title: Conservation of the ST6Gal I gene and its expression in the mammary gland.
abstract: Milk sialoglycoconjugates can protect the gastrointestinal tract of the suckling neonate by competitively binding to invading pathogens and promoting growth of beneficial flora, and their potential role in postnatal brain development is of particular interest in human infant nutrition. Although the concentration and the distribution of sialoglycoconjugates have been extensively studied in the milk of various species, the investigation of sialyltransferase gene expression in the mammary gland, in the context of lactation, has been limited. The sialyltransferase enzyme ST6Gal I transfers sialic acid from CMP-sialic acid to type 2 (Galβ1,4GlcNAc) free disaccharides or the termini of N- or O-linked oligosaccharides using an α2,6-linkage. Expression of the ST6Gal I gene is primarily regulated at the level of transcription through the use of several cell and development-specific promoters, producing transcripts with divergent 5' untranslated regions (UTR). In the mouse mammary gland, the novel 5'UTR exon (L) appears to be associated with a drastic increase in ST6Gal I gene expression during lactation. We find that rats also possess an exon (L), suggesting conservation of this regulatory mechanism in rodents. In contrast, an exon (L)-containing transcript was not detected in the lactating bovine or human mammary gland. We also observed a trend of increasing ST6Gal I gene expression in the bovine mammary gland, culminating in involution. This is in contrast to species such as mice where the greatest change in ST6Gal I gene expression occurs between pregnancy and lactation, suggesting different roles in rodents vs. other mammals for α2,6-sialylated oligosaccharides present in milk.
authors.affiliation: Centre for Reproduction and Development, Monash Institute of Medical Research, Clayton 3168, Australia. jovana.maksimovic@mcri.edu.au
authors.forename: Jovana
authors.initials: J
authors.lastname: Maksimovic
authors.forename: Julie A
authors.initials: JA
authors.lastname: Sharp
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Nicholas
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Cocks
authors.forename: Keith
authors.initials: K
authors.lastname: Savin
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D017124:Conserved Sequence; D005091:Exons; D005260:Female; D006801:Humans; D007774:Lactation / Q000502:physiology; D008099:Liver / Q000378:metabolism; D008198:Lymph Nodes / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism* / Q000502:physiology; D042361:Mammary Glands, Human / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D011247:Pregnancy; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D012799:Sialyltransferases / Q000235:genetics* / Q000378:metabolism; D013045:Species Specificity; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
chemical_list: D020121:5' Untranslated Regions; D012333:RNA, Messenger; D014157:Transcription Factors; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase