RESUMO
BACKGROUND: Atypical/Nor98 scrapie (AS) is an idiopathic infectious prion disease affecting sheep and goats. Recent findings suggest that zoonotic prions from classical bovine spongiform encephalopathy (C-BSE) may copropagate with atypical/Nor98 prions in AS sheep brains. Investigating the risk AS poses to humans is crucial. METHODS: To assess the risk of sheep/goat-to-human transmission of AS, we serially inoculated brain tissue from field and laboratory isolates into transgenic mice overexpressing human prion protein (Met129 allele). We studied clinical outcomes as well as presence of prions in brains and spleens. RESULTS: No transmission occurred on the primary passage, with no clinical disease or pathological prion protein in brains and spleens. On subsequent passages, 1 isolate gradually adapted, manifesting as prions with a phenotype resembling those causing MM1-type sporadic Creutzfeldt-Jakob disease in humans. However, further characterization using in vivo and in vitro techniques confirmed both prion agents as different strains, revealing a case of phenotypic convergence. Importantly, no C-BSE prions emerged in these mice, especially in the spleen, which is more permissive than the brain for C-BSE cross-species transmission. CONCLUSIONS: The results obtained suggest a low zoonotic potential for AS. Rare adaptation may allow the emergence of prions phenotypically resembling those spontaneously forming in humans.
Assuntos
Encéfalo , Síndrome de Creutzfeldt-Jakob , Cabras , Camundongos Transgênicos , Príons , Scrapie , Zoonoses , Animais , Síndrome de Creutzfeldt-Jakob/transmissão , Síndrome de Creutzfeldt-Jakob/patologia , Síndrome de Creutzfeldt-Jakob/metabolismo , Humanos , Scrapie/transmissão , Scrapie/patologia , Camundongos , Zoonoses/transmissão , Encéfalo/patologia , Encéfalo/metabolismo , Ovinos , Bovinos , Príons/metabolismo , Fenótipo , Baço/patologia , Encefalopatia Espongiforme Bovina/transmissão , Encefalopatia Espongiforme Bovina/patologia , Encefalopatia Espongiforme Bovina/metabolismo , Doenças das Cabras/transmissão , Doenças das Cabras/patologia , Modelos Animais de DoençasRESUMO
The kinesin light chain 3 protein (KLC3) is the only member of the kinesin light chain protein family that was identified in post-meiotic mouse male germ cells. It plays a role in the formation of the sperm midpiece through its association with both spermatid mitochondria and outer dense fibers (ODF). Previous studies showed a significant correlation between its expression level and sperm motility and quantitative semen parameters in humans, while the overexpression of a KLC3-mutant protein unable to bind ODF also affected the same traits in mice. To further assess the role of KLC3 in fertility, we used CRISPR/Cas9 genome editing in mice and investigated the phenotypes induced by the invalidation of the gene or of a functional domain of the protein. Both approaches gave similar results, i.e. no detectable change in male or female fertility. Testis histology, litter size and sperm count were not altered. Apart from the line-dependent alterations of Klc3 mRNA levels, testicular transcriptome analysis did not reveal any other changes in the genes tested. Western analysis supported the absence of KLC3 in the gonads of males homozygous for the inactivating mutation and a strong decrease in expression in males homozygous for the allele lacking one out of the five tetratricopeptide repeats. Overall, these observations raise questions about the supposedly critical role of this kinesin in reproduction, at least in mice where its gene mutation or inactivation did not translate into fertility impairment.
