Genetic variation in ICOS regulates mRNA levels of ICOS and splicing isoforms of CTLA4.
Genetic and functional studies suggest that polymorphism in cytotoxic T lymphocyte-associated antigen-4 (CTLA4) and inducible costimulator (ICOS) genes, both reported to harbour autoimmune susceptibility loci, could regulate the immune activation through affecting their expression and splicing of CTLA4. To address this, we studied expression of CTLA4 and ICOS and the role of polymorphisms in the gene region by measuring the relative amounts of transcripts, including the soluble CTLA4 (sCTLA4) splicing isoform in healthy volunteers. We combined a physiologically relevant in vitro activation for human CD4(+) T lymphocytes and a quantitative RT-PCR. The susceptibility allele CT60G in CTLA4 gene was confirmed to be associated with a decreased amount of sCTLA4, but only in resting cells. During the T cell activation two genetic variants in ICOS gene, IVS1+173T/C and c.1624C/T, affected expression of CTLA4 isoforms and ICOS, respectively. We could not confirm that the level of sCTLA4 is down-regulated following T lymphocyte activation, instead the levels of CTLA4 splicing isoforms correlated to each others. Our results indicate that genetic variation in this gene region regulates the expression of both CTLA4 and ICOS and not only the splicing of sCTLA4 as suggested earlier.
Kaartinen
Tanja
T
Research and Development, Finnish Red Cross Blood Service, Kivihaantie 7, FI-00310 Helsinki, Finland. tanja.kaartinen@bts.redcross.fi
Lappalainen
Jani
J
Haimila
Katri
K
Autero
Matti
M
Partanen
Jukka
J
D000328:Adult; D017398:Alternative Splicing; D015703:Antigens, CD / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D000943:Antigens, Differentiation / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen; D005260:Female; D005786:Gene Expression Regulation; D014644:Genetic Variation; D006801:Humans; D060889:Inducible T-Cell Co-Stimulator Protein; D008213:Lymphocyte Activation; D008297:Male; D011110:Polymorphism, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism
D015703:Antigens, CD; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C556692:ICOS protein, human; D060889:Inducible T-Cell Co-Stimulator Protein; D020033:Protein Isoforms; D012333:RNA, Messenger