Polymorphism and molecular characteristics of the <i>CSN1S2</i> gene in river and swamp buffalo

Abstract

The αS2-casein (αS2-CN) is a member of the casein family associated with milk traits in ruminants, but so far the buffalo CSN1S2 gene has not been well understood. In this work, the polymorphisms of CSN1S2 in river and swamp buffalo were detected using direct sequencing of polymerase chain reaction (PCR) products. As a result, 13 single nucleotide polymorphisms (SNPs) were identified in the coding sequence (CDS) of CSN1S2 in two types of buffalo, of which eight SNPs were non-synonymous. The amino acid changes caused by c.580T>C and c.642C>G may affect the function of buffalo αS2-CN. A total of 11 CSN1S2 CDS haplotypes were defined, and accordingly 11 variants of buffalo αS2-CN were inferred and named. The CSN1S2 CDSs of both types of buffalo were 669 nucleotides, which encoded a precursor of 222 amino acids (AAs), and the first 15 AAs constitute a signal peptide. The composition and physicochemical characteristics of two types of buffalo αS2-CNs were similar but slightly different from those of cattle αS2-CN. The αS2-CN mature peptides of buffalo and the species of Bos genus contained a casein domain, and their secondary structures were highly consistent, indicating that they are functionally similar. The results here provide initial insights into the variation, characteristics and biological function of buffalo CSN1S2.