Assuntos
Cinesinas , Motilidade dos Espermatozoides , Animais , Feminino , Humanos , Masculino , Camundongos , Fertilidade/genética , Cinesinas/genética , Cinesinas/metabolismo , Camundongos Knockout , Mutação , Proteínas/metabolismo , Sêmen , Motilidade dos Espermatozoides/genética , Espermatogênese/fisiologia , Espermatozoides/metabolismo , Testículo/metabolismoRESUMO
BACKGROUND: The mesenchymal subtype of colorectal cancer (CRC), associated with poor prognosis, is characterized by abundant expression of the cellular prion protein PrPC, which represents a candidate therapeutic target. How PrPC is induced in CRC remains elusive. This study aims to elucidate the signaling pathways governing PrPC expression and to shed light on the gene regulatory networks linked to PrPC. METHODS: We performed in silico analyses on diverse datasets of in vitro, ex vivo and in vivo models of mouse CRC and patient cohorts. We mined ChIPseq studies and performed promoter analysis. CRC cell lines were manipulated through genetic and pharmacological approaches. We created mice combining conditional inactivation of Apc in intestinal epithelial cells and overexpression of the human prion protein gene PRNP. Bio-informatic analyses were carried out in two randomized control trials totalizing over 3000 CRC patients. RESULTS: In silico analyses combined with cell-based assays identified the Wnt-ß-catenin and glucocorticoid pathways as upstream regulators of PRNP expression, with subtle differences between mouse and human. We uncover multiple feedback loops between PrPC and these two pathways, which translate into an aggravation of CRC pathogenesis in mouse. In stage III CRC patients, the signature defined by PRNP-CTNNB1-NR3C1, encoding PrPC, ß-catenin and the glucocorticoid receptor respectively, is overrepresented in the poor-prognosis, mesenchymal subtype and associates with reduced time to recurrence. CONCLUSIONS: An unleashed PrPC-dependent vicious circle is pathognomonic of poor prognosis, mesenchymal CRC. Patients from this aggressive subtype of CRC may benefit from therapies targeting the PRNP-CTNNB1-NR3C1 axis.
Assuntos
Neoplasias do Colo , Neoplasias Colorretais , Humanos , Camundongos , Animais , Proteínas Priônicas/genética , Proteínas Priônicas/metabolismo , beta Catenina/metabolismo , Glucocorticoides , Neoplasias do Colo/genética , Neoplasias Colorretais/genética , Fenótipo , Prognóstico , Via de Sinalização Wnt , Regulação Neoplásica da Expressão Gênica , Linhagem Celular TumoralRESUMO
The recent emergence of chronic wasting disease (CWD) in Europe has become a new public health risk for monitoring of wild and farmed cervids. This disease, due to prions, has proliferated in North America in a contagious manner. In several mammalian species, polymorphisms in the prion protein gene (PRNP) play a crucial role in the susceptibility to prions and their spread. To obtain a reliable picture of the distribution of PRNP polymorphisms in the two most common cervid species in France, we sequenced the open reading frame (ORF) of this gene in 2114 animals, 1116 roe deer (Capreolus capreolus) and 998 red deer (Cervus elaphus). Selection criteria such as historical origin, spatial distribution and sex ratio have been integrated to establish this sample collection. Except for one heterozygous animal with a non-synonymous mutation at codon 37 (G37A), all the 1116 French roe deer were monomorphic. Red deer showed greater variation with two non-synonymous substitutions (T98A; Q226E), three synonymous substitutions (codons 21, 78 and 136) and a new 24pb deletion (Δ69-77). We found significant regional variations between French regions in the frequency of the identified substitutions. After cloning of the PRNP ORF from animals presenting multiple non-synonymous polymorphisms, we identified six haplotypes and obtained a total of twelve genotypes. As in other European countries, we highlighted the apparent homogeneity of PRNP in the French roe deer and the existence of a greater diversity in the red deer. These results were in line with European phylogeographic studies on these two species.
Assuntos
Cervos , Fases de Leitura Aberta , Animais , França , Polimorfismo Genético , Príons/genética , Doença de Emaciação Crônica/genética , Proteínas Priônicas/genéticaRESUMO
Gene knockout experiments have shown that many genes are dispensable for a given biological function. In this review, we make an assessment of male and female germ cell-specific genes dispensable for the function of reproduction in mice, the inactivation of which does not affect fertility. In particular, we describe the deletion of a 1 Mb block containing nineteen paralogous genes of the oogenesin/Pramel family specifically expressed in female and/or male germ cells, which has no consequences in both sexes. We discuss this notion of dispensability and the experiments that need to be carried out to definitively conclude that a gene is dispensable for a function.
