Genotyping Two Promoter Polymorphisms in the MIF Gene: A -794 CATT Microsatellite Repeat and a -173 G/C SNP.

Macrophage migration inhibitory factor (MIF) is an upstream proinflammatory cytokine encoded by a functionally polymorphic locus. The promoter region of the human MIF gene contains two polymorphisms. A variable nucleotide tandem repeat at position -794 comprises five to eight CATT repeats (referred to henceforth by numbers from 5 to 8, rs5844572). Gene reporter assays show a proportional increase in transcription with CATT repeat number; the 5-repeat allele leads to low expression, and the 6-, 7-, and 8-repeat alleles lead to correspondingly higher expression of MIF. A second MIF promoter polymorphism comprises a G-to-C single nucleotide polymorphism (SNP) at position -173 (rs755622), which is in strong linkage disequilibrium with -794 7-CATT and is associated with arthritis clinical severity and higher serum and synovial fluid MIF levels. This allele also has been reported to confer improved survival in patients with outpatient pneumonia. In this chapter, we will introduce the methods of genotyping CATT repeats and the MIF -173 G/C from human samples.