Newer Insights Into Premeiotic Development of Germ Cells in Adult Human Testis Using Oct-4 as a Stem Cell Marker

Abstract

The transcription factor octamer-binding transforming factor 4 (Oct-4) is central to the gene regulatory network responsible for self-renewal, pluripotency, and lineage commitment in embryonic stem (ES) cells and induced pluripotent stem cells (PSCs). This study was undertaken to evaluate differential localization and expression of two major transcripts of Oct-4, viz. Oct-4A and Oct-4B, in adult human testis. A novel population of 5- to 10-μm PSCs with nuclear Oct-4A was identified by ISH and immunolocalization studies. Besides Oct-4, other pluripotent markers like Nanog and TERT were also detected by RT-PCR. A(dark) spermatogonial stem cells (SSCs) were visualized in pairs and chains undergoing clonal expansion and stained positive for cytoplasmic Oct-4B. Quantitative PCR and Western blotting revealed both the transcripts, with higher expression of Oct-4B. It is proposed that PSCs undergo asymmetric cell division and give rise to A(dark) SSCs, which proliferate and initiate lineage-specific differentiation. The darkly stained nuclei in A(dark) SSCs may represent extensive nuclear reprogramming by epigenetic changes when a PSC becomes committed. Oct-4B eventually disappeared in mature germ cells, viz. spermatocytes, spermatids, and sperm. Besides maintaining normal testicular homeostasis, PSCs may also be implicated in germ cell tumors and ES-like colonies that have recently been derived from adult human testicular tissue.

Studying the expression patterns of OCT4 and SOX2 proteins in regenerating rabbit ear tissue

“…Similar to our results, this antibody showed nuclear and also weak cytoplasmic signals (Warthemann et al, 2012). The authors suggested that this antibody was not capable of distinction between OCT4A and OCT4B isoforms and could also detect an unrelated epitope to OCT4 (Bhartiya et al, 2010;Warthemann et al, 2012). OCT4A is a nuclear protein that is involved in stemness and pluripotency, while OCT4B isoform is mainly present in cytoplasm and it is related to stress response of the cells (Cauffman et al, 2005).…”

Pluripotent Stem Cells in Bone Marrow and Cord Blood

“…We have reported for the first time the presence of a distinct population of VSELs with nuclear OCT-4 in adult mouse [48] and human [47] testis, located towards the basement membrane of the seminiferous tubules. Besides, we also detected a progenitor stem cell population with cytoplasmic OCT-4, which was slightly bigger and had abundant cytoplasm.…”

“…The Umbilical Cord Blood (UCB)-purified VSELs have also been reported to differentiate into neural cells [44] and after co-culture over OP-9 stroma cells were specified into HSCs similar to murine BM-derived VSELs [45]. Apart from umbilical cord blood and bone marrow, VSELs have also been reported in Wharton's jelly and gonadal tissue [46][47][48][49][50][51]. Their presence amongst the MSCs in the Wharton's jelly is in agreement with observations made by other groups that MSCs contain a sub-population of more primitive stem cells [52] or even as postulated by Taichman and group [53] that VSELs are precursors of MSCs.…”

FSH–FSHR3–stem cells in ovary surface epithelium: basis for adult ovarian biology, failure, aging, and cancer

“…Although the concept of stem cells in adult ovaries is still not well accepted -the conflict appears to be more technical (Bhartiya 2012, Bhartiya et al 2013a) and hopefully will be resolved in due course. In addition to the seminal contributions made by Jonathan Tilly's group in the field, recently equating ovarian stem cells (OSCs) to spermatogonial stem cells (SSCs) in testis , and their protocols to isolate OSCs , our group has reported an additional population of stem cells (VSELs) in both ovary and testis (Bhartiya et al 2010, 2013b, Parte et al 2011, in addition to the OSCs/OGSCs.…”

“…On comparing POF in women with azoospermia in men, it is indeed intriguing that similar to POF, genetic basis for azoospermia is also not yet deciphered and no significant association is reported with the FSHR gene (or any other) and male infertility. VSELs exist in human (Bhartiya et al 2010) and mouse (Anand et al 2014) testis as in the ovaries and nuclear OCT4 is a specific and sensitive marker for testicular cancers (Jones et al 2004). Studies are currently ongoing in our laboratory to study the effect of FSH on testicular stem cells before we implicate FSH-FSHR3-stem cell interaction in testicular biology and azoospermia as well.…”