Assuntos
Infertilidade Masculina , Testículo , Animais , Feminino , Masculino , Camundongos , Fertilidade/genética , Células Germinativas , Infertilidade Masculina/genética , Camundongos Knockout , Reprodução , Espermatogênese/genéticaRESUMO
Prions are pathogens formed from abnormal conformers (PrPSc) of the host-encoded cellular prion protein (PrPC). PrPSc conformation to disease phenotype relationships extensively vary among prion strains. In particular, prions exhibit a strain-dependent tropism for lymphoid tissues. Prions can be composed of several substrain components. There is evidence that these substrains can propagate in distinct tissues (e.g. brain and spleen) of a single individual, providing an experimental paradigm to study the cause of prion tissue selectivity. Previously, we showed that PrPC expression levels feature in prion substrain selection in the brain. Transmission of sheep scrapie isolates (termed LAN) to multiple lines of transgenic mice expressing varying levels of ovine PrPC in their brains resulted in the phenotypic expression of the dominant sheep substrain in mice expressing near physiological PrPC levels, whereas a minor substrain replicated preferentially on high expresser mice. Considering that PrPC expression levels are markedly decreased in the spleen compared to the brain, we interrogate whether spleen PrPC dosage could drive prion selectivity. The outcome of the transmission of a large cohort of LAN isolates in the spleen from high expresser mice correlated with the replication rate dependency on PrPC amount. There was a prominent spleen colonization by the substrain preferentially replicating on low expresser mice and a relative incapacity of the substrain with higher-PrPC level need to propagate in the spleen. Early colonization of the spleen after intraperitoneal inoculation allowed neuropathological expression of the lymphoid substrain. In addition, a pair of substrain variants resulting from the adaptation of human prions to ovine high expresser mice, and exhibiting differing brain versus spleen tropism, showed different tropism on transmission to low expresser mice, with the lymphoid substrain colonizing the brain. Overall, these data suggest that PrPC expression levels are instrumental in prion lymphotropism.
Assuntos
Proteínas Priônicas/metabolismo , Baço/metabolismo , Animais , Encéfalo/metabolismo , Camundongos , Camundongos Transgênicos , Doenças Priônicas/metabolismoRESUMO
The Shadoo and PrP prion protein family members are thought to be functionally related, but previous knockdown/knockout experiments in early mouse embryogenesis have provided seemingly contradictory results. In particular, Shadoo was found to be indispensable in the absence of PrP in knockdown analyses, but a double-knockout of the two had little phenotypic impact. We investigated this apparent discrepancy by comparing transcriptomes of WT, Prnp0/0 and Prnp0/0Sprn0/0 E6.5 mouse embryos following inoculation by Sprn- or Prnp-ShRNA lentiviral vectors. Our results suggest the possibility of genetic adaptation in Prnp0/0Sprn0/0 mice, thus providing a potential explanation for their previously observed resilience.
Assuntos
Proteínas Priônicas , Príons , Animais , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Priônicas/genética , Príons/genética , RNA Interferente Pequeno , Proteínas Recombinantes , Fatores de TranscriçãoRESUMO
BACKGROUND: The palate is a structure separating the oral and nasal cavities and its integrity is essential for feeding and breathing. The total or partial opening of the palate is called a cleft palate and is a common malformation in mammals with environmental or hereditary aetiologies. Generally, it compromises life expectancy in the absence of surgical repair. A new form of non-syndromic cleft palate arose recently in Limousine cattle, with animals referred to the French National Observatory of Bovine Abnormalities since 2012. Since the number of affected animals has increased steadily, this study was undertaken to identify the cause of this disease. RESULTS: Based on pedigree analysis, occurrence of cleft palate in Limousine cattle was concordant with an autosomal recessive mode of inheritance. Genotyping of 16 affected animals and homozygosity mapping led to the identification of a single disease-associated haplotype on Bos taurus chromosome (BTA)19. The genome of two affected animals was sequenced, and their sequences were compared to the ARS-UCD1.2 reference genome to identify variants. The likely causal variants were compared to the variant database of the 1000 bull genome project and two fully linked mutations in exon 24 of the MYH3 (myosin heavy chain) gene were detected: a 1-bp non-synonymous substitution (BTA19:g.29609623A>G) and a 11-bp frameshift deletion (BTA19:g.29609605-29609615del). These two mutations were specific to the Limousine breed, with an estimated allele frequency of 2.4% and are predicted to be deleterious. The frameshift leads to a premature termination codon. Accordingly, mRNA and protein analyses in muscles from wild-type and affected animals revealed a decrease in MYH3 expression in affected animals, probably due to mRNA decay, as well as an absence of the MYH3 protein in these animals. MYH3 is mostly expressed in muscles, including craniofacial muscles, during embryogenesis, and its absence may impair palate formation. CONCLUSIONS: We describe a new form of hereditary cleft palate in Limousine cattle. We identified two fully linked and deleterious mutations, ultimately leading to the loss-of-function of the MYH3 protein. The mutations were included on the Illumina EuroG10k v8 and EuroGMD v1 SNP chips and are used to set up a reliable eradication strategy in the French Limousine breed.
