Diversity of the bovine genes IRAK1 and IRAK4 in the Toll-like receptor signaling pathway

Innate immunity is the organism’s first line of defence, and the receptors of immune cells play a key role. Interleukin 1 receptor-associated kinase 1 and 4 (IRAK1 and IRAK4) are necessary for signal transmission from Toll-like receptors, which are the most important receptors of immune cells. The main objective of this study was to investigate the gene polymorphisms of IRAK1 and IRAK4 in Czech Fleckvieh cattle (CF) and to compare their diversity with other cattle breeds as there is still little information about these genes. PacBio Technology of next-generation sequencing (NGS) was used to detect genetic variability in 164 CF bulls. The results revealed 17 single nucleotide variants (SNVs) in the IRAK1 gene and 12 SNVs and three deletions in the IRAK4 gene. Three methods were then used to determine allelic variability: Sanger sequencing, the primer extension method and Illumina DNA BeadChip microarray in cooperation with the Czech Moravian Breeder’s Corporation. Sanger sequencing enabled analysis of the population variability in single nucleotide polymorphisms (SNPs) rs210710958 and rs48726521 of IRAK1 in 164 CF bulls. SNaPshot genotyping was employed to determine the allelic frequencies of SNP rs211379365 and a novel polymorphism in IRAK1, and rs380202447 in the IRAK4 gene. DNA microarray method, which was applied to 74 CF dairy cows, revealed the allelic frequency of IRAK1 rs110533802 including the frequency 0.07 of mutant allele T. Additional microarray data allowed the comparison of the allelic frequencies among the Czech and Hungarian populations of Holstein dairy cows and beef breed populations. The results show that the functionally significant diversity in the IRAK1 and IRAK4 genes in the studied CF population is rather limited. The higher frequency 0.4 of the T mutant allele of SNP rs110533802 of IRAK1 in Holstein cattle could be the consequence of breeding for milk performance.