proc mutants develop spontaneous thrombosis with secondary coagulopathy. (A) Schematic of laser-mediated endothelial injury that was performed to evaluate for intravascular thrombus formation. The laser injures the endothelium of the PCV, and TTO was measured for up to 2 minutes. (B) Homozygous proc mutants demonstrated a partial defect in hemostasis manifested by a significant prolonged TTO compared to wild-type and heterozygous siblings. n = 26, 41, 26 in proc^+/+, proc^+/−, and proc^−/−, respectively. Bars indicate median TTO. Values of P were calculated by Mann-Whitney U test. (C) The proc mutation was bred into the Tg^fgb-eGFP transgenic background so that spontaneous thrombosis could be visually observed and scored through green fluorescence. A representative image of spontaneous PCV thrombosis in proc^−/− larvae, which was not observed in wild-type and heterozygous siblings. Scale bar 100 μm. (D) Quantification by a blinded observer demonstrated significant spontaneous thrombosis only in the homozygous proc mutants. P <.0001 for comparison of both wild-type and homozygous siblings, and between heterozygous and homozygous siblings (Fishers exact test). The fibrin deposition scale indicates the number of thrombi counted in each larva, binned into 4 groups. ns, not significant.