Abstrakt
TLR genes coding for Toll-like receptors are considered as prospective targets for health breeding in livestock species, along with other PRRs. In cattle (Bos taurus L.), ten paralogs denoted as TLR1-TLR10 have differentiated.
As a prerequisite for correct association studies, we explored the haplotype structure of anti-bacterial TLR1, -2, -4, -5 and -6 in Czech Red Pied cattle. SNP was detected by hybrid resequencing with two platforms: amplicon resequencing with PacBio RSII and WGS with HiSeq X Ten.
Subsequent genotyping was performed using primer extension. 15 haplotypes directly read in TLR2 formed two distinct groups when visualized as a tree in the Network program. This was confirmed in haplotypes statistically reconstructed from individual genotyping.
Similarly, the bimodal distribution was detectable in the haplotypes of TLR5 and -6, while only a trend was seen in TLR4 and -1. A match with the previously reported clustering of TLR haplotypes in panel of breeds can be stated.
The question is how two clusters of haplotypes are stably supported in a population. Fluctuating selection should lead to the loss of this structure due to the stochastic processes.
We suggest that the balancing selection might originate from two different essential functions performed by the TLR genes or their products simultaneously. An example might be interactions of the TLR2 product with TLR1 and TLR6, forming two functional dimers with different recognized ligands.
The TLR haplotypes will be interpreted in the context of the haplotype-resolved genomes and by using NGS newly designed large amplicons.