Variants in the SP110 gene are associated with genetic susceptibility to tuberculosis in West Africa

Abstract

The sst1 locus has been identified in a mouse model to control resistance and susceptibility of Mycobacterium tuberculosis infection. Subsequent studies have now identified Ipr1 (intracellular pathogen resistance 1) to be the gene responsible. Ipr1 is encoded within the sst1 locus and is expressed in the tuberculosis lung lesions and macrophages of sst1-resistant, but not sst1-susceptible mice. We have therefore examined the closest human homologue of Ipr1, SP110, for its ability to control susceptibility to M. tuberculosis infection in humans. In a study of families from The Gambia we have identified three polymorphisms that are associated with disease. On examination of additional families from Guinea-Bissau and the Republic of Guinea, two of these associations were independently replicated. These variants are in strong linkage disequilibrium with each other and lie within a 31-kb block of low haplotypic diversity, suggesting that a polymorphism within this region has a role in genetic susceptibility to tuberculosis in humans.

Fig. 1.

Pairwise LD between SP110 markers as measured by the D′ statistic. D′ values between 0.5 and 0.7 are shaded light blue, values between 0.7 and 0.9 are medium blue, and values >0.9 are dark blue.

Fig. 2.

ldmap analysis of the SP110 gene. LD maps are scaled in LD units (LDUs) against the physical map of the markers. Plateaus are a reflection of low haplotype diversity.