Hebrew University scientists reveal mechanism that triggers differentiation of em...( Jerusalem December 21 2008 The mecha...)

Jerusalem, December 21, 2008 The mechanism whereby embryonic cells stop being flexible and turn into more mature cells that can develop into specific tissues has been discovered by scientists at the Hebrew University of Jerusalem. The discovery has significant consequences towards furthering research that will eventually make possible medical cell replacement therapy based on the use of embryonic cells.

At a very early stage of human development, all cells of the embryo are identical, but unlike adult cells are very flexible and carry within them the potential to become any tissue type, whether it be muscle, skin, liver or brain.

This cell differentiation process begins at about the time that the embryo settles into the uterus. In terms of the inner workings of the cell, this involves two main control mechanisms. On the one hand, the genes that keep the embryo in their fully potent state are turned off, and at the same time, tissue-specific genes are turned on. By activating a certain set of genes, the embryo can make muscle cells. By turning on a different set, these same immature cells can become liver. Other gene sets are responsible for additional tissues.

In a recent paper, published in the journal, Nature Structural and Molecular Biology, Professors Yehudit Bergman and Howard Cedar of the Hebrew University-Hadassah Medical School have deciphered the mechanism whereby embryonic cells stop being flexible and turn into more mature cells that can differentiate into specific tissues. Bergman is the Morley Goldblatt Professor of Cancer Research and Experimental Medicine and Cedar is the Harry and Helen L. Brenner Professor of Molecular Biology at the Medical School.

They found in their experiments, using embryos from laboratory mice and cells that grow in culture, that this entire process is actually controlled by a single gene, called G9a, which itself is capable of directing a whole program of changes that invol
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