Genetic diversity in leucine-rich repeats (LRR) of toll-like receptor-2 and -4 genes in three species of South American camelids

Abstract

Toll-like receptors (TLRs) are responsible for the innate immune response to detect and activate pathways against pathogens in animals. Polymorphisms within these genes have been related to susceptibility or resistance to different diseases. A high variability present in these sequences allows the population to develop a better adaptive potential while the opposite will make them more susceptible to new diseases. This variability decrease may occur because of external factors such as bottlenecks or artificial selection. The objective of this study was to verify the genetic diversity in the leucine-rich repeats (LRR) of TLR2 and TLR4 in three species of camelids from the new world. The genetic diversity was evaluated in the LRR of the TLR2 and TLR4 genes of 120 individuals that belong to the population of alpacas (Vicugna pacos), llamas (Lama glama) and vicuñas (Vicugna vicugna). Different polymorphisms were found, as well as the possible parental sequences and haplotype frequencies. Genetic diversity values, the degree of population differentiation, and amino acid variations were analyzed. The tests showed a very low genetic diversity (TLR2, π = 0.00525; TLR4, π = 0.00118) but a medium-high haplotype diversity (TLR2, Hd=0.923; TLR4, Hd=0.476) among the three species analyzed. There are both polymorphisms and haplotypes that are shared between these species and private haplotypes for each species. The demographic fixation index indicates no gene flow between groups of animal populations. Certain amino acid changes detected in the protein structure change its characteristic of it, making this to be a harmful variation. These results suggest that years of interference in the natural development of South American camelids have led to a drastic decrease in the diversity of their TLRs.