POU5F1 Isoforms Show Different Expression Patterns in Human Embryonic Stem Cells and Preimplantation Embryos

Abstract

The contribution of the POU domain, class 5, transcription factor-1 (POU5F1) in maintaining totipotency in human embryonic stem cells (hESCs) has been repeatedly proven. In humans, two isoforms are encoded: POU5F1_iA and POU5F1_iB. So far, no discrimination has been made between the isoforms in POU5F1 studies, and it is unknown which isoform contributes to the undifferentiated phenotype.Using immunocytochemistry, expression of POU5F1_iA and POU5F1_iB was examined in hESCs and all stages of human preimplantation development to look for differences in expression, biological activity, and relation to totipotency. POU5F1_iA and POU5F1_iB displayed different temporal and spatial expression patterns. During human preimplantation development, a significant POU5F1_iA expression was seen in all nuclei of compacted embryos and blastocysts and a clear POU5F1_iB expression was detected from the four-cell stage onwards in the cytoplasm of all cells. The cytoplasmic localization might imply no or other biological functions beyond transcription activation for POU5F1_iB. The stemness properties of POU5F1 can be assigned to POU5F1_iA because hESCs expressed POU5F1_iA but not POU5F1_iB. However, POU5F1_iA is not the appropriate marker to identify totipotent cells, because POU5F1_iA was also expressed in the nontotipotent trophectoderm and was not expressed in zygotes and early cleavage stage embryos, which are assumed to be totipotent. The expression pattern of POU5F1_iA may suggest that POU5F1_iA alone cannot sustain totipotency and that coexpression with other stemness factors might be the key to totipotency.

Expression Pattern of Stemness-Related Genes in Human Endometrial and Endometriotic Tissues

“…The OCT4 splice variants OCT4-A and OCT4-B share an identical C-terminal domain, whereas the recently discovered OCT4-B1 lacks the C-terminal domain because of a stop codon in the cryptic exon 2b, and consequently the IHC data we obtained were potentially related to the OCT4-A and -B isoforms. Nonetheless, because we obtained a clear nuclear localization of the IHC signal for OCT4 (Figure 3), we can argue that it corresponds to the OCT4-A variant, as it has been reported that the OCT-4B variant is localized in the cytoplasm (40,41).…”

Comparative Analysis of Oct4 in Different Histological Subtypes of Esophageal Squamous Cell Carcinomas in Different Clinical Conditions

“…There are two studies (Tai et al, 2005;He et al, 2012) who had reported Oct4 expression by dysplastic and hyperplastic esophageal mucosa confining to the proliferative zone, and not expressed by the normal mucosa. Oct4 positivity is reported in certain adult tissue including benign endometrial stromal cells (Atlasi et al, 2006;Cauffman et al, 2006;Mathai et al, 2006;Katona et al, 2007;Zangrossi et al, 2007;Atlasi et al, 2008;Forte et al, 2009). We observed slightly higher sensitivity by PCR technique than by the conventional immunohistochemistry method in detecting Oct4 expression, which is similar to other reported data (Atlasi et al, 2006;Xi et al, 2011;.…”

In Vivo Osteoprogenitor Potency of Human Stromal Cells from Different Tissues Does Not Correlate with Expression of POU5F1 or Its Pseudogenes

“…We focused on the expression of POU5F1, a pivotal transcriptional regulator of the pluripotent state in embryonic stem cells. POU5F1 exists in two isoforms, POU5F1A and POU5F1B, of which POU5F1A is nuclear-localized and transcriptionally active [8,17]. But, the POU5F1B isoform, which lacks the N-terminal transactivation domain (supplemental online Fig.…”

“…But, the POU5F1B isoform, which lacks the N-terminal transactivation domain (supplemental online Fig. 5), is localized mainly in the cytoplasm of human ESCs [17] and, more importantly, does not sustain self-renewal of ESCs [19]. Primer pairs designed to amplify only true POU5F1A and not its pseudogenes confirmed the expression of POU5F1A in embryonic carcinoma cells but failed to amplify PCR products from peripheral blood mononuclear cells (PBMNC), suggesting POU5F1A is not transcribed in these cells [20].…”

“…Real-time PCR analyses, however, demonstrated a remarkable difference in the level of expression of both POU5F1 transcripts in the pluripotent EC cells compared with MSC and MSC-like cells. The POU5F1A transcript, which encodes a nuclear protein [17] including the complete DNA transactivating N-terminal region, was 970-fold and 205-fold more abundant in EC cells compared with BM-MSC and UVSC, respectively ( Fig. 2B; supplemental online Fig.…”