Biomedical subjects

Joseph M Verdi

Publications and source records attributed to Joseph M Verdi.

12 recordsLinked to original sources

PubMed2006

Inhibition of Notch signaling induces myotube hypertrophy by recruiting a subpopulation of reserve cells.

During muscle differentiation, a population of quiescent undifferentiated myoblasts (reserve cells) emerges among mature muscle cells. However, the molecular mechanisms underlying such cell segregation and the characterization of this subpopulation of myoblasts remain to be determined. Notch is known to control the behavior and fate of murine muscle stem cells. In this study, we examined the role of Notch in myoblast segregation. We showed that inhibition of Notch activity by either overexpressing Numb or by using a pharmacological gamma-secretase inhibitor (DAPT) enhanced differentiation of murine and human myoblasts. This effect was not restricted to in vitro culture systems since DAPT-treated zebrafish embryos also showed increased differentiation. Using C2.7 myoblasts as a model, we showed that inhibition of Notch induced myotube hypertrophy by recruiting reserve cells that do not normally fuse. We further showed that endogenous Notch-signaling components were differentially expressed and activated in reserve cells with respect to Notch 1 and CD34 expression. We identified CD34 negative reserve cells as the subpopulation of myoblasts recruited to fuse into myotubes during differentiation in response to Notch inhibition. Therefore, we showed here that the activation of Notch 1 is important to maintain a subpopulation of CD34 negative reserve cells in an undifferentiated state.

Animals↗

PubMed2005

The RNA-binding protein Musashi-1 regulates neural development through the translational repression of p21WAF-1.

RNA-binding proteins regulate cell fate decisions during nervous system development. The Msi family of RNA-binding proteins is expressed in multipotential neural progenitors, and is required for maintaining cells in a proliferative state. We demonstrate that Msi-1's ability to regulate progenitor maintenance is through the translational inhibition of the cyclin-dependent kinase inhibitor p21WAF-1. Msi-1 ectopic expression increases the proliferation rate and the capacity to regulate p21WAF-1 protein expression, independent of p53. The 3' untranslated region (UTR) of the native p21(WAF-1) mRNA contains a Msi-1 consensus-binding site that permits Msi-1 to directly repress the translation of p21WAF-1 protein. Reduction of Msi-1 through antisense leads to aberrant p21WAF-1 expression, which significantly impairs neural differentiation. A double knockdown for p21WAF-1 and Msi-1 rescues the production of mature MAP+ neurons. Our results further elucidate the symbiotic relationship between cell cycle withdrawal and the onset of differentiation in the developing nervous system, as well as increasing the understanding of the influence that RNA-binding proteins serve in regulating these processes.

Cell Cycle↗

PubMed2005

A defect in lineage fate decision during fetal thymic invariant NKT cell development may regulate susceptibility to type 1 diabetes.

A numerical and functional deficiency in invariant NKT (iNKT) cells detectable by 3 wk of age in the thymus and spleen mediates the pathogenesis of type 1 diabetes in NOD mice, but the stage of T cell development at which this deficiency first occurs is unknown. We report in this study that this deficiency develops after the CD4(+)CD8(+) double-positive stage of thymic T cell development and is due to a lineage-specific depletion of CD4(-)CD8(-) double-negative alphabeta T cells and iNKT cells from the thymus between embryonic day 18 and day 1 after birth. Thus, an inheritable defect in a lineage fate decision that elicits a deficiency in fetal thymic iNKT cell development may predispose to susceptibility to type 1 diabetes.

Animals↗

PubMed2005

NRAGE mediates p38 activation and neural progenitor apoptosis via the bone morphogenetic protein signaling cascade.

Understanding the molecular events that govern neural progenitor lineage commitment, mitotic arrest, and differentiation into functional progeny are germane to our understanding of neocortical development. Members of the family of bone morphogenetic proteins (BMPs) play pivotal roles in regulating neural differentiation and apoptosis during neurogenesis through combined actions involving Smad and TAK1 activation. We demonstrate that BMP signaling is required for the induction of apoptosis of neural progenitors and that NRAGE is a mandatory component of the signaling cascade. NRAGE possesses the ability to bind and function with the TAK1-TAB1-XIAP complex facilitating the activation of p38. Disruption of NRAGE or any other member of the noncanonical signaling cascaded is sufficient to block p38 activation and thus the proapoptotic signals generated through BMP exposure. The function of NRAGE is independent of Smad signaling, but the introduction of a dominant-negative Smad5 also rescues neural progenitor apoptosis, suggesting that both canonical and noncanonical pathways can converge and regulate BMP-mediated apoptosis. Collectively, these results establish NRAGE as an integral component in BMP signaling and clarify its role during neural progenitor development.

Animals↗

PubMed2004

Insulin acts as a myogenic differentiation signal for neural stem cells with multilineage differentiation potential.

