ABSTRACT
OBJECTIVES: Altered signalling in B cells is a predominant feature of systemic lupus erythematosus (SLE). The genes BANK1 and BLK were recently described as associated with SLE. BANK1 codes for a B-cell-specific cytoplasmic protein involved in B-cell receptor signalling and BLK codes for an Src tyrosine kinase with important roles in B-cell development. To characterise the role of BANK1 and BLK in SLE, a genetic interaction analysis was performed hypothesising that genetic interactions could reveal functional pathways relevant to disease pathogenesis. METHODS: The GPAT16 method was used to analyse the gene-gene interactions of BANK1 and BLK. Confocal microscopy was used to investigate co-localisation, and immunoprecipitation was used to verify the physical interaction of BANK1 and BLK. RESULTS: Epistatic interactions between BANK1 and BLK polymorphisms associated with SLE were observed in a discovery set of 279 patients and 515 controls from northern Europe. A meta-analysis with 4399 European individuals confirmed the genetic interactions between BANK1 and BLK. As BANK1 was identified as a binding partner of the Src tyrosine kinase LYN, the possibility that BANK1 and BLK could also show a protein-protein interaction was tested. The co-immunoprecipitation and co-localisation of BLK and BANK1 were demonstrated. In a Daudi cell line and primary naive B cells endogenous binding was enhanced upon B-cell receptor stimulation using anti-IgM antibodies. CONCLUSION: This study shows a genetic interaction between BANK1 and BLK, and demonstrates that these molecules interact physically. The results have important consequences for the understanding of SLE and other autoimmune diseases and identify a potential new signalling pathway.
Subject(s)
Adaptor Proteins, Signal Transducing/genetics , B-Lymphocytes/immunology , Lupus Erythematosus, Systemic/genetics , Membrane Proteins/genetics , src-Family Kinases/genetics , Adaptor Proteins, Signal Transducing/metabolism , Case-Control Studies , Epistasis, Genetic/genetics , Female , Genetic Predisposition to Disease , Genome-Wide Association Study , Genotype , Humans , Lupus Erythematosus, Systemic/immunology , Male , Membrane Proteins/metabolism , Polymorphism, Single Nucleotide , Protein Binding/genetics , Signal Transduction/genetics , Signal Transduction/immunologyABSTRACT
BACKGROUND: Apart from inactivation of the MEN1 gene, the molecular mechanisms involved in tumorigenesis of the endocrine organs and MEN1-associated non-endocrine lesions remain unknown. MATERIALS AND METHODS: In order to learn more about down-stream effects upon MEN1 gene inactivation BON1 cells were transfected with a MEN1 gene construct (BON/M1C), and both RT-differential display and oligonucleotide microarrays were performed. RESULTS: Three genes (SMARCC1, OVCA2 and SRp55) found to be differentially regulated on differential display were corroborated by northern blots on cell line RNA when comparing MEN1 transfected cells with control (empty vector transfection). When comparing two different passages of BON/M1C with two passages of vector control using oligonucleotide microarrays, 25 up-regulated genes and 64 down-regulated genes could be found using a cut-off of >or=1.6 times. CONCLUSION: These findings might contribute to the understanding of the molecular pathways involved in MEN1 tumorigenesis, and may also provide knowledge of genes involved in sporadic endocrine tumorigenesis.
