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HSCs either self-renew or differentiate to give rise to multipotent cells whose progeny provide blood cell precursors. However, surprisingly little is known about the factors that regulate this choice of self-renewal versus differentiation. One candidate is the Notch signaling pathway, with ex vivo studies suggesting that Notch regulates HSC differentiation, although a functional role for Notch in HSC self-renewal in vivo remains controversial. Here, we have shown that Notch2, and not Notch1, inhibits myeloid differentiation and enhances generation of primitive [Sca-1.sup.+]c-[kit.sup.+] progenitors following in vitro culture of enriched HSCs with purified Notch ligands. In mice, Notch2 enhanced the rate of formation of short-term repopulating multipotential progenitor cells (MPPs) as well as long-term repopulating HSCs, while delaying myeloid differentiation in BM following injury. However, consistent with previous reports, once homeostasis was achieved, neither Notch1 nor Notch2 affected repopulating cell self-renewal. These data indicate a Notch2-dependent role in assuring orderly repopulation by HSCs, MPPs, myeloid cells, and lymphoid cells during BM regeneration., Introduction HSCs either self-renew or give rise to multipotent cells whose progeny provide precursors committed to the lymphoid and myeloid lineages. Recent studies have identified factors that maintain HSCs in [...]

Haloperidol is a commonly used, typical, antipsychotic drug (APD) that acts strongly against positive symptoms, but has fewer therapeutic effects on, or may even aggravate, negative symptoms and cognitive deficits in patients with schizophrenia. Loss of oligodendrocytes has been suggested as a factor associated with the negative symptoms of schizophrenia. Recent study shows that chronic haloperidol treatment induced down-regulation of oligodendrocyte-related genes in certain brain regions of mouse. In this study, we used primary oligodendrocyte progenitor cell cultures from 1- to 3-day-postnatal rats to investigate the direct effects of haloperidol on the proliferation and differentiation of oligodendrocyte progenitor cells. Our results showed that (i) haloperidol (0-10.0 µmol x [L.sup.-1]) facilitated the proliferation of oligodendrocyte progenitor cells, (ii)chronic haloperidol (0.5 µmol x [L.sup.-1]) treatment decreased the number of myelin basic protein positive oligodendrocytes and reduced the oligodendrocytes cells possessing myelin-like membranes, resulting in inhibition of the terminal differentiation of oligodendrocytes, and (iii) D3 receptor mRNA was detected in oligodendrocyte progenitor cells, and haloperidol treatment induced a down-regulation of D3 receptor mRNA. These results suggest that the typical antipsychotic drug haloperidol affects the development of oligodendrocyte progenitor cells, and that D3 receptor down regulation may be involved. Our observations provide new insight into possible cellular mechanisms responsible for the side effects of typical antipsychotic drugs and support the concept that abnormality of oligodendrocytes may be involved in the pathogenesis of schizophrenia. Key words: haloperidol, oligodendrocyte progenitor cell, proliferation, schizophrenia, dopamine receptor. L'haloperidol, un medicament antipsychotique typique, agit fortement contre les symptomes positifs mais exerce moins d'effets theerapeutiques, ou aggrave meme les symptomes negatifs et les deficits cognitifs des patients souffrant de schizophrenie. La perte d'oligodendrocytes a ete suggeree comme facteur associe aux symptomes negatifs de la schizophrenie. Des etudes recentes montrent qu'un traitement chronique a l'haloperidol induisait une diminution de l'expression de genes relies aux oligodendrocytes dans certaines regions du cerveau de la souris. Dans cette etude, nous avons utilise; des cultures primaires de cellules progenitrices d'oligodendrocytes de rats aux jours post-nataux 1-3, pour examiner les effets directs de l'haloperidol sur la proliferation et la differentiation des cellules progenitrices d'oligodendrocytes. Nous resultats ont montre que (i) l'haloperidol (0-10,0 µmol x [L.sup.-1]) facilitait la proliferation des cellules progenitrices d'oligodendrocytes, (ii) un traitement chronique a l'haloperidol (0,5 µmol x [L.sup.-1]) diminuait le nombre d'oligodendrocytes possedant des membranes de type myeline, resultant en une inhibition de la differenciation terminale des oligodendrocytes et (iii) l'ARNm du recepteur D3 etait detecte dans les cellules progenitrices d'oligodendrocytes, et le traitement a l'haloperidol induisait une diminution de l'expression de l'ARNm du recepteur D3. Ces resultats suggerent que l'haloperidol, un medicament antipsychotique typique, affecte le developpement des cellules progenitrices des oligodendrocytes, et que la diminution de l'expression du recepteur D3 pourrait etre impliquee. Nos observations donnent un nouvel apercu des mecanismes cellulaires possiblement responsables des effets secondaires des medicaments antipsychotiques typiques et appuient le concept qu'une anomalie des oligodendrocytes puisse etre impliquee dans la pathogenese de la schizophrenie. Mots-cles: haloperidol, cellule progenitrice d'oligodendrocytes, proliferation, differentiation, schizophrenie, recepteur de la dopamine. [Traduit par la Redaction], Introduction Haloperidol is a commonly used, typical, antipsychotic drug (APD). It has been shown to act strongly against positive symptoms, such as psychoses, hallucinations, and disordered thought processes, likely due [...]

