Characterization and Cloning of the mRNAs Specific for the Lactating Mouse Mammary Gland

Open Access
Publisher Website
Google Scholar
Abstract
We have characterized and cloned the lactation-specific mRNAs of mouse mammary glands. The group of eight milk-protein-specific mRNAs were identified (a) by size and antigenic properties of their translation products in vitro and (b) by characterization of their respective cDNA clones. Two α-caseins (43 kDa and 39 kDa) are encoded by mRNAs of 1600 nucleotides and two β-caseins (26 kDa) are encoded by mRNAs of 1450 nucleotides in length. Three smaller caseins, γ-casein (23.7 kDa), δcasein (21 kDa) and £-casein (14.5 kDa) are synthesized by mRNAs of 880, 1150 and 860 nucleotides. Beside these casein mRNAs a mammary specific 620 nucleotide mRNA codes for a novel acidic whey protein (13.7 kDa). cDNA clones corresponding to the mRNAs for the lactation-specific proteins have been isolated from a mammary-specific cDNA library. Cloned α-casein cDNA hybridizes to both β-casein specific mRNAs and cloned β-casein cDNAs hybridize with both β-casein specific mRNAs. By RNA blot analysis we show that the cloned β -casein cDNAs for mouse α-casein, β-casein, γ-casein and &-casein and the acidic whey protein cross-hybridize with mRNAs of the rat, demonstrating partial sequence homology between the corresponding mRNAs of those species.