RESUMO
BACKGROUND: The cytokine-deficiency-induced colitis susceptibility (Cdcs)1 locus is a major modifier of murine inflammatory bowel disease (IBD) and was originally identified in experimental crosses of interleukin-10-deficient (Il10(-/-)) mice. Congenic mice, in which this locus was reciprocally transferred between IBD-susceptible C3H/HeJBir-Il10(-/-) and resistant C57BL/6J-Il10(-/-) mice, revealed that this locus likely acts by inducing innate hypo- and adaptive hyperresponsiveness, associated with impaired NF-kappaB responses of macrophages. The aim of the present study was to dissect the complexity of Cdcs1 by further development and characterization of reciprocal Cdcs1 congenic strains and to identify potential candidate genes in the congenic interval. METHODS: In total, 15 reciprocal congenic strains were generated from Il10(-/-) mice of either C3H/HeJBir or C57BL/6J genetic backgrounds by 10 cycles of backcrossing. Colitis activity was monitored by histological grading. Candidate genes were identified by fine mapping of congenic intervals, sequencing, microarray analysis, and a high-throughput real-time reverse-transcription polymerase chain reaction (RT-PCR) approach using bone marrow-derived macrophages. RESULTS: Within the originally identified Cdcs1-interval, 3 independent regions were detected that likely contain susceptibility-determining genetic factors (Cdcs1.1, Cdcs1.2, and Cdcs1.3). Combining results of candidate gene approaches revealed Fcgr1, Cnn3, Larp7, and Alpk1 as highly attractive candidate genes with polymorphisms in coding or regulatory regions and expression differences between susceptible and resistant mouse strains. CONCLUSIONS: Subcongenic analysis of the major susceptibility locus Cdcs1 on mouse chromosome 3 revealed a complex genetic structure. Candidate gene approaches revealed attractive genes within the identified regions.
Assuntos
Biomarcadores Tumorais/genética , Colite/genética , Predisposição Genética para Doença , Interleucina-10/fisiologia , Animais , Biomarcadores Tumorais/metabolismo , Western Blotting , Colite/patologia , Feminino , Perfilação da Expressão Gênica , Masculino , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , NF-kappa B/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Chromatin adapts a distinct structure and epigenetic state in embryonic stem cells (ESCs), but how chromatin is three-dimensionally organized within the ESC nucleus is poorly understood. Because nuclear location can influence gene expression, we examined the nuclear distributions of chromatin with key epigenetic marks in ESC nuclei. We focused on chromatin at the nuclear periphery, a compartment that represses some but not all associated genes and accumulates facultative heterochromatin in differentiated cells. Using a quantitative, cytological approach, we measured the nuclear distributions of genes in undifferentiated mouse ESCs according to epigenetic state and transcriptional activity. We found that trimethyl histone H3 lysine 27 (H3K27-Me(3)), which marks repressed gene promoters, is enriched at the ESC nuclear periphery. In addition, this compartment contains 10-15% of chromatin with active epigenetic marks and hundreds of transcription sites. Surprisingly, comparisons with differentiated cell types revealed similar nuclear distributions of active chromatin. By contrast, H3K27-Me(3) was less concentrated at the nuclear peripheries of differentiated cells. These findings demonstrate that the nuclear periphery is an epigenetically dynamic compartment that might be distinctly marked in pluripotent ESCs. In addition, our data indicate that the nuclear peripheries of multiple cell types can contain a significant fraction of both active and repressed genes.
Assuntos
Compartimento Celular/genética , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Membrana Nuclear/genética , Transcrição Gênica , Animais , Cromatina/metabolismo , Epigênese Genética , Fibroblastos/citologia , Fibroblastos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Camundongos , Células NIH 3T3 , Neurônios/citologia , Neurônios/metabolismo , Especificidade de Órgãos/genéticaRESUMO
Mice of the I/LnJ inbred strain are unique in their ability to mount a robust and sustained humoral immune response capable of neutralizing infection with a betaretrovirus, mouse mammary tumor virus (MMTV). Virus-neutralizing antibodies (Abs) coat MMTV virions secreted by infected cells, preventing virus spread and hence the formation of mammary tumors. To investigate whether I/LnJ mice resist infection with other retroviruses besides MMTV, the animals were infected with murine leukemia virus (MuLV), a gammaretrovirus. MuLV-infected I/LnJ mice produced virus-neutralizing Abs that block virus transmission and virally induced disease. Generation of virus-neutralizing Abs required gamma interferon but was independent of interleukin-12. This unique mechanism of retrovirus resistance is governed by a single recessive gene, virus infectivity controller 1 (vic1), mapped to chromosome 17. In addition to controlling the antivirus humoral immune response, vic1 is also required for an antiviral cytotoxic response. Both types of responses were maintained in mice of the susceptible genetic background but congenic for the I/LnJ vic1 locus. Although the vic1-mediated resistance to MuLV resembles the mechanism of retroviral recovery controlled by the resistance to Friend virus 3 (rfv3) gene, the rfv3 gene has been mapped to chromosome 15 and confers resistance to MuLV but not to MMTV. Thus, we have identified a unique virus resistance mechanism that controls immunity against two distinct retroviruses.