Reactive oxygen species (ROS), produced during various electron transfer reactions in vivo, are generally considered to be deleterious to cells (1). In the mammalian haematopoietic system, haematopoietic stem cells contain low levels of ROS. However, unexpectedly, the common myeloid progenitors (CMPs) produce significantly increased levels of ROS (2). The functional significance of this difference in ROS level in the two progenitor types remains unresolved (2,3). Here we show that Drosophila multipotent haematopoietic progenitors, which are largely akin to the mammalian myeloid progenitors (4), display increased levels of ROS under in vivo physiological conditions, which are downregulated on differentiation. Scavenging the ROS from these haematopoietic progenitors by using in vivo genetic tools retards their differentiation into mature blood cells. Conversely, increasing the haematopoietic progenitor ROS beyond their basal level triggers precocious differentiation into all three mature blood cell types found in Drosophila, through a signalling pathway that involves JNK and FoxO activation as well as Polycomb downregulation. We conclude that the developmentally regulated, moderately high ROS level in the progenitor population sensitizes them to differentiation, and establishes a signalling role for ROS in the regulation of haematopoietic cell fate. Our results lead to a model that could be extended to reveal a probable signalling role for ROS in the differentiation of CMPs in mammalian haematopoietic development and oxidative stress response., The Drosophila lymph gland is a specialized haematopoietic organ which produces three blood cell types--plasmatocytes, crystal cells and lamellocytes--with functions reminiscent of the vertebrate myeloid lineage (5,6). During the first [...]

The rarity and inaccessibility of the earliest primordial germ cells (PGCs) in the mouse embryo thwart efforts to investigate molecular mechanisms of germ-cell specification. stella (also called Dppa3) marks the rare founder population of the germ lineage (1,2). Here we differentiate mouse embryonic stem cells carrying a stella-transgenic reporter into putative PGCs in vitro. The [Stella.sup.+] cells possess a transcriptional profile similar to embryo-derived PGCs, and like their counterparts in vivo, lose imprints in a time-dependent manner. Using inhibitory RNAs to screen candidate genes for effects on the development of [Stella.sup.+] cells in vitro, we discovered that Lin28, a negative regulator of let-7 microRNA processing (3-6), is essential for proper PGC development. Furthermore, we show that Blimp1 (also called Prdm1), a let-7 target and a master regulator of PGC specification (7-9), can rescue the effect of Lin28 deficiency during PGC development, thereby establishing a mechanism of action for Lin28 during PGC specification. Overexpression of Lin28 promotes formation of [Stella.sup.+] cells in vitro and PGCs in chimaeric embryos, and is associated with human germ-cell tumours. The differentiation of putative PGCs from embryonic stem cells in vitro recapitulates the early stages of gamete development in vivo, and provides an accessible system for discovering novel genes involved in germ-cell development and malignancy., The transcriptional program responsible for specifying PGCs has been investigated through molecular analysis of cDNA created from single cells (10,11), but because transgenic or knockout methods required to verify roles [...]

