Coordinated action of the ECM and gene expression in the ovarian stem cell niche

Abstract

Most of the studied tissues harbour stem cell populations necessary for both tissue homeostasis and repair after damage. Stem cells are found generally in microenvironments or `niches¿ that regulate their proliferation and prevent the pull towards differentiation characteristic of most cell types. One such a niche has been described in the Drosophila ovary, which contains two populations of stem cells, one of germline origin (Germline Stem Cells; GSCs) and one of somatic origin (Follicle Stem Cells; FSCs) and that are both ultimately responsible for the continuous production of new eggs during adulthood. The correct functioning of the niche relies, among other factors, on stem cell-niche cell signalling and on the extracellular matrix (ECM), which provides physical support to the homed stem cells. The biomechanical properties of niches are recognised as essential factors in stem cells activity and thus tissue homeostasis, and the ECM is a key component in the determination of the biophysical properties of the niche. During the past few years we have determined that timp mutant GSCs lengthened the S phase and shortened the G2 phase during their divisions. In addition, we have also measured the dynamics of centrosome movements during the cell cycle in control and timp mutant GSCs. Our preliminary data indicate that both centrosomes in control GSCs behave differently so that the centrosome to remain within the GSC daughter is less motile than the future CB centrosome. On the contrary, mutant centrosomes are more dynamic than control ones.