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Molecular and Cellular Biology, April 2003, p. 2907-2913, Vol. 23, No. 8
0270-7306/03/$08.00+0 DOI: 10.1128/MCB.23.8.2907-2913.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Klaus von der Mark,1 Clementine Hofmann,1,2,
and Ernst Pöschl1*
Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Zentrum, Experimentelle Medizin I, Erlangen,1 GSF-Forschungszentrum für Umwelt und Gesundheit, Institut für Säugetiergenetik, Neuherberg, Oberschleissheim-Munich, Germany2
Received 16 September 2002/ Returned for modification 23 October 2002/ Accepted 10 December 2002
| ABSTRACT |
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| INTRODUCTION |
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-helices are grouped symmetrically around a central pore (10, 20). Although protein and gene structures as well as the biochemical features of annexins were analyzed extensively, the in vivo functions of the individual members of the annexin family remain unclear (23). In vitro experiments have linked the functions of annexins to signal transduction events, apoptosis (32), blood coagulation processes (45), and vesicle trafficking, as well as calcium signaling and transport (4), but the demonstration of these functions in vivo is still pending. The coexpression of different annexins with potentially overlapping functions in most tissues complicates the in vivo analysis of individual annexins. Annexin A5 was originally purified from chondrocytes as a potential receptor for collagen type II (24, 41) and independently isolated from placenta as a protein with anticoagulant activity (5). Later, its capacity to form voltage-dependent calcium channels in phospholipid bilayers was recognized and investigated in great detail (9, 11, 19). It became evident that annexin A5 is located inside of cells but that it can also be secreted and is thereby detected in blood plasma. Additionally, annexin A5 is able to bind to the outer surfaces of cells, mediated by its high affinity to phosphatidylserine (2, 29). Surface presentation of this phospholipid represents a characteristic event during the early stages of apoptosis, and therefore, annexin A5 binding has become an important tool for detecting apoptotic changes (16).
An essential role of annexin A5 during the mineralization of tissues has been assumed, especially during the process of endochondral ossification (40). By interacting with the extracellular matrix components collagen II and X, annexin A5 can mediate the influx of Ca2+ into the matrix vesicles secreted from hypertrophic cartilage at the growth plate and thereby initiate the calcification of cartilage (12, 13). Furthermore, this observation is supported by in vivo expression studies showing that the annexin A5 gene (Anxa5) is specifically expressed in skeletal elements during embryogenesis (1). In the early stages of development (9.5- to 12.5-days-postcoitum embryos), Anxa5 expression was detected in cells associated with the developing vasculature. In later stages (>13.5 days postcoitum), a strong expression was observed in cartilage anlagen, such as the vertebral bodies, neural arches, and ribs, as well as the digits of the limb buds. In adult mice, Anxa5 gene expression is maintained in cartilaginous tissues as well as in bone. Therefore, these data suggest a potential role of annexin A5 during skeletal development.
Here, we analyze the consequences of annexin A5 deficiency, generated by a gene-targeting approach, for the development of skeletal elements in the mouse. Annexin A5-deficient mice are viable and fertile and show no obviously altered phenotype. The lack of significant changes in the development of cartilage and bone indicates that either only marginal contributions of annexin A5 to the ossification processes were made or that this could be due to the functional compensation by other members of the annexin family.
| MATERIALS AND METHODS |
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Immunohistochemistry and detection of ß-galactosidase expression. Embryos, organs, and limbs of newborn mice were isolated and snap frozen in Tissue-Tek (Sakura, Tokyo, Japan). Immunostainings of microtome sections (5 to 10 µm thick) were performed with primary antibodies specific for annexin A5 (rabbit polyclonal antibody; Hyphen BioMed) and Cy5-labeled secondary antibodies (Dianova) as described earlier (1, 33). Sections were stained for ß-galactosidase activity, and calcium deposits were visualized by staining with 0.5% (wt/vol) alizarin red as described previously (8).
