Genome-Wide in-silico Identification and Analysis of Uridine Diphospho N-Acetylgalactosaminyltransferase (GALNT) Family of Genes in Cattle

Uridine diphospho N-acetylgalactosaminyltransferases (GALNT) are a family of enzymes involved in mucin-type O-glycosylation of serine and threonine residues of polypeptide acceptors. A total of 20 members of the GALNT family of genes were identified and analyzed in the bovine genome which included 14 UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GALNT) and 6 UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase-like (GALNTL) genes. Chromosomal locations, genomic structures, identity and similarity between family members, secondary and tertiary structures, phylogenetic analysis and sequence motifs and domains were determined. The genes are located across the bovine genome in chromosomes 1, 2, 4, 5, 7, 8, 10, 11, 15, 17, 24, 25 and 28. Number of exons ranged from 1 exon in GALNT4 to 15 exons in GALNT2. Family members shared a high identity index which ranged from 32% (GALNTL2 and GALNTL4) to 85% (GALNT1 and GALNT13). Similarity indices of 49% between GALNTL2 and GALNTL4 and 93% between GALNT1 and GALNT13 in their amino acid sequences confirmed that these genes are paralogs and belonged to the same family. They consist of mixed structures in their secondary structures predicted using the GORIV tool. All family members possess the glycosyltransferase and ricin domains except GALNT9 and GALNTL5 which possessed only the glycosyltransferase domain confirming shared similar functions. Genetic diversity analysis in other mammalian species showed that GALNT9 was the most polymorphic while GALNT1 was the least. Differences in DNA and protein sequences, structure and possession of other functional domains and motifs suggest additional member-specific functions in addition to glycosylation.