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A Locus on Chromosome 7 Determines Dramatic Up-Regulation of Osteopontin in Dystrophic Cardiac Calcification in Mice

Authors
Journal
American Journal Of Pathology
0002-9440
Publisher
Elsevier
Publication Date
Volume
164
Issue
4
Identifiers
DOI: 10.1016/s0002-9440(10)63224-5
Keywords
  • Opn In Dystrophic Calcification

Abstract

Calcification of necrotic tissue is frequently observed in chronic inflammation and atherosclerosis. A similar response of myocardium to injury, referred to as dystrophic cardiac calcinosis (DCC), occurs in certain inbred strains of mice. We now examined a putative inhibitor of calcification, osteopontin, in DCC after transdiaphragmal myocardial freeze-thaw injury. Strong osteopontin expression was found co-localizing with calcification in DCC-susceptible strain C3H/HeNCrlBr, which exhibited low osteopontin plasma concentrations otherwise. Osteopontin mRNA induction was 20-fold higher than in resistant strain C57BL/6NCrlBr, which exhibited fibrous lesions without calcification and little osteopontin expression. Sequence analysis identified several polymorphisms in calcium-binding and phosphorylation sites in osteopontin cDNA. Their potential relevance for DCC was tested in congenic mice, which shared the osteopontin locus with C57BL/6NCrlBr, but retained a chromosomal segment from C3H/HeNCrlBr on proximal chromosome 7. These mice exhibited strong osteopontin expression and DCC comparable to C3H/HeNCrlBr suggesting that a trans- activator of osteopontin transcription residing on chromosome 7 and not the osteopontin gene on chromosome 5 was responsible for the genetic differences in osteopontin expression. A known osteopontin activator encoded by a gene on chromosome 7 is the transforming growth factor-β1, which was more induced (3.5×) in C3H/HeNCrlBr than in C57BL/6NCrlBr mice.

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