A transcription factor, Cbfa1, which belongs to the runt-domain gene family, is expressed restrictively in fetal development. To elucidate the function of Cbfa1, we generated mice with a mutated Cbfa1 locus. Mice with a homozygous mutation in Cbfa1 died just after birth without breathing. Examination of their skeletal systems showed a complete lack of ossification. Although immature osteoblasts, which expressed alkaline phophatase weakly but not Osteopontin and Osteocalcin, and a few immature osteoclasts appeared at the perichondrial region, neither vascular nor mesenchymal cell invasion was observed in the cartilage. Therefore, our data suggest that both intramembranous and endochondral ossification were completely blocked, owing to the maturational arrest of osteoblasts in the mutant mice, and demonstrate that Cbfa1 plays an essential role in osteogenesis.

Several lines of evidence indicate that very large G-protein-coupled receptor 1 (Vlgr1) makes up the ankle links that connect the stereocilia of hair cells at their base. Here, we show that the transmembrane protein usherin, the putative transmembrane protein vezatin, and the PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain-containing submembrane protein whirlin are colocalized with Vlgr1 at the stereocilia base in developing cochlear hair cells and are absent in Vlgr1 Ϫ/Ϫ mice that lack the ankle links. Direct in vitro interactions between these four proteins further support their involvement in a molecular complex associated with the ankle links and scaffolded by whirlin. In addition, the delocalization of these proteins in myosin VIIa defective mutant mice as well as the myosin VIIa tail direct interactions with vezatin, whirlin, and, we show, Vlgr1 and usherin, suggest that myosin VIIa conveys proteins of the ankle-link complex to the stereocilia. Adenylyl cyclase 6, which was found at the base of stereocilia, was both overexpressed and mislocated in Vlgr1 Ϫ/Ϫ mice. In postnatal day 7 Vlgr1 Ϫ/Ϫ mice, mechanoelectrical transduction currents evoked by displacements of the hair bundle toward the tallest stereocilia (i.e., in the excitatory direction) were reduced in outer but not inner hair cells. In both cell types, stimulation of the hair bundle in the opposite direction paradoxically resulted in significant transduction currents. The absence of ankle-linkmediated cohesive forces within hair bundles lacking Vlgr1 may account for the electrophysiological results. However, because some long cadherin-23 isoforms could no longer be detected in Vlgr1 Ϫ/Ϫ mice shortly after birth, the loss of some apical links could be involved too. The premature disappearance of these cadherin isoforms in the Vlgr1 Ϫ/Ϫ mutant argues in favor of a signaling function of the ankle links in hair bundle differentiation.

Core binding factor 13 (CBF,B) is considered to be a transcriptional coactivator that dimerizes with transcription factors core binding factor a 1 (CBFA1), -2, and -3, and enhances DNA binding capacity of these transcription factors. CBFI3 and CBFA2, which is also called acute myeloid leukemia 1 gene, are frequently involved in chromosomal translocations in human leukemia. To elucidate the function of CBFP, mice carrying a mutation in the Cbfb locus were

Neural precursor cells (NPCs) differentiate into neurons, astrocytes, and oligodendrocytes in response to intrinsic and extrinsic changes. Notch signals maintain undifferentiated NPCs, but the mechanisms underlying the neuronal differentiation are largely unknown. We show that SIRT1, an NAD ؉ -dependent histone deacetylase, modulates neuronal differentiation. SIRT1 was found in the cytoplasm of embryonic and adult NPCs and was transiently localized in the nucleus in response to differentiation stimulus. SIRT1 started to translocate into the nucleus within 10 min after the transfer of NPCs into differentiation conditions, stayed in the nucleus, and then gradually retranslocated to the cytoplasm after several hours. The number of neurospheres that generated Tuj1 ؉ neurons was significantly decreased by pharmacological inhibitors of SIRT1, dominant-negative SIRT1 and SIRT1-siRNA, whereas overexpression of SIRT1, but not that of cytoplasm-localized mutant SIRT1, enhanced neuronal differentiation and decreased Hes1 expression. Expression of SIRT1-siRNA impaired neuronal differentiation and migration of NPCs into the cortical plate in the embryonic brain. Nuclear receptor corepressor (N-CoR), which has been reported to bind SIRT1, promoted neuronal differentiation and synergistically increased the number of Tuj1 ؉ neurons with SIRT1, and both bound the Hes1 promoter region in differentiating NPCs. Hes1 transactivation by Notch1 was inhibited by SIRT1 and/or N-CoR. Our study indicated that SIRT1 is a player of repressing Notch1-Hes1 signaling pathway, and its transient translocation into the nucleus may have a role in the differentiation of NPCs.

BackgroundMicroglia are the resident macrophage population of the central nervous system (CNS) and play essential roles, particularly in inflammation-mediated pathological conditions such as ischemic stroke. Increasing evidence shows that the population of vascular cells located around the blood vessels, rather than circulating cells, harbor stem cells and that these resident vascular stem cells (VSCs) are the likely source of some microglia. However, the precise traits and origins of these cells under pathological CNS conditions remain unclear.MethodsIn this study, we used a mouse model of cerebral infarction to investigate whether reactive pericytes (PCs) acquire microglia-producing VSC activity following ischemia.ResultsWe demonstrated the localization of ionized calcium-binding adaptor molecule 1 (Iba1)-expressing microglia to perivascular regions within ischemic areas. These cells expressed platelet-derived growth factor receptor-β (PDGFRβ), a hallmark of vascular PCs. PDGFRβ+ PCs isolated from ischemic, but not non-ischemic, areas expressed stem/undifferentiated cell markers and subsequently differentiated into various cell types, including microglia-like cells with phagocytic capacity.ConclusionsThe study results suggest that vascular PCs acquire multipotent VSC activity under pathological conditions and may thus be a novel source of microglia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0523-9) contains supplementary material, which is available to authorized users.