Localisation of alpha-lactalbumnin gene expression in sheep
mammary tissue
A.J. Molenaar, S.R. Davis, R.J. Wilkins
MAF Technology, Ruakura Agricultural Centre, Private Bag,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1991, 51: 97-102
Mammary tissues from virgin, prepartum and lactating ewes were
examined by in situ hybridisation with a 35S labelled cRNA probe
derived from the bovine alpha-lactalbumin gene. Expression of alpha-
lactalbumin was absent in the virgin udders. In the pregnant gland,
alpha-lactabumin expression was found in some secretory alveoli but not
in others, even though they appeared histologically similar, containing
milk or colostrum and fat globules. Fully lactating ewes have several
levels of alpha-lactalbumin expression. In secretory epithelium, it was
high in collapsed thick walled lactating alveoli, slightly less in
distended thin walled lactating alveoli with homogeneous contents and
absent from alveoli containing an abundance of large fat globules.
Beta-cytophasmic actin expression was the reverse of this. These
observations are intriguing and suggest a number of hypotheses.
Firstly; that alpha-lactalbumin gene expression is linked to the long
term secretory activity of cells and drops off once cells are resting or
regressing. Secondly; that alpha-lactalbumin gene expression is highest
in those alveoli which are "filling up" and lowest in those which are
full or have just been milked out. That is, there are cyclical
variation in expression. And thirdly; that there is distinct
compartmentalisation in the lactating gland, and synthesis of alpha-
lactalbumin mRNA (and the protein?) occurs in cells which synthesise
little fat.
Keywords: NZSAPAB;
alpha-lactabumin; milk gene expression; in situ
hybridisation; mammary
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Last Updated 25-01-1997
