University of Oulu

Tolonen, J.-P., Salo, A.M., Finnilä, M., Aro, E., Karjalainen, E., Ronkainen, V.-P., Drushinin, K., Merceron, C., Izzi, V., Schipani, E. and Myllyharju, J. (2022), Reduced Bone Mass in Collagen Prolyl 4-Hydroxylase P4ha1+/−; P4ha2−/− Compound Mutant Mice. JBMR Plus, 6: e10630.

Reduced bone mass in collagen prolyl 4-hydroxylase P4ha1+/-; P4ha2-/- compound mutant mice

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Author: Tolonen, Jussi-Pekka1,2,3; Salo, Antti M.1,2,3; Finnilä, Mikko4;
Organizations: 1Oulu Center for Cell-Matrix Research, University of Oulu, Oulu, Finland
2Biocenter Oulu, University of Oulu, Oulu, Finland
3Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
4Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, University of Oulu, Oulu, Finland
5Departments of Orthopaedic Surgery, Medicine, and Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, MI, USA
6Research Unit of Biomedicine, Faculty of Medicine, University of Oulu, Oulu, Finland
7Finnish Cancer Institute, Helsinki, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.7 MB)
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Language: English
Published: John Wiley & Sons, 2022
Publish Date: 2022-09-09


Proper deposition of the extracellular matrix and its major components, the collagens, is essential for endochondral ossification and bone mass accrual. Collagen prolyl 4-hydroxylases (C-P4Hs) hydroxylate proline residues in the -X-Pro-Gly- repeats of all known collagen types. Their product, 4-hydroxyproline, is essential for correct folding and thermal stability of the triple-helical collagen molecules in physiological body temperatures. We have previously shown that inactivation of the mouse P4ha1 gene, which codes for the catalytic α subunit of the major C-P4H isoform, is embryonic lethal, whereas inactivation of the P4ha2 gene produced only a minor phenotype. Instead, mice with a haploinsufficiency of the P4ha1 gene combined with a homozygous deletion of the P4ha2 gene present with a moderate chondrodysplasia due to transient cell death of the growth plate chondrocytes. Here, to further characterize the bone phenotype of the P4ha1+/−; P4ha2−/− mice, we have carried out gene expression analyses at whole-tissue and single-cell levels, biochemical analyses, microcomputed tomography, histomorphometric analyses, and second harmonic generation microscopy to show that C-P4H α subunit expression peaks early and that the C-P4H deficiency leads to reduced collagen amount, a reduced rate of bone formation, and a loss of trabecular and cortical bone volume in the long bones. The total osteoblast number in the proximal P4ha1+/−; P4ha2−/− tibia and the C-P4H activity in primary P4ha1+/−; P4ha2−/− osteoblasts were reduced, whereas the population of osteoprogenitor colony-forming unit fibroblasts was increased in the P4ha1+/−; P4ha2−/− marrow. Thus, the P4ha1+/−; P4ha2−/− mouse model recapitulates key aspects of a recently recognized congenital connective tissue disorder with short stature and bone dysplasia caused by biallelic variants of the human P4HA1 gene. Altogether, the data demonstrate the allele dose-dependent importance of the C-P4Hs to the developing organism and a threshold effect of C-P4H activity in the proper production of bone matrix.

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Series: JBMR plus
ISSN: 2473-4039
ISSN-E: 2473-4039
ISSN-L: 2473-4039
Volume: 6
Article number: e10630
DOI: 10.1002/jbm4.10630
Type of Publication: A1 Journal article – refereed
Field of Science: 1182 Biochemistry, cell and molecular biology
Funding: This work was funded by the Academy of Finland project grant 296498 (JM), the Academy of Finland Center of Excellence 2012-2017 grant 251314 (JM), the Sigrid Jusélius Foundation (JM), the Jane and Aatos Erkko Foundation (JM), Fibrogen Inc. (JM), the Emil Aaltonen Foundation (J-PT), the Maud Kuistila Memorial Foundation (J-PT), and RO1 AR073022 (ES).
Academy of Finland Grant Number: 251314
Detailed Information: 251314 (Academy of Finland Funding decision)
296498 (Academy of Finland Funding decision)
Copyright information: © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.