POU5F1 isoforms show different expression patterns in human embryonic stem cells and preimplantation embryos

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Molecular Genetics

Background:

• POU domain, class 5, transcription factor-1 (POU5F1) is crucial for totipotency in human embryonic stem cells (hESCs).
• Two human isoforms, POU5F1_iA and POU5F1_iB, exist, but their specific roles in totipotency remain unclear.
• Previous studies have not differentiated between POU5F1 isoforms, potentially obscuring their individual contributions to the undifferentiated phenotype.

Purpose of the Study:

• To investigate the distinct expression patterns and biological activities of POU5F1_iA and POU5F1_iB during human preimplantation development and in hESCs.
• To determine which POU5F1 isoform contributes to the undifferentiated phenotype and totipotency.
• To assess the suitability of POU5F1_iA as a marker for totipotent cells.

Main Methods:

• Immunocytochemistry was employed to examine the expression of POU5F1_iA and POU5F1_iB.
• Expression analysis was conducted in human embryonic stem cells (hESCs) and across all stages of human preimplantation development.
• Localization and temporal expression patterns of both isoforms were analyzed.

Main Results:

• POU5F1_iA and POU5F1_iB exhibit differential temporal and spatial expression during human preimplantation development.
• POU5F1_iA was predominantly found in the nuclei of compacted embryos and blastocysts, while POU5F1_iB was detected in the cytoplasm from the four-cell stage.
• hESCs expressed POU5F1_iA but not POU5F1_iB, suggesting POU5F1_iA is associated with stemness properties.

Conclusions:

• The stemness properties of POU5F1 in hESCs are attributable to POU5F1_iA.
• POU5F1_iA is not a definitive marker for totipotency as it is expressed in the trophectoderm and absent in early totipotent stages.
• Totipotency likely depends on the coexpression of POU5F1_iA with other stemness factors, rather than POU5F1_iA alone.