Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals

Lefevre, Christophe, Sharp, Julie A. and Nicholas, Kevin R. 2009, Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals, Reproduction, fertility and development, vol. 21, no. 8, pp. 1015-1027, doi: 10.1071/RD09083.

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Title Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals
Author(s) Lefevre, Christophe
Sharp, Julie A.ORCID iD for Sharp, Julie A.
Nicholas, Kevin R.
Journal name Reproduction, fertility and development
Volume number 21
Issue number 8
Start page 1015
End page 1027
Total pages 13
Publisher CSIRO Publishing
Place of publication Collingwood, Vic.
Publication date 2009
ISSN 1031-3613
Keyword(s) lactation
Summary Using a milk-cell cDNA sequencing approach we characterised milk-protein sequences from two monotreme species, platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus) and found a full set of caseins and casein variants. The genomic organisation of the platypus casein locus is compared with other mammalian genomes, including the marsupial opossum and several eutherians. Physical linkage of casein genes has been seen in the casein loci of all mammalian genomes examined and we confirm that this is also observed in platypus. However, we show that a recent duplication of β-casein occurred in the monotreme lineage, as opposed to more ancient duplications of α-casein in the eutherian lineage, while marsupials possess only single copies of α- and β-caseins. Despite this variability, the close proximity of the main α- and β-casein genes in an inverted tail-tail orientation and the relative orientation of the more distant kappa-casein genes are similar in all mammalian genome sequences so far available. Overall, the conservation of the genomic organisation of the caseins indicates the early, pre-monotreme development of the fundamental role of caseins during lactation. In contrast, the lineage-specific gene duplications that have occurred within the casein locus of monotremes and eutherians but not marsupials, which may have lost part of the ancestral casein locus, emphasises the independent selection on milk provision strategies to the young, most likely linked to different developmental strategies. The monotremes therefore provide insight into the ancestral drivers for lactation and how these have adapted in different lineages.
Language eng
DOI 10.1071/RD09083
Field of Research 060409 Molecular Evolution
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1 Refereed article in a scholarly journal
HERDC collection year 2009
Copyright notice ©2009, CSIRO
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