SparcTm1Cam129SvEv bone vs 129Sv/Evcontrol bone

ABSTRACT: Sparc null mutants have been generated independently via two targeted mutations in exons 4 and 6. Previous studies have identified low turnover osteopenia in the exon 4 knockout (on a mixed 129Sv/C57Bl/6 background). Since both Sparc null mutations have been shown to result in complete absence of Sparc protein, similar phenotypic outcomes are likely. However, genetic background and/or linkage disequilibrium effects can influence phenotype; abnormalities attributed to a given mutation have often been later found to be caused by closely linked genetic anomalies or strain effects. Ideally therefore, different inactivating mutations should be tested in various mouse strains; similar phenotypic outcomes can then confidently be assigned to the mutated gene. We have evaluated the bone phenotype in the Sparctm1cam exon 6 knockout on a purebred 129Sv/Ev background at 4 and 9 months, using physical measurement, mechanical strength tests and DXA scanning. We have also quantified bone marrow adiposity and circulating leptin levels to assess adipose tissue regulation anomalies in these mice. 129Sv/EvSparctm1cam null mice show decreased bone mineral density and bone mineral content. Increased mechanical fragility of bone was also evident, largely in line with previous studies. However, differences were also noted. Increased body weight and levels of bone marrow adiposity, but decreased circulating leptin concentrations were identified at 4 months, but not at 9 months. Circulating leptin concentrations were reportedly increased in Sparc exon 4 null animals, suggesting that leptin concentrations may be influenced more by genetic background than by the absence of Sparc. 129Sv/EvSparctm1cam null mice have shorter femurs; this difference was not noted in prior studies, possibly due to increased variation owing to use of a hybrid strain. Molecular phenotyping was carried out using mouse HGMP NIA microarrays with cortical femur samples at various ages, using semi-quantitative RT PCR validation. Array studies have identified 429 genes expressed in normal bone. Six genes (Sparc, Zfp162, Bysl, E2F4 and two ESTs) are differentially regulated in 129Sv/EvSparctm1cam cortical femur versus 129Sv/Ev controls. We confirm low turnover osteopenia as a feature of the Sparc null phenotype, identifying the usefulness of this mouse as a model for human osteoporosis. Keywords: disease state analysis, time course, genetic modification, osteoporosis, knockout mouse

ORGANISM(S): Mus musculus

PROVIDER: GSE8381 | GEO | 2007/07/11

SECONDARY ACCESSION(S): PRJNA101421

REPOSITORIES: GEO