The beauty of stem cells is not only in their ability to become other cell types, but also in their ability for self-renewal.  A recent paper in the Journal of Cell Science describes the role of a major signaling network in sperm stem cell self-renewal.

When a stem cell divides, it produces a specialized cell type and another stem cell.  This ability of a stem cell to keep producing more stem cells is referred to as “self-renewal.”  A great example of self-renewal is the population of sperm stem cells, which must provide an organism with life-long sperm production.  Recently, a group looked at sperm stem cell self-renewal, and found a role for the Wnt signaling pathway in the process.  Wnt is a major signaling protein that is important in many processes during the development of an organism, as well as in some cancers.  In this paper, Yeh and colleagues used cultures of sperm stem cells from mice to show that a Wnt protein promotes the maintenance of sperm stem cells as a “cell-extrinsic” factor (meaning it comes from outside of the stem cells).  In addition, Yeh and colleagues found that this Wnt protein is expressed in cells of the testes of newborn mice, as seen in the image above.  Wnt5a gene expression is in red, while the Sertoli cells, which nurture other cells in the testes, are in green.

For a more scientifically detailed description of this image, check out my post on The Node, the community forum for and by developmental biologists.