Browsing by Subject "bone matrix"

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    An osteocalcin-deficient mouse strain without endocrine abnormalities
    (PLOS, 2020-05-28) Diegel, Cassandra R.; Hann, Steven; Ayturk, Ugur M.; Hu, Jennifer C. W.; Lim, Kyung-eun; Droscha, Casey J.; Madaj, Zachary B.; Foxa, Gabrielle E.; Izaguirre, Isaac; Core, VAI Vivarium and Transgenics; Paracha, Noorulain; Pidhaynyy, Bohdan; Dowd, Terry L.; Robling, Alexander G.; Warman, Matthew L.; Williams, Bart O.; Anatomy and Cell Biology, School of Medicine
    Osteocalcin (OCN), the most abundant noncollagenous protein in the bone matrix, is reported to be a bone-derived endocrine hormone with wide-ranging effects on many aspects of physiology, including glucose metabolism and male fertility. Many of these observations were made using an OCN-deficient mouse allele (Osc–) in which the 2 OCN-encoding genes in mice, Bglap and Bglap2, were deleted in ES cells by homologous recombination. Here we describe mice with a new Bglap and Bglap2 double-knockout (dko) allele (Bglap/2p.Pro25fs17Ter) that was generated by CRISPR/Cas9-mediated gene editing. Mice homozygous for this new allele do not express full-length Bglap or Bglap2 mRNA and have no immunodetectable OCN in their serum. FTIR imaging of cortical bone in these homozygous knockout animals finds alterations in the collagen maturity and carbonate to phosphate ratio in the cortical bone, compared with wild-type littermates. However, μCT and 3-point bending tests do not find differences from wild-type littermates with respect to bone mass and strength. In contrast to the previously reported OCN-deficient mice with the Osc−allele, serum glucose levels and male fertility in the OCN-deficient mice with the Bglap/2pPro25fs17Ter allele did not have significant differences from wild-type littermates. We cannot explain the absence of endocrine effects in mice with this new knockout allele. Possible explanations include the effects of each mutated allele on the transcription of neighboring genes, or differences in genetic background and environment. So that our findings can be confirmed and extended by other interested investigators, we are donating this new Bglap and Bglap2 double-knockout strain to the Jackson Laboratories for academic distribution.
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    Osteocytic connexin 43 is not required for the increase in bone mass induced by intermittent PTH administration in male mice
    (ISMNI, 2016-03) Pacheco-Costa, R.; Davis, Hannah M.; Atkinson, Emily G.; Katchburian, E.; Plotkin, Lilian I.; Reginato, R. D.; Department of Anatomy & Cell Biology, IU School of Medicine
    Objective: To investigate whether osteocytic connexin 43 (Cx43) is required for the bone response to intermittent PTH administration, and whether the connexin is involved in maintaining the bone matrix. Methods: Human PTH(1-34) was injected to adult male mice expressing (Cx43fl/fl) or not osteocytic Cx43 (Cx43fl/fl;DMP1-8kb-Cre) daily (100 μg/kg/d) for 14 days. Results: Cx43fl/fl;DMP1-8kb-Cre mice have no difference in body weight and BMD from 1 to 4 months of age. Intermittent PTH administration increased BMD and BV/TV and induced a similar increase in type I collagen, alkaline phosphatase, runx2, osteocalcin, and bone sialoprotein expression in mice from both genotypes. On the other hand, osteocytic deletion of Cx43 did not alter mRNA levels of glycosaminoglycans, proteoglycans, collagens and osteoblast-related genes. In addition, expression of collagens assessed by immunohistochemistry was not affected by deleting osteocytic Cx43. However, PTH administration increased type II collagen only in Cx43fl/fl control mice, whereas hormone increased type I collagen expression only in Cx43fl/fl;DMP1-8kb-Cre mice. Furthermore, PTH increased maturity of collagen fibers in control, but not in Cx43-deficient mice. Conclusion: Expression of Cx43 in osteocytes is dispensable for bone anabolism induced by intermittent PTH administration; but it can modulate, at least in part, the effect of PTH on the bone matrix environment.