RESUMEN
Tumor-initiating cells have been suggested to be rare in many cancers. We tested this in mouse malignant peripheral nerve sheath tumors (MPNSTs) and found that 18% of primary and 49% of passaged MPNST cells from Nf1(+/-); Ink4a/Arf(-/-) mice formed tumors upon transplantation, whereas only 1.8% to 2.6% of MPNST cells from Nf1(+/-); p53(+/-) mice did. MPNST cells of both genotypes require laminin binding to ß1-integrin for clonogenic growth. Most MPNST cells from Nf1(+/-); Ink4a/Arf(-/-) mice expressed laminin, whereas most MPNST cells from Nf1(+/-); p53(+/-) mice did not. Exogenous laminin increased the percentage of MPNST cells from Nf1(+/-); p53(+/-) but not Nf1(+/-); Ink4a/Arf(-/-) mice that formed tumorigenic colonies. Tumor-forming potential is common among MPNST cells, but the assay conditions required to detect it vary with tumor genotype.
Asunto(s)
Transformación Celular Neoplásica , Neoplasias de la Vaina del Nervio/patología , Animales , Proliferación Celular , Genotipo , Integrina beta1/metabolismo , Integrina beta1/fisiología , Laminina/metabolismo , Ratones , Neoplasias de la Vaina del Nervio/genética , Neoplasias de la Vaina del Nervio/metabolismo , Células Tumorales CultivadasRESUMEN
The polycomb gene Bmi-1 is required for the self-renewal of stem cells from diverse tissues, including the central nervous system (CNS). Bmi-1 expression is elevated in most human gliomas, irrespective of grade, raising the question of whether Bmi-1 over-expression is sufficient to promote self-renewal or tumorigenesis by CNS stem/progenitor cells. To test this we generated Nestin-Bmi-1-GFP transgenic mice. Analysis of two independent lines with expression in the fetal and adult CNS demonstrated that transgenic neural stem cells formed larger colonies, more self-renewing divisions, and more neurons in culture. However, in vivo, Bmi-1 over-expression had little effect on CNS stem cell frequency, subventricular zone proliferation, olfactory bulb neurogenesis, or neurogenesis/gliogenesis during development. Bmi-1 transgenic mice were born with enlarged lateral ventricles and a minority developed idiopathic hydrocephalus as adults, but none of the transgenic mice formed detectable CNS tumors, even when aged. The more pronounced effects of Bmi-1 over-expression in culture were largely attributable to the attenuated induction of p16(Ink4a) and p19(Arf) in culture, proteins that are generally not expressed by neural stem/progenitor cells in young mice in vivo. Bmi-1 over-expression therefore has more pronounced effects in culture and does not appear to be sufficient to induce tumorigenesis in vivo.
Asunto(s)
Encéfalo/anomalías , Neurogénesis/fisiología , Neuronas/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Represoras/metabolismo , Células Madre/metabolismo , Animales , Encéfalo/embriología , Encéfalo/crecimiento & desarrollo , Neoplasias Encefálicas/embriología , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patología , Proliferación Celular , Transformación Celular Neoplásica/metabolismo , Células Cultivadas , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Glioma/embriología , Glioma/metabolismo , Glioma/patología , Humanos , Hidrocefalia/embriología , Hidrocefalia/metabolismo , Hidrocefalia/patología , Proteínas de Filamentos Intermediarios/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteínas del Tejido Nervioso/metabolismo , Nestina , Neuroglía/citología , Neuroglía/metabolismo , Neuronas/citología , Proteínas Nucleares/genética , Complejo Represivo Polycomb 1 , Proteínas Proto-Oncogénicas/genética , Proteínas Represoras/genética , Células Madre/citologíaRESUMEN
Neurofibromatosis is caused by the loss of neurofibromin (Nf1), leading to peripheral nervous system (PNS) tumors, including neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs). A long-standing question has been whether these tumors arise from neural crest stem cells (NCSCs) or differentiated glia. Germline or conditional Nf1 deficiency caused a transient increase in NCSC frequency and self-renewal in most regions of the fetal PNS. However, Nf1-deficient NCSCs did not persist postnatally in regions of the PNS that developed tumors and could not form tumors upon transplantation into adult nerves. Adult P0a-Cre+Nf1(fl/-) mice developed neurofibromas, and Nf1(+/-)Ink4a/Arf(-/-) and Nf1/p53(+/-) mice developed MPNSTs, but NCSCs did not persist postnatally in affected locations in these mice. Tumors appeared to arise from differentiated glia, not NCSCs.
