Lack of functional alpha-lactalbumin prevents involution in Cape fur seals and identifies the protein as an apoptotic milk factor in mammary gland involution.
BACKGROUND
The mammary gland undergoes a sophisticated programme of developmental changes during pregnancy/lactation. However, little is known about processes involving initiation of apoptosis at involution following weaning. We used fur seals as models to study the molecular process of involution as these animals display a unique mammary gland phenotype. Fur seals have long lactation periods whereby mothers cycle between secreting copious quantities of milk for 2 to 3 days suckling pups on land, with trips to sea alone to forage for up to 23 days during which time mammary glands remain active without initiating apoptosis/involution.


RESULTS
We show the molecular basis by which alpha-lactalbumin (LALBA), a secreted milk protein, is absent in Cape fur seals and demonstrate an apoptotic function for LALBA when exposed to mammary cells.


CONCLUSIONS
We propose that apoptosis does not occur in fur seal mammary glands due to lack of LALBA in fur seal milk, allowing evasion of involution during a foraging trip. Our work identifies LALBA as a milk factor that feeds back on the mammary gland to regulate involution.
Sharp
Julie A
JA
CRC for Innovative Dairy Products, Department of Zoology, University of Melbourne, VIC 3010, Australia. jasharp@unimelb.edu.au
Lefèvre
Christophe
C
Nicholas
Kevin R
KR
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002478:Cells, Cultured; D005260:Female; D046069:Fur Seals / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D007768:Lactalbumin / Q000235:genetics / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000737:chemistry* / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D009154:Mutation; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012322:RNA Precursors / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D013997:Time Factors
D012322:RNA Precursors; D012333:RNA, Messenger; D007768:Lactalbumin