Spermatogenesis in mammals occurs in the testes to produce mature sperm for reproductive purposes. Spermatogonia are derived from primordial germ cells. Undifferentiated spermatogonia are thought to arise from a small population of cells arranged around the basal membrane of the seminiferous tubule, called spermatogonial stem cells (SSCs). SSCs divide either symmetrically or asymmetrically to maintain the stem cell pool and give rise to daughter cells. The identity of the spermatogenic stem cell remains unclear. Numerous researchers have attempted to isolate the SSC population but in most cases they also labeled progeny of the SSCs, so a definitive population of SSCs has yet to be isolated. Oct4 is a protein that is expressed in pluripotent cells and has been described as being expressed in undifferentiated SSCs. In adult male Oct4:CreER mTmG transgenic mice GFP expression indicating Oct4 driven tamoxifen inducible CreER recombination is observed only in the testes. Here we describe using this transgenic mouse to identify and lineage trace the progeny of Oct4:CreER expressing cells in the adult mouse testes using multiple tamoxifen pulse and chase experiments. In 4-day chase experiments single GFP expressing cells along the edge of the basal lamina are observed. Longer 10-day chase experiments show aligned spermatogonia expressing GFP in chains of 2, 4 and 8 cells linearly placed on the basal lamina of the tubule. Fallowing extended chase periods after tamoxifen administration GFP expressing cells are seen in all stages of spermatogenesis. Our results are consistent with the cells labeled immediately after tamoxifen addition being the spermatogenic stem cell.
University of Minnesota M.S. thesis. December 2013. Major: Stem Cells Biology. Advisor: Dr.James Dutton. 1 computer file (PDF); vii, 53 pages.
Haider, Kerri Tana.
Oct4 lineage tracing of spermatogonial stem cells in the adult mouse testes.
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