Skeletal casein kinase activity defect in the HYP mouse

L. Rifas, S. L. Cheng, L. R. Halstead, A. Gupta, K. A. Hruska, L. V. Avioli

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The Hyp mouse, a model for human X-linked hypophosphatemia (XLH), is characterized by phosphate wasting and defective mineralization. Since osteopontin (OPN) is considered pivotal for biological mineralization, we examined the biosynthesis of OPN in osteoblasts of +/Y and Hyp/Y mice. Immunoprecipitation analyses using a specific antibody to OPN revealed that Hyp/Y and +/Y osteoblasts secrete similar levels of OPN as determined by [35S]-methionine biosynthetic labeling, but a reduced phosphorylation was noted after 32P-PO4 biosynthetic labeling. Northern blot hybridization analysis of +/Y and Hyp/Y mice osteoblast mRNAs, using a cDNA probe for mouse OPN, revealed no difference in the steady state levels of osteopontin mRNA. Analysis of casein kinase II activity in +/Y and Hyp/Y mice osteoblast, kidney, heart and liver membrane fractions revealed that casein kinase II activity in the Hyp/Y mice osteoblasts and kidney is only 35%-50%, respectively, of that of the +/Y mice tissues. The accumulated data are consistent with a post-translational defect in the Hyp/Y mouse osteoblast which results in the underphosphorylation of osteopontin and subsequent under-mineralization of bone matrix.

Original languageEnglish
Pages (from-to)256-259
Number of pages4
JournalCalcified Tissue International
Issue number3
StatePublished - Sep 1997


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