Remaining LVs after efficient deletion of S1PR1 express valve markers normally. The mesenteric vasculature of P10 S1pr1^f/f (TM@P1–7) and S1pr1^iΔLEC (TM@P1–7) littermates was analyzed using the indicated antibodies. (A and B) The expression of valve markers PROX1 (A and B), GATA2 (B), and integrin-α9 (A) appeared normal in the remaining LVs of mutants. Statistics: n = 3 pups per genotype.