参考文献

The understanding of the function of alpha(1)-adrenergic receptors in the brain has been limited due to a lack of specific ligands and antibodies. We circumvented this problem by using transgenic mice engineered to overexpress either wild-type receptor tagged with enhanced green fluorescent protein or constitutively active mutant alpha(1)-adrenergic receptor subtypes in tissues in which they are normally expressed. We identified intriguing alpha(1A)-adrenergic receptor subtype-expressing cells with a migratory morphology in the adult subventricular zone that coexpressed markers of neural stem cell and/or progenitors. Incorporation of 5-bromo-2-deoxyuridine in vivo increased in neurogenic areas in adult alpha(1A)-adrenergic receptor transgenic mice or normal mice given the alpha(1A)-adrenergic receptor-selective agonist,cirazoline. Neonatal neurospheres isolated from normal mice expressed a mixture of alpha(1)-adrenergic receptor subtypes,and stimulation of these receptors resulted in increased expression of the alpha(1B)-adrenergic receptor subtype,proneural basic helix-loop-helix transcription factors,and the differentiation and migration of neuronal progenitors for catecholaminergic neurons and interneurons. alpha(1)-Adrenergic receptor stimulation increased the apoptosis of astrocytes and regulated survival of neonatal neurons through phosphatidylinositol 3-kinase signaling. However,in adult normal neurospheres,alpha(1)-adrenergic receptor stimulation increased the expression of glial markers at the expense of neuronal differentiation. In vivo,S100-positive glial and betaIII tubulin neuronal progenitors colocalized with either alpha(1)-adrenergic receptor subtype in the olfactory bulb. Our results indicate that alpha(1)-adrenergic receptors can regulate both neurogenesis and gliogenesis that may be developmentally dependent. Our findings may lead to new therapies to treat neurodegenerative diseases. View Publication

Objective: Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) constitute unique sources of pluripotent cells,although the molecular mechanisms involved in their differentiation into specific lineages are just beginning to be defined. Here we evaluated the ability of MEDII (medium conditioned by HepG2 cells,a human hepatocarcinoma cell line) to selectively enhance generation of mesodermal derivatives,including hematopoietic cells,from hESCs and hiPSCs. Materials and Methods: Test cells were exposed to MEDII prior to being placed in conditions that promote embryoid body (EB) formation. Hematopoietic activity was measured by clonogenic assays,flow cytometry,quantitative real-time polymerase chain reaction of specific transcript complementary DNAs and the ability of cells to repopulate sublethally irradiated nonobese diabetic/severe combined immunodeficient interleukin-2 receptor ??-chain-null mice for almost 1 year. Results: Exposure of both hESCs and hiPSCs to MEDII induced a rapid and preferential differentiation of hESCs into mesodermal elements. Subsequently produced EBs showed a further enhanced expression of transcripts characteristic of multiple mesodermal lineages,and a concurrent decrease in endodermal and ectodermal cell transcripts. Frequency of all types of clonogenic hematopoietic progenitors in subsequently derived EBs was also increased. In vivo assays of MEDII-treated hESC-derived EBs also showed they contained cells able to undertake low-level but longterm multilineage repopulation of primary and secondary nonobese diabetic/severe combined immunodeficient interleukin-2 receptor ??-chain-null mice. Conclusions: MEDII treatment of hESCs and hiPSCs alike selectively enhances their differentiation into mesodermal cells and allows subsequent generation of detectable levels of hematopoietic progenitors with in vitro and in vivo differentiating activity. ?? 2009 ISEH - Society for Hematology and Stem Cells. View Publication

BACKGROUND: Inflammatory processes play important roles in both neuropathic and inflammatory pain states,but the effects of inflammation per se within the sensory ganglia are not well understood. The cytokine growth-related oncogene (GRO/KC; CXCL1) shows strong,rapid upregulation in dorsal root ganglion (DRG) in both nerve injury and inflammatory pain models. We examined the direct effects of GRO/KC on small diameter DRG neurons,which are predominantly nociceptive. Whole cell voltage clamp technique was used to measure voltage-activated potassium (K) currents in acutely cultured adult rat small diameter sensory neurons. Fluorescently labeled isolectin B4 (IB4) was used to classify cells as IB4-positive or IB4-negative. RESULTS: In IB4-negative neurons,voltage-activated K current densities of both transient and sustained components were increased after overnight incubation with GRO/KC (1.5 nM),without marked changes in voltage dependence or kinetics. The average values for the slow and fast decay time constants at 20 mV were unchanged by GRO/KC. The amplitude of the fast inactivating component increased significantly with no large shifts in the voltage dependence of inactivation. The increase in K currents was completely blocked by co-incubation with protein synthesis inhibitor cycloheximide (CHX) or NF-kappaB inhibitors pyrrolidine dithiocarbamate (PDTC) or quinazoline (6-Amino-4-(4-phenoxypheny lethylamino;QNZ). In contrast,the voltage-activated K current of IB4-positive neurons was unchanged by GRO/KC. GRO/KC incubation caused no significant changes in the expression level of eight selected voltage-gated K channel genes in quantitative PCR analysis. CONCLUSION: The results suggest that GRO/KC has important effects in inflammatory processes via its direct actions on sensory neurons,and that activation of NF-kappaB is involved in the GRO/KC-induced enhancement of K currents. View Publication

