Fig. 4: Asymmetric MMP expression is essential for DVE migration.

a Schematics of the embryo stages from pre- to early post-implantation subjected to scRNAseq. Inner Cell Mass, ICM; Trophectoderm and Extraembryonic Ectoderm, TE and ExE; Primitive Endoderm and Embryonic Visceral Endoderm, PE and EmVE; Extraembryonic Visceral Endoderm, ExVE; Epiblast, EPI; Parietal Endoderm, PaE. b Dot plots showing the average expression of genes presented as z-score normalized across embryonic stages and fraction of cells expressing Mmp25, and Mmp15 from scRNAseq of E3.5 to E5.5 embryos. Mmp15 is primarily expressed in the PE and VE from E4.5 to E5.25. Mmp25 is expressed in EPI from E4.5 to E5.25. c At E4.75, four major cell types were identified: EPI, ExE, VE, and decidual cells. Mmp25 is differentially expressed in a subset of EPI cells. Mmp15 is differentially expressed in a subset of VE cells. n = 2586 cells. d At E5.0, in addition to EPI and ExE, VE was divided into two clusters: EmVE and ExVE. Mmp25 is differentially expressed in a subset of EPI cells. Mmp15 is differentially expressed in a subset of the EmVE cells. n = 5531 cells. e–i HCR targeting Mmp15 (green) and Lefty1 (magenta) transcripts at E4.5 (e), E4.75 (f), early 5.0 (g), late E5.0 (h), and E5.25 (i). Post-implantation Lefty1 expressions in the EmVE marked with yellow asterisks. n = 6, 6, 4, 5, and 5 embryos. Scale bars: 20 μm. j, k Snapshots from time-lapse confocal imaging of E5.25 Cerl-GFP (green) embryos cultured either with DMSO as control (j) or 2 μM Batimastat (k). Magnified images at 15 h showing several non-cohesive, individually migrating GFP⁺ DVE cells in (k) compared to (j). Scale bars:20 μm. l Quantification of DVE migration cohesiveness of from embryos cultured with either DMSO as control or 2 μM Batimastat for 15 h. A higher percentage of Batimastat-treated embryos showed non-cohesive DVE migration. n = 15 and 19 embryos.