The researchers at Johns Hopkins have uncovered the molecular underpinnings of one of the earliest steps in human development using human embryonic stem cells. Researchers also say this element of stem cell biology is essentially human and something not applicable to the mouse or any other. The research is an outcome of the attempt to study a rare human blood disorder in the gene called PIG-A.

So using a conventional genetic engineering tool, the researchers tried for years-literally-to knock out PIG-A in adult stem cells, without success. They then turned to knocking out PIG-A in human embryonic stem cells. The researchers however, took one more step to verify that their engineered embryonic stem cells behaved like normal stem cells. “We just wanted to make sure that our knockout cells could still differentiate and specialize,” says Cheng, one of the researchers.

One of the earliest steps of embryonic stem cell differentiation in normal embryonic development is the development of the trophoblast, a layer of seed cells that later develops into the placenta. Only when they added the PIG-A gene back into their cells, BMP-4 does its work and cause the cells to become trophoblasts, allowing the researchers to conclude that trophoblast differentiation depends on certain cell surface proteins to receive the BMP-4 signal.

Source: Johns Hopkins