Germline Quotes

“Though the Drosophilia ovary is a structure with a different purpose - one designed to make fly eggs, not blood cells - the ovary, and specifically, the substructure of the ovary known as the 'germarium', have similarities with what was described for hematopoiesis. The organization of the cells that make up the germarium can be likened to a knitted winter hat pulled over the wearer's head. The extreme end - the pompon - comprises a set of cells called the 'terminal filament' cells; the top of the hat is formed by anterior 'cap' cells; and the sides of the hat are made up of more lateral 'inner sheath' cells that surround the GSCs themselves. Within this small cluster of cells, precise positions matter. When a GSC divides in two, one cell remains in contact with the cap cells and the other loses this immediate proximity. The cell that remains in contact with cap cells remains a GSC. The more posterior-positioned cell, by contrast, goes on to form an egg. A similar setup exists in the Drosophilia testes, in which 'hub' cells sit immediately anterior to the male GSCs. A question arises, what is special about the proximity of a GSC to a cap cell that keeps one daughter of a recently divided stem a stem cell while its sister goes on to form an egg?”
― Stephanie Elizabeth Mohr, First in Fly: Drosophila Research and Biological Discovery

“The study of stem cell niches in mammalian systems presents an 'arduous endeavor'; in comparison, the fly germarium is relatively easy to manipulate. In the 1990s, H. Lin, A.C. Spradling, and others used of a number of approaches to study Drosophilia GSCs and their niche, including killing specific cells in the germarium with precisely directed lasers; transplantation of cells from the ovary of one fly to another; and genetic perturbations that included the dialing up or down of Hh pathway signaling. The researchers found that following laser ablation of cells surrounding the GSCs - that is killing the niche cells - all the GSCs went on to form eggs, and the system was quickly depleted of its GSC reserve. Moreover, through genetic analyses the researchers identified specific genes required in the niche cells to maintain GSCs within the niche, as would be deduced for a gene that, when disrupted in niche cells, has the same effect as laser ablation of those cells. These studies are credited with providing the first clear experimental evidence of a stem cell niche, as well as defining what genes - what signaling pathways and other cellular activities - are important to the process. Many of the same pathways relevant in other cell types proved relevant to communication between the niche and GSCs, including the Hh pathway. The genes required for suppression of transposon mobilization by the piRNA system also have relevance to the GSC niche; disruption of the piwi gene, for example, can lead to uncontrolled proliferation of GSCs.”
― Stephanie Elizabeth Mohr, First in Fly: Drosophila Research and Biological Discovery