Assuntos
Fissura Palatina , Bovinos/genética , Animais , Masculino , Fissura Palatina/genética , Fissura Palatina/veterinária , Linhagem , Mutação , Mutação da Fase de Leitura , Haplótipos , Mamíferos/genéticaRESUMO
Inherited fatty acid oxidation diseases in their mild forms often present as metabolic myopathies. Carnitine Palmitoyl Transferase 2 (CPT2) deficiency, one such prototypical disorder is associated with compromised myotube differentiation. Here, we show that CPT2-deficient myotubes exhibit defects in focal adhesions and redox balance, exemplified by increased SOD2 expression. We document unprecedented alterations in the cellular prion protein PrPC, which directly arise from the failure in CPT2 enzymatic activity. We also demonstrate that the loss of PrPC function in normal myotubes recapitulates the defects in focal adhesion, redox balance and differentiation hallmarks monitored in CPT2-deficient cells. These results are further corroborated by studies performed in muscles from Prnp-/- mice. Altogether, our results unveil a molecular scenario, whereby PrPC dysfunction governed by faulty CPT2 activity may drive aberrant focal adhesion turnover and hinder proper myotube differentiation. Our study adds a novel facet to the involvement of PrPC in diverse physiopathological situations.
Assuntos
Carnitina O-Palmitoiltransferase/genética , Adesões Focais/genética , Fibras Musculares Esqueléticas/metabolismo , Doenças Musculares/genética , Proteínas Priônicas/genética , Animais , Carnitina O-Palmitoiltransferase/deficiência , Células Cultivadas , Adesões Focais/metabolismo , Humanos , Camundongos Knockout , Fibras Musculares Esqueléticas/citologia , Doenças Musculares/metabolismo , Fator Regulador Miogênico 5/genética , Fator Regulador Miogênico 5/metabolismo , Oxirredução , Doenças Priônicas/genética , Doenças Priônicas/metabolismo , Proteínas Priônicas/deficiência , Interferência de RNA , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismoRESUMO
Shadoo and PrP belongs to the same protein family, whose biological function remains poorly understood. Previous experiments reported potential functional redundancies or antagonisms between these two proteins, depending on the tissue analysed. While knockdown experiments suggested the requirement of Shadoo in the absence of PrP during early mouse embryogenesis, knockout ones, on the contrary, highlighted little impact, if any, of the double-knockout of these two loci. In the present study, we reinvestigated the phenotype associated with the concomitant knockout of these two genes using newly produced FVB/N Sprn knockout mice. In this genetic background, the combined two genes' knockout induces intra-uterine growth retardations, likely resulting from placental failures highlighted by transcriptomic analyses that revealed potential redundant or antagonist roles of these two proteins in different developmental-related pathways. It also induced an increased perinatal-lethality and ascertained the role of these two loci in the lactation process.
Assuntos
Proteínas do Tecido Nervoso/metabolismo , Proteínas Priônicas/metabolismo , Reprodução/fisiologia , Animais , Animais Recém-Nascidos/crescimento & desenvolvimento , Desenvolvimento Embrionário , Feminino , Proteínas Ligadas por GPI , Genes Letais , Lactação/genética , Lactação/fisiologia , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Proteínas do Tecido Nervoso/deficiência , Proteínas do Tecido Nervoso/genética , Fenótipo , Placentação , Gravidez , Proteínas Priônicas/deficiência , Proteínas Priônicas/genética , Reprodução/genética , TranscriptomaRESUMO
To date, chronic wasting disease (CWD) is the most infectious form of prion disease affecting several captive, free ranging and wild cervid species. Responsible for marked population declines in North America, its geographical spread is now becoming a major concern in Europe. Polymorphisms in the prion protein gene (PRNP) are an important factor influencing the susceptibility to prions and their rate of propagation. All reported cervid PRNP genotypes are affected by CWD. However, in each species, some polymorphisms are associated with lower attack rates and slower progression of the disease. This has potential consequences in terms of genetic selection, CWD diffusion and strain evolution. CWD also presents a zoonotic risk due to prions capacity to cross species barriers. This review summarizes our current understanding of CWD control, focusing on PRNP genetic, strain diversity and capacity to infect other animal species, including humans.
