The incidence of osteosarcoma is increased 500-fold in patients who inherit mutations in the RB gene. To understand why the retinoblastoma protein (pRb) is specifically targeted in osteosarcoma, we studied its function in osteogenesis. Loss of pRb but not p107 or p130 blocks late osteoblast differentiation. pRb physically interacts with the osteoblast transcription factor, CBFA1, and associates with osteoblast-specific promoters in vivo in a CBFA1-dependent fashion. Association of pRb with CBFA1 and promoter sequences results in synergistic transactivation of an osteoblast-specific reporter. This transactivation function is lost in tumor-derived pRb mutants, underscoring a potential role in tumor suppression. Thus, pRb functions as a direct transcriptional coactivator promoting osteoblast differentiation, which may contribute to the targeting of pRb in osteosarcoma.

Platelet-derived growth factor (PDGF) is a potent mitogenic and migratory factor that regulates the tyrosine phosphorylation of a variety of signalling proteins via intracellular production of H2O2 (refs 1, 2-3). Mammalian 2-Cys peroxiredoxin type II (Prx II; gene symbol Prdx2) is a cellular peroxidase that eliminates endogenous H2O2 produced in response to growth factors such as PDGF and epidermal growth factor; however, its involvement in growth factor signalling is largely unknown. Here we show that Prx II is a negative regulator of PDGF signalling. Prx II deficiency results in increased production of H2O2, enhanced activation of PDGF receptor (PDGFR) and phospholipase Cgamma1, and subsequently increased cell proliferation and migration in response to PDGF. These responses are suppressed by expression of wild-type Prx II, but not an inactive mutant. Notably, Prx II is recruited to PDGFR upon PDGF stimulation, and suppresses protein tyrosine phosphatase inactivation. Prx II also leads to the suppression of PDGFR activation in primary culture and a murine restenosis model, including PDGF-dependent neointimal thickening of vascular smooth muscle cells. These results demonstrate a localized role for endogenous H2O2 in PDGF signalling, and indicate a biological function of Prx II in cardiovascular disease.

The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest. Runx2 physically interacts with the hypophosphorylated form of pRb, a known coactivator of runx2, thereby completing a feed-forward loop in which progressive cell cycle exit promotes increased expression of the osteoblast phenotype. Loss of p27KIP1 perturbs transient and terminal cell cycle exit in osteoblasts. Consistent with the incompatibility of malignant transformation and permanent cell cycle exit, loss of p27KIP1 expression correlates with dedifferentiation in high-grade human osteosarcomas. Physiologic coupling of osteoblast differentiation to cell cycle withdrawal is mediated through runx2 and p27KIP1, and these processes are disrupted in osteosarcoma.

Disrupted-in-schizophrenia 1 (DISC1) has emerged as a schizophrenia-susceptibility gene affecting various neuronal functions. In this study, we characterized Mitofilin, a mitochondrial inner membrane protein, as a mediator of the mitochondrial function of DISC1. A fraction of DISC1 was localized to the inside of mitochondria and directly interacts with Mitofilin. A reduction in DISC1 function induced mitochondrial dysfunction, evidenced by decreased mitochondrial NADH dehydrogenase activities, reduced cellular ATP contents, and perturbed mitochondrial Ca 2+ dynamics. In addition, deficiencies in DISC1 and Mitofilin induced a reduction in mitochondrial monoamine oxidase-A activity. The mitochondrial dysfunctions evoked by the deficiency of DISC1 were partially phenocopied by an overexpression of truncated DISC1 that is associated with schizophrenia in human. DISC1 deficiencies induced the ubiquitination of Mitofilin, suggesting that DISC1 is critical for the stability of Mitofilin. Finally, the mitochondrial dysfunction induced by DISC1 deficiency was partially reversed by coexpression of Mitofilin, confirming a functional link between DISC1 and Mitofilin for the normal mitochondrial function. According to these results, we propose that DISC1 plays essential roles for mitochondrial function in collaboration with a mitochondrial interacting partner, Mitofilin.IMMT | mitochondrial dysfunctions | hyperdopaminergia | calcium buffering | psychiatric disorders

