Journal of Stem Cell Research & Therapy

Abstract

The Universality of Asymmetric Division

Matilde Canelles

Asymmetric division, a process by which stem cells divide to generate the diversity of cell types that populate adult organisms, has been extensively studied in the last decade. This has led to many exciting discoveries that help us understand how this complicated process is orchestrated. In 1996, Zhong [1] first described this phenomenon in the mammalian neural system: stem cells segregate the fate determinant Numb asymmetrically, thus generating daughter cells with different doses of Numb and different fates. Later, it has been established that one of them usually terminally differentiates, while the other continues proliferating and retains stem cell properties. The ratio between symmetric and asymmetric division is, therefore, a crucial means to maintain a balance between the number of precursors and differentiated cells at each developmental stage. Asymmetric division has been found in virtually all developing systems where stem cells need to simultaneously proliferate and generate differentiated cells: brain, skin, gut, mammary gland, hematopoiesis of mammals (see [2] for a comprehensive review), also in plants [3] and algae [4]. This phenomenon is so ubiquitous that the focus of current research has moved from describing its existence in a certain system to establishing its still enigmatic mechanism; the discovery of links to cancer in Drosophila and hematopoiesis [5] has added momentum to an already very dynamic research area.