Researchers at the University of California, San Diego School of Medicine, and collaborating institutions have identified a protein critical to hematopoietic stem cell function and blood formation. The finding has potential as a new target for treating leukemia because cancer stem cells rely upon the same protein to regulate and sustain their growth. Hematopoietic stem cells give rise to all other blood cells. Writing in the February 2, 2014 advance online issue of Nature Genetics, principal investigator Tannishtha Reya, Ph.D., professor in the Department of Pharmacology, and colleagues found that a protein called Lis1 fundamentally regulates asymmetric division of hematopoietic stem cells, assuring that the stem cells correctly differentiate to provide an adequate, sustained supply of new blood cells. Asymmetric division occurs when a stem cell divides into two daughter cells of unequal inheritance: One daughter differentiates into a permanently specialized cell type while the other remains undifferentiated and capable of further divisions. "This process is very important for the proper generation of all the cells needed for the development and function of many normal tissues," said Dr. Reya. When cells divide, Lis1 controls orientation of the mitotic spindle, an apparatus of subcellular fibers that segregates chromosomes during cell division. "During division, the spindle is attached to a particular point on the cell membrane, which also determines the axis along which the cell will divide," Dr. Reya said. "Because proteins are not evenly distributed throughout the cell, the axis of division, in turn, determines the types and amounts of proteins that get distributed to each daughter cell. By analogy, imagine the difference between cutting the Earth along the equator versus halving it longitudinally.
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