Germline stem cell niches

Germline stem cells (GSCs) can generate haploid gametes, sperms or oocyte, which are responsible for transmitting genetic information from generation to generation. Because GSCs can be easily identified and gene functions can be readily manipulated in Drosophila and C. elegans, their niches were among the first to be functionally and anatomically defined. Genetic and cell biological studies in these systems have first shown that stem cell function is controlled by extracellular cues from the niche, and intrinsic genetic programs within the stem cells. Important progress has also recently been made in localizing GSCs in the mouse testis. Here I will review recent progress and compare the differences and commonalities of GSC niches from different systems. Since the studies on GSC niches in Drosophila and C. elegans have provided guiding principles for initial identification of niches in other systems, I hope that this review will provide some stimulating thoughts about niche structures and functions of adult stem cells in somatic systems.