The role of intercellular bridges in fetal germ cell development

Objective: Intercellular bridges (ICBs) are transient structures which form during cytokinesis step of somatic cell division. They transform into permanent structures with the presence of TEX14 protein in differentiating mice germ cells. The role of ICBs in mammalian female germ cell development is still unclear. In our study, we analyzed the role of ICBs in the synchronization of meiosis and establishment of germ cell pool by using 3D analyzing method and Tex14 mutant (Tex14-/-) mice, which lack ICBs in germ cells. Method: Wholemount immunofluorescent staining was performed, Tex14+/+ and Tex14-/- germ cells were labelled with meiosis and apoptosis markers. 3D maps of ovaries were created by using Imaris software and MATLAB. Clustering analysis of germ cells was also applied. Germ cell elimination was analyzed in the absence or presence of ICBs in Tex14+/+ and Tex14-/- ovaries which were subjected to chemical stress. Results: Meiosis first started as a radial meiotic wave and anterior-posterior (AP) meiotic wave was effective in the ovaries earliest at E13.5. The radial wave was absent and pre-mature meiotic entry was observed in Tex14-/-. Germ cell numbers were decreased and germ cell death were increased in Tex14-/- compared to Tex14+/+ when germ cell elimination occurred through apoptosis. Unlike Tex14+/+, Tex14-/- germ cells were eliminated randomly. When ovaries were subjected to chemical stress, further increase of apoptosis following chemical stress was modest in Tex14-/- compared to Tex14+/+ ovaries. Conclusion:In our study, the roles of ICBs in the regulation of radial meiotic wave and in calibrating the threshold of apoptosis in germ cells in the developing ovary were revealed for the first time. Studying germ cell development in great detail will allow us to gain deeper understanding in mechanisms which play a role during the establishment of ovarian reserve and will enlighten infertility, subfertility and aneuploidy defects in females.