Immunoblotting. Tissue samples (150 mg) were homogenized on ice in 2 ml of lysis buffer (20 mM Tris-HCl [pH 7.4], 150 mM NaCl, 1% NP-40, 0.05% Triton X-100, 0.5% sodium deoxycholate, 2.5 mM EGTA, 2 mM phenylmethylsulfonyl fluoride). After centrifugation, the supernatants were collected and protein concentrations were determined (Pierce, Rockford, Ill.). Equal amounts of protein (20 µg) were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (10% acrylamide) and transferred onto reinforced nitrocellulose membranes (Schleicher & Schuell, Dassel, Germany). Primary antibodies specific for annexin A2 (goat polyclonal antibody, 1:20; Santa Cruz), annexin A5 (rabbit polyclonal antibody, 1:100; Hyphen BioMed), annexin A6 (goat polyclonal antibody, 1:100; Santa Cruz), and annexin A7 (mouse monoclonal hybridoma supernatant; kindly provided by A. A. Noegel, Cologne, Germany) were used for immunoblotting and detected by species-specific secondary antibodies labeled with horseradish peroxidase (Bio-Rad). Peroxidase activity was visualized by chemoluminescence according to standard procedures.
Analysis of biochemical parameters in blood plasma. Sex- and age-matched mice (six animals per genotype, 5 month of age) were anesthetized with ether, and blood samples were taken by puncturing the retro-orbital sinus. The samples were quickly frozen on dry ice and analyzed for biomedical parameters as described previously (31).
Staining of the skeleton in newborn mice. Skeletal preparation and staining of newborns with 0.5% alizarin red and 0.015% alcian blue were performed as described previously (8).
Chondrocyte culture. Chondrocytes were isolated from the epiphyseal cartilage of the forelimbs and hindquarters of newborn mice by trypsin digestion (1%) for 30 min at 37°C followed by collagenase digestion (1 mg/ml; Roche, Basel, Switzerland) overnight in Dulbecco's modified Eagle's medium-F12 (DMEM-F12; Gibco) containing 10% fetal calf serum (Gibco). Chondrocytes were washed three times in DMEM-F12, and 2 x 105 cells were plated onto 12-well plates (Becton Dickinson) in DMEM-F12 containing 10% (vol/vol) fetal calf serum, 50 U of penicillin/ml, 0.1 mg of streptomycin/ml, and 1 mM pyruvate. When chondrocytes reached confluence (day 7), 10 mM glycerophosphate, 10 mM CaCl2, and 50 µg of ascorbate/ml were added. The cultures were incubated at 37°C in 10% CO2, and the medium was changed daily. Eight days after adding supplements, the cells were fixed for 5 min in 100% methanol and washed three times with phosphate-buffered saline. To localize calcium deposits, cells were stained with 0.5% alizarin red for 10 min at room temperature, washed three times with phosphate-buffered saline, and cleared with 2% potassium hydroxide. Stainings were analyzed by light microscopy and quantified by histogram software (Adobe Photoshop).
| RESULTS |
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PCR genotyping of 147 offspring from heterozygous intercrosses demonstrated Mendelian inheritance of the mutated allele (+/+, 24%; +/-, 48%; -/-, 27%). Therefore, the deficiency of the Anxa5 gene causes no significant effect on embryonic development. Heterozygous as well as homozygous Anxa5-deficient mice were vital and fertile and showed no obvious phenotypic or behavioral abnormalities.
The ablation of Anxa5 mRNA expression was confirmed by reverse transcription-PCR analysis. No correct full-length Anxa5 mRNA could be detected in homozygous mice (data not shown). Yet small amounts of a truncated mRNA were detected by using reverse transcription-PCR with specific primers from exons 3 and 6 (data not shown), which represented an aberrantly spliced variant. However, no corresponding protein could be detected by immunoblotting or immunohistochemistry in mice with mutated Anxa5 alleles (Fig. 2 and 4). Additionally, recombinant expression of this aberrant mutant protein is instable and lost the characteristic biochemical property of annexin A5 to bind to phosphatidylserine (data not shown).
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Clinical-chemical parameters are normal in annexin A5-deficient mice. In order to test for biochemical defects, we examined a number of clinically relevant parameters in the blood plasma of age-matched (5 months) females from wild-type and homozygous mutants (Table 1).
