The TLR2 gene encodes a cell-surface protein belonging to the Toll-Like Receptor (TLR) family. TLRs play a key role in the innate immune response of the human body by identifying pathogen-associated molecular patterns (PAMPs). TLR2 is specifically activated by gram-positive cell wall components such as peptidoglycan and lipoteichoic acid, mycobacterial cell-wall components such as lipoarabinomannan and mycolylarabinogalactan, and the yeast cell-wall zymosan. Upon activation, TLR2 upregulates several signalling pathways leading to NF-kappa-B activation, cytokine secretion and the inflammatory response.
Dysregulation of the innate immune response can have strong pathological consequences. Hence polymorphisms in the TLR2 gene have been associated with an increased risk of several diseases. These include an increased susceptibility to Colorectal Cancer, Leprosy and Mycobacterium Tuberculosis.
The TLR2 gene is located on the long arm of chromosome 4. It spans a length of 21.8 kb of DNA and its coding sequence is contained within 5 exons. The protein product encoded by this gene has a molecular mass of 89.8 kDa and consists of 784 amino acids. The gene is specifically expressed in the peripheral blood leukocytes as well as in the bone marrow, lymph node and spleen. The SNP R677W has been associated with susceptibility to leprosy, while R753Q has been implicated in mycobacterium tuberculosis.
Semlali et al. (2017) attempted to identify an association between 3 TLR2 SNPs (rs3804100, rs4696480, and rs3804099) and the development of breast cancer (BC) in the Saudi population. 126 BC affected women were recruited to the study along with 146 healthy controls. Genotyping and statistical analysis found that there was no correlation between these TLR2 polymorphisms and an increased risk of BC in Saudi Arab females. The cohort was then further stratified by age as well as Estrogen Receptor (ER) status. The SNPs did not show an association with BC in the different age groups or in the ER+ group. However, in the ER- cases, the T allele of SNP rs3804099 showed a significant correlation with BC compared to controls (OR, 1.61, p=0.005). The authors noted that this finding could possibly be attributed to a small sample size.
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