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Molecular evolution of monotreme and marsupial whey acidic protein genes
journal contribution
posted on 2007-07-01, 00:00 authored by Julie SharpJulie Sharp, C Lefèvre, Kevin NicholasWhey acidic protein (WAP), a major whey protein present in milk of a number of mammalian species has characteristic cysteine-rich domains known as four-disulfide cores (4-DSC). Eutherian WAP, expressed in the mammary gland throughout lactation, has two 4-DSC domains, (DI-DII) whereas marsupial WAP, expressed only during mid-late lactation, contains an additional 4-DSC (DIII), and has a DIII-D1-DII configuration. We report the expression and evolution of echidna (Tachyglossus aculeatus) and platypus (Onithorhynchus anatinus) WAP cDNAs. Predicted translation of monotreme cDNAs showed echidna WAP contains two 4-DSC domains corresponding to DIII-DII, whereas platypus WAP contains an additional domain at the C-terminus with homology to DII and has the configuration DIII-DII-DII. Both monotreme WAPs represent new WAP protein configurations. We propose models for evolution of the WAP gene in the mammalian lineage either through exon loss from an ancient ancestor or by rapid evolution via the process of exon shuffling. This evolutionary outcome may reflect differences in lactation strategy between marsupials, monotremes, and eutherians, and give insight to biological function of the gene products. WAP four-disulfide core domain 2 (WFDC2) proteins were also identified in echidna, platypus and tammar wallaby (Macropus eugenii) lactating mammary cells. WFDC2 proteins are secreted proteins not previously associated with lactation. Mammary gland expression of tammar WFDC2 during the course of lactation showed WFDC2 was elevated during pregnancy, reduced in early lactation and absent in mid-late lactation.
History
Journal
Evolution and DevelopmentVolume
9Issue
4Season
July/AugustPagination
378 - 392Publisher
Wiley-Blackwell PublishingLocation
Hoboken, N.J.Publisher DOI
ISSN
1520-541XLanguage
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2007, The AuthorsUsage metrics
Keywords
Amino Acid SequenceAnimalsBase SequenceEvolution, MolecularMarsupialiaMilk ProteinsMolecular Sequence DataMonotremataProtein Structure, TertiaryScience & TechnologyLife Sciences & BiomedicineEvolutionary BiologyDevelopmental BiologyGenetics & HereditySEQUENCE HOMOLOGYBRUSHTAIL POSSUMTAMMAR WALLABYMILK WHEYEXPRESSIONMOUSELACTATIONFAMILYCDNAHE-4Evolutionary BiologyZoology
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