RESUMEN
The trisomy of human chromosome 21 (Down syndrome) is the leading genetic cause of learning difficulties in children, and predisposes this population to the early onset of the neurodegeneration of Alzheimer's disease. Down syndrome is associated with increased interferon (IFN) sensitivity resulting in unexpectedly high levels of IFN inducible gene products including Fas, complement factor C3, and neuronal HLA I which could result in a damaging inflammatory reaction in the brain. Consistent with this possibility, we report here that the trisomy 16 mouse fetus has significantly increased whole brain IFN-gamma and Fas receptor immunoreactivity and that cultured whole brain trisomy 16 mouse neurons have increased basal levels of caspase 1 activity and altered homeostasis of intracellular calcium and pH. The trisomic neurons also showed a heightened sensitivity to the increase in both Fas receptor levels and caspase 1 activity we observed when IFN-gamma was added to the neuron culture media. Because of the autoregulatory nature of IFN activity, and the IFN inducing capability of caspase-1-activated cytokine activity, our data argue in favor of the possibility of an interferon-mediated, self-perpetuating, inflammatory response in the trisomy brain that could subserve the loss of neuron viability seen in this trisomy 16 mouse model for Down syndrome.
Asunto(s)
Apoptosis/inmunología , Caspasa 1/metabolismo , Encefalitis/inmunología , Interferón gamma/inmunología , Neuronas/inmunología , Trisomía/inmunología , Enfermedad de Alzheimer/inmunología , Animales , Química Encefálica/genética , Química Encefálica/inmunología , Calcio/metabolismo , Supervivencia Celular/inmunología , Células Cultivadas , Síndrome de Down/inmunología , Encefalitis/genética , Encefalitis/metabolismo , Femenino , Feto/citología , Homeostasis/inmunología , Concentración de Iones de Hidrógeno , Masculino , Ratones , Ratones Endogámicos C3H , Ratones Mutantes , Neuronas/citología , Neuronas/enzimología , Translocación Genética , Receptor fas/metabolismoRESUMEN
The trisomy 16 mouse fetus is a well-studied model for Down syndrome (trisomy 21), the leading genetic cause of mental retardation in the newborn population. Human chromosome 21 and mouse chromosome 16 each carry a large cluster of genes that code for components of the interferon (IFN)-alpha/beta and IFN-gamma receptors, and Down syndrome cells display significantly increased sensitivity to IFN action. We have previously reported that in utero anti-IFN IgG treatment of mice pregnant with trisomy 16 fetuses results in a significant improvement in trisomy 16 fetus growth and morphology and that anti-IFN-gamma IgG treatment can prevent the premature death of trisomy 16 fetal mouse cortical neurons in culture. We have now used IFN receptor subunit knockout mice to produce mouse fetuses that carry three No. 16 chromosomes and one copy each of disabled IFN-gamma receptor (IFNGR) and IFN-alpha/beta receptor (IFNAR-2) component genes. We report here that this partial IFN receptor knockout trisomy (PIRKOT) mouse fetus has significantly improved growth and yields cortical neurons whose viability is the equivalent of that seen in their euploid counterparts.
Asunto(s)
Receptores de Interferón/genética , Trisomía , Animales , Apoptosis , Supervivencia Celular , Corteza Cerebral/patología , Modelos Animales de Enfermedad , Síndrome de Down/genética , Síndrome de Down/inmunología , Síndrome de Down/patología , Desarrollo Embrionario y Fetal/genética , Desarrollo Embrionario y Fetal/inmunología , Femenino , Humanos , Masculino , Proteínas de la Membrana , Ratones , Ratones Noqueados , Ratones Mutantes , Neuronas/patología , Fenotipo , Embarazo , Receptor de Interferón alfa y beta , Translocación Genética , Receptor de Interferón gammaRESUMEN
Previous reports have indicated that human trisomy 21 and mouse trisomy 16 neurons exhibit decreased viability in culture when compared to euploid control cultures and that trisomic cells are significantly more sensitive to the anti-cellular effects of the interferons. In the study reported here, cortical neurons from euploid and trisomy 16 mouse fetuses were treated with either anti-gamma-interferon or non-specific IgG and neuron morphology and viability measured photographically. The addition of anti-gamma-interferon IgG to the culture media had no effect on euploid neurons, but significantly increased trisomy neuron viability throughout the 5-day culture period. Assay of both DNA fragmentation and phosphatidylserine externalization suggested that the trisomic neurons were undergoing apoptosis at a significantly higher rate than their euploid counterparts and that this increase in apoptosis could be almost completely prevented by addition of either ligand purified monoclonal or ligand purified polyclonal anti-gamma-interferon IgG. Taken together, these data suggest that endogenous interferon plays an important role in the premature death of the trisomy neuron.
