New Research on Stem Cell Development
A press release from the University of San Francisco
available from EurekAlert
discusses research on the molecules in cells which control embryonic growth and development. The family of molecules known as Hedgehog molecules send messages from one cell to another, telling the second cell what to do (divide, become a particular kind of cell, etc.). This process is known as signal transduction and occurs continually during embryonic development.
A protein known as Smoothened is a critical part of signal transduction, and defects in the protein can lead to some forms of cancer and birth defects. In the study, scientists were able to identify how the Smoothened protein works and where it is located in the cell: on a structure known as the primary cilium, whose purpose until now has been unknown.
According to the press release,
Hedgehog signals play an important role in prompting embryonic and adult stem cells to differentiate into some of the specialized cells that make up the body's tissues -- such as those of the brain, pancreas and skin. The new finding, says Reiter, will advance scientists [sic] efforts to use signaling molecules to direct the differentiation of embryonic stem cells in the culture dish, with the goal of using them to replace or replenish damaged tissues in patients.
The discovery could be particularly important for neural stem cell research, says Arnold Kriegstein, MD, PhD, director of the UCSF Institute for Stem Cell and Tissue Biology. Kriegstein, a neural stem cell scientist, was not an author on the study.
The study was performed in several steps. First, the scientists studied where Smoothened was expressed in the embryonic cell and found that it was on the primary cilium. They then tested how Smoothened behaved when exposed to Hedgehog signals and when blocked from Hedgehog signals. When blocked, it did not appear on the cilium. Thirdly, they investigated whether a particular amino acid was necessary for the movement of the protein to the cilium (it was). They concluded by testing if the protein could still function when it could no longer move to the cilium, and found that it did not.
Clearly the study is not going to lead immediately to any medical treatments or even to improved ways to culture stem cells of any type. But the more that is known about cell biology, the more future research can be targeted to specific goals.