CD20 plays a role in human B cell proliferation and is an effective target for immunotherapy. In this study, mouse CD20 expression and biochemistry were assessed for the first time using a new panel of CD20-specific mAb, with CD20 function assessed using CD20-deficient (CD20(-/-)) mice. CD20 expression was B cell restricted and was initiated during late pre-B cell development. The frequency and density of CD20 expression increased during B cell maturation in the bone marrow, with a subpopulation of transitional IgM(hi) B cells expressing higher CD20 levels than the majority of mature recirculating B cells. Transitional T1 B cells in the spleen also expressed high CD20 levels, providing a useful new marker for this B cell subset. In CD20(-/-) mice, immature and mature B cell IgM expression was approximately 20-30% lower relative to B cells from wild-type littermates. In addition, CD19-induced intracellular calcium responses were significantly reduced in CD20(-/-) B cells, with a less dramatic effect on IgM-induced responses. These results reveal a role for CD20 in transmembrane Ca(2+) movement in mouse primary B cells that complements previous results obtained using human CD20 cDNA-transfected cell lines. Otherwise, B cell development, tissue localization, signal transduction, proliferation, T cell-dependent antibody responses and affinity maturation were normal in CD20(-/-) mice. Thus, mouse and human CD20 share similar patterns of expression and function. These studies thereby provide an animal model for studying CD20 function in vivo and the molecular mechanisms that influence anti-CD20 immunotherapy.

Among the main bacteria implicated in the pathology of periodontal disease, Aggregatibacter actinomycetemcomitans (Aa) is well known for causing loss of periodontal attachment and systemic disease. Recent studies have suggested that secreted extracellular RNAs (exRNAs) from several bacteria may be important in periodontitis, although their role is unclear. Emerging evidence indicates that exRNAs circulate in nanosized bilayered and membranous extracellular vesicles (EVs) known as outer membrane vesicles (OMVs) in gram-negative bacteria. In this study, we analyzed the small RNA expression profiles in activated human macrophage-like cells (U937) infected with OMVs from Aa and investigated whether these cells can harbor exRNAs of bacterial origin that have been loaded into the host RNA-induced silencing complex, thus regulating host target transcripts. Our results provide evidence for the cytoplasmic delivery and activity of microbial EV-derived small exRNAs in host gene regulation. The production of TNF-a was promoted by exRNAs via the TLR-8 and NF-kB signaling pathways. Numerous studies have linked periodontal disease to neuroinflammatory diseases but without elucidating specific mechanisms for the connection. We show here that intracardiac injection of Aa OMVs in mice showed successful delivery to the brain after crossing the blood-brain barrier, the exRNA cargos increasing expression of TNF-a in the mouse brain. The current study indicates that host gene regulation by microRNAs originating from OMVs of the periodontal pathogen Aa is a novel mechanism for host gene regulation and that the transfer of OMV exRNAs to the brain may cause neuroinflammatory diseases like Alzheimer's.

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Osteoclasts differentiate from precursor cells of the monocyte-macrophage lineage and subsequently become activated to be competent for bone resorption through programs primarily governed by receptor activator of nuclear factor-kappaB ligand in cooperation with macrophage colony-stimulating factor. Proteins prominently expressed at late phases of osteoclastogenesis and with a supportive role in osteoclast function are potential therapeutic targets for bone-remodeling disorders. In this study, we used a proteomics approach to show that abundance of the brain-type cytoplasmic creatine kinase (Ckb) is greatly increased during osteoclastogenesis. Decreasing Ckb abundance by RNA interference or blocking its enzymatic activity with a pharmacological inhibitor, cyclocreatine, suppressed the bone-resorbing activity of osteoclasts grown in vitro via combined effects on actin ring formation, RhoA GTPase activity and vacuolar ATPase function. Activities of osteoclasts derived from Ckb-/- mice were similarly affected. In vivo studies showed that Ckb-/- mice were better protected against bone loss induced by ovariectomy, lipopolysaccharide challenge or interleukin-1 treatment than wild-type controls. Furthermore, administration of cyclocreatine or adenoviruses harboring Ckb small hairpin RNA attenuated bone loss in rat and mouse models. Our findings establish an important role for Ckb in the bone-resorbing function of osteoclasts and underscore its potential as a new molecular target for antiresorptive drug development.

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Growth and differentiation factor 11 (GDF11) and myostatin (MSTN) are closely related transforming growth factor β (TGF-β) family members, but their biological functions are quite distinct. While MSTN has been widely shown to inhibit muscle growth, GDF11 regulates skeletal patterning and organ development during embryogenesis. Postnatal functions of GDF11, however, remain less clear and controversial. Due to the perinatal lethality ofGdf11null mice, previous studies used recombinant GDF11 protein to prove its postnatal function. However, recombinant GDF11 and MSTN proteins share nearly identical biochemical properties, and most GDF11-binding molecules have also been shown to bind MSTN, generating the possibility that the effects mediated by recombinant GDF11 protein actually reproduce the endogenous functions of MSTN. To clarify the endogenous functions of GDF11, here, we focus on genetic studies and show thatGdf11null mice, despite significantly down-regulatingMstnexpression, exhibit reduced bone mass through impaired osteoblast (OB) and chondrocyte (CH) maturations and increased osteoclastogenesis, while the opposite is observed inMstnnull mice that display enhanced bone mass. Mechanistically,Mstndeletion up-regulatesGdf11expression, which activates bone morphogenetic protein (BMP) signaling pathway to enhance osteogenesis. Also, mice overexpressing follistatin (FST), a MSTN/GDF11 inhibitor, exhibit increased muscle mass accompanied by bone fractures, unlikeMstnnull mice that display increased muscle mass without fractures, indicating that inhibition of GDF11 impairs bone strength. Together, our findings suggest that GDF11 promotes osteogenesis in contrast to MSTN, and these opposing roles of GDF11 and MSTN must be considered to avoid the detrimental effect of GDF11 inhibition when developing MSTN/GDF11 inhibitors for therapeutic purposes.

Plasma membrane calcium ATPases PMCA1 and PMCA4 regulate osteoclast differentiation and survival by regulating NFATc1 and NO.