Asunto(s)
Antineoplásicos/farmacología , Interferón gamma/inmunología , Neuronas/citología , Trisomía , Animales , Apoptosis/efectos de los fármacos , Células Cultivadas , Corteza Cerebral/citología , Fragmentación del ADN , Síndrome de Down/tratamiento farmacológico , Femenino , Inmunoglobulina G/farmacología , Masculino , Ratones , Ratones Endogámicos C3H , Neuronas/efectos de los fármacosRESUMEN
A hypothesis relating interferon action and the chromosome 21 trisomy genotype and phenotype was presented in this journal in 1980. Since that time a number of additional genes involved in interferon action have been mapped to the distal Down Syndrome region of chromosome 21 and a growing literature has documented highly relevant pleiotropic effects of interferon in the brain. Thus, interferon continues to provide a potential basis for the phenotypic anomalies seen in the interferon supersensitive Down Syndrome patient. Further, the hypothesis that ribosomal RNA gene "satellite association" induced by interferon action is involved in the induction of chromosome 21 misdistribution at meiosis, is supported by extension of the cyclic correlation of Down Syndrome prevalence and virus epidemics, first observed by Stoller & Collmann in Australia from 1942 to 1964, to incidence data gathered by the CDC in the U.S. from 1968 to 1992. In addition, data from spontaneous abortuses and gametes assembled from the literature argue for a uniquely high frequency of chromosome 21 hyperploidy which suggests that the genes present on chromosome 21 play a role in its frequent misdistribution at meiosis. Taken together, these observations provide continued support for the hypothesis presented in 1980 that interferon action could be involved in the induction of both the trisomy 21 genotype and its resultant phenotype.
Asunto(s)
Síndrome de Down/genética , Interferones/fisiología , Síndrome de Down/embriología , Genotipo , Humanos , Meiosis/genética , Virosis/complicacionesRESUMEN
Mouse trisomy 16 is a well-studied model for human chromosome 21 trisomy (Down's syndrome). The late stage trisomy 16 mouse fetus exhibits significant growth retardation, inappropriately opened eyes, and convex rather than concave back curvature. The interferons (alpha, beta, and gamma) have potent growth retarding activity, and sensitivity to these cytokines is controlled by genes that map to mouse chromosome 16 and human chromosome 21. In experiments designed to determine if the interferons induce or aggravate the trisomy phenotype, mice pregnant with trisomy 16 fetuses were injected with a combination of anti-alpha, -beta, and -gamma interferon IgG. This maternal anti-interferon treatment was found to provide measurable benefit to the development and growth of the trisomic fetuses with significant return-toward-normal values observed for overall fetal growth, eye opening, and back curvature.
Asunto(s)
Desarrollo Embrionario y Fetal , Inmunoglobulinas/farmacología , Interferón Tipo I/fisiología , Interferón gamma/fisiología , Columna Vertebral/embriología , Trisomía/genética , Animales , Femenino , Interferón Tipo I/inmunología , Interferón gamma/inmunología , Masculino , Ratones , Ratones Mutantes , Fenotipo , Embarazo , Columna Vertebral/anomalías , Translocación GenéticaRESUMEN
Aberrant expression of the amyloid precursor protein (APP) gene may contribute to the beta-amyloid deposition seen in Alzheimer's disease and Down syndrome patients. Genomic DNA was isolated from human brain tissue and digested with HpaII, an enzyme sensitive to CpG methylation. Southern-blot analysis revealed the absence of methylation at a site in the APP gene of an Alzheimer's disease subject. This site was methylated in a nondemented subject and a subject with a non-Alzheimer's type of dementia (Pick's disease). This is the first report of an epigenetic defect in an Alzheimer's disease patient and the observation suggests that hypomethylation of the APP gene may be one of several factors contributing to aberrant gene expression in Alzheimer's disease.
