Evolutionary Conservation of pou5f3 Genomic Organization and Its Dynamic Distribution during Embryogenesis and in Adult Gonads in Japanese Flounder Paralichthys olivaceus.

Jinning Gao,Quanqi Zhang,Xubo Wang

doi:10.3390/ijms18010231

Jinning Gao, Quanqi Zhang + Show 1 more

Open Access

https://doi.org/10.3390/ijms18010231

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Abstract

Octamer-binding transcription factor 4 (Oct4) is a member of POU (Pit-Oct-Unc) transcription factor family Class V that plays a crucial role in maintaining the pluripotency and self-renewal of stem cells. Though it has been deeply investigated in mammals, its lower vertebrate homologue, especially in the marine fish, is poorly studied. In this study, we isolated the full-length sequence of Paralichthys olivaceus pou5f3 (Popou5f3), and we found that it is homologous to mammalian Oct4. We identified two transcript variants with different lengths of 3′-untranslated regions (UTRs) generated by alternative polyadenylation (APA). Quantitative real-time RT-PCR (qRT-PCR), in situ hybridization (ISH) and immunohistochemistry (IHC) were implemented to characterize the spatial and temporal expression pattern of Popou5f3 during early development and in adult tissues. Our results show that Popou5f3 is maternally inherited, abundantly expressed at the blastula and early gastrula stages, then greatly diminishes at the end of gastrulation. It is hardly detectable from the heart-beating stage onward. We found that Popou5f3 expression is restricted to the adult gonads, and continuously expresses during oogenesis while its dynamics are downregulated during spermatogenesis. Additionally, numerous cis-regulatory elements (CRE) on both sides of the flanking regions show potential roles in regulating the expression of Popou5f3. Taken together, these findings could further our understanding of the functions and evolution of pou5f3 in lower vertebrates, and also provides fundamental information for stem cell tracing and genetic manipulation in Paralichthys olivaceus.

Highlights

Octamer-binding transcription factor 4 (Oct4) is a member of the POU transcription factor family Class V, which is essential for maintaining the pluripotency and self-renewal of stem cells
A study found that the expression of pou5f3 in differentiated medaka embryonic stem cells (ESCs) is reduced more than four-fold compared to their level in undifferentiated state ESCs, which reveals its crucial role in maintaining stem cell pluripotency [22]
The deduced PoPou5f3 contained an open reading frame (ORF) with 1428 bp encoding a protein of 475 amino acids with a calculated molecular mass (MM) of 51.98 kDa and a theoretical isoelectric point (PI) of 6.28 (GenBank accession number: KJ522774) (Figure 1A and Figure S1)

Summary

Introduction

Octamer-binding transcription factor 4 (Oct4) is a member of the POU transcription factor family Class V, which is essential for maintaining the pluripotency and self-renewal of stem cells. As with other Oct proteins, Oct can recognize and bind to the octamer motif through its DNA-binding segments on the POU domain to activate or inhibit the transcription of downstream target genes [2] It can cooperatively interact with Sox to form complexes by binding to Oct-Sox motif to drive pluripotent-specific gene expression [3,4]. In addition to pluripotency regulation, zebrafish pou5f3 (originally named pou2/spg) has some new roles as well as partial function loss when compared with other species. It has a different expression pattern after the gastrula stage, which is expressed in developing brain and plays an important role in regionalization [16]. Medaka pou5f3 is able to reprogram somatic cells into pluripotent cells [23]

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Conclusion