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Normal development of skeletal elements in annexin A5-deficient mice. Annexin A5-deficient animals are indistinguishable in size and behavior from wild-type mice up to an age of 1 year. Adult mice lacking annexin A5 displayed no obvious abnormalities in the developing skeleton, and no skeletal elements were missing or deformed. Further, X-ray analysis of the skeleton from 6-month-old animals revealed no apparent differences in size or in the density of the bone (data not shown). To exclude a possible delay in skeletal development, we focused our interest on the early development of skeletal structures in newborn animals by staining cartilaginous and bony structures with alcian blue and alizarin red (Fig. 3). The size of the skeletal elements and the relative ratio of cartilage to bone in annexin A5-deficient mice were indistinguishable from those of wild-type animals. Histological analysis of the tibia from newborn animals (Fig. 4D) displayed no overt changes in the organization of the growth plate in the absence of annexin A5. Significant differences in the level of the calcification of cartilage between wild-type and annexin A5-deficient tibia were not detected (Fig. 4G and H). Although annexin A5 was found highly expressed in cartilage and bone, as shown by expression of the Anxa5-LacZ fusion protein (Fig. 4H) and the immunohistochemical distribution of annexin A5 (Fig. 4C and E), the deficiency causes no obvious consequences during development and in adulthood.
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| DISCUSSION |
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Surprisingly, the data presented here clearly indicate that the presence of annexin A5 is not essential for cartilage development, endochondral ossification, or the formation of bone. Neither the formation nor the structure and function of the developing skeleton is affected in annexin A5-deficient newborns and in adult animals, as indicated by unchanged levels of calcium and alkaline phosphatase in the blood plasma, by X-ray studies of the skeleton, and by histological analysis of the growth plate. The obtained result was not expected due to the fact that the protein is detected at high levels in the bone and cartilage during embryonic development as well as during adulthood (1, 15, 35). A potential explanation relies on the redundant functions of annexins, which could functionally compensate for the annexin A5 deficiency. Indeed, two other annexins with selective calcium channel activity, annexins A6 and A2, are also found in matrix vesicles within the growth plate (3). It is conceivable that these annexins may be sufficient for the calcification process. This suggestion is further supported by the finding that the in vitro calcification of isolated chondrocytes is comparable between wild-type and annexin A5-deficient animals. However, there is no indication for a significant compensatory upregulation of annexin A2, A6, or A7 in different organs in mice lacking annexin A5. The normal level of annexin A6 especially was unexpected, as annexin A6 colocalizes with annexin A5 in some other tissues also, like the bile duct of the liver (39) or the heart (22). A comparable result was described previously for annexin A6-deficient mice, which also did not show any upregulation of other members of the annexin family, including annexin A5 (7).
Recently, an annexin A5-deficient mutant was established in the DT40 cell line and in these cells, a reduced susceptibility to various apoptotic stimuli was observed (6, 17). Although these data point to a role of annexin A5 in calcium-dependent apoptosis, the lack of annexin A5 may be largely tolerable in vivo. Yet we cannot exclude at the moment whether, under various stress conditions, specific phenotypes will become apparent.
It has been proposed that annexin A5 plays a role in pregnancy loss associated with antiphospholipid syndrome in humans (30). Annexin A5 should form an antithrombotic shield on the syncytium of the placental villi, and a disruption of this shield by autoimmune antibodies could induce placental thrombosis and intrauterine growth retardation. This is further supported by the finding that the injection of annexin A5-specific antibodies into pregnant mice leads to placental infarction and fetal losses (42). Therefore, we expected an impact of annexin A5 deficiency on the developing fetuses and/or litter size or deviations from Mendelian inheritance. No significant differences were seen upon heterozygous crossings. To exclude the possibility of a functional substitution of annexin A5 from maternal tissues, we also tested intercrosses of homozygous mutants (data not shown). Again, we could not detect a significant reduction in the litter size, but extended analyses of embryonic stages and litter sizes may be essential for a final conclusion. This finding may also be due to the fact that the placental structures in the mouse and human are organized differently; hence, the results of annexin A5-deficient mice most likely do not fully reflect the situation in humans (36). Additionally, there are controversial data about the role of annexin A5 in antiphospholipid syndrome. Some studies failed to detect anti-annexin A5 antibodies or did not find any correlation between annexin A5 displacement by antiphospholipid antibodies and increased thrombogenicity of the cell surface (18, 37).