Assuntos
Cervos , Proteínas Priônicas/genética , Doença de Emaciação Crônica/genética , Animais , Genótipo , Polimorfismo Genético , Proteínas Priônicas/metabolismo , Seleção GenéticaRESUMO
Hereditary spastic paraplegias (HSPs) are clinically and genetically heterogeneous human neurodegenerative diseases. Amongst the identified genetic causes, mutations in genes encoding motor proteins such as kinesins have been involved in various HSP clinical isoforms. Mutations in KIF1C are responsible for autosomal recessive spastic paraplegia type 58 (SPG58) and spastic ataxia 2 (SPAX2). Bovines also develop neurodegenerative diseases, some of them having a genetic aetiology. Bovine progressive ataxia was first described in the Charolais breed in the early 1970s in England and further cases in this breed were subsequently reported worldwide. We can now report that progressive ataxia of Charolais cattle results from a homozygous single nucleotide polymorphism in the coding region of the KIF1C gene. In this study, we show that the mutation at the heterozygous state is associated with a better score for muscular development, explaining its balancing selection for several decades, and the resulting high frequency (13%) of the allele in the French Charolais breed. We demonstrate that the KIF1C bovine mutation leads to a functional knock-out, therefore mimicking mutations in humans affected by SPG58/SPAX2. The functional consequences of KIF1C loss of function in cattle were also histologically reevaluated. We showed by an immunochemistry approach that demyelinating plaques were due to altered oligodendrocyte membrane protrusion, and we highlight an abnormal accumulation of actin in the core of demyelinating plaques, which is normally concentrated at the leading edge of oligodendrocytes during axon wrapping. We also observed that the lesions were associated with abnormal extension of paranodal sections. Moreover, this model highlights the role of KIF1C protein in preserving the structural integrity and function of myelin, since the clinical signs and lesions arise in young-adult Charolais cattle. Finally, this model provides useful information for SPG58/SPAX2 disease and other demyelinating lesions.
Assuntos
Doenças dos Bovinos/genética , Bovinos/genética , Cinesinas/metabolismo , Bainha de Mielina/metabolismo , Degenerações Espinocerebelares/veterinária , Sequência de Aminoácidos , Animais , Doenças dos Bovinos/diagnóstico , Modelos Animais de Doenças , Feminino , Heterozigoto , Homozigoto , Deficiência Intelectual/diagnóstico , Deficiência Intelectual/genética , Deficiência Intelectual/veterinária , Cinesinas/genética , Masculino , Espasticidade Muscular/diagnóstico , Espasticidade Muscular/genética , Espasticidade Muscular/veterinária , Mutação de Sentido Incorreto , Atrofia Óptica/diagnóstico , Atrofia Óptica/genética , Atrofia Óptica/veterinária , Polimorfismo de Nucleotídeo Único , Paraplegia Espástica Hereditária/diagnóstico , Paraplegia Espástica Hereditária/genética , Paraplegia Espástica Hereditária/veterinária , Ataxias Espinocerebelares/diagnóstico , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/veterinária , Degenerações Espinocerebelares/diagnóstico , Degenerações Espinocerebelares/genética , Sequenciamento Completo do GenomaRESUMO
Neuropathies are neurodegenerative diseases affecting humans and other mammals. Many genetic causes have been identified so far, including mutations of genes encoding proteins involved in mitochondrial dynamics. Recently, the "Turning calves syndrome", a novel sensorimotor polyneuropathy was described in the French Rouge-des-Prés cattle breed. In the present study, we determined that this hereditary disease resulted from a single nucleotide substitution in SLC25A46, a gene encoding a protein of the mitochondrial carrier family. This mutation caused an apparent damaging amino-acid substitution. To better understand the function of this protein, we knocked out the Slc25a46 gene in a mouse model. This alteration affected not only the nervous system but also altered general metabolism, resulting in premature mortality. Based on optic microscopy examination, electron microscopy and on biochemical, metabolic and proteomic analyses, we showed that the Slc25a46 disruption caused a fusion/fission imbalance and an abnormal mitochondrial architecture that disturbed mitochondrial metabolism. These data extended the range of phenotypes associated with Slc25a46 dysfunction. Moreover, this Slc25a46 knock-out mouse model should be useful to further elucidate the role of SLC25A46 in mitochondrial dynamics.