Asunto(s)
Neoplasias/patología , Cresta Neural/citología , Neurofibromina 1/deficiencia , Células Madre/citología , Animales , Animales Recién Nacidos , Diferenciación Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Tracto Gastrointestinal/efectos de los fármacos , Tracto Gastrointestinal/metabolismo , Péptidos y Proteínas de Señalización Intercelular/farmacología , Ratones , Mutación/genética , Vaina de Mielina/efectos de los fármacos , Vaina de Mielina/patología , Neoplasias de la Vaina del Nervio/patología , Cresta Neural/efectos de los fármacos , Neurofibroma Plexiforme/patología , Neuroglía/citología , Neuroglía/efectos de los fármacos , Sistema Nervioso Periférico/efectos de los fármacos , Sistema Nervioso Periférico/embriología , Sistema Nervioso Periférico/metabolismo , Células de Schwann/efectos de los fármacos , Células de Schwann/patología , Transducción de Señal/efectos de los fármacos , Células Madre/efectos de los fármacos , Proteína p53 Supresora de Tumor/metabolismo , Proteínas ras/metabolismoRESUMEN
Canonical Wnt signaling instructively promotes sensory neurogenesis in early neural crest stem cells (eNCSCs) (Lee, H.Y., M. Kleber, L. Hari, V. Brault, U. Suter, M.M. Taketo, R. Kemler, and L. Sommer. 2004. Science. 303:1020-1023). However, during normal development Wnt signaling induces a sensory fate only in a subpopulation of eNCSCs while other cells maintain their stem cell features, despite the presence of Wnt activity. Hence, factors counteracting Wnt signaling must exist. Here, we show that bone morphogenic protein (BMP) signaling antagonizes the sensory fate-inducing activity of Wnt/beta-catenin. Intriguingly, Wnt and BMP act synergistically to suppress differentiation and to maintain NCSC marker expression and multipotency. Similar to NCSCs in vivo, NCSCs maintained in culture alter their responsiveness to instructive growth factors with time. Thus, stem cell development is regulated by combinatorial growth factor activities that interact with changing cell-intrinsic cues.
Asunto(s)
Proteínas Morfogenéticas Óseas/metabolismo , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Cresta Neural/embriología , Células Madre Pluripotentes/fisiología , Transducción de Señal/fisiología , Animales , Diferenciación Celular/fisiología , Linaje de la Célula/fisiología , Células Cultivadas , Proteínas del Citoesqueleto/metabolismo , Ratones , Cresta Neural/citología , Células Madre Pluripotentes/citología , Ratas , Transactivadores/metabolismo , Proteínas Wnt , beta CateninaRESUMEN
Point mutations affecting PMP22 can cause hereditary demyelinating and dysmyelinating peripheral neuropathies. In addition, duplication and deletion of PMP22 are associated with Charcot-Marie-Tooth disease Type 1A (CMT1A) and Hereditary Neuropathy with Liability to Pressure Palsy (HNPP), respectively. This study was designed to elucidate disease processes caused by misexpression of Pmp22 and, at the same time, to gain further information on the controversial molecular function of PMP22. To this end, we took advantage of the unique resource of a set of various Pmp22 mutant mice to carry out comparative expression profiling of mutant and wild-type sciatic nerves. Tissues derived from Pmp22-/- ("knockout"), Pmp22tg (increased Pmp22 copy number), and Trembler (Tr; point mutation in Pmp22) mutant mice were analyzed at two developmental stages: (i) at postnatal day (P)4, when normal myelination has just started and primary causative defects of the mutations are expected to be apparent, and (ii) at P60, with the goal of obtaining information on secondary disease effects. Interestingly, the three Pmp22 mutants exhibited distinct profiles of gene expression, suggesting different disease mechanisms. Increased expression of genes involved in cell cycle regulation and DNA replication is characteristic and specific for the early stage in Pmp22-/- mice, supporting a primary function of PMP22 in the regulation of Schwann cell proliferation. In the Tr mutant, a distinguishing feature is the high expression of stress response genes. Both Tr and Pmp22tg mice show strongly reduced expression of genes important for cholesterol synthesis at P4, a characteristic that is common to all three mutants at P60. Finally, we have identified a number of candidate genes that may play important roles in the disease process or in myelination per se.
Asunto(s)
Dosificación de Gen , Proteínas de la Mielina/genética , Enfermedades del Sistema Nervioso Periférico/genética , Mutación Puntual , Animales , Animales Recién Nacidos , Regulación de la Expresión Génica/genética , Genes cdc/fisiología , Ratones , Ratones Noqueados , Ratones Transgénicos , Proteínas de la Mielina/biosíntesis , Proteínas de la Mielina/fisiología , Enfermedades del Sistema Nervioso Periférico/metabolismo , Enfermedades del Sistema Nervioso Periférico/patologíaRESUMEN
Schwann cells develop from multipotent neural crest stem cells and are important for neuronal survival, maintenance of axonal integrity, and myelination. We used transgenic mice expressing green fluorescent protein in a tissue-specific manner to isolate viable, pure populations of neural crest stem cells and developing Schwann cells, which are not readily accessible by microdissection. Starting with the minute amounts of RNA obtained, a two-round amplification procedure was used to achieve reproducible DNA array hybridizations. We validated our screening procedure by comparisons with the literature and by in situ hybridization. Stage-to-stage comparisons and hierarchical clustering for neural crest and five stages of Schwann cell development suggest a wealth of candidates for genes involved in stem cell regulation and in early Schwann cell development. The combination of methods applied in this study should be generally useful for isolating and profiling other stem cell and difficult to isolate cell populations.