In this paper, we describe the generation of an annexin A5-deficient mouse model by gene targeting and the analysis of its in vivo consequences. Our data imply that the ablation of annexin A5 has no significant pathological effect on vitality or fertility or on the formation of cartilage and bone, especially during endochondral ossification. Hence, the major questions for future studies will focus on the detailed analysis of subtle pathological consequences and on the analysis of potentially compensatory effects by other annexins.
| ACKNOWLEDGMENTS |
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Vector pNeoflox-8 was kindly provided by W. Müller, Cologne, Germany. Analysis of blood samples was kindly performed by M. Mohr and E. Wolf, Munich, Germany. We thank A. A. Noegel for providing us with the annexin A7 antibody.
| FOOTNOTES |
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Present address: Max-Planck-Institut für Psychiatrie, Munich, Germany. ![]()
| REFERENCES |
|---|
|
|
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2. Flaherty, M. J., S. West, R. L. Heimark, K. Fujikawa, and J. F. Tait. 1990. Placental anticoagulant protein-I: measurement in extracellular fluids and cells of the hemostatic system. J. Lab. Clin. Med. 115:174-181.[Medline]
3. Genge, B. R., L. N. Wu, and R. E. Wuthier. 1989. Identification of phospholipid-dependent calcium-binding proteins as constituents of matrix vesicles. J. Biol. Chem. 264:10917-10921.
4. Gerke, V., and S. E. Moss. 1997. Annexins and membrane dynamics. Biochim. Biophys. Acta 1357:129-154.[Medline]
5. Grundmann, U., K. J. Abel, H. Bohn, H. Lobermann, F. Lottspeich, and H. Kupper. 1988. Characterization of cDNA encoding human placental anticoagulant protein (PP4): homology with the lipocortin family. Proc. Natl. Acad. Sci. USA 85:3708-3712.
6. Hawkins, T. E., D. Das, B. Young, and S. E. Moss. 2002. DT40 cells lacking the Ca2+-binding protein annexin 5 are resistant to Ca2+-dependent apoptosis. Proc. Natl. Acad. Sci. USA 99:8054-8059.
7. Hawkins, T. E., J. Roes, D. Rees, J. Monkhouse, and S. E. Moss. 1999. Immunological development and cardiovascular function are normal in annexin VI null mutant mice. Mol. Cell. Biol. 19:8028-8032.
8. Hogan, B., R. Beddington, F. Costantini, and E. Lacy. 1994. Manipulating the mouse embryo: a laboratory manual. Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.
9. Huber, R., R. Berendes, A. Burger, M. Schneider, A. Karshikov, H. Luecke, J. Romisch, and E. Paques. 1992. Crystal and molecular structure of human annexin V after refinement. Implications for structure, membrane binding and ion channel formation of the annexin family of proteins. J. Mol. Biol. 223:683-704.[CrossRef][Medline]
10. Huber, R., J. Romisch, and E. P. Paques. 1990. The crystal and molecular structure of human annexin V, an anticoagulant protein that binds to calcium and membranes. EMBO J. 9:3867-3874.[Medline]
11. Huber, R., M. Schneider, I. Mayr, J. Romisch, and E. P. Paques. 1990. The calcium binding sites in human annexin V by crystal structure analysis at 2.0 Å resolution. Implications for membrane binding and calcium channel activity. FEBS Lett. 275:15-21.[CrossRef][Medline]
12. Kirsch, T., G. Harrison, E. E. Golub, and H. D. Nah. 2000. The roles of annexins and types II and X collagen in matrix vesicle-mediated mineralization of growth plate cartilage. J. Biol. Chem. 275:35577-35583.
13. Kirsch, T., Y. Ishikawa, F. Mwale, and R. E. Wuthier. 1994. Roles of the nucleational core complex and collagens (types II and X) in calcification of growth plate cartilage matrix vesicles. J. Biol. Chem. 269:20103-20109. [Erratum, 269:25234.]
