Trps1 deficiency enlarges the proliferative zone of growth plate cartilage by upregulation of Pthrp.
We have reported that elongation of the columnar proliferative zone of long bone growth plates in Trps1-/- mice during the late fetal stage in the previous study [1]. Since expression of Trps1 protein was found to overlap with that of mRNAs for Indian hedgehog (Ihh), PTH/PTHrP receptor (PPR), and PTHrP, we hypothesized that Trps1 may inhibit the hypertrophic differentiation of chondrocytes by interacting with the Ihh/PTHrP feedback loop. To investigate whether Trps1 has a role in this Ihh/PTHrP feedback loop, we compared the growth plates of Trps1-/- mice and wild-type (Trps1+/+) mice. Immunohistochemistry showed that Trps1 protein was strongly expressed in the periarticular and prehypertrophic zones of the fetal growth plate in wild-type mice on embryonic day 18.5 (E18.5). On the other hand, Ihh, PPR, and PTHrP mRNAs were predominantly expressed in the prehypertrophic zone at this stage of development. While expression of Ihh and PPR by prehypertrophic chondrocytes was unaffected in the growth plates of Trps1-/- mice, the range of PTHrP expression was expanded toward the proliferating zone in these mice. Quantitative real-time PCR analysis demonstrated upregulation of PTHrP in the epiphyseal growth plates of Trps1-/- mice. Furthermore, promoter analysis combined with the chromatin immunoprecipitation (ChIP) assay demonstrated that direct binding of Trps1 to the PTHrP promoter suppressed the transcription of PTHrP. Finally, organ culture of E14.5 tibiae in the absence or the presence of Pthrp revealed that the proliferative zone of the tibial growth plate was elongated by culture with Pthrp compared to that of control tibiae. Taken together, these data provide the first genetic evidence that lack of Trps1 leads to overexpression of PTHrP, and that Trps1 is required to maintain the normal organization of chondrocytes in the growth plate.
Nishioka
Katsuhiro
K
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Itoh
Shunji
S
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Suemoto
Hiroki
H
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Kanno
Seiji
S
Department of Orthopedic Surgery, Wakayama Medical University School of Medicine, Wakayama, 641-0012, Japan.
Gai
Zhibo
Z
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Kawakatsu
Motohisa
M
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Tanishima
Hiroyuki
H
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Morimoto
Yoshifumi
Y
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Hatamura
Ikuji
I
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan.
Yoshida
Munehito
M
Department of Orthopedic Surgery, Wakayama Medical University School of Medicine, Wakayama, 641-0012, Japan.
Muragaki
Yasuteru
Y
First Department of Pathology, Wakayama Medical University School of Medicine, 811-1 Kimiidera, Wakayama 641-0012, Japan. Electronic address: ymuragak@wakayama-med.ac.jp.
D000818:Animals; D001483:Base Sequence; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D050980:GATA Transcription Factors / Q000235:genetics / Q000502:physiology*; D006132:Growth Plate / Q000166:cytology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000502:physiology*
D017931:DNA Primers; D050980:GATA Transcription Factors; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D012097:Repressor Proteins; C525953:Trps1 protein, mouse