title: Characterization of equine CSN1S2 variants considering genetics, transcriptomics, and proteomics.
abstract: Currently, research interest is increasing in horse milk composition and its effect on human health. Despite previously published studies describing the presence of intra- and interbreed variability of equine milk components, no investigations have focused on the genetic background of this variation. Among horse caseins and the genes encoding them, least is known about the structure and expression of the α-S2 casein gene, CSN1S2. Herein, based on direct sequencing of the equine CSN1S2 coding sequence, we describe the presence of 51-bp insertion-deletion (in/del) polymorphism, which significantly changes the protein sequence (lack or presence of 17-amino acid serine-rich peptide). Bioinformatic analysis revealed that the observed in/del polymorphism spanned exactly 2 exons; therefore, we hypothesized that we were observing different CSN1S2 splicing isoforms. However, further investigation indicated that the detected sequence variation was caused by a large (1.3-kb) deletion in the genomic DNA. We found that the polymorphic forms (A, longer; B, shorter; KP658381 and KP658382 GenBank records, respectively) were unevenly distributed among different horse breeds (the highest frequency of variant B was observed in coldblood horses and Haflingers). We propose that the analyzed polymorphism is associated with CSN1S2 expression level (the highest expression was recorded for individuals carrying the BB genotype), which was much more pronounced for milk CSN1S2 protein content than for relative transcript abundance (measured in milk somatic cells). Our results provide insight into the equine CSN1S2 structure and lay a foundation for further functional analyses regarding, for example, allergenicity or physiochemical properties of the observed CSN1S2 variants.
authors.affiliation: Department of Horse Breeding, and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland. Electronic address: jcieslak@up.poznan.pl.
authors.forename: Jakub
authors.initials: J
authors.lastname: Cieslak
authors.affiliation: Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Pawlak
authors.affiliation: Department of Horse Breeding, and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Wodas
authors.affiliation: Department of Horse Breeding, and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland.
authors.forename: Alicja
authors.initials: A
authors.lastname: Borowska
authors.affiliation: Department of Horse Breeding, and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Stachowiak
authors.affiliation: Department of Animal Science, Cattle Breeding Division, Warsaw University of Life Sciences, Ciszewskiego 8, 02-786 Warsaw, Poland.
authors.forename: Kamila
authors.initials: K
authors.lastname: Puppel
authors.affiliation: Department of Animal Science, Cattle Breeding Division, Warsaw University of Life Sciences, Ciszewskiego 8, 02-786 Warsaw, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Kuczynska
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Luczak
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Marczak
authors.affiliation: Department of Horse Breeding, and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Mackowski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001947:Breeding; D002364:Caseins / Q000737:chemistry / Q000235:genetics*; D004247:DNA / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006736:Horses / Q000235:genetics*; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000032:analysis; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011110:Polymorphism, Genetic / Q000235:genetics; D040901:Proteomics; D012333:RNA, Messenger / Q000032:analysis; D059467:Transcriptome / Q000235:genetics*
chemical_list: D002364:Caseins; D008894:Milk Proteins; D012333:RNA, Messenger; D004247:DNA
keywords: casein polymorphism; gene expression; horse milk