Milk protein gene expression in the rat mammary gland.

Abstract

For the studies of the expression of milk proteins during the functional development of the rat mammary gland and in mammary tumor MTW9, milk proteins were purified, their mRNAs isolated, and the cDNA sequences complementary to these mRNAs cloned in E. coli cells. Results of such studies show: (1) rat α‐LA is unique in that it is larger than any known α‐LAs and is glycosylated; (2) rat milk contains unique whey phosphoproteins not found in other milks; (3) more than one plasmid DNA with differences in the restriction maps have been identified for several of these milk proteins, suggesting eithera presence of a family of genes or allelic differences for these proteins; (4) the expression of individual milk proteins is dependent on the functional stage of the gland; (5) there is an inverse relationship between the expression of milk proteins and the methylation of their gene sequences; (6) mammotrophic hormones required for synthesis and stability of milk proteins and their mRNAs, when withdrawn arrest the ...