Assuntos
Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/genética , Proteínas de Transporte de Fosfato/genética , Polineuropatias/genética , Proteômica , Substituição de Aminoácidos/genética , Animais , Bovinos , Humanos , Camundongos , Mitocôndrias/genética , Mitocôndrias/patologia , Mutação , Fenótipo , Polineuropatias/patologia , Polineuropatias/veterináriaRESUMO
DNAJC2 protein, also known as ZRF1 or MPP11, acts both as chaperone and as chromatin regulator. It is involved in stem cell differentiation and its expression is associated with various cancer malignancies. However, the role of Dnajc2 gene during mouse embryogenesis has not been assessed so far. To this aim, we invalidated Dnajc2 gene in FVB/Nj mice using the CrispR/Cas9 approach. We showed that this invalidation leads to the early post-implantation lethality of the nullizygous embryos. Furthermore, using siRNAs against Dnajc2 in mouse 1-cell embryos, we showed that maternal Dnajc2 mRNAs may allow for the early preimplantation development of these embryos. Altogether, these data demonstrate for the first time the requirement of DNAJC2 for early mouse embryogenesis.
Assuntos
Proteínas de Ligação a DNA/genética , Embrião de Mamíferos/embriologia , Regulação da Expressão Gênica no Desenvolvimento , Camundongos/embriologia , Chaperonas Moleculares/genética , Proteínas de Ligação a RNA/genética , Animais , Sistemas CRISPR-Cas , Implantação do Embrião , Perda do Embrião/genética , Embrião de Mamíferos/metabolismo , Desenvolvimento Embrionário , Feminino , Deleção de Genes , Camundongos/genética , GravidezRESUMO
Congenital microcoria (MCOR) is a rare autosomal-dominant disorder characterized by inability of the iris to dilate owing to absence of dilator pupillae muscle. So far, a dozen MCOR-affected families have been reported worldwide. By using whole-genome oligonucleotide array CGH, we have identified deletions at 13q32.1 segregating with MCOR in six families originating from France, Japan, and Mexico. Breakpoint sequence analyses showed nonrecurrent deletions in 5/6 families. The deletions varied from 35 kbp to 80 kbp in size, but invariably encompassed or interrupted only two genes: TGDS encoding the TDP-glucose 4,6-dehydratase and GPR180 encoding the G protein-coupled receptor 180, also known as intimal thickness-related receptor (ITR). Unlike TGDS which has no known function in muscle cells, GPR180 is involved in the regulation of smooth muscle cell growth. The identification of a null GPR180 mutation segregating over two generations with iridocorneal angle dysgenesis, which can be regarded as a MCOR endophenotype, is consistent with the view that deletions of this gene, with or without the loss of elements regulating the expression of neighboring genes, are the cause of MCOR.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 13/genética , Distúrbios Pupilares/congênito , Receptores de Superfície Celular/genética , Sequência de Bases , Hibridização Genômica Comparativa , Componentes do Gene , Genes Dominantes/genética , Humanos , Hidroliases/genética , Dados de Sequência Molecular , Mutação/genética , Análise de Sequência com Séries de Oligonucleotídeos , Linhagem , Distúrbios Pupilares/genética , Distúrbios Pupilares/patologia , Receptores Acoplados a Proteínas G , Análise de Sequência de DNARESUMO
The prion protein is infamous for its involvement in a group of neurodegenerative diseases known as Transmissible Spongiform Encephalopathies. In the longstanding quest to decipher the physiological function of its cellular isoform, PrPC , the discovery of its participation to the self-renewal of hematopoietic and neural stem cells has cast a new spotlight on its potential role in stem cell biology. However, still little is known on the cellular and molecular mechanisms at play. Here, by combining in vitro and in vivo murine models of PrPC depletion, we establish that PrPC deficiency severely affects the Notch pathway, which plays a major role in neural stem cell maintenance. We document that the absence of PrPC in a neuroepithelial cell line or in primary neurospheres is associated with drastically reduced expression of Notch ligands and receptors, resulting in decreased levels of Notch target genes. Similar alterations of the Notch pathway are recovered in the neuroepithelium of Prnp-/- embryos during a developmental window encompassing neural tube closure. In addition, in line with Notch defects, our data show that the absence of PrPC results in altered expression of Nestin and Olig2 as well as N-cadherin distribution. We further provide evidence that PrPC controls the expression of the epidermal growth factor receptor (EGFR) downstream from Notch. Finally, we unveil a negative feedback action of EGFR on both Notch and PrPC . As a whole, our study delineates a molecular scenario through which PrPC takes part to the self-renewal of neural stem and progenitor cells. Stem Cells 2017;35:754-765.
