Sequence-based structural analysis and evaluation of polymorphism in buffalo Nod-like receptor-1 gene

In this study, we have sequence characterized and analyzed the polymorphism in buffalo NOD1 (nucleotide-binding oligomerization domain 1) gene as well as its expression analysis. Full-length sequence analysis of NOD1 revealed this gene in buffalo being conserved with respect to the domain structures, similar to other species. Alternate splice variants having exon3 skipping also identified for the first time in the gene expressed in buffalo-purified peripheral blood mononuclear cells (PBMCs). Phylogenetically ruminant species were found to be clustering together and buffalo displaying maximum similarity with cattle. Sequencing of NOD1 across 12 Indian buffalo breeds identified 23 polymorphic sites within coding region, among which 16 were synonymous and 7 changes found to be non-synonymous. Four SNPs (single nucleotide polymorphisms) of them were genotyped in 393 animals belonging to 12 riverine, swamp and hybrid (riverine × swamp) buffalo populations of diverse phenotypes and utilities, showing variable allelic frequencies. Principal component analysis revealed, riverine and swamp buffaloes being distinctly placed with the distribution of breeds within the group based on the geographical isolation. Further, quantitative real-time PCR detected NOD1 expression in multiple tissues with PBMCs and lungs showing highest expression among the tissues examined. Structural analysis based on the translated amino acid sequence of buffalo NOD1 identified four protein interaction motifs LxxLL important for ligand binding. Molecular interaction analysis of iE-DAP and NOD1-LRR and their complex stability and binding-free energy studies indicated variable binding energies in buffalo and cattle NOD1. Overall, the study reveals unique structural features in buffalo NOD1, important for species-specific ligand interaction.