Fig. 1: METTL3 marks cytotrophoblasts in human placentas in vivo.

a The uniform manifold approximation and projection (UMAP) of the published snRNA-seq data of human placenta at early pregnancy (8–10 week)⁴². b Dot plots showing trophoblast marker genes, m⁶A writers, erasers, and readers expression in the snRNA-seq data. Dot sizes indicate the percentage of cells in each cluster expressing the corresponding gene, and colors indicate scale average expression level. The yellow background indicates the CTB populations during early pregnancy, and the arrowhead indicates the CTB-fusion population (cluster 11) with substantially low METTL3 and METTL14 expression relative to other CTB sub-populations. c UMAP visualization of the expression of METTL3 and METTL14, CTB marker gene PEG10, and STB marker gene SDC1. The color intensity indicates the gene expression level. d Immunofluorescence of METTL3, METTL14, hCG, and PEG10 in human placental villi of 8-week pregnancy. The white dash lines indicate the layer of CTBs. Scale bar, 20 µm. e Quantification of METTL3 and METTL14 levels in CTBs and STBs of human placental villi (8-week pregnancy). The numbers of examined CTBs were 49 for METTL3 staining and 85 for METTL14 staining; of examined STBs were 67 for METTL3 staining and 130 for METTL14 staining. Data are presented as means ± SD, and p values are from two-tailed Student’s t-test.