Febrary 26, 2014

Not all stem cells are created equally. Some are totipotent, meaning they can divide and differentiate into any cell type, while some are unipotent, meaning they can differentiate into one specific cell type. Understanding the potenty of various stem cells is an important step towards understanding how tissues are developed, remodeled, and maintained. Today’s beautiful images are from a study of stem cells in the mammary gland.

Mammary glands go through a lot of changes during both puberty and adulthood, and are made up of two main cell lineages—myoepithelial and luminal. The function of mammary stem cells was previously unclear—in one model, bipotent stem cells contribute to the development and maintenance of adult mammary glands, while in the other model, those stem cells are unipotent and separately control mammary gland lineages. A recent cell fate mapping study by Rios and colleagues featured the use of multicolor reporters and 3D imaging. Rios and colleagues found that mammary stem cells are indeed bipotent, and function in ductal remodeling and homeostasis in the adult mammary gland. In the image above, the sea of colorful cells seen in the mid-puberty mouse mammary gland (top) indicates the presence of multiple progenitors. The arrow and arrowhead in the inset image point to myoepithelial and luminal cells, respectively. As puberty progressed (bottom), discreet regions of similarly-colored cells indicate clonal expansion and a shift towards adulthood.

Rios, A., Fu, N., Lindeman, G., & Visvader, J. (2014). In situ identification of bipotent stem cells in the mammary gland Nature, 506 (7488), 322-327 DOI: 10.1038/nature12948
Adapted by permission from Macmillan Publishers Ltd, copyright ©2014