Mouse totipotent stem cells captured and maintained through spliceosomal repression

Since the establishment of the first embryonic stem cells (ESCs), in vitro culture of totipotent cells functionally and molecularly comparable to in vivo blastomeres with embryonic and extraembryonic developmental potency is unviable. Spliceosomes are responsible for mRNA splicing and maturation. Here, we report that spliceosomal repression in mouse ESCs drives pluripotent-to-totipotent state transition. Using the splicing inhibitor Pladienolide B, we realize in vitro culturing of totipotent ESCs comparable to 2- and 4-cell blastomeres at molecular levels for long-time passages, which are therefore termed as totipotent blastomere-like cells (TBLCs). Mouse chimeric assays combined with single-cell RNA-seq technology demonstrate that TBLCs own a robust bidirectional development capability to generate multiple embryonic and extraembryonic cell lineages. Mechanically, spliceosomal repression causes widespread splicing inhibition of pluripotent genes, whereas the totipotent genes featured with few short introns are efficiently spliced and transcriptionally activated. Our study provides a principle for capturing and maintenance of totipotent stem cells. Poly(A) RNA-seq were performed from mESCs with siRNAs against different splicing factors cultured in Serum/LIF medium, TBLCs cultured in SLP medium and mESCs/H1299 upon high concentration treatment. TBLCs cultured in SLP medium and extracted the RNA and DNA for highthrough sequencing.