2002-12-31 17:00:09 -0400
By Linda Carroll
By knocking out a gene in mice, researchers have discovered it plays a key role in embryonic stem cell development.
The gene, dubbed Sox2, helps maintain the ability of these stem cells to grow into a variety of different types of cells, according to a report published in the journal Genes & Development.
Sox2 is the second gene discovered that helps stem cells maintain "plasticity," according to study co-author Dr. Robin Lovell-Badge, a researcher in the Division of Developmental Genetics at the MRC National Institute for Medical Research in London. The first gene was called Oct4.
"In the absence of either gene, these cells lose their plasticity and can no longer be this type of cell," Lovell-Badge said in an interview with Reuters Health. "Rather than die, they become one of the specialized cell types found in the early embryo."
Researchers have been trying to tease out the process by which embryonic stem cells develop in order to design therapies for a variety of conditions, including brain and nerve damage, says Gregory Stock, director of the Program on Medicine, Technology and Society at the University of California Los Angeles School of Public Health.
"Undifferentiated cells go through a pathway of differentiation to all the various structures and cell types in the body," Stock explained in an interview with Reuters Health. "What researchers are trying to do is to find out how cells move down these pathways to becoming particular tissue types,"
Ultimately, the goal is to be able to take stem cells and guide them into becoming specific types of cells, Stock said. "You could perhaps shepherd them down a pathway to tissue that could be transplanted into the brain or spinal cord for people with injuries to these areas," he added.
Sox2 and Oct4--and perhaps some other yet-to-be discovered genes--act as a committee to direct early embryo growth, Lovell-Badge said.
These two genes come into play early in the development of the embryo, when it is just a rolling ball of cells known as a blastocyst. At this point in development, the cells of the embryo start to specialize.
Those on the surface of the blastocyst become trophoblast cells, which eventually turn into the placenta. The cells on the inside of the blastocyst--the inner cell mass--give rise to two kinds of cells: The epiblast cells, which ultimately grow into a fetus, and hypoblast cells, which become the yolk sac.
Mouse embryos that lack Sox2 fail after day 6 of development. The mother seems to provide adequate levels of the factor before this point. But without the ability to make its own Sox2, the embryo can produce no epiblast cells and fails to develop further, according to the report.
SOURCE: Genes & Development January 1, 2003.
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