Endocardial Cell Heterogeneity at the Origin of Valvular Cell Clones
Batoul Fahrat1, Thomas Moore-Morris1, Michel Pucéat1,*
1INSERM UMR910 Aix-Marseille University, Marseille, France
Cardiac valves derive from the process of endothelio-mesenchymal transition (EMT) of endocardial cells in the atrioventricular canal and in the outflow tract of embryonic hearts at E9.5 and E10.5, respectively. How EMT is specifically triggered in a subset of endocardial cells is still poorly understood. The embryological origin of endocardial cells is several including the early mesoderm, the second heart field and a subset of the endoderm. We thus hypothesized that endocardial cells were heterogeneous and possibly already committed or determined in a valvular cell specific lineage.
Tie2Cre/+ male mice were bred with Rosa26tDTomato females. The AVC and OFT regions were dissected out from E9.5 mouse embryos and enzymatically dissociated. Tomato+ cells were collected by FACS sorting or a micropipette and used for single cell analysis.
Cytbow mice1 were bred with CAGERT2Cre/+, Tie2Cre/+ or VE-cadherinERT2Cre/+ mice. Multicolor clones were scored and analysed at different stages of heart development including in valves at E16.5 Images acquired from embryonic and heart sections were processed using the 3D deconvolution software Autoquant and a cell lineage module,
Real time PCR of single cells as well as single cell sequencing revealed a heterogeneous pattern of gene expression and uncover a rare cell subpopulation To further understand how such a cell heterogeneity could be set in the valvular progenitor cells, we used a cell lineage tracing with a multicolor (CYTBOW) reporter mouse model.
We observed multiple oriented clones in both the endothelium and the different layers of the valves. The pattern of genes expression of these clones is being analyzed in single cell approach.
Analysis of cell heterogeneity at the early onset of valvulogenesis may turn to be helpful to better understand valvulopathies