Genome wide analysis of the bovine mucin genes and their gastrointestinal transcription profile

BACKGROUND: Mucins are large glycoproteins implicated in protection of all mucosal surfaces. In humans and rodents, the mucin gene family has been well described and previous studies have investigated the distribution and function of mucins in the gastrointestinal (GI) tract. In contrast, little data is available on the mucin gene family in polygastric species, such as cattle. The aim of the current study was to identify all members of the bovine mucin family by genome mining and subsequently investigate the transcription pattern of these mucins in the GI tract. RESULTS: Nine bovine membrane-associated mucins (MUC1, MUC3A, MUC4, MUC12, MUC13, MUC15, MUC16, MUC20 and MUC21) and six secreted mucins (MUC2, MUC5AC, MUC5B, MUC6, MUC7 and MUC19) were identified in the bovine genome. No homologues could be identified for MUC3B, MUC8 and MUC17. In general, domain architecture of the membrane-associated mucins was found to be similar between humans and cattle, while the protein architecture of the gel-forming mucins appeared to be less conserved. Further analysis of the genomic organization indicated that the previously reported bovine submaxillary mucin (BSM) may be part of a larger gene encoding for MUC19. Analysis of the transcription profile showed that the secreted mucins were transcribed from the abomasum onwards, whereas the membrane associated mucins MUC1 and MUC20 were transcribed throughout the whole GI tract. In contrast to humans, MUC5B transcript was found in both the small and large intestine, but was absent in oesophageal tissue. CONCLUSIONS: This study provides the first characterization of the mucin gene family in cattle and their transcriptional regulation in the GI tract. The data presented in this paper will allow further studies of these proteins in the physiology of the GI tract in ruminants and their interactions with pathogens.