Assuntos
Células-Tronco Neurais/metabolismo , Proteínas Priônicas/metabolismo , Receptores Notch/metabolismo , Transdução de Sinais , Animais , Biomarcadores/metabolismo , Caderinas/metabolismo , Comunicação Celular , Linhagem Celular , Linhagem da Célula , Embrião de Mamíferos/metabolismo , Desenvolvimento Embrionário , Receptores ErbB/metabolismo , Retroalimentação Fisiológica , CamundongosRESUMO
UNLABELLED: Mammalian prions are proteinaceous infectious agents composed of misfolded assemblies of the host-encoded, cellular prion protein (PrP). Physiologically, the N-terminal polybasic region of residues 23 to 31 of PrP has been shown to be involved in its endocytic trafficking and interactions with glycosaminoglycans or putative ectodomains of membrane-associated proteins. Several recent reports also describe this PrP region as important for the toxicity of mutant prion proteins and the efficiency of prion propagation, both in vitro and in vivo. The question remains as to whether the latter observations made with mouse PrP and mouse prions would be relevant to other PrP species/prion strain combinations given the dramatic impact on prion susceptibility of minimal amino acid substitutions and structural variations in PrP. Here, we report that transgenic mouse lines expressing ovine PrP with a deletion of residues 23 to 26 (KKRP) or mutated in this N-terminal region (KQHPH instead of KKRPK) exhibited a variable, strain-dependent susceptibility to prion infection with regard to the proportion of affected mice and disease tempo relative to findings in their wild-type counterparts. Deletion has no major effect on 127S scrapie prion pathogenesis, whereas mutation increased by almost 3-fold the survival time of the mice. Deletion marginally affected the incubation time of scrapie LA19K and ovine bovine spongiform encephalopathy (BSE) prions, whereas mutation caused apparent resistance to disease. IMPORTANCE: Recent reports suggested that the N-terminal polybasic region of the prion protein could be a therapeutic target to prevent prion propagation or toxic signaling associated with more common neurodegenerative diseases such as Alzheimer's disease. Mutating or deleting this region in ovine PrP completes the data previously obtained with the mouse protein by identifying the key amino acid residues involved.
Assuntos
Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Proteínas PrPC/genética , Proteínas PrPC/metabolismo , Doenças Priônicas/patologia , Animais , Modelos Animais de Doenças , Camundongos Transgênicos , Mutação de Sentido Incorreto , Deleção de Sequência , OvinosRESUMO
Transmissible spongiform encephalopathies (TSEs) are a group of neurodegenerative diseases affecting a wide range of mammalian species. They are caused by prions, a proteinaceous pathogen essentially composed of PrPSc, an abnormal isoform of the host encoded cellular prion protein PrPC. Constrained steric interactions between PrPSc and PrPC are thought to provide prions with species specificity, and to control cross-species transmission into other host populations, including humans. Transgenetic expression of foreign PrP genes has been successfully and widely used to overcome the recognized resistance of mouse to foreign TSE sources. Rabbit is one of the species that exhibit a pronounced resistance to TSEs. Most attempts to infect experimentally rabbit have failed, except after inoculation with cell-free generated rabbit prions. To gain insights on the molecular determinants of the relative resistance of rabbits to prions, we generated transgenic rabbits expressing the susceptible V136R154Q171 allele of the ovine PRNP gene on a rabbit wild type PRNP New Zealand background and assessed their experimental susceptibility to scrapie prions. All transgenic animals developed a typical TSE 6-8 months after intracerebral inoculation, whereas wild type rabbits remained healthy more than 700 days after inoculation. Despite the endogenous presence of rabbit PrPC, only ovine PrPSc was detectable in the brains of diseased animals. Collectively these data indicate that the low susceptibility of rabbits to prion infection is not enciphered within their non-PrP genetic background.
