A Single Gene May Regulate Differentiation of Embryonic Cells

Israeli cell biologists have identified the gene whose enzyme product is the main regulator of the gene activity that separates pluripotent embryonic cells from differentiated adult cell types.

Early in the fetal developmental process embryonic cells, which have the potential to develop into all the tissues that make up the organs in the body, come under tight and directed genetic control. When this mechanism kicks in, cells are locked into a specific phenotype. This means, for example, that liver cells can make new liver cells but not lung cells.

In modern medicine there is great interest in the used of pluripotent cells to treat disease syndromes characterized by the loss or death of cells. The use of embryonic tissue to treat Parkinson's disease is one example. However, use of embryonic tissue from fetal sources is complicated by ethical considerations. Another possibility is to return adult cells to an embryonic state. These cells would then be channeled into developing into a different type of tissue.

To date, attempts to convince adult cell types to regress have met with only limited success. Thus, data published in the November 2008 issue of the journal Nature Structural and Molecular Biology by researchers from the Hebrew University of Jerusalem (Israel) is of particular relevance. This study reported that a single gene known as G9a controls the differentiation process. G9a encodes for a histone methyltransferase that affects gene activity in two ways. By catalyzing the methylation of histone proteins, it blocks gene reactivation, and by controlling the methylation of DNA, it prevents reprogramming of genes to the undifferentiated state. Thus, G9a keeps cells locked into their differentiated phenotypes.

Armed with the knowledge generated in this study it may become possible to control or reverse G9a activity in order to produce embryonic-like cells from adult tissues.

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Hebrew University of Jerusalem