Molecular variation and gene expression of toll like receptor 22 in atlantic killifish, fundulus heteroclitus.

Abstract

Toll-like receptors (TLRs) are a type of transmembrane I protein that play a key role in the innate immune system. Variation in immune system genes such as TLRs may be a reflection of environment and pathogen co-evolution. This variation allows the immune system to have greater diversity and thus to better co-evolve with pathogens. The purpose of this study was three-fold: (1) to verify the putative gene model for the TLR 22 incorrect reference genome (v.3.02), (2) to determine the expression patterns of TLR 22 among various tissues in Fundulus heteroclitus and (3) to study levels of genomic variation at the TLR 22 region within and among four populations of Fundulus heteroclitus. Results of this study confirmed the gene model for TLR 22 using primer pairs that stepped through the entire gene to sequence DNA and cDNA samples. Additionally, results showed that TLR 22 has the highest expression in the spleen tissue, with substantial expression levels also found in gill, brain, and muscle tissues. Liver tissue was found to have the lowest expression levels. Notably, there was a substantial difference of expression levels among biological samples. Finally, little can be said of the variation at the 5’UTR region of TLR 22 among all populations due to a difficulty when sequencing through an identified microsatellite and Insertion/deletion INDEL region. Substantial variation at the exon region of TLR 22 was found within and among the Massachusetts populations, with the Scorton Creek population having the highest mean observed heterozygosity. Further studies need to be completed in order to gauge the implications of this variation and whether it is selection pressures or genetic drift acting on polymorphic sites.