ANA deficiency enhances bone morphogenetic protein-induced ectopic bone formation via transcriptional events.
Ectopic bone formation after joint replacement or brain injury in humans is a serious complication that causes immobility of joints and severe pain. However, mechanisms underlying such ectopic bone formation are not fully understood. Bone morphogenetic protein (BMPs) are defined as inducers of ectopic bone formation, and they are regulated by several types of inhibitors. ANA is an antiproliferative molecule that belongs to Tob/BTG family, but its activity in bone metabolism has not been known. Here, we examined the role of ANA on ectopic bone formation activity of BMP. In ANA-deficient and wild-type mice, BMP2 was implanted to induce ectopic bone formation in muscle. ANA deficiency increased mass of newly formed bone in vivo compared with wild-type based on 3D-muCT analyses. ANA mRNA was expressed in bone in vivo as well as in osteoblastic cells in vitro. Such ANA mRNA levels were increased by BMP2 treatment in MC3T3-E1 osteoblastic cells. Overexpression of ANA suppressed BMP-induced expression of luciferase reporter gene linked to BMP response elements in these cells. Conversely, ANA mRNA knockdown by small interference RNA enhanced the BMP-dependent BMP response element reporter expression. It also enhanced BMP-induced osteoblastic differentiation in muscle-derived C2C12 cells. Immunoprecipitation assay indicated that ANA interacts with Smad8. Thus, ANA is a suppressor of ectopic bone formation induced by BMP, and this inhibitory ANA activity is a part of the negative feedback regulation of BMP function.
Miyai
Kentaro
K
Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Japan.
Yoneda
Mitsuhiro
M
Hasegawa
Urara
U
Toita
Sayaka
S
Izu
Yayoi
Y
Hemmi
Hiroaki
H
Hayata
Tadayoshi
T
Ezura
Yoichi
Y
Mizutani
Shuki
S
Miyazono
Kohei
K
Akiyoshi
Kazunari
K
Yamamoto
Tadashi
T
Noda
Masaki
M
D016475:3T3 Cells; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology; D018797:Cell Cycle Proteins; D017930:Genes, Reporter; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051904:Smad8 Protein / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D019485:Bone Morphogenetic Proteins; C433628:Btg3 protein, mouse; D018797:Cell Cycle Proteins; D020033:Protein Isoforms; D011506:Proteins; D034741:RNA, Small Interfering; D051904:Smad8 Protein