Osx-Cre Targets Multiple Cell Types besides Osteoblast Lineage in Postnatal Mice

Abstract

Osterix (Osx or Sp7) is a zinc-finger-family transcriptional factor essential for osteoblast differentiation in mammals. The Osx-Cre mouse line (also known as Osx1-GFP::Cre) expresses GFP::Cre fusion protein from a BAC transgene containing the Osx regulatory sequence. The mouse strain was initially characterized during embryogenesis, and found to target mainly osteoblast-lineage cells. Because the strain has been increasingly used in postnatal studies, it is important to evaluate its targeting specificity in mice after birth. By crossing the Osx-Cre mouse with the R26-mT/mG reporter line and analyzing the progenies at two months of age, we find that Osx-Cre targets not only osteoblasts, osteocytes and hypertrophic chondrocytes as expected, but also stromal cells, adipocytes and perivascular cells in the bone marrow. The targeting of adipocytes and perivascular cells appears to be specific to those residing within the bone marrow, as the same cell types elsewhere are not targeted. Beyond the skeleton, Osx-Cre also targets the olfactory glomerular cells, and a subset of the gastric and intestinal epithelium. Thus, potential contributions from the non-osteoblast-lineage cells should be considered when Osx-Cre is used to study gene functions in postnatal mice.

SHIP1 Regulates MSC Numbers and Their Osteolineage Commitment by Limiting Induction of the PI3K/Akt/β-Catenin/Id2 Axis

“…If human SHIP1 deficiency is found to be linked to disease in these kindreds, then our findings suggest that a hematopoietic marrow graft to replace a hyper-resorptive OC compartment may not be beneficial as the disease pathology is likely caused by SHIP1 deficiency in mesenchymal-derived OB that are not replenished from donor HSC following BMT. [41]. Consistent with their elegant demonstration of OSXCre-mediated gene deletion in MSCderived lineages, here we have demonstrated ablation of SHIP1 expression MSCs derived from OSXCreSHIP flox/flox mice.…”

“…We hypothesized then that SHIP1 might play a cell intrinsic role in the ability of the MS/PC compartment to generate mature OB and thus bone growth. To test this we developed mice harboring a floxed SHIP locus [25] combined with a Cre recombinase transgene under the control of the Osterix promoter that enables selective deletion in preosteoblastic mesenchymal stem/ progenitors [26,41]. We first confirmed ablation of SHIP1 expression in MS/PC prepared from adult OSXCreSHIP flox/flox mice by western blot analysis of lysates from MS/PC cultured in a primitive, uninduced state and following induction of osteogenic differentiation (Fig.…”

Loss of Gsα in the Postnatal Skeleton Leads to Low Bone Mass and a Blunted Response to Anabolic Parathyroid Hormone Therapy

“…Expression of Cre recombinase results in expression of ␤-galactosidase, which is detected by staining with X-Gal. Chen et al (51) reported that the extraskeletal expression of Osx1-GFP::Cre is limited to the olfactory bulb, gastric, and intestinal epithelial cells; therefore we focused on X-Gal staining in bone. Following withdrawal of doxycycline at birth, we found abundant X-Gal staining of osteocytes and osteoblasts in Osx1-GFP::Cre ϩ mice, indicating Cre expression ( Fig.…”

“…It is also important to note that G s ␣-mediated PTH1R signaling in other tissues such as the kidney is presumably preserved. Careful analysis of postnatal extraskeletal Osx-Cre expression by Chen et al (51) revealed that although Osx-Cre targets cells in the olfactory bulb, gastric, and intestinal epithelia there is no expression in the kidney, liver, or other organs. Therefore indirect effects of PTH, for example on systemic mineral metabolism, may also influence skeletal homeostasis.…”

Site-1 protease regulates skeletal stem cell population and osteogenic differentiation in mice

“…The bone marrow is a niche for mesenchymal-derived skeletal stem cells (SSCs) and recent studies have identified specific SSCs with temporal and lineage-specific contributions to skeletal development (Chan et al, 2015;Worthley et al, 2015). Besides, Osx is active in bone marrow stromal cells (BMSCs) (Chen et al, 2014;Mizoguchi et al, 2014), suggesting that S1P ablation in these cells could affect the postnatal bone marrow compartment and, consequently, skeletal development. Therefore, we first analyzed the ability of BMSCs from P21 WT, S1P…”