Reports of non-neural differentiation of neural stem cells (NSCs) have been challenged by alternative explanations for expanded differentiation potentials. In an attempt to demonstrate the plasticity of NSC, neurospheres were generated from single retrovirally labeled embryonic cortical precursors. In a defined serum-free insulin-containing media, 40% of the neurospheres contained both myogenic and neurogenic differentiated progeny. The number of NSCs displaying multilineage differentiation potential declines through gestation but does exist in the adult animal. In this system, insulin appears to function as a survival and dose-dependent myogenic differentiation signal for multilineage NSCs (MLNSC). MLNSC-derived cardiomyocytes contract synchronously, respond to sympathetic and parasympathetic stimulation, and regenerate injured heart tissues. These studies provide support for the hypothesis that MLNSCs exist throughout the lifetime of the animal, and potentially provide a population of stem cells for cell-based regenerative medicine strategies inside and outside of the nervous system.

Animals↗

PubMed2003

Characterization of NADE, NRIF and SC-1 gene expression during mouse neurogenesis.

The p75 neurotrophin receptor (p75NTR) is a member of the tumor necrosis factor receptor superfamily. p75NTR signaling events have been implicated in both cell cycle arrest and apoptosis depending on which effector molecules are associated with its intracellular domain after ligand binding. Two such effector proteins, p75NTR-associated cell death executor (NADE) and neurotrophin receptor interacting factor (NRIF) promote p75NTR-mediated apoptosis, whereas Schwann cell factor-1 (SC-1) mediates neurotrophin-dependent withdrawal from the cell cycle. An understanding of the expression profiles of these three interacting proteins and p75NTR during embryogenesis is critical for addressing whether these effector proteins might function outside of p75NTR-mediated signaling events. The distribution of NADE, NRIF and SC-1 mRNAs during murine development suggests that the action of these genes is in fact not limited to regions of p75NTR expression. Specifically, a detailed comparison of the spatial and temporal expression domains of NADE, NRIF and SC-1 during brain development revealed regions of co-expression with p75NTR but also illustrates a distinct and discordant spatial and temporal expression. These results yield novel insights into the unique developmental characteristics of the three p75NTR-interacting proteins, thus revealing their diverse signaling potential during embryonic development.

Aging↗

PubMed2003

Genomic organization and comparative sequence analysis of the mouse and human FRS2, FRS3 genes.

The signaling adapter proteins FRS2 and FRS3 are implicated in the transmission of extracellular signals from nerve growth factor (NGF) or fibroblast growth factor (FGF) receptors to the Ras/mitogen-activated protein kinase signaling cascade. This study presents the genomic sequence and exon-intron organization of the mouse FRS2 and FRS3 loci as well as their evolutionary conservation with their human counterparts. Both FRS2 and FRS3 contain 5 coding exons spanning over 7 kb of genomic sequence with similar exon sizes and organization. Comparative genomic sequence analyses show a highly conserved genomic organization between mouse and human in both FRS2 and FRS3 genes. Non-coding sequences, highly conserved between mouse and human, were identified in the FRS3 introns that may potentially function as regulatory elements. To assay potential differences in their patterns of expression, RT-PCR analysis was used to assay FRS2 and FRS3 expression in the developing embryo and neural tube (NT) during the time of neurogenesis.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Developmental changes in Notch1 and numb expression mediated by local cell-cell interactions underlie progressively increasing delta sensitivity in neural crest stem cells.

Neural stem cells become progressively less neurogenic and more gliogenic with development. Here, we show that between E10.5 and E14.5, neural crest stem cells (NCSCs) become increasingly sensitive to the Notch ligand Delta-Fc, a progliogenic and anti-neurogenic signal. This transition is correlated with a 20- to 30-fold increase in the relative ratio of expression of Notch and Numb (a putative inhibitor of Notch signaling). Misexpression experiments suggest that these changes contribute causally to increased Delta sensitivity. Moreover, such changes can occur in NCSCs cultured at clonal density in the absence of other cell types. However, they require local cell-cell interactions within developing clones. Delta-Fc mimics the effect of such cell-cell interactions to increase Notch and decrease Numb expression in isolated NCSCs. Thus, Delta-mediated feedback interactions between NCSCs, coupled with positive feedback control of Notch sensitivity within individual cells, may underlie developmental changes in the ligand-sensitivity of these cells.

Animals↗

PubMed2002

Expression analysis of a novel p75(NTR) signaling protein, which regulates cell cycle progression and apoptosis.

