Fig. 1: Generation of intercellular genetic systems based on CD19 or mCherry for tracing cell‒cell contact in vivo.

a Schematic diagrams showing the canonical Notch pathway and the synNotch pathway. b A schematic diagram showing the gTCCC2 system for genetic tracing of cell‒cell contact. c A schematic diagram showing knockin strategies for R26-L-mCD19, R26-R-mCD19, and Cdh5-αCD19NtTA-tdT line. d A schematic diagram showing the experimental design. e Immunostaining for Myc-tag, tdT, and CDH5 on E11.5 embryonic sections in d (left panel). Quantification of the percentage of ECs expressing Myc-tag or tdT (right panel). Data are presented as means ± SEM; n = 5. f A schematic diagram showing the gTCCC2 system for genetic tracing of CDH5⁺ ECs that have contact with TNNI3⁺ cells. g A schematic diagram showing the experimental design. h, i Sectional immunostaining for tdT, CDH5, and TNNI3 on P5 heart sections. Quantification of the percentage of ECs expressing tdT (i, right panel). Data are presented as means ± SEM; n = 5. j A cartoon image showing the ECs adjacent to cardiomyocytes (CM) are labeled by tdT. k Sectional immunostaining for tdT and CDH5 on P5 liver sections. White arrowheads, tdT⁺CDH5⁺ ECs. l A schematic diagram showing the synNotch pathway of gTCCC3 system. m The knockin strategies of Pdgfra-mCherry, Cdh5-αmCh2NtTA-BFP, and Cdh5-αmCh4NtTA-BFP mice. n Immunostaining for mCherry, PDGFRa, and CDH5 on E13.5 embryonic sections. Quantification of the percentage of the PDGFRa⁺ fibroblasts expressing mCherry. o A cartoon image showing the EC is distributed adjacent to fibroblast (Fb). p Immunostaining for Myc-tag, CDH5, and BFP on P0 heart sections. q Immunostaining for BFP, Flag, and CDH5 on P0 heart sections. r A schematic diagram showing the gTCCC3 system for genetic tracing of CDH5⁺ ECs that have contact with PDGFRa⁺ cells. s A schematic diagram showing the experimental design. t Immunostaining for BFP and CDH5 on P0 tissue sections. u Quantification of the percentage of ECs expressing BFP in t. Data are means ± SEM; n = 5. P > 0.05. n.s., not significant. v A cartoon image showing the ECs adjacent to Fb are labeled by BFP. Scale bars: white, 100 µm; yellow, 1 mm.