Genomic characterization of equine interleukin-4 receptor alpha-chain (IL4R).

The study focused on characterizing and mapping the equine version of the Interleukin-4 receptor alpha-chain gene (IL4R), comparing its similarities and differences with human, murine and bovine IL4R, and identifying coding-region single nucleotide polymorphisms (SNPs).

Genomic Characterization and Comparison

• Researchers cloned and sequenced three fragments of the equine IL4R gene to get a complete 3553 bp gene sequence.
• This gene sequence in horses showed similarities with its counterparts in humans, mice, and cows, confirming shared evolutionary paths.
• Notably, it shared certain features with IL4R in other species like the positions of intron-exon boundaries and characteristic amino acid sequence motifs of type I cytokine receptors. This shows that IL4R retains essential shared features across species, implied to be important for its function.

Localization of IL4R Gene

• By using synteny mapping, the researchers were able to determine that the IL4R gene locates in the horse chromosome ECA13. This will help further studies investigating the function and associated disorders of IL4R in horses.

Evidence for Alternative Splice Variant

• An examination of genomic sequence indicated the potential for an alternative splice variant of IL4R. This was then confirmed via RT-PCR on equine monocyte RNA.
• Alternative splicing is a process through which one gene may produce several different mRNA transcripts depending on how the introns and exons are combined. This increases gene expression diversity and is a common phenomenon in complex or higher organism.

Polymorphism of Equine IL4R

• The researchers identified 11 coding-region SNPs in the largest exon of IL4R, similar to the twelfth exon of the human IL4R gene. This was done through a polymorphism screen on DNA from 60 horses of different breeds.
• Of these SNPs, 7 were synonymous (causing no change in the proteins synthesized) and 4 were non-synonymous (cause changes in protein synthesis).
• Three of these four non-synonymous SNPs appeared at high frequencies and in a position very close to a conserved tyrosine residue. Such polymorphisms could potentially affect the function or expression of IL4R in horses.