Researchers at the Gladstone Institute for Cardiovascular Disease found a genetic factor that helps in the earliest stages of heart development as the primitive tube loops around on itself and forms the separate chambers. This factor — a short relative of DNA called microRNA — has an identical counterpart in humans, leading the researchers to believe that their work in fish is likely to relate directly to human heart development. When the researchers interfered with this microRNA while the heart was developing, the immature heart muscle cells failed to mature and the heart chambers didn’t form normally. These heart muscle precursors are a stage in between the embryonic stem cell and the mature heart muscle cell. The heart is among the first organs to develop and also the most critical. When the heart doesn’t develop properly the embryo dies. What’s more, common birth defects involve abnormalities in how these chambers form. Understanding all the steps between an embryonic stem cell and the mature heart cell could help researchers prevent or treat birth defects of the heart.
Researchers at the Stanford University School of Medicine have found that clusters of embryonic stem cells in a lab dish share some unexpected similarities with actual embryos. These clumps, called embryoid bodies, consist of hundreds of cells, many of which begin to form more mature cell types. For example, they often contain groups of primitive heart muscle cells that beat visibly. In this work the researchers found that the embryoid bodies also contain a line of cells that resemble an embryonic structure called the primitive streak. This streak is the first indication that the embryo has a top and bottom or back and front. Blocking molecules found in the embryoid body primitive streak pushed those cells to form a group of cells that make up skin and nerves. Enhancing those molecules pushed the cells to form cell types like muscle and intestine. This work could help researchers learn how to push embryonic stem cells to form particular cell types, which is a necessary step in developing stem cell-based therapies.
Related Information: Press release, Stanford Stem Cell Biology and Regenerative Medicine Institute, Nusse lab page
Researchers at UC, San Francisco developed a novel way of finding out the role of DNA-relatives called microRNA. These molecules are known to turn genes on and off and appear to regulate whether embryonic stem cells remain as stem cells or develop into mature cell types, but learning which genes are controlled by each microRNA has been a challenge. Using this screen, the researchers found 14 microRNAs that speed up cell division; of those, five are commonly found in human embryonic stem cells. It turns out these microRNAs deactivate genes that slow the cell cycle, essentially releasing the brakes on cell division. Identifying the role of these and other microRNAs could help researchers understand how to hold embryonic stem cells in their immature state, guide how those cells mature, or even develop treatments for cancer.