Age-dependent association between pulmonary tuberculosis and common TOX variants in the 8q12-13 linkage region.

American journal of human genetics

PubMedID: 23415668

Grant AV, El Baghdadi J, Sabri A, El Azbaoui S, Alaoui-Tahiri K, Abderrahmani Rhorfi I, Gharbaoui Y, Abid A, Benkirane M, Raharimanga V, Richard V, Orlova M, Boland A, Migaud M, Okada S, Nolan DK, Bustamante J, Barreiro LB, Schurr E, Boisson-Dupuis S, Rasolofo V, Casanova JL, Abel L. Age-dependent association between pulmonary tuberculosis and common TOX variants in the 8q12-13 linkage region. Am J Hum Genet. 2013;92(3):407-14.
Only a small fraction of individuals infected with Mycobacterium tuberculosis develop clinical tuberculosis (TB) in their lifetime. Genetic epidemiological evidence suggests a genetic determinism of pulmonary TB (PTB), but the molecular basis of genetic predisposition to PTB remains largely unknown. We used a positional-cloning approach to carry out ultrafine linkage-disequilibrium mapping of a previously identified susceptibility locus in chromosomal region 8q12-13 by genotyping 3,216 SNPs in a family-based Moroccan sample including 286 offspring with PTB. We observed 44 PTB-associated SNPs (p < 0.01), which were genotyped in an independent set of 317 cases and 650 controls from Morocco. A single signal, consisting of two correlated SNPs close to TOX, rs1568952 and rs2726600 (combined p = 1.1 × 10(-5) and 9.2 × 10(-5), respectively), was replicated. Stronger evidence of association was found in individuals who developed PTB before the age of 25 years (combined p for rs1568952 = 4.4 × 10(-8); odds ratio of PTB for AA versus AG/GG = 3.09 [1.99-4.78]). The association with rs2726600 (p = 0.04) was subsequently replicated in PTB-affected subjects under 25 years in a study of 243 nuclear families from Madagascar. Stronger evidence of replication in Madagascar was obtained for additional SNPs in strong linkage disequilibrium with the two initial SNPs (p = 0.003 for rs2726597), further confirming the signal. We thus identified around rs1568952 and rs2726600 a cluster of SNPs strongly associated with early-onset PTB in Morocco and Madagascar. SNP rs2726600 is located in a transcription-factor binding site in the 3' region of TOX, and further functional explorations will focus on CD4 T lymphocytes.