14. Kirsch, T., H. D. Nah, D. R. Demuth, G. Harrison, E. E. Golub, S. L. Adams, and M. Pacifici. 1997. Annexin V-mediated calcium flux across membranes is dependent on the lipid composition: implications for cartilage mineralization. Biochemistry 36:3359-3367.[CrossRef][Medline]
15. Kirsch, T., and R. E. Wuthier. 1994. Stimulation of calcification of growth plate cartilage matrix vesicles by binding to type II and X collagens. J. Biol. Chem. 269:11462-11469.
16. Koopman, G., C. P. Reutelingsperger, G. A. Kuijten, R. M. Keehnen, S. T. Pals, and M. H. van Oers. 1994. Annexin V for flow cytometric detection of phosphatidylserine expression on B cells undergoing apoptosis. Blood 84:1415-1420.
17. Kubista, H., T. E. Hawkins, D. R. Patel, H. T. Haigler, and S. E. Moss. 1999. Annexin 5 mediates a peroxide-induced Ca(2+) influx in B cells. Curr. Biol. 9:1403-1406.[CrossRef][Medline]
18. Lakasing, L., J. S. Campa, R. Poston, M. A. Khamashta, and L. Poston. 1999. Normal expression of tissue factor, thrombomodulin, and annexin V in placentas from women with antiphospholipid syndrome. Am. J. Obstet. Gynecol. 181:180-189.[CrossRef][Medline]
19. Liemann, S., J. Benz, A. Burger, D. Voges, A. Hofmann, R. Huber, and P. Gottig. 1996. Structural and functional characterisation of the voltage sensor in the ion channel human annexin V. J. Mol. Biol. 258:555-561.[CrossRef][Medline]
20. Liemann, S., and R. Huber. 1997. Three-dimensional structure of annexins. Cell. Mol. Life Sci. 53:516-521.[CrossRef][Medline]
21. Liemann, S., and A. Lewit-Bentley. 1995. Annexins: a novel family of calcium- and membrane-binding proteins in search of a function. Structure 3:233-237.[Medline]
22. Matteo, R. G., and C. S. Moravec. 2000. Immunolocalization of annexins IV, V and VI in the failing and non-failing human heart. Cardiovasc. Res. 45:961-970.
23. Mollenhauer, J. 1997. Annexins: what are they good for? Cell. Mol. Life Sci. 53:506-507.[CrossRef][Medline]
24. Mollenhauer, J., and K. von der Mark. 1983. Isolation and characterization of a collagen-binding glycoprotein from chondrocyte membranes. EMBO J. 2:45-50.[Medline]
25. Morgan, R. O., and M. P. Fernandez. 1997. Annexin gene structures and molecular evolutionary genetics. Cell. Mol. Life Sci. 53:508-515.[CrossRef][Medline]
26. Morgan, R. O., and M. Pilar Fernandez. 1997. Distinct annexin subfamilies in plants and protists diverged prior to animal annexins and from a common ancestor. J. Mol. Evol. 44:178-188.[CrossRef][Medline]
27. Moss, S., H. C. Edwards, and M. J. Crumpton. 1991. Diversity in the annexin family, p. 535-566. In C. W. Heizmann (ed.), Novel calcium-binding proteins. Springer-Verlag KG, Berlin, Germany.
28. Neubauer, H., A. Cumano, M. Muller, H. Wu, U. Huffstadt, and K. Pfeffer. 1998. Jak2 deficiency defines an essential developmental checkpoint in definitive hematopoiesis. Cell 93:397-409.[CrossRef][Medline]
29. Pfaffle, M., F. Ruggiero, H. Hofmann, M. P. Fernandez, O. Selmin, Y. Yamada, R. Garrone, and K. von der Mark. 1988. Biosynthesis, secretion and extracellular localization of anchorin CII, a collagen-binding protein of the calpactin family. EMBO J. 7:2335-2342. [Erratum, 9:1336, 1990.]
