cKO P2 mice show thrombocytopenia but no early lethality, whereas cKO P2/H1 die prematurely. (A) Thrombocyte concentrations in the blood of WT and cKO P2 mice until adulthood reveal a significant reduction of circulating platelets per volume of blood in cKO P2 mice (n = 5-10). WT is represented by black squares and cKO P2 by red triangles. (B) Eight- to 10-week-old mice were bled and thrombocytes measured in a fixed volume of blood showing thrombocytopenia in cKO and cKO P2/H1 mice compared with WT and cKO P2/H2 mice (n = 6-7). (C-D) WT and cKO P2 kidneys stained with acid Fuchsin orange-G show no signs of microvascular thrombosis suggesting that platelets are not trapped within blood clots. (E) Instead, the total blood volume of cKO P2 mice was significantly increased compared with WT mice (n = 9-10). (F) 9 cKO P2 mice (5 females and 4 males) were kept for 20 months. Mice were bled every 4 months to measure HCTs. No significant differences in HCTs were found and none of the mice died before the end of the experiment. (G) cKO P2/H1 (n = 17) and cKO P2 (n = 15) mice were followed for 20 weeks. cKO P2/H1 mice began to die from week 5 after birth. By week 16, 16 of 17 mice were deceased. No cKO P2 mice died during the course of this experiment. Scale bars represent 100 μm. All data are mean ± SEM (**P < .01, ***P < .001).