The control of tyrosine phosphorylation depends on the fine balance between kinase and phosphatase activities. Protein tyrosine phosphatase 1B (PTP-1B) and T cell protein tyrosine phosphatase (TC-PTP) are 2 closely related phosphatases known to control cytokine signaling. We studied the functional redundancy of PTP-1B and TC-PTP by deleting 1 or both copies of these genes by interbreeding TC-PTP and PTP-1B parental lines. Our results indicate that the double mutant (tcptp(-/-)ptp1b(-/-)) is lethal at day E9.5-10.5 of embryonic development with constitutive phosphorylation of Stat1. Mice heterozygous for TC-PTP on a PTP-1B-deficient background (tcptp(+/-)ptp1b(-/-)) developed signs of inflammation. Macrophages from these animals were highly sensitive to IFN-gamma,as demonstrated by increased Stat1 phosphorylation and nitric oxide production. In addition,splenic T cells demonstrated increased IFN-gamma secretion capacity. Mice with deletions of single copies of TC-PTP and PTP-1B (tcptp(+/-)ptp1b(+/-)) exhibited normal development,confirming that these genes are not interchangeable. Together,these data indicate a nonredundant role for PTP-1B and TC-PTP in the regulation of IFN signaling. View Publication

BACKGROUND: Human tonsils are a rich source of B lymphocytes exhibiting a variety of phenotypes and activation states. Existing methods of purification are time consuming or costly. The aim of the present study was to optimize conditions to isolate large numbers of highly purified primary B lymphocytes from tonsils in a short and cost-effective single step,using a commercially available reagent designed for purifying cells from whole blood (RosetteSep). This technique relies on the presence of the large excess of red blood cells in whole blood for the formation of immunorosettes,whereas single cell suspensions from tonsils contain relatively few red blood cells. RESULTS: B cell enrichment from tonsils was achieved using RosetteSep with no modification to the whole blood procedure; however,the degree of purity depended on the extent of red blood cell contamination of the starting tonsil cell suspension. Addition of a 50-fold excess of allogeneic human red blood cells,but not sheep red blood cells,reproducibly resulted in high levels of purity. Depletion of mononuclear cells from the donor red blood cells eliminated potential contamination with allogeneic B cells. CONCLUSION: RosetteSep reagent can be used in combination with allogeneic human red blood cells to reproducibly isolate tonsil B lymphocytes to high levels of purity with no change in phenotype or loss of cells. This method provides considerable time and cost savings compared to other methods. View Publication

Nuclear retinoic acid receptors (RARs) are transcriptional regulators controlling the expression of specific subsets of genes in a ligand-dependent manner. The basic mechanism for switching on transcription of cognate target genes involves RAR binding at specific response elements and a network of interactions with coregulatory protein complexes,the assembly of which is directed by the C-terminal ligand-binding domain of RARs. In addition to this scenario,new roles for the N-terminal domain and the ubiquitin-proteasome system recently emerged. Moreover,the functions of RARs are not limited to the regulation of cognate target genes,as they can transrepress other gene pathways. Finally,RARs are also involved in nongenomic biological activities such as the activation of translation and of kinase cascades. Here we will review these mechanisms,focusing on how kinase signaling and the proteasome pathway cooperate to influence the dynamics of RAR transcriptional activity. View Publication