30. Rand, J. H. 2000. Antiphospholipid antibody-mediated disruption of the annexin-V antithrombotic shield: a thrombogenic mechanism for the antiphospholipid syndrome. J. Autoimmun. 15:107-111.[CrossRef][Medline]
31. Rathkolb, B., T. Decker, E. Fuchs, D. Soewarto, C. Fella, S. Heffner, W. Pargent, R. Wanke, R. Balling, M. Hrabe de Angelis, H. J. Kolb, and E. Wolf. 2000. The clinical-chemical screen in the Munich ENU Mouse Mutagenesis Project: screening for clinically relevant phenotypes. Mamm. Genome 11:543-546.[CrossRef][Medline]
32. Reutelingsperger, C. P., and W. L. van Heerde. 1997. Annexin V, the regulator of phosphatidylserine-catalyzed inflammation and coagulation during apoptosis. Cell. Mol. Life Sci. 53:527-532.[CrossRef][Medline]
33. Ringelmann, B., C. Röder, R. Hallmann, M. A. Maley, M. J. Davies, M. D. Grounds, and L. M. Sorokin. 1999. Expression of laminin
1,
2,
4, and
5 chains, fibronectin, and tenascin-C in skeletal muscle of dystrophic 129ReJ Dy/Dy mice. Exp. Cell. Res. 246:165-182.[CrossRef][Medline]
34. Rodriguez-Garcia, M. I., R. O. Morgan, M. R. Fernandez, P. Bances, and M. P. Fernandez. 1999. Mouse annexin V genomic organization includes an endogenous retrovirus. Biochem. J. 337:125-131.
35. Rojas, E., N. Arispe, H. T. Haigler, A. L. Burns, and H. B. Pollard. 1992. Identification of annexins as calcium channels in biological membranes. Bone Miner. 17:214-218.[CrossRef][Medline]
36. Rossant, J., and J. C. Cross. 2001. Placental development: lessons from mouse mutants. Nat. Rev. Genet. 2:538-548.[Medline]
37. Siaka, C., M. Lambert, C. Caron, J. Amiral, E. Hachulla, P. Y. Hatron, and J. Goudemand. 1999. Low prevalence of anti-annexin V antibodies in antiphospholipid syndrome with fetal loss. Rev. Med. Interne. 20:762-765. (In French.)
38. Thomas, J. T., R. P. Boot-Handford, and M. E. Grant. 1990. Modulation of type X collagen gene expression by calcium beta-glycerophosphate and levamisole: implications for a possible role for type X collagen in endochondral bone formation. J. Cell Sci. 95:639-648.
39. Thorin, B., G. Gache, T. Dubois, R. Grataroli, N. Domingo, F. Russo-Marie, and H. Lafont. 1995. Annexin VI is secreted in human bile. Biochem. Biophys. Res. Commun. 209:1039-1045.[CrossRef][Medline]
40. von der Mark, K., and J. Mollenhauer. 1997. Annexin V interactions with collagen. Cell. Mol. Life Sci. 53:539-545.[CrossRef][Medline]
41. von der Mark, K., J. Mollenhauer, P. K. Muller, and M. Pfaffle. 1985. Anchorin CII, a type II collagen-binding glycoprotein from chondrocyte membranes. Ann. N. Y. Acad. Sci. 460:214-223.[Medline]
42. Wang, X., B. Campos, M. A. Kaetzel, and J. R. Dedman. 1999. Annexin V is critical in the maintenance of murine placental integrity. Am. J. Obstet. Gynecol. 180:1008-1016.[CrossRef][Medline]
43. Wurst, W., and A. L. Joyner. 1993. Production of targeted embryonic stem cell clones. IRL Press, Oxford University Press, Oxford, United Kingdom.
44. Wuthier, R. E., L. N. Wu, G. R. Sauer, B. R. Genge, T. Yoshimori, and Y. Ishikawa. 1992. Mechanism of matrix vesicle calcification: characterization of ion channels and the nucleational core of growth plate vesicles. Bone Miner. 17:290-295.[CrossRef][Medline]
45. Yoshizaki, H., S. Tanabe, K. Arai, A. Murakami, Y. Wada, M. Ohkuchi, Y. Hashimoto, and M. Maki. 1992. Effects of calphobindin II (annexin VI) on procoagulant and anticoagulant activities of cultured endothelial cells. Chem. Pharm. Bull. (Tokyo) 40:1860-1863.
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