Analysis of genetic variations across regulatory and coding regions of kappa-casein gene of Indian native cattle (Bos indicus) and buffalo (Bubalus bubalis)

• The κ-casein gene (κ-CN) and its promoter region was sequence characterized in 15 Indian native cattle and 8 buffalo breeds.
• Among the identified variations, four were located within TFBSs in Indian cattle, while all TFBSs were conserved in buffaloes.
• The κ-CN CDS was highly conserved with only 3 and 2 non-synonymous changes for Indian cattle and buffaloes, respectively.
• Across promoter and CDS, − 427 C/T was found to be in LD with variation at codons 136 and 148.

The promoter region of kappa-casein (κ-CN) gene in Indian native cattle and buffalo breeds was sequenced and analyzed for nucleotide variations. Sequence comparison across breeds of Indian cattle revealed a total of 7 variations in the promoter region, of which − 515 G/T, − 427 C/T, − 385 C/T, − 283 A/G and − 251 C/T were located within consensus binding sites for octamer-binding protein (OCT1)/pregnancy specific mammary nuclear factor (PMF), activator protein-2 (AP2), hepatocyte nuclear factor (HNF-1) and GAL4 transcription factors (TFs), respectively. These variations might be involved in gain or loss of potential transcription factor binding sites (TFBSs). Unlike the other 4 variants, the − 283 (A/G) variant located within HNF-1 TFBS was specific to Indian cattle as this change has not been observed in the Bos taurus sequence. Other TFBSs viz., MGF, TBP, NF-1, milk box and C/EBP were conserved across species. For the Indian native buffalo breeds, only 3 changes were identified in the promoter region; − 305 (A/C), − 160 (T/C) and − 141 (A/G) and most of the TFBSs were found to be conserved. However, deletion of two adjacent nucleotides located in and around binding site for C/EBP TF was identified in buffalo when compared with promoter sequence of bovine κ-CN. For κ-CN of Indian native cattle, a strong linkage disequilibrium (LD) was observed for variations 515 G/T, − 427 C/T and − 385 C/T in the promoter region; and for variations at codons 136 and 148 of exon-IV. Further, among intragenic haplotypes, variation − 427 C/T was found to be in LD with variations at codons 136 and 148. The information generated in the present work provides comprehensive characterization of κ-CN gene promoter and coding regions in Indian cattle and buffaloes and reported variations could become important candidates for carrying out further research in dairy traits.

Variation analysis of regulatory and coding regions of kappa casein gene in Indian cattle and buffalo breeds of IndiaFigure optionsDownload as PowerPoint slide