Assuntos
Proteínas PrPC/genética , Scrapie/genética , Sequência de Aminoácidos , Animais , Animais Geneticamente Modificados , Feminino , Immunoblotting , Masculino , Espectrometria de Massas , Dados de Sequência Molecular , Coelhos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Ovinos , Especificidade da EspécieRESUMO
UNLABELLED: The dietary exposure of the human population to the prions responsible for the bovine spongiform encephalopathy (BSE) epizooty has led to the emergence of variant Creutzfeldt-Jakob disease (vCJD). This fatal, untreatable neurodegenerative disorder is a growing public health concern because the prevalence of the infection seems much greater than the disease incidence and because secondary transmission of vCJD by blood transfusion or use of blood products has occurred. A current limitation in variant CJD risk assessment is the lack of quantitative information on the infectivity of contaminated tissues. To address this limitation, we tested the potential of a transgenic mouse line overexpressing human prion protein (PrP), which was previously reported to propagate vCJD prions. Endpoint titration of vCJD infectivity in different tissues was evaluated by two different methods: (i) the "classical" bioassay, based on the appearance of clinical symptoms and the detection of pathological prion protein in tissues of the inoculated mouse, and (ii) a shortened bioassay based on the detection of the protein in the mouse spleen at defined time points. The two methods proved equally sensitive in quantifying infectivity, even after very-low-dose inoculation of infected material, but the time schedule was shortened from ~2.5 years to ~1 year with the spleen bioassay. Compared to the "gold-standard" RIII model routinely used for endpoint titration of vCJD/BSE prions, either method improved the sensitivity by >2 orders of magnitude and allowed reevaluating the infectious titer of spleen from a vCJD individual at disease end stage to >1,000-fold-higher values. IMPORTANCE: Here, we provide key reevaluation of the infectious titer of variant CJD brain and spleen tissues. The highly sensitive, accelerated spleen-based assay should thus constitute a key advance for variant CJD epidemiological and risk assessment purposes and should greatly facilitate future titration studies, including, for example, those aimed at validating decontamination procedures. The overlooked notion that the lymphoid tissue exhibits a higher capacity than the brain to replicate prions even after low-dose infection raises new questions about the molecular and/or cellular determinant(s) involved, a key issue regarding potent silent carriers of variant CJD in the lymphoid tissue.
Assuntos
Técnicas de Laboratório Clínico/métodos , Síndrome de Creutzfeldt-Jakob/diagnóstico , Príons/análise , Baço/química , Animais , Bioensaio , Humanos , Camundongos , Camundongos Transgênicos , Sensibilidade e Especificidade , Fatores de TempoRESUMO
Azoospermia (the complete absence of spermatozoa in the semen) is a common cause of male infertility. The etiology of azoospermia is poorly understood. Whole-genome analysis of azoospermic men has identified a number of candidate genes, such as the X-linked testis-expressed 11 (TEX11) gene. Using a comparative genomic hybridization array, an exonic deletion (exons 10-12) of TEX11 had previously been identified in two non-apparent azoospermic patients. However, the putative impact of this genetic alteration on spermatogenesis and the azoospermia phenotype had not been validated functionally. We therefore used a CRISPR/Cas9 system to generate a mouse model (Tex11Ex9-11del/Y) with a partial TEX11 deletion that mimicked the human mutation. Surprisingly, the mutant male Tex11Ex9-11del/Y mice were fertile. The sperm concentration, motility, and morphology were normal. Similarly, the mutant mouse line's testis transcriptome was normal, and the expression of spermatogenesis genes was not altered. These results suggest that the mouse equivalent of the partial deletion observed in two infertile male with azoospermia has no impact on spermatogenesis or fertility in mice, at least of a FVB/N genetic background and until 10 months of age. Mimicking a human mutation does not necessarily lead to the same human phenotype in mice, highlighting significant differences species.