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Monotremes are the only oviparous mammals and exhibit a fascinating combination of reptilian and mammalian characters. They represent a component of synapsidal reproduction by laying shelled eggs which are incubated outside the mother’s body. This is accompanied by a prototherian lactation process, marking them as representatives of early mammals. The only extant monotremes are the platypus, and the short- and long-beaked echidnas, and their distributions are limited to Australia and New Guinea. Apart for a short weaning period, milk is the sole source of nutrition and protection for the hatchlings which are altricial and immunologically naive. The duration of lactation in these mammals is prolonged relative to the gestational length and period of incubation of eggs. Much of the development of monotreme young occurs in the non-sterile ex-utero environment. Therefore the role of milk in the growth, development and disease protection of the young is of significant interest. By sequencing the cDNA of cells harvested from monotreme milk, we have identified a novel monotreme-specific transcript, and the corresponding gene was designated as the EchAMP. The expression profile of this gene in various tissues revealed that it is highly expressed in milk cells. The peptides corresponding to the EchAMP protein have been identified in a sample of echidna milk. In silico analysis indicated putative antimicrobial potential for the cognate protein of EchAMP. This was further confirmed by in vitro assays using a host of bacteria. Interestingly, EchAMP did not display any activity against a commensal gut floral species. These results support the hypothesis of enhancement of survival of the young by antimicrobial bioactives of mammary gland origin and thus emphasize the protective, non- nutritional role of milk in mammals.

Item Type:	Refereed Article
Keywords:	evolution, sex chromosomes, Y chromosomes, mediator complex, sex determination, mammals, Tachyglossus aculeatus, Ornithorhynchus anatinus
Research Division:	Biological Sciences
Research Group:	Zoology
Research Field:	Animal physiological ecology
Objective Division:	Environmental Management
Objective Group:	Fresh, ground and surface water systems and management
Objective Field:	Assessment and management of freshwater ecosystems
UTAS Author:	Nicol, SC (Associate Professor Stewart Nicol)
ID Code:	81941
Year Published:	2013
Web of Science® Times Cited:	15
Deposited By:	Zoology
Deposited On:	2013-01-11
Last Modified:	2017-11-01
Downloads:	491 View Download Statistics