Asunto(s)
Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/genética , Encéfalo/metabolismo , Lóbulo Temporal/metabolismo , Anciano , Anciano de 80 o más Años , Precursor de Proteína beta-Amiloide/biosíntesis , Autopsia , ADN/química , Demencia/genética , Demencia/metabolismo , Fosfatos de Dinucleósidos/análisis , Femenino , Expresión Génica , Humanos , Metilación , Valores de Referencia , Mapeo RestrictivoRESUMEN
Alzheimer's disease is characterized by the accumulation of the beta/A4 fragment of the amyloid precursor protein in the hippocampal regions of the brain. We report here the isolation of genomic clones carrying exons 15, 16 and 17 of the beta/A4 coding region of the rabbit amyloid precursor protein gene. The complete sequence of these exons predicts that all three peptides are identical to their human counterparts. An unexpectedly high concentration of CpG dinucleotides seen in exon 15 were conserved and continued into the intron 15 region. MspI/HpaII southern blot analysis revealed the presence of a number of methylated CpG dinucleotides in the cloned region of the gene. These data suggest that the rabbit amyloid precursor protein gene could provide a new and useful model for the study of this important gene.
Asunto(s)
Precursor de Proteína beta-Amiloide/genética , Exones , Secuencia de Aminoácidos , Animales , Secuencia de Bases , ADN/genética , Genes , Humanos , Intrones , Hígado/fisiología , Metilación , Ratones , Datos de Secuencia Molecular , Sondas de Oligonucleótidos , Conejos , Mapeo Restrictivo , Homología de Secuencia de Ácido NucleicoRESUMEN
In the rabbit, ovulation and conception occur during an 8-10 hour period immediately following mating ("reflex ovulation"). We report here that live Newcastle disease virus (NDV; an avian paramyxovirus) injected into rabbits immediately following mating resulted in a high frequency of embryo death at a wide range of developmental stages. When measured at midterm, a greater than threefold increase in embryo mortality was observed (24.7% vs. 6.8%). Aneuploidy of a small acrocentric chromosome was observed in three of 60 live midterm embryos recovered from NDV-injected does. No aneuploidy was observed in 52 live midterm embryos from control, saline-injected does. These observations suggest that the NDV-exposed rabbit can provide a useful model for the study of the teratological effects of virus exposure occurring at or about the time of meiosis, ovulation, and conception.
Asunto(s)
Aneuploidia , Muerte Fetal/etiología , Virus de la Enfermedad de Newcastle/patogenicidad , Animales , Anomalías Congénitas/etiología , Modelos Animales de Enfermedad , Femenino , Fertilización , Ovulación , Embarazo , ConejosRESUMEN
We have used a microcomputer program to test eukaryotic mRNA 5'-leader sequences for complementarity to the 3'-terminus of 18S rRNA. No mismatched bases, bulge loops, or viral mRNA's were utilized. At least one-fourth of the more than 200 mRNA's studied were found to have two distinct regions of complementarity which resulted in an ability to bind to two separate rRNA regions (GAAGG and UUUGG). The analysis of 60 mRNAs with these dual sites resulted in a consensus structure that was a mean distance of 11.75 bases 5' from the initiator AUG and had an average predicted interstrand binding strength of delta G = -13.40 kcal. These characteristics compare favorably to those observed for the prokaryotic 16S rRNA-mRNA Shine and Dalgarno bond.
