Researchers have made a finding in the mouse embryo that they say provides a fundamental insight into how the body forms in mammals. And this information, they say, might be useful in the future in regulating the differentiation of embryonic stem cells.

The investigators, including Cambridge University's Magdalena Zernicka-Goetz, PhD, and UC San Francisco's Roger Pedersen, PhD, discovered that the tiny mass of cells that forms in the first days following fertilization of the egg has already taken on an organizational structure and begun to initiate events that predict the spatial patterning of the later embryo.

They made their discovery by tracing the fate and behavior of a key group of cells in the early embryo, known as the inner cell mass, from its origin in the so-called blastocyst stage -- when the embryo is a free-floating, hollow ball of cells -- through to its progression into the later embryo, implanted in the uterine wall.

The finding, which showed that the inner cell mass projected a clear and consistent pattern of organization from the preimplantation blastocyst to the implanted embryo -- when the body forms -- offers profound insight into the timing and process by which mammals begin to take shape. The discovery, made by scientists at the Wellcome/CRC Institute, University of Cambridge and UCSF, is published in the current issue of Development.

The researchers conducted their study by focusing on the development of a type of cell known as visceral endoderm, which emerges in the embryo as it begins to implant in the uterine wall. They believe that the cell plays a role in the organization of the embryo at the next stage of development, gastrulation -- a process that gives rise to the three primary tissues from which all organs and cells of the body emerge, including pancreas, beating heart and brain cells.

These three primary tissues, endoderm, mesoderm and ectoderm, originate from the inner cell
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Contact: Jennifer O'Brien
jobrien@pubaff.ucsf.edu
415-476-2557
University of California - San Francisco
19-Dec-1999