RESUMEN
We have completed a genome wide linkage scan using >5700 informative single-nucleotide polymorphism (SNP) markers (Illumina IV SNP linkage panel) in 642 Caucasian families containing affected sibling pairs with rheumatoid arthritis (RA), ascertained by the North American Rheumatoid Arthritis Consortium. The results show striking new evidence of linkage at chromosomes 2q33 and 11p12 with logarithm of odds (LOD) scores of 3.52 and 3.09, respectively. In addition to a strong and broad linkage interval surrounding the major histocompatibility complex (LOD>16), regions with LOD>2.5 were observed on chromosomes 5 and 10. Additional linkage evidence (LOD scores between 1.46 and 2.35) was also observed on chromosomes 4, 7, 12, 16 and 18. This new evidence for multiple regions of genetic linkage is partly explained by the significantly increased information content of the Illumina IV SNP linkage panel (75.6%) compared with a standard microsatellite linkage panel utilized previously (mean 52.6%). Stratified analyses according to whether or not the sibling pair members showed elevated anticyclic citrullinated peptide titers indicates significant variation in evidence for linkage among strata on chromosomes 4, 5, 6 and 7. Overall, these new linkage data should reinvigorate efforts to utilize positional information to identify susceptibility genes for RA.
Asunto(s)
Artritis Reumatoide/genética , Artritis Reumatoide/inmunología , Cromosomas Humanos Par 11/genética , Cromosomas Humanos Par 2/genética , Polimorfismo de Nucleótido Simple , Autoanticuerpos/inmunología , Femenino , Ligamiento Genético , Predisposición Genética a la Enfermedad , Humanos , Masculino , Péptidos Cíclicos/inmunología , Hermanos , Población Blanca/genéticaRESUMEN
Previous studies have shown that the chicken beta B1-crystallin promoter (-434/+30) contains all of the signals necessary to specifically direct high level expression of heterologous genes to the lens fiber cells of mice. In the present study, the mouse beta B1-crystallin gene was cloned, and its regulation was investigated to further elucidate the mechanisms controlling lens fiber cell-specific gene expression. Phylogenetic footprinting analysis of the 5' flanking sequence from the mouse, rat, human and chicken beta B1-crystallin genes identified several known and putative functional cis elements including the PL2 element which is required for lens-specific expression of the chicken beta B1 promoter. Surprisingly, however, all six mouse beta B1-crystallin/CAT constructs tested (-1493/+44, -1493/+30, -870/+30, -250/+30, -135/+30 and -98/+30) were inactive in three different mammalian lens-derived cell lines while only the -870/+30 and -98/+30 constructs were active in chicken primary patched lens epithelial cells. In contrast, the chicken beta B1-crystallin promoter (-434/+30) was transcriptionally active in all lens-derived cells tested. Transgenic mice harboring a mouse beta B1-crystallin -1493/+44 CAT construct did express the transgene specifically in lens fiber cells, however, at lower levels than that previously reported for a chicken -434/+30 CAT construct. These data suggest that, as in other crystallin genes, the regulatory signals controlling lens fiber cell-specific expression are conserved between chicken and mouse. However, the inability of the mouse beta B1-crystallin promoter to function in mammalian lens-derived cultured cells implies that this gene has acquired additional cis-regulatory elements to ensure lens fiber cell specificity.
Asunto(s)
Cristalinas/genética , Regulación de la Expresión Génica/genética , Cristalino/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Línea Celular , Pollos , Clonación Molecular , Huella de ADN , ADN Complementario/biosíntesis , ADN Complementario/química , Células Epiteliales/metabolismo , Inmunohistoquímica , Ratones , Ratones Transgénicos , Datos de Secuencia Molecular , Filogenia , Alineación de Secuencia , Transfección , Cadena B de beta-CristalinaRESUMEN
Rheumatoid arthritis (RA) is an autoimmune/inflammatory disorder with a complex genetic component. We report the first major genomewide screen of multiplex families with RA gathered in the United States. The North American Rheumatoid Arthritis Consortium, using well-defined clinical criteria, has collected 257 families containing 301 affected sibling pairs with RA. A genome screen for allele sharing was performed, using 379 microsatellite markers. A nonparametric analysis using SIBPAL confirmed linkage of the HLA locus to RA (P < .00005), with lambdaHLA = 1.79. However, the analysis also revealed a number of non-HLA loci on chromosomes 1 (D1S235), 4 (D4S1647), 12 (D12S373), 16 (D16S403), and 17 (D17S1301), with evidence for linkage at a significance level of P<.005. Analysis of X-linked markers using the MLOD method from ASPEX also suggests linkage to the telomeric marker DXS6807. Stratifying the families into white or seropositive subgroups revealed some additional markers that showed improvement in significance over the full data set. Several of the regions that showed evidence for nominal significance (P < .05) in our data set had previously been implicated in RA (D16S516 and D17S1301) or in other diseases of an autoimmune nature, including systemic lupus erythematosus (D1S235), inflammatory bowel disease (D4S1647, D5S1462, and D16S516), multiple sclerosis (D12S1052), and ankylosing spondylitis (D16S516). Therefore, genes in the HLA complex play a major role in RA susceptibility, but several other regions also contribute significantly to overall genetic risk.