Asunto(s)
Células/análisis , Células Eucariotas/análisis , ARN Mensajero , ARN Ribosómico , Animales , Secuencia de Bases , Pollos , Patos , Humanos , Ratones , Microcomputadores , Conformación de Ácido Nucleico , Células Procariotas/análisis , Conejos , Ratas , Programas Informáticos , Termodinámica , XenopusAsunto(s)
Síndrome de Down/etiología , Interferones , Células Cultivadas , Femenino , Fibroblastos , Genes , Humanos , Embarazo , ARN Ribosómico , Virosis/complicacionesRESUMEN
Antiviral and cell-growth-inhibitory activities of human interferon were shown to be related to the activity of a gene or genes present on chromosome 21. The 18s rRNA is vital to cell growth; it is capable of a viral-mRNA-recognition function and it is coded for by genes a portion of which are present on chromosome-21. A previously reported ability of human interferon to affect rRNA metabolism is characterized by a decrease in the sucrose-gradient-peak ratio of radiolabelled 28S to 18S rRNA in extracts from the cytoplasm of interferon-treated human fibroblasts. In the present report, interferon dose-response curves are presented demonstrating a direct relationship between a decrease in this ratio and interferon concentrations in the media. By using this virus-independent cytoplasmic rRNA assay, eight human fibroblast lines, differing in chromosome 21 ploidy, were tested for sensitivity to human interferon. Two monosomy-21, two euploid-21 and four trisomy-21 cell lines were tested. The monosomy-21 cell populations were significantly less sensitive to interferon than the other six cell types tested. Of the cell lines tested, the most sensitive, by a wide margin, was a trisomy-21 line. Trisomy-21 cell monolayer sensitivity, however, varied widely within the range from normal to supersensitive. These observations suggest that interferon's ability to affect rRNA metabolism is related to the activity of a gene or genes present on chromosome 21.
Asunto(s)
Cromosomas Humanos 21-22 e Y , Interferones/farmacología , Ploidias , ARN Ribosómico/metabolismo , Línea Celular , Relación Dosis-Respuesta a Droga , Fibroblastos/metabolismo , Genes , Humanos , Técnicas In Vitro , Virus de la Enfermedad de Newcastle , ARN/biosíntesisRESUMEN
Ribosomal RNA (rRNA) has been shown to be involved in the binding of bacterial messenger RNA (mRNA) and an analogous 18 S rRNA.mRNA complex has been reported in eukaryotic systems. Thus, qualitative changes in host rRNA may be involved in the development of the interferon mediated antiviral state, a process thought to involve the inability of host ribosomes to bind and recognize viral mRNA. Data are reported which suggest that trisomy 21 human fibroblasts respond to human interferon with a marked reduction in cytoplasmic rRNA. [3H]Uridine was used to radioactively label the polysomal RNAs for 24 h beginning 12 h after interferon addition. Subsequent sucrose gradient analysis of the phenol or SDS-extracted RNA revealed that the reduction in radioactive rRNA was nearly complete for the 28 S rRNA. In contrast, considerable residual uridine incorporation was found in the 18 S rRNA species. Corollary data suggesting a net increase in mRNA synthesis and a net decrease in protein synthesis are reported.
Asunto(s)
Interferones/farmacología , ARN Ribosómico/metabolismo , Línea Celular , Citoplasma/metabolismo , Cinética , Poli A/metabolismo , Biosíntesis de Proteínas , ARN Mensajero/metabolismoRESUMEN
Numerous reports have demonstrated that specific protein synthesis in response to specific inducers is markedly stimulated by a simultaneous brief exposure to protein synthesis inhibitors such as cycloheximide. This phenomenon is known as "superinduction" and is most often attributed to the accumulation of cytoplasmic messenger RNA during the inhibition period. Messenger RNA, as defined by rapid labeling, oligo (dt)-cellulose binding, and cell free protein synthesis stimulation was measured in cycloheximide treated human fibroblasts. In spite of a consistent 40% decrease in total polysomal 3H-uridine labeled RNA, a 1.5- to 2-fold increase in extractable mRNA was observed. These data provide direct evidence that protein synthesis inhibition stimulates the appearance of cytoplasmic mRNA and/or completely blocks its degradation and, are consistent with the hypothesis that mRNA accumulation partly underlies the superinduction phenomena.