Platypus Induced Pluripotent Stem Cells: the Unique Pluripotency Signature of a Monotreme

Abstract

Summary StatementThe generation and transcriptome analysis of the first induced pluripotent stem cells from the platypus reveals SOX2 has been a key driver of the expanded pluripotency regulatory network in placental mammals.ABSTRACTThe mechanisms by which pluripotency has evolved remain unclear. To gain insight into the evolution of mammalian pluripotency we have generated induced pluripotent stem cells (piPSCs) from the platypus. Deep sequencing of the piPSC transcriptome revealed that piPSCs robustly express the core eutherian pluripotency factors OCT4, SOX2 and NANOG. Given the more extensive role of SOX3 over SOX2 in avian pluripotency, our data indicate that between 315 million years and 166 million years ago primitive mammals replaced the role of SOX3 in the vertebrate pluripotency network with SOX2. DAX1/NR0B1 is not expressed in piPSCs and an analysis of the platypus DAX1 promoter revealed the absence of a proximal SOX2-binding DNA motif known to be critical for DAX1 expression in eutherian pluripotent stem cells, suggesting that the acquisition of SOX2 responsiveness by DAX1 has facilitated its recruitment into the pluripotency network of eutherians. We further show that the expression ratio of X chromosomes to autosomes (X1-5 X1-5:AA) is approximately equal to 1 indicating that there is no upregulation of X-linked genes and that there is no preference for silencing of maternal or paternal alleles (ie imprinting).

Genetic Signatures of Evolution of the Pluripotency Gene Regulating Network across Mammals

“…ESRRB has been proposed to be recruited to the Eutheria PGRN after the divergence of marsupials and Eutheria because neither Tasmanian devil nor platypus iPSCs express ESRRB ( Weeratunga et al. 2018 ; Whitworth et al. 2019 ).…”

“…2013 ), Metatheria ( Weeratunga et al. 2018 ), Monotremata ( Whitworth et al. 2019 ), Perissodactyla ( Ben-Nun et al.…”

Induced pluripotent stem cells throughout the animal kingdom: Availability and applications

“…Additional exotic animals for which iPSCs have been generated include platypus[164] and mink[165] (Supplemental material 8). In contrast, it has proven challenging to generate iPSCs from more common but non-mammals model species such as drosophila and zebrafish.…”

A stem cell-based approach to the treatment of devil facial tumour disease (DFTD) in the Tasmanian devil (Sarcophilus harrisii)

“…OCT4 arose by duplication of the ancestral gene, POU2, early in the evolution of tetrapods, and while POU2 has been lost from the genome of eutherian mammals, it persists in the genomes of marsupials and monotremes (Frankenberg et al, 2010) (Figure 5-1). However, recent data shows that in platypus iPSCs the level of POU2 transcription is below the threshold considered to represent expression (Whitworth et al, 2019). In devil iPSCs, in addition to the co-expression of both OCT4 and POU2, the expression level of POU2 was several fold higher than the expression level of OCT4.…”

“…Expression of DAX1 in DeviPSCs, but not in monotreme iPSCs (Whitworth et al, 2019), suggests the recruitment of DAX1 to the therian pluripotency network before the divergence of marsupials and eutherians. Expression of ESRRB in the eutherian pluripotency network clearly indicates a more recent co-option of ESRRB into the therian pluripotency network.…”