Several recent reports are filling in the gaps of what we know about the earliest days and weeks of human prenatal development. Rather than attempting to image human embryos, researchers are tracking gene expression – that is, which genes a particular cell turns on or off at a particular time, providing a view of overall function.
The early embryos that are being investigated are donated by women undergoing assisted reproductive technologies, or are nurtured from induced pluripotent stem cells, which are created by culturing skin cells (fibroblasts) in a brew of growth factors. The stem cells divide and differentiate into early embryos, but with only partial supportive structures, like the amnion and placenta, so development ceases before the fetal period begins at 8 weeks after fertilization. The stem cells provide a Goldilocks solution, glimpsing early embryos, but not sustaining their development past a few weeks.
Three New Reports
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