of this delicate process get out of sync with their neighbors and jeopardize the life of the embryo. The whole endeavor is complicated, and may explain why human embryonic development is so precarious and unique.
The research also highlights the importance of studying human embryos, which currently cannot be supported by federal funds. (Every year since 1996, Congress has approved a provision known as the Dicky-Wicker amendment that prohibits the use of federal funds for research in which a human embryo is destroyed even ones that would otherwise be discarded.)
"In mice, about 80 to 90 percent of embryos develop to the blastocyst stage. In humans, it's about 30 percent," said Reijo Pera. "In addition, about one in 100 mouse embryos are chromosomally abnormal, versus about seven out of 10 human embryos. That's why human studies like these are so important. Women, their families and their physicians want to increase the chances of having one healthy baby and avoid high-risk pregnancies, miscarriages or other adverse maternal and fetal outcomes. It's truly a women's health issue that affects the broader family."
The research was
|Contact: Krista Conger|
Stanford University Medical Center