It has been suggested that decreased replication capacity of mesenchymal stem cells (MSCs) or decreased MSCs activity in the bone marrow is related to nontraumatic osteonecrosis (ON). However, little is known about differentiation ability of MSCs according to the risk factor of nontraumatic ON. We hypothesize that differentiation abnormalities in MSCs of the bone marrow of the proximal femurs might be related to nontraumatic ON of the femoral head. The purpose of this study was to investigate the osteogenic and adipogenic differentiation ability of MSCs in patients with nontraumatic ON of the femoral head. We examined the differentiation ability of MSCs in cultures derived from the bone marrow of the proximal femurs obtained from 10 patients with hip osteoarthritis (OA) and 37 patients with nontraumatic ON of the femoral head undergoing hip replacement surgery. We analyzed the osteogenic and adipogenic differentiation ability of MSCs according to the risk factor [alcohol-induced (15 patients), idiopathic (12 patients) and steroidinduced (10 patients)] of nontraumatic ON of the femoral head separately and compared it with patients with hip OA. The osteogenic activity was measured as the extracellular matrix calcification by alizarin red S staining and the alkaline phosphatase activity, and the adipogenic activity was measured as the accumulation of Oil red O-positive lipid vacuoles. The osteogenic differentiation ability of MSCs in patients with alcohol-induced and idiopathic ON was significantly reduced compared with that in patients with OA (p < 0.05 and p < 0.05, respectively). In patients with steroidinduced ON, the osteogenic differentiation ability was found to be increased, but the difference was not statistically significant. The adipogenic differentiation ability of MSCs was not significantly changed in patients with alcohol-induced, idiopathic, and steroid-induced ON compared to patients with OA. Our results indicate that altered osteogenic differentiation ability in MSCs is related to nontraumatic ON of the femoral head and the differentiation potential of MSCs in patients with nontraumatic ON differs according to its risk factor. ß

The neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1) affects the cerebellum and inferior olive, though previous research has focused primarily on the cerebellum. As a result, it is unknown what molecular alterations are present in the inferior olive, and whether these changes are found in other affected tissues. This study addresses these questions for the first time using two different SCA1 mouse models. We found that differentially regulated genes in the inferior olive segregated into several biological pathways. Comparison of the inferior olive and cerebellum demonstrates that vulnerable tissues in SCA1 are not uniform in their gene expression changes, and express largely discrete but some commonly enriched biological pathways. Importantly, we also found that brain-region-specific differences occur early in disease initiation and progression, and they are shared across the two mouse models of SCA1. This suggests different mechanisms of degeneration at work in the inferior olive and cerebellum.

Background and purpose: The availability and promise of effective treatments for neurodegenerative disorders are increasing the importance of early diagnosis. Having molecular and biochemical markers of Alzheimer's disease (AD) would complement clinical approaches, and further the goals of early and accurate diagnosis. Combining multiple biomarkers in evaluations significantly increases the sensitivity and specificity of the biochemical tests.Methods: In this study, we used color-coded bead-based Luminex technology to test the potential of using chemokines and cytokines as biochemical markers of AD. We measured the levels of 22 chemokines and cytokines in the serum and cerebrospinal fluid (CSF) of 32 de novo patients (13 controls, 11 AD, and 8 Parkinson's disease [PD]).Results: MCP-1 was the only cytokine detectable in CSF, and its levels did not differ between control and disease groups. However, the serum concentration of eotaxin was significantly higher in AD patients than in the control group.Conclusions: The analysis of multiple inflammatory mediators revealed marginal differences in their CSF and serum concentrations for the differential diagnosis of AD and PD. These results provide evidence that immunological responses are not major contributors to the pathogenesis of AD and PD.

Chronic redox imbalance in erythrocytes of individuals with sickle cell disease (SCD) contributes to oxidative stress and likely underlies common etiologies of hemolysis. We measured the amounts of six antioxidant enzymes-SOD1, catalase, glutathione peroxidase 1 (GPx1), as well as peroxiredoxins (Prxs) I, II, and VI-in red blood cells (RBCs) of SCD patients and control subjects. The amounts of SOD1 and Prx VI were reduced by about 17% and 20%, respectively, in SCD RBCs compared with control cells. The amounts of Prx II and GPx1 did not differ between SCD and normal RBCs. However, about 18% of Prx II was inactivated in SCD RBCs as a result of oxidation to sulfinic Prx II, whereas inactive Prx II was virtually undetectable in control cells. Furthermore, GPx1 activity was reduced by about 33% in SCD RBCs, and the loss of activity was correlated with hemolysis in SCD patients. RBCs from SCD patients taking hydroxyurea demonstrated 90% higher GPx1 activity than did those from untreated SCD patients, with no differences seen for the other catalytic antioxidants. Hydroxyurea induced GPx1 expression in multiple cultured cell lines in a manner dependent on both p53 and NO-cGMP signaling pathways. GPx1 expression represents a previously unrecognized potential benefit of hydroxyurea treatment in SCD patients. Antioxid. Redox Signal. 13, 1-11.