DNA Polymorphisms and Mutations of the Tumor Necrosis Factor-α(TNF-α) Promoter in Langerhans Cell Histiocytosis (LCH)

Abstract

Langerhans cell histiocytosis (LCH) is a clonal proliferation of dendritic histiocytes expressing elevated levels of tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 (IL-1), and leukemia inhibitory factor (LIF). The cause of the increased cytokine levels is unknown, but DNA sequence changes in promoters could alter expression. The TNF-alpha and IFN-gamma promoter DNA sequences of 12 LCH patients were studied and compared with normal individuals by dideoxy fingerprinting and DNA sequencing. Functional consequences of polymorphic or mutated sequences were assessed by cloning altered and control promoter sequences into a luciferase reporter gene vector. Electrophoretic mobility shifts (EMSA) after binding of nuclear extracts from a macrophage cell line (U-937) by mutated promoters were compared with controls. Five of 12 LCH patients had alterations in the TNF-alpha promoter DNA sequence. None were found in the IFN-gamma gene promoter. Of the 5 with TNF-alpha DNA alterations, 2 were at position -308, which has been described as a G-A polymorphism associated with upregulation of TNF-alpha in some patients with infections or immune-mediated diseases. The polymorphism at -308 but not the other TNF-alpha promoter mutations caused a 3-fold to 7-fold increased production of the luciferase reporter gene. EMSA showed that the -308 mutant promoters bound fewer nuclear proteins than normals. Polymorphisms of the TNF-alpha promoter in LCH patients could increase the production of that cytokine.

Is there a future for TNF promoter polymorphisms?

“…186 In contrast, a study by Wilson et al 187 has received considerable attention since its publication and showed large differences in transcriptional activity between allelic constructs, with the -308A construct having over eight-fold higher basal activity in Raji B cells. Unlike several other similar studies that analysed constructs differing at À308, 46,188 , which suffered from obvious technical weaknesses, the only clear anomaly of the Wilson study was the resistance of the TNF construct to induction by PMA. We have used various TNF À308G promoter constructs in transfection of the Raji B cell line and never found these to be resistant to induction.…”

Genes and (auto)immunity in primary biliary cirrhosis

“…47 A polymorphism of the gene promoter region produces the more frequent variant TNF1, and the less frequent variant TNF2, 48 with TNF2 associated with increased transcription. [49][50][51] The prevalence of the TNF2 allele was reportedly protective against PBC onset, 52 while two other studies independently failed to detect any difference in genotype distributions between patients and controls. 15,53 We note that, in the study from Tanaka et al, heterozygous patients had a significantly worse prognosis compared to homozygous TNF1/TNF1 patients, 53 as indicated by higher Mayo score value, currently the only validated index for PBC.…”

Investigations of genetic polymorphisms related to Behcet\s disease in Turkish population

“…TNF- düzenlenmesinin transkripsiyonel seviyede olduğu ve bu genin promotör bölgesindeki çeşitli tek nükleotid polimorfizmlerin bu sitokinin ekspresyon seviyesindeki değişikliklerle ilişkili olduğu üzerinde durulmaktadır. TNF- için belirlenmiş olan -238, 308 ve 376 G/A polimorfizmlerinde guanin adenin yerine geçmektedir ve GA genotipi daha düşük TNF- üretimi ile ilişkilidir (21)(22)(23)(24)(25). TNF- 1031 T/C polimorfizminde timidin sitozinin yerine geçmektedir ve TNF--1031CC genotipi TNFüretiminde artışla ilişkilidir (26).…”