Browsing by Subject "Oct4"
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Item Oct4 lineage tracing of spermatogonial stem cells in the adult mouse testes(2013-12) Haider, Kerri TanaSpermatogenesis 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.Item A study of primary and secondary heart field populations in iPS cell-derived embryoid bodies(2013-12) Johnson, Caitlin M.As an embryo develops, the heart is the first functional organ to form. There are four cell populations that are the primary contributors to the developing heart during embryogenesis. The populations which comprise the majority of the organ are the primary and secondary heart fields. The primary heart field commits to the cardiac lineage slightly before the secondary heart field in development. During cardiac lineage commitment, cells pass through a series of stages before becoming terminally differentiated. Prior to differentiation, cells express the transcription factor Oct4 which functions to maintain the pluripotent state of the cell. Oct4 has been also proposed to play a direct role in early stages of cardiac lineage commitment. We used an Oct4-CreER reporter iPS cell line with embryoid body differentiation to determine presence of Oct4 transcript at a given time to study the cells of primary and secondary heart fields. Use of this system allowed us to separate cells based on Oct4 expression, and further characterize the gene expression in these populations. We probed for the gene expression patterns of the heart fields to test the role of Oct4 expression in the individual fields.