Fig. 3: Loss of the primary decidual zone barrier in Blimp1 mutants.

a IHC identifies invasion of Eomes positive trophoblasts into the PDZ in Blimp1 mutant decidua (n = 5 decidua per genotype). b IF staining of Oct4 and Eomes in isolated E5.5 embryos from wild-type and Blimp1 mutant mice counterstained with DAPI. Embryos isolated from Blimp1 mutant deciduae display normal epiblast morphology but distinct disruption of the extraembryonic ectoderm (n = 5 embryos per genotype). c Immunofluorescence staining of RFP (to identify embryonic cells) and K8 (trophoblasts) in wild type; mTmG and Blimp1 mutant; mTmG decidua (E5.5) counterstained with DAPI. White dotted lines outline embryos. White arrows in Blimp1 mutant;mTmG images indicate migrating trophoblast cells. RFP-labelled embryos from Blimp1 mutant; mTmG mice are highly disrupted and invade into the PDZ (n = 5 per genotype). d IF staining of E-cad (embryo) and ZO-1 in E5.5 mutant and wild-type decidua counterstained with DAPI. Reduced ZO-1 staining indicates impaired tight junction formation in the PDZ of mutants (n = 5 per genotype). White dotted lines outline the PDZ. e Reduced ZO-1 positive area forming a ‘complete barrier’ in the PDZ of E5.5 mutants demonstrates impaired barrier formation. Data from 12 tissue sections from four samples per genotype are shown. Bars represent mean. Two-tailed unpaired Student’s t-test ***p = 2.01 × 10⁻¹². Source data are provided as a Source Data file. f TEM of E6.5 PDZ confirms loss of a complete barrier in mutants (n = 3 per genotype). Top panel shows sections of resin embedded samples counterstained with toluidine blue for general morphology before TEM was undertaken. Yellow arrows indicate tight junctions at cell–cell borders. Asterisks mark intercellular spaces. E = embryo, M = mesometrial, AM = antimesometrial, a.u. = arbitrary units. Scale bars = 100 μm unless otherwise indicated.