CD8 T cells, which have a crucial role in immunity to infection and cancer, are maintained in constant numbers, but on antigen stimulation undergo a developmental program characterized by distinct phases encompassing the expansion and then contraction of antigen-specific effector ([T.sub.E]) populations, followed by the persistence of long-lived memory ([T.sub.M]) cells (1,2). Although this predictable pattern of CD8 T-cell responses is well established, the underlying cellular mechanisms regulating the transition to [T.sub.M] cells remain undefined (1,2). Here we show that tumour necrosis factor (TNF) receptor-associated factor 6 (TRAF6), an adaptor protein in the TNF-receptor and interleukin-1R/Toll-like receptor superfamily, regulates CD8 [T.sub.M]-cell development after infection by modulating fatty acid metabolism. We show that mice with a T-cell-specific deletion of TRAF6 mount robust CD8 [T.sub.E]-cell responses, but have a profound defect in their ability to generate [T.sub.M] cells that is characterized by the disappearance of antigen-specific cells in the weeks after primary immunization. Microarray analyses revealed that TRAF6-deficient CD8 T cells exhibit altered expression of genes that regulate fatty acid metabolism. Consistent with this, activated CD8 T cells lacking TRAF6 display defective AMP-activated kinase activation and mitochondrial fatty acid oxidation (FAO) in response to growth factor withdrawal. Administration of the anti-diabetic drug metformin restored FAO and CD8 [T.sub.M]-cell generation in the absence of TRAF6. This treatment also increased CD8 [T.sub.M] cells in wild-type mice, and consequently was able to considerably improve the efficacy of an experimental anti-cancer vaccine., A prevailing paradigm in immunology is that antigenic signal strength drives progressive T-cell differentiation (3). To investigate this model regarding [T.sub.M] cells, we studied CD8 T-cell responses to bacterial infection [...]

The intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. We have recently demonstrated the presence of about six cycling [Lgr5.sup.+] stem cells at the bottoms of small-intestinal crypts (1). Here we describe the establishment of long-term culture conditions under which single crypts undergo multiple crypt fission events, while simultanously generating villus-like epithelial domains in which all differentiated cell types are present. Single sorted [Lgr5.sup.+] stem cells can also initiate these crypt-villus organoids. Tracing experiments indicate that the [Lgr5.sup.+] stem-cell hierarchy is maintained in organoids. We conclude that intestinal crypt-villus units are self-organizing structures, which can be built from a single stem cell in the absence of a non-epithelial cellular niche., The self-renewing epithelium of the small intestine is ordered into crypts and villi (2). Cells are newly generated in the crypts and are lost by apoptosis at the tips of [...]

In the absence of leukemia inhibitory factor, murine embryonic stem cells cultured in vitro spontaneously aggregate to from three-dimensional embryoid bodies that differentiate to produce hematopoietic, endothelial, muscle, and neuronal cell lineages in a manner recapitulating the events of early embryogenesis. Cardiomyogenesis in embryoid bodies was recently demonstrated to be promoted by PYS-2-derived native SPARC (secreted protein, acidic and rich in cysteine), whose expression is upregulated in parietal endoderm at the onset of the epithelial to mesenchymal transition. Here, we confirm the stimulatory effects of mouse SPARC on cardiomyogenesis using a recombinant baculovirus-produced protein (rmSPARC). Embryoid bodies cultured in the presence of glycosylated rmSPARC, or an unglycosylated peptide spanning the C-terminal EF-hand domain, developed greater numbers of beating cardiomyocytes than did time-matched controls, with enhanced expression of cardiac marker genes including Nkx2.5, Troponin, BMP-2, and MHCα. Histochemical analysis revealed an expansion of the peripheral endoderm, with thicker layers of extracellular matrix (ECM) material observed atop underlying cells. Embryoid bodies treated with SPARC also displayed increased adherence to polystyrene culture dishes, with enhanced expression of ECM mRNAs including collagen IVα3, collagen IVα5, and laminin α1. These results indicate that, in addition to the promotion of cardiomyogenesis, SPARC may also help regulate the molecular composition and organization of ECM secreted by the mesenchymal parietal endoderm. Key words: cardiomyogenesis, SPARC, parietal endoderm, embryoid bodies, epithelial to mesenchymal transition (EMT). Resume : En absence de la chimiokine LIF (<< leukemia inhibitory factor >>), les cellules souches embryonnaires de souris cultivees in vitro s'agregent spontanement pour former des corps embryoides tridimensionnels qui se differencient pour produire des lignees cellulaires hematopoietiques, musculaires et neuronales d'une facon qui recapitule les etapes de l'embryogenese precoce. L'on a demontre recemment que la cardiomyogenese est favorisee par la proteine native SPARC (<< secreted protein, acidic and rich in cysteine >>) produite par les cellules PYS-2, dont l'expression est stimulee lors de la transition epithelium a mesenchyme. Nous confirmons ici les effets stimulateurs de la SPARC de souris sur la cardiomyogenese a l'aide d'une proteine recombinante produite chez le baculovirus (rsSPARC). Les corps embryoides cultives en presence de rsSPARC glycosylee ou d'un peptide non glycosyle qui comprend le domaine EF-hand C-terminal, formaient un plus grand nombre de cardiomyocytes pulsatiles relativement aux controles apparies en fonction du temps. Ceci etait accompagne d'une augmentation de l'expression de marqueurs cardiaques dont les genes Nkx2,5, Troponin, BMP-2 et MHCα. Des analyses histochimiques ont revele une expansion de l'endoderme peripherique et un epaississement de la couche de composantes de la matrice extracellulaire (MEC) observee sur les cellules sous-jacentes. Les corps embryoides traites a la SPARC adheraient davantage au polystyrene des plats de culture et les ARNm des composantes de la MEC, dont le collagene IVα3, le collagene IV α5 et la laminine αl, etaient plus fortement exprimes. Ces resultats indiquent que, en plus de promouvoir la cardiomyogenese, la SPARC peut aussi aider a reguler la composition moleculaire et l'organisation de la MEC secretee par l'endoderme parietal du mesenchyme. [Traduit par la Redaction], Introduction The directed differentiation of embryonic stems cells into cardiomyocytes is emerging as a promising source of cells for cardiac tissue engineering and cell transplantation therapies in the treatment of [...]

