RESUMO
The role for inhibitory Fc gamma receptors class IIb (FcgammaRIIb) in the onset, progression and severity of several animal models of autoimmune diseases is well established. By contrast, the pathogenic potential of FcgammaRIIb in human autoimmune diseases remains largely unknown. Here we report the identification of a polymorphism in the human FCGR2B promoter (dbSNP no. rs3219018) that is associated in homozygosity with systemic lupus erythematosus (SLE) phenotype in European-Americans (OR=11.1, P=0.003). Experimental evidence correlates the polymorphism (a G-C substitution at position -343 relative to the start of transcription) with altered FcgammaRIIb expression and function. The G-C substitution correlated with decreased transcription of the FCGR2B promoter, and resulted in decreased binding of the AP1 transcription complex to the mutant promoter sequence. The surface expression of FcgammaRIIb receptors was significantly reduced in activated B cells from (-343 C/C) SLE patients. These findings suggest that genetic defects may lead to deregulated expression of the FCGR2B gene in -343 C/C homozygous subjects, and may play a role in the pathogenesis of human SLE.
Assuntos
Lúpus Eritematoso Sistêmico/genética , Polimorfismo de Nucleotídeo Único/genética , Regiões Promotoras Genéticas/genética , Receptores de IgG/genética , Transcrição Gênica/genética , Linfócitos B/metabolismo , Regulação para Baixo/genética , Ligação Genética/genética , Homozigoto , Humanos , Lúpus Eritematoso Sistêmico/metabolismo , Ativação Linfocitária/genética , Receptores de IgG/biossíntese , Fator de Transcrição AP-1/metabolismoRESUMO
OBJECTIVE: Development of a systematic mutation detection assay strategy for denaturing high performance liquid chromatography (DHPLC). DESIGN: Adaptation of Guanine and Cytosine (GC)-clamping from denaturing gradient gel electrophoresis (DGGE) to DHPLC. METHODS: Three target sequences harboring known allelic variants were studied to develop a general DHPLC assay design strategy. These were exon 10 of the human RET (REarranged during Transfection) gene, exon 52 of the mouse Col1a2 gene, and exon 9 of the human FAS (APO-1, CD-95) gene. Available software was used to analyze melting curves and determine assay conditions. GC clamps of 20 bp or 36 bp were added to polymerase chain reaction (PCR) primers to introduce a high melting temperature (T(m)) domain to each of the target molecules. DHPLC was performed under partially denaturing conditions. RESULTS: DHPLC assays of PCR-amplified sequences can be developed using a personal computer. The following three steps allowed for mutation detection in all three targets. The target sequence should have a uniform T(m)GC clamps of length sufficient to introduce a second melting domain with a T(m) > or = 8 degrees above that of the target sequence should be appended to one of the primers. The DHPLC assay should be performed at the highest temperature at which the target sequence is predicted to be > or = 90% double stranded CONCLUSION: Addition of GC-clamps to primers facilitates mutation detection by DHPLC. The theoretical basis for this observation is identical to that underlying the utility of GC-clamps in DGGE.
