Zscan4 transiently reactivates early embryonic genes during the generation of induced pluripotent stem cells

Abstract

The generation of induced pluripotent stem cells (iPSCs) by the forced expression of defined transcription factors in somatic cells holds great promise for the future of regenerative medicine. However, the initial reprogramming mechanism is still poorly understood. Here we show that Zscan4, expressed transiently in 2-cell embryos and embryonic stem cells (ESCs), efficiently produces iPSCs from mouse embryo fibroblasts when coexpressed with Klf4, Oct4, and Sox2. Interestingly, the forced expression of Zscan4 is required only for the first few days of iPSC formation. Microarray analysis revealed transient and early induction of preimplantation-specific genes in a Zscan4-dependent manner. Our work indicates that Zscan4 is a previously unidentified potent natural factor that facilitates the reprogramming process and reactivates early embryonic genes.

Zscan4 promotes genomic stability during reprogramming and dramatically improves the quality of iPS cells as demonstrated by tetraploid complementation

“…We found that Zscan4f strongly enhanced reprogramming efficiency in combination with OSK or OSKM ( Figure 1B), while the other two factors did not enhance iPS cell formation. This is consistent with a recent independent study, which also showed the enhancement of reprogramming efficiency by Zscan4 [27].…”

“…In our study, we identified Zscan4 as a factor, essential for cleavage development of mouse embryos [23], which not only remarkably promotes the efficiency of iPS cell generation, but also significantly improves the quality of iPS cells by stabilizing the genomic and telomere DNA and promoting the telomere elongation at early stage of reprogramming. Consistently, a recent independent study [27] also verified that Zscan4 can improve the reprogramming efficiency.…”

Generation of induced pluripotent stem cells without genetic defects by small molecules

“…Zscan4 promotes the efficiency and quality of iPSC generation, although it is only transiently activated for the initial few days during the early reprogramming process [32,33]. This finding strongly suggests that activation of Zscan4 may improve the quality of iPSCs during early reprogramming and long-term culture.…”

“…Considering the beneficial effects of Zscan4 gene expression in previous studies [31,32,35], we examined whether the small molecules enhance Zscan4 expression and preserve the genomic stability of iPSCs during reprogramming. Zscan4 promotes telomere elongation without activation of telomerase [33] and plays important roles in the maintenance of genomic stability in ESCs and iPSCs [31,33].…”

Inferring the choreography of parental genomes during fertilization from ultralarge-scale whole-transcriptome analysis

“…Approximately 45% (173 out of 383) of the transcripts also showed up-regulation during the 1C-to-2C transition; as 150 of these were expressed in sperm, this again suggested that the majority were sperm-primed nascent transcripts. These genes included Spz1, Smad7, and the Oocyte 1C 2C 4C MEF p1C p4C miscRNA 4128 5242 6184 6547 8428 4259 6196 asRNA 236 273 269 245 310 233 215 snoRNA 152 148 159 167 164 153 160 Pseudo 142 143 140 135 108 127 134 miRNA 18 19 40 46 112 15 46 snRNA 10 10 10 12 11 9 8 Total 4686 5835 6802 7152 9133 4796 6759 potential pluripotency regulators Pramel1, Pramel6, and Pramel7 (Wang et al 2001;Casanova et al 2011;Hirata et al 2012). We also identified a dramatic change in expression during the 1C-to-2C transition, in which 4967 and 4082 transcripts were down-regulated and up-regulated, respectively, at 2C relative to 1C.…”