Fig. 6.

RTL1 rescues excessive loss of iPSC-derived fetuses and has broad influence in mammals. (A) Cloned fetuses at GD25 derived from pig iPSCs, RTL1-iPSCs, and natural fertilization (WT). The RTL1-iPSC–derived fetuses show normal morphology similar with WT fetuses. (Scale bars, 5 mm.) (B) One-week-old cloned piglets derived from RTL1 overexpressed iPSCs. (C) RTL1 has wide-ranging influence in pig, cattle, and human for embryo development in postimplantation. (Left) RTL1 shows a lower expression in abnormal SCNT fetuses compared with the naturally fertilized fetuses (P = 0.04, two-tailed Student’s t test) in pigs. The bar graph (Right) represents the average of RTL1 expression in the three groups. (Center) RTL1 shows a lower expression in the allantois of NT-derived conceptuses in cattle. The bar graph (Right) is the average of RTL1 expression in the AI and NT groups. RTL1 shows a lower expression in SCNT fetuses compared with the AI fetuses (P = 0.0438, DEGseq P value). The Right shows the relative expression of RTL1 in human first trimester placental chorionic villi derived from eight electively terminated pregnancy (ETP) individuals and one recurrent pregnancy loss individual. RTL1 expression is scaled according to gene expression in ETP, which is considered normal. Bars indicate the relative expression; DEGseq P values are shown. (D) RTL1 expression is negatively correlated with the developmental potential of SCs in mammal. (Left) The RTL1 expression in different mouse SC lines. The 4N-competent groups indicate the iPSC cell lines (MEF as starting cell) that support the development of all-iPSC mice using tetraploid (4N) embryo complementation. The 4N-incompetent groups indicate the iPSC lines which fail to support the development of all-iPSC mice. The 4N-incompetent iPSCs show significantly lower expression than 4N-competent iPSCs (P = 0.027, one-tailed Student’s t test). (Center) The 4N-competent groups indicate the ES cell lines which support the development of all-ESC rat using tetraploid complementation. The 4N-incompetent groups indicate the ESC lines, which fail support the development of all-ESC rat using tetraploid complementation. (Right) The RTL1 expression in different human stem cell lines. The human naïve ESC showed significantly higher expression than human primed ESC and human iPSC (P < 0.001, two-tailed Student’s t test). (E) Model for RTL1 as an important marker for the imprinting status of donor cells for NT, ESCs/iPSCs for tetraploid complementation/chimera formation. Lack of RTL1 in these processes all results in fetal demise and abortion.