Abstract
The developmental potential within pluripotent cells in the canonical model is restricted to embryonic tissues, whereas totipotent cells can differentiate into both embryonic and extraembryonic tissues. Currently, the ability to culture in vitro totipotent cells possessing molecular and functional features like those of an early embryo in vivo has been a challenge. Recently, it was reported that treatment with a single spliceosome inhibitor, pladienolide B (plaB), can successfully reprogram mouse pluripotent stem cells into totipotent blastomere-like cells (TBLCs) in vitro. The TBLCs exhibited totipotency transcriptionally and acquired expanded developmental potential with the ability to yield various embryonic and extraembryonic tissues that may be employed as novel mouse developmental cell models. However, it is disputed whether TBLCs are ‘true’ totipotent stem cells equivalent to in vivo two-cell stage embryos. To address this question, single-cell RNA sequencing was applied to TBLCs and cells from early mouse embryonic developmental stages and the data were integrated using canonical correlation analyses. Differential expression analyses were performed between TBLCs and multi-embryonic cell stages to identify differentially expressed genes. Remarkably, a subpopulation within the TBLCs population expressed a high level of the totipotent-related genes Zscan4s and displayed transcriptomic features similar to mouse two-cell stage embryonic cells. This study underscores the subtle differences between in vitro derived TBLCs and in vivo mouse early developmental cell stages at the single-cell transcriptomic level. Our study has identified a new experimental model for stem cell biology, namely ‘cluster 3’, as a subpopulation of TBLCs that can be molecularly defined as near totipotent cells.
Highlights
Life starts from a single fertilized egg, proliferates into two, four, eight, and sixteen cells, and into blastocysts
To analyze the transcriptomic profile of in vivo mouse early developmental stages and totipotent blastomere-like cells (TBLCs), scRNA-seq datasets were downloaded from the Gene Expression Omnibus (GEO) website Available online:https://www.ncbi.nlm.nih.gov/geoprofiles/
12 July 2021) Through unsupervised clustering followed by UMAP dimensional reduction plotting, TBLCs and in vivo mouse early development cells were segregated into clusters and each cluster was labeled (Figure 3A,B)
Summary
Life starts from a single fertilized egg, proliferates into two, four, eight, and sixteen cells, and into blastocysts. But not the later blastocyst cells, are considered totipotent. The stringent definition of totipotency is the ability of a single cell to develop into an entire organism. The remaining single blastomere was subsequently transferred to a surrogate mother, from which a newborn was developed to term. This experiment was the first to prove that individual two-cell blastomere cells have the developmental potential equivalent to a zygote, both of which are currently considered as totipotent. For the more lenient definition, interestingly, a recent study identified a transient subpopulation within mouse pluripotent stem cell (PSC) cultures that share totipotent features and developmental potential equivalent to the two-cell stage embryonic cells, which are referred to as ‘2-cell-like cells’ (2CLCs). The 2CLCs have provided an in vitro cell culture model for further studies on cellular totipotency [5,6]
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