Genetic association study suggests a role for SP110 variants in lymph node tuberculosis but not pulmonary...

Ethnic specificity is a key determinant in understanding the association of genetic variants with outcome of disease susceptibility. SP110, a component of the nuclear body, has been subjected to association studies with conflicting results. In this study we probed SP110 variants in pulmonary (PTB) and lymph node tuberculosis (LNTB) cases to explore their role in controlling susceptibility to Mycobacterium tuberculosis infection in north Indians. We genotyped 24 SP110 variants in over 140 north Indian tuberculosis cases and 78 ethnicity-matched controls. The SP110 gene variants were available from public databases. The cases and controls were free of any population stratification when subjected to Eigenstrat principal component analysis. Genotyping was carried out using the Sequenom MassARRAY platform. Applying exclusion criteria, 11 single nucleotide polymorphisms (SNPs) of the LNTB panel and 13 SNPs of the PTB panel passed all filters and were analyzed further. No significant association was observed between SP110 variants and PTB. Surprisingly, we discovered evidence of an association of SP110 variants with LNTB, a form of extrapulmonary tuberculosis, at 3 loci, namely, rs6436915, rs1427294, and rs1346311. When permutations analysis (n = 10,000) of allelic p values was undertaken, only rs1427294 passed the test with its p value remaining statistically significant. The C allele of rs1427294 exhibited a 5-fold risk of developing LNTB. No significant haplotypes were observed. In the pilot study presented here, our results provide evidence for the first time that SP110 may be a risk determinant locus in LNTB while confirming a doubtful role of SP110 in PTB in north Indians. In general, the results might indicate a role of SP110 variants in extrapulmonary tuberculosis rather than PTB.