Assuntos
Lúpus Eritematoso Sistêmico/história , Doenças Linfáticas/história , Transtornos Linfoproliferativos/história , Receptor fas/história , Animais , Apoptose , História do Século XX , Lúpus Eritematoso Sistêmico/imunologia , Doenças Linfáticas/imunologia , Transtornos Linfoproliferativos/imunologia , Camundongos , Mutação , Receptor fas/genética , Receptor fas/imunologiaRESUMO
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) result from the disturbance of imprinted gene expression within human chromosome 15q11-q13. Some cases of PWS and AS are caused by microdeletions near the SNRPN gene that disrupt a regulatory element termed the imprinting center (IC). The IC has two functional components; an element at the promoter of SNRPN involved in PWS (PWS-IC) and an element 35 kilobases (kb) upstream of SNRPN involved in AS (AS-IC). To further understand the function of the IC, we sought to create a mouse model for AS-IC mutations. We have generated two deletions at a location analogous to that of the human AS-IC. Neither deletion produced an imprinting defect as indicated by DNA methylation and gene expression analyses. These results indicate that no elements critical for AS-IC function in mouse reside within the 12.8-kb deleted region and suggest that the specific location of the AS-IC is not conserved between human and mouse.
Assuntos
Autoantígenos/genética , Impressão Genômica/genética , Ribonucleoproteínas Nucleares Pequenas/genética , Deleção de Sequência/genética , Síndrome de Angelman/genética , Animais , Sequência de Bases , Metilação de DNA , Padrões de Herança/genética , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Repressoras/genética , Ribonucleoproteínas/genética , Ubiquitina-Proteína Ligases/genética , Proteínas Centrais de snRNPRESUMO
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are caused by the loss of imprinted gene expression from chromosome 15q11-q13. Imprinted gene expression in the region is regulated by a bipartite imprinting centre (IC), comprising the PWS-IC and the AS-IC. The PWS-IC is a positive regulatory element required for bidirectional activation of a number of paternally expressed genes. The function of the AS-IC appears to be to suppress PWS-IC function on the maternal chromosome through a methylation imprint acquired during female gametogenesis. Here we have placed the entire mouse locus under the control of a human PWS-IC by targeted replacement of the mouse PWS-IC with the equivalent human region. Paternal inheritance of the human PWS-IC demonstrates for the first time that a positive regulatory element in the PWS-IC has diverged. These mice show postnatal lethality and growth deficiency, phenotypes not previously attributed directly to the affected genes. Following maternal inheritance, the human PWS-IC is able to acquire a methylation imprint in mouse oocytes, suggesting that acquisition of the methylation imprint is conserved. However, the imprint is lost in somatic cells, showing that maintenance has diverged. This maternal imprinting defect results in expression of maternal Ube3a-as and repression of Ube3a in cis, providing evidence that Ube3a is regulated by its antisense and creating the first reported mouse model for AS imprinting defects.
Assuntos
Síndrome de Angelman/genética , Impressão Genômica/genética , Animais , Autoantígenos , Sequência Conservada , Metilação de DNA , Modelos Animais de Doenças , Regulação da Expressão Gênica , Inativação Gênica , Humanos , Recém-Nascido/crescimento & desenvolvimento , Padrões de Herança , Camundongos , Camundongos Endogâmicos C57BL , Obesidade/genética , Fenótipo , Síndrome de Prader-Willi/genética , Regiões Promotoras Genéticas/genética , Ribonucleoproteínas Nucleares Pequenas/genética , Ubiquitina-Proteína Ligases/genética , Proteínas Centrais de snRNPRESUMO
Prader-Willi syndrome (PWS), most notably characterized by infantile hypotonia, short stature and morbid obesity, results from deficiencies in multiple genes that are subject to genomic imprinting. The usefulness of current mouse models of PWS has been limited by postnatal lethality in affected mice. Here, we report the survival of the PWS-imprinting center (IC) deletion mice on a variety of strain backgrounds. Expression analyses of the genes affected in the PWS region suggest that while there is low-level expression from both parental alleles in PWS-IC deletion pups, this expression does not explain their survival on certain strain backgrounds. Rather, the data provide evidence for strain-specific modifier genes that support the survival of PWS-IC deletion mice.
Assuntos
Deleção de Genes , Genes Letais , Síndrome de Prader-Willi/genética , Animais , Sequência de Bases , Northern Blotting , Primers do DNA , Feminino , Masculino , Camundongos , Camundongos Endogâmicos , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Most cases of Angelman syndrome (AS) result from loss or inactivation of ubiquitin protein ligase 3A (UBE3A), a gene displaying maternal-specific expression in brain. Epigenetic silencing of the paternal UBE3A allele in brain appears to be mediated by a non-coding UBE3A antisense (UBE3A-ATS). In human, UBE3A-ATS extends approximately 450 kb to UBE3A from the small nuclear ribonucleoprotein N (SNURF/SNRPN) promoter region that contains a cis-acting imprinting center (IC). The concept of a single large antisense transcript is difficult to reconcile with the observation that SNURF/SNRPN shows a ubiquitous pattern of expression while the more distal part of UBE3A-ATS, which overlaps UBE3A, is brain specific. To address this problem, we examined murine transcripts initiating from several alternative exons dispersed within a 500 kb region upstream of Snurf/Snrpn. Similar to Ube3a-ATS, these upstream (U) exon-containing transcripts are expressed at neuronal stages of differentiation in a cell culture model of neurogenesis. These findings suggest the novel hypothesis that brain-specific transcription of Ube3a-ATS is regulated by the U exons rather than Snurf/Snrpn exon 1 as previously suggested from human studies. In support of this hypothesis, we describe U-Ube3a-ATS transcripts where U exons are spliced to Ube3a-ATS with the exclusion of Snurf-Snrpn. We also show that the murine U exons have arisen by genomic duplication of segments that include elements of the IC, suggesting that the brain specific silencing of Ube3a is due to multiple alternatively spliced IC-Ube3a-ATS transcripts.
Assuntos
Processamento Alternativo , Encéfalo/metabolismo , Éxons , Impressão Genômica , Camundongos/genética , RNA Antissenso/genética , Ubiquitina-Proteína Ligases/genética , Alelos , Animais , Autoantígenos , Sequência de Bases , Diferenciação Celular , Linhagem Celular Tumoral , Inativação Gênica , Íntrons , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Neurônios/citologia , Neurônios/metabolismo , Proteínas Nucleares/genética , RNA Antissenso/metabolismo , RNA Nucleolar Pequeno/metabolismo , Ratos , Ribonucleoproteínas Nucleares Pequenas/genética , Alinhamento de Sequência , Proteínas Centrais de snRNPRESUMO
alpha(1)-Proteinase inhibitor (alpha(1)-PI) is a member of the serpin superfamily of serine proteinase inhibitors, which function in maintaining homeostasis through regulation of numerous proteolytic processes. In laboratory mice (Mus musculus domesticus), alpha(1)-PI occurs in multiple isoforms encoded by a family of three to five genes that are polymorphic among inbred strains and that are located at the Serpina1 locus on chromosome 12. In the present study, we have characterized the alpha(1)-PI gene family of inbred mice in more detail. We show that mice express seven isoforms, all of which are encoded by genes that map to the Serpina1 locus. In addition, polymorphism at the locus is defined by three haplotypes (Serpina1(b), Serpina1(c), and Serpina1(l)) that differ with regard to both the number and identity of alpha(1)-PI genes. Finally, we present the complete sequence of an 84-kb region of Serpina1 containing a tandem repeat of two alpha(1)-PI genes.
