Evidence for a diffusible factor influencing the switching of
ovine and bovine milk gene expression leads to identification of factors
potentially involved.
A.J. Molenaar, D.R. Musgrave, R.J. Wilkins
AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123,
Hamilton, New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 303-306
Our earlier in situ hybridisation studies have shown heterogeneous
expression of milk protein genes. At some sites, a sharp demarcation of
mRNA expression is seen at the basement membrane between 'active' and
'inactive' tissue, while at other nearby sites, a reciprocal gradient of mRNA
expression about 10 cells wide is seen. The alveoli in these latter 'inactive'
sites contain leucocytes which indicates that they have been 'inactive' longer
than the former. This suggests a factor could be diffusing between 'inactive'
and 'active' tissues and influencing milk gene expression. We used a
consensus oligomer corresponding to the linkers between the fingers of zinc
finger DNA binding proteins in a polymerase chain reaction performed on
cDNA from 'active' versus 'inactive' mammary mRNA. Differences and
similarities were observed in the sizes of the DNA products from each sample.
Several of the bands present in the 'active' cDNA and absent from the
'inactive' cDNA were cloned and some were found to have homologies to zinc
finger and other DNA binding proteins. It is possible that we have partially
isolated a component of the pathway that maintains lactation.
Keywords: NZSAPAB;
in:situ:hybridisation; milk:gene:expression; zinc:finger; mammary.
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