Lenalidomide is the first karyotype-selective therapeutic approved for the treatment of myelodysplastic syndromes (MDS) owing to high rates of erythroid and cytogenetic response in patients with chromosome 5q deletion [del(5q)]. Although haploinsufficiency for the RPS14 gene and others encoded within the common deleted region (CDR) have been implicated in the pathogenesis of the del(5q) phenotype,the molecular basis of the karyotype specificity of lenalidomide remains unexplained. We focused our analysis on possible haplodeficient enzymatic targets encoded within the CDR that play key roles in cell-cycle regulation. We show that the dual specificity phosphatases,Cdc25C and PP2Acalpha,which are coregulators of the G(2)-M checkpoint,are inhibited by lenalidomide. Gene expression was lower in MDS and acute myeloid leukemia (AML) specimens with del(5q) compared with those with alternate karyotypes. Lenalidomide inhibited phosphatase activity either directly (Cdc25C) or indirectly (PP2A) with corresponding retention of inhibitory phospho-tyrosine residues. Treatment of del(5q) AML cells with lenalidomide induced G(2) arrest and apoptosis,whereas there was no effect in nondel(5q) AML cells. Small interfering RNA (shRNA) suppression of Cdc25C and PP2Acalpha gene expression recapitulated del(5q) susceptibility to lenalidomide with induction of G(2) arrest and apoptosis in both U937 and primary nondel(5q) MDS cells. These data establish a role for allelic haplodeficiency of the lenalidomide inhibitable Cdc25C and PP2Acalpha phosphatases in the selective drug sensitivity of del(5q) MDS. View Publication

After DNA replication,sister chromatids must be untangled,or decatenated,before mitosis so that chromatids do not tear during anaphase. Topoisomerase IIalpha (Topo IIalpha) is the major decatenating enzyme. Topo IIalpha inhibitors prevent decatenation,causing cells to arrest during mitosis. Here we report that acute myeloid leukemia cells fail to arrest at the mitotic decatenation checkpoint,and their progression through this checkpoint is regulated by the DNA repair component Metnase (also termed SETMAR). Metnase contains a SET histone methylase and transposase nuclease domain,and is a component of the nonhomologous end-joining DNA double-strand break repair pathway. Metnase interacts with Topo IIalpha and enhances its decatenation activity. Here we show that multiple types of acute leukemia cells have an attenuated mitotic arrest when decatenation is inhibited and that in an acute myeloid leukemia (AML) cell line this is mediated by Metnase. Of further importance,Metnase permits continued proliferation of these AML cells even in the presence of the clinical Topo IIalpha inhibitor VP-16. In vitro,purified Metnase prevents VP-16 inhibition of Topo IIalpha decatenation of tangled DNA. Thus,Metnase expression levels may predict AML resistance to Topo IIalpha inhibitors,and Metnase is a potential therapeutic target for small molecule interference. View Publication

Immune dysfunction develops in patients with many cancer types and may contribute to tumor progression and failure of immunotherapy. Mechanisms underlying cancer-associated immune dysfunction are not fully understood. Efficient IFN signaling is critical to lymphocyte function; animals rendered deficient in IFN signaling develop cancer at higher rates. We hypothesized that altered IFN signaling may be a key mechanism of immune dysfunction common to cancer. To address this,we assessed the functional responses to IFN in peripheral blood lymphocytes from patients with 3 major cancers: breast cancer,melanoma,and gastrointestinal cancer. Type-I IFN (IFN-alpha)-induced signaling was reduced in T cells and B cells from all 3 cancer-patient groups compared to healthy controls. Type-II IFN (IFN-gamma)-induced signaling was reduced in B cells from all 3 cancer patient groups,but not in T cells or natural killer cells. Impaired-IFN signaling was equally evident in stage II,III,and IV breast cancer patients,and downstream functional defects in T cell activation were identified. Taken together,these findings indicate that defects in lymphocyte IFN signaling arise in patients with breast cancer,melanoma,and gastrointestinal cancer,and these defects may represent a common cancer-associated mechanism of immune dysfunction. View Publication

Ectopic expression of defined transcription factors can reprogram somatic cells to induced pluripotent stem (iPS) cells,but the utility of iPS cells is hampered by the use of viral delivery systems. Small molecules offer an alternative to replace virally transduced transcription factors with chemical signaling cues responsible for reprogramming. In this report we describe a small-molecule screening platform applied to identify compounds that functionally replace the reprogramming factor Klf4. A series of small-molecule scaffolds were identified that activate Nanog expression in mouse fibroblasts transduced with a subset of reprogramming factors lacking Klf4. Application of one such molecule,kenpaullone,in lieu of Klf4 gave rise to iPS cells that are indistinguishable from murine embryonic stem cells. This experimental platform can be used to screen large chemical libraries in search of novel compounds to replace the reprogramming factors that induce pluripotency. Ultimately,such compounds may provide mechanistic insight into the reprogramming process. View Publication