Interleukin (IL)-17-producing [CD4.sup.+] T lymphocytes ([T.sub.H]17 cells) constitute a subset of T-helper cells involved in host defence and several immune disorders (1,2). An intriguing feature of [T.sub.H]17 cells is their [...]

I. INTRODUCTION: ION CHANNELS, ASCIDIAN EMBRYOS, AND NEURAL INDUCTION Electrical excitability involving characteristic sets of voltage-dependent ion channels is an essential property of neurons working as the elements of a [...]

The myogenic basic helix-loop-helix (bBHLH) and MEF2 transcription factors are expressed in the myotome of developing somites and cooperatively activate skeletal muscle gene expression. The bHLH protein Twist is expressed throughout the epithelial somite and is subsequently excluded from the myotome. Ectopically expressed mouse Twist (Mtwist) was shown to inhibit myogenesis by blocking DNA binding by MyoD, by titrating E proteins, and by inhibiting trans-activation by MEF2. For inhibition of MEF2, Mtwist required heterodimerization with E proteins and an intact basic domain and carboxyl-terminus. Thus, Mtwist inhibits both families of myogenic regulators and may regulate myotome formation temporally or spatially., Members of the bBHLH family of transcription factors play important roles in controlling cell type determination and differentiation in both vertebrates and invertebrates (1). Vertebrate skeletal muscle development is controlled [...]

Transdifferentiation is a relatively rare phenomenon in which cells of one differentiated type and function switch to a second discrete identity. In vertebrate embryos, smooth muscle and skeletal muscle are distinct tissues that arise from separate compartments of the mesoderm. The musculature of the mouse esophagus was found to undergo a conversion from smooth muscle in the fetus to skeletal muscle during early postnatal development. The switch from smooth to skeletal muscle features the transitory appearance of individual cells expressing a mixed phenotype, which suggests that this conversion is a result of programmed transdifferentiation., Skeletal and smooth muscles of vertebrates differ with respect to structure, innervation, function, and developmental origin [1]. For example, skeletal muscle is composed of fused multinucleate myotubes containing striated fibers, [...]

Owens, Gary K. Regulation of Differentiation of Vascular Smooth Muscle Cells. Physiol. Rev. 75: 487-517, 1995. -- The vascular smooth muscle cell (SMC) in mature animals is a highly specialized [...]

I. INTRODUCTION TO ONTOGENESIS OF THE METANEPHRIC KIDNEY Most parenchymal epithelial organs follow a fairly simple scheme of embryonic organogenesis. An epithelial sheet or tube that is derived from one [...]

THE BIOLOGICAL ACTIVITIES OF NGF, like those of EGF, are mediated by cell-surface receptor proteins that span the plasma membrane [1, 2]. Receptors for NGF exist in a high- and [...]