The Transient Receptor Potential Channel TRPV6 Is Dynamically Expressed in Bone Cells But Is Not Crucial for Bone Mineralization in Mice BRAM C.J. VAN DER EERDEN, 1 PETRA WEISSGERBER, 2 NADJA FRATZL-ZELMAN, 3 JENNY OLAUSSON, 2 JOOST G.J. HOENDEROP, 4 MARIJKE SCHREUDERS-KOEDAM, 1 MARCO EIJKEN, 1 PAUL ROSCHGER, 3 TEUN J. DE VRIES, 5 HIDEKI CHIBA, 6 KLAUS KLAUSHOFER, 3 VEIT FLOCKERZI, 2 RENE ´ J.M. BINDELS, 4 MARC FREICHEL, 2 AND JOHANNES P.T.M. VAN LEEUWEN 1 * 1 Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands 2 Experimentelle und Klinische Pharmakologie und Toxikologie, Universita¨t des Saarlandes, Homburg, Germany 3 Ludwig Boltzman Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Vienna, Austria 4 Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands 5 Department of Periodontology, Oral Cell Biology, Academic Center of Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands 6 Department of Basic Pathology, Fukushima Medical University, Fukushima, Japan Bone is the major store for Ca 2þ in the body and plays an important role in Ca 2þ homeostasis. During bone formation and resorption Ca 2þ must be transported to and from bone by osteoblasts and osteoclasts, respectively. However, little is known about the Ca 2þ transport machinery in these bone cells. In this study, we examined the epithelial Ca 2þ channel TRPV6 in bone. TRPV6 mRNA is expressed in human and mouse osteoblast-like cells as well as in peripheral blood mononuclear cell-derived human osteoclasts and murine tibial bone marrow-derived osteoclasts. Also other transcellular Ca 2þ transport genes, calbindin-D 9k and/or -D 28K , Na þ /Ca 2þ exchanger 1, and plasma membrane Ca 2þ ATPase (PMCA1b) were expressed in these bone cell types. Immunofluorescence and confocal microscopy on human osteoblasts and osteoclasts and mouse osteoclasts revealed TRPV6 protein at the apical domain and PMCA1b at the osteoidal domain of osteoblasts, whereas in osteoclasts TRPV6 was predominantly found at the bone-facing site. TRPV6 was dynamically expressed in human osteoblasts, showing maximal expression during mineralization of the extracellular matrix. 1,25-Dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) did not change TRPV6 expression in both mineralizing and non-mineralizing SV-HFO cultures. Lentiviral transduction-mediated overexpression of TRPV6 in these cells did not alter mineralization. Bone microarchitecture and mineralization were unaffected in Trpv6 D541A/D541A mice in which aspartate 541 in the pore region was replaced with alanine to render TRPV6 channels non-functional. In summary, TRPV6 and other proteins involved in transcellular Ca 2þ transport are dynamically expressed in bone cells, while TRPV6 appears not crucial for bone metabolism and matrix mineralization in mice. J. Cell. Physiol. 227: 1951–1959, 2012. ß 2011 Wiley Periodicals, Inc. Additional Supporting Information may be found in the online version of this article. Contract grant sponsor: Dutch Organization of Scientific Research; Contract grant number: Zon-Mw 902.18.298. Contract grant sponsor: European Science Foundation (EURYI); Contract grant number: Zon-Mw 916.56.021. Contract grant sponsor: Deutsche Forschungsgemeinschaft. Contract grant sponsor: Fonds der Chemischen Industrie and Sander-Stiftung. Contract grant sponsor: Forschungsausschuss, the ‘‘HOMFOR’’ Program. Contract grant sponsor: Forschungsausschuss der Universita ¨t des Saarlandes. *Correspondence to: Johannes P.T.M. van Leeuwen, Department of Internal medicine, Erasmus MC, room Ee585d, PO Box 2040, 3000 CA Rotterdam, The Netherlands. E-mail: j.vanleeuwen@erasmusmc.nl Received 23 June 2011; Accepted 24 June 2011 Published online in Wiley Online Library (wileyonlinelibrary.com), 5 July 2011. DOI: 10.1002/jcp.22923 ORIGINAL RESEARCH ARTICLE 1951 Journal of Journal of Cellular Physiology Cellular Physiology ß 2011 WILEY PERIODICALS, INC.