Analysis of Atf4_osb^−/− mice. (A) Specificity of α1(I) Collagen–Cre-driven deletion of Atf4 allele in bone. (B) Expression level of the ATF4 protein in bone. (C) Bone histomorphometric analysis of Atf4_osb^−/− mice at 12 wk of age (control, n = 10; Atf4_osb^−/−, n = 9). BV/TV, bone volume over tissue volume; Ob.Nb/T.Ar, number of osteoblasts per trabecular area; Oc.S/T.Ar, osteoclast surface per trabecular area. (D) µCT analysis of control (n = 5) and Atf4_osb^−/− (n = 5) proximal tibiae at 12 wk of age. (E and F) Expression of various genes in control (n = 9) and Atf4_osb^−/− (n = 9) bone at 12 wk of age. (G) Serum CTx levels of control (n = 8) and Atf4_osb^−/− mice (n = 8) at 12 wk of age. (H–K) Bone histomorphometric analysis of Atf4_osb^−/− mice after leptin ICV infusion at 12 wk of age shown as percentage compared with control mice treated with vehicle ICV infusion (control mice with vehicle ICV infusion, n = 10; control mice with leptin ICV infusion, n = 9; Atf4_osb^−/− mice with vehicle ICV infusion, n = 9; Atf4_osb^−/− mice with leptin ICV infusion, n = 9). (L) Bone histomorphometric analysis of 12-wk-old Atf4_osb^−/− mice after leptin ICV infusion. All experiments were performed independently at least twice, and representative data are shown. Results are shown as mean ± SEM. Statistical analysis was performed by Student’s t test. For all panels: *, P < 0.05.