Weizmann Institute scientists' new technique gets to the root...( In two complementary studies Weizma...),Health

In two complementary studies, Weizmann Institute scientists have developed a new method for reconstructing a cell's 'family tree,' and have applied this technique to trace the history of the development of cancer.

The quest to understand a cell's path of descent, called a cell lineage tree, is shared by many branches of biology and medicine as gleaning such knowledge is key to answering many fundamental questions, such as whether neurons in our brain can regenerate, or whether new eggs are created in adult females.

So far, only tree lineages of tiny organisms, such as worms, which possess only a thousand cells, or 'branches,' have been determined. Now, Prof. Ehud Shapiro of the Institute's Biological Chemistry, and Computer Science and Applied Mathematics Departments, together with Doctoral students Dan Frumkin and Adam Wasserstrom have developed a novel way to reconstruct, in principle, trees for larger organisms, including humans.

The human body is made of about 100 trillion cells, all of which are descendants of a single cell the fertilized egg (zygote). Cells that have undergone a small number of cell divisions are relatively close descendants (akin to branches representing children and grandchildren etc., on a family tree), while some cells may have undergone hundreds or even thousands of divisions ('distant cell generations'). Knowing the number of cell divisions since the zygote, known as the depth of cells, would enable scientists to address questions about the behavior of the body under physiological and pathological conditions.

Until now, estimates of cell depth were based on theoretical calculations and assumptions, but Shapiro provides a practical way of determining cell depth precisely. The concept behind their new method is simple: Previous research indicated that each time a cell divides, harmless mutations are introduced, and that 'cell relatives' of distant generations tend to acquire more mutations, dr
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