Neurotrophin receptor-interacting MAGE (NRAGE) is the most recently identified p75 neurotrophin receptor (p75(NTR)) intracellular binding protein. Previously, NRAGE over-expression was shown to mediate cell cycle arrest and facilitate nerve growth factor (NGF) dependent apoptosis of sympathetic neuroblasts in a p75(NTR) specific manner. Here we have examined the temporal and spatial expression patterns of NRAGE over the course of murine embryogenesis to determine whether NRAGE's expression is consistent with its proposed functions. We demonstrate that NRAGE mRNA and protein are expressed throughout embryonic and adult tissues. The mRNA is constitutively expressed within each tissue across development. However, expression of NRAGE protein displays a tight temporal tissue specific regulation. During early CNS development, NRAGE protein is expressed throughout the neural tube, but by later stages of neurogenesis, NRAGE protein is restricted within the ventricular zone, subplate and cortical plate. Moreover, NRAGE protein expression is limited to proliferative neural subpopulations as we fail to detect NRAGE expression co-localized with mature/differentiation associated neuronal markers. Interestingly, NRAGE's expression is not restricted solely to areas of p75(NTR) expression suggesting that NRAGE may mediate proliferation and/or apoptosis from other environmental signals in addition to NGF within the CNS. Our data support previously characterized roles for NRAGE as a mediator of precursor apoptosis and a repressor of cell cycle progression in neural development.

Animals↗

PubMed2002

Beta-arrestins regulate a Ral-GDS Ral effector pathway that mediates cytoskeletal reorganization.

beta-Arrestins are important in chemoattractant receptor-induced granule release, a process that may involve Ral-dependent regulation of the actin cytoskeleton. We have identified the Ral GDP dissociation stimulator (Ral-GDS) as a beta-arrestin-binding protein by yeast two-hybrid screening and co-immunoprecipitation from human polymorphonuclear neutrophilic leukocytes (PMNs). Under basal conditions, Ral-GDS is localized to the cytosol and remains inactive in a complex formed with beta-arrestins. In response to formyl-Met-Leu-Phe (fMLP) receptor stimulation, beta-arrestin Ral-GDS protein complexes dissociate and Ral-GDS translocates with beta-arrestin from the cytosol to the plasma membrane, resulting in the Ras-independent activation of the Ral effector pathway required for cytoskeletal rearrangement. The subsequent re-association of beta-arrestin Ral-GDS complexes is associated with the inactivation of Ral signalling. Thus, beta-arrestins regulate multiple steps in the Ral-dependent processes that result in chemoattractant-induced cytoskeletal reorganization.

Animals↗

PubMed2002

Numb isoforms containing a short PTB domain promote neurotrophic factor-induced differentiation and neurotrophic factor withdrawal-induced death of PC12 Cells.

The development of the nervous system is regulated by trophic signals that control cell proliferation, differentiation, and survival. Numb is an evolutionarily conserved protein identified by its ability to control cell fate in the nervous system of Drosophila. Mammals express four isoforms of Numb that differ in the length of a phosphotyrosine-binding (PTB) domain and a proline-rich region (PRR). Using PC12 cells stably expressing each of the human isoforms, we show that Numb regulates sensitivity of the cells to neurotrophic factor-induced differentiation and neurotrophic factor withdrawal-induced death in an isoform-specific manner. Numb isoforms containing a short PTB domain enhance the differentiation response to NGF and enhance apoptosis upon NGF withdrawal; Numb isoforms containing a long PTB domain exhibit the same sensitivity to NGF as vector-transfected cells. These effects of Numb were found to be independent of the length of the PRR. In undifferentiated conditions, the levels of full-length TrkA and of phosphorylated p44/p42 mitogen-activated protein kinase (MAPK) are increased in cells expressing Numb isoforms with a short PTB domain, indicating an up-regulation of NGF signaling pathways. Furthermore, we provide evidence that the mechanism whereby short PTB domain Numb isoforms sensitize cells to trophic factor deprivation-induced apoptosis involves elevations in intracellular calcium concentrations. Our results suggest that Numb sensitizes cells to neurotrophin responses in an isoform-specific manner, an effect that may play an important role in the development and plasticity of the nervous system.

Animals↗

PubMed1994

CNTF, FGF, and NGF collaborate to drive the terminal differentiation of MAH cells into postmitotic neurons.

The differentiation of neuronal cell progenitors depends on complex interactions between intrinsic cellular programs and environmental cues. Such interactions have recently been explored using an immortalized sympathoadrenal progenitor cell line, MAH. These studies have revealed that depolarizing conditions, in combination with exposure to FGF, can induce responsiveness to NGF. Here we report that CNTF, which utilizes an intracellular signaling pathway distinct from that of both FGF and NGF, can collaborate with FGF to promote efficiently the differentiation of MAH progenitor cells to a stage remarkably reminiscent of NGF-dependent, postmitotic sympathetic neurons. We also find that similar collaborative interactions can occur during transdifferentiation of normal cultured chromaffin cells into sympathetic neurons.

Animals↗