Milk Lacking α-Casein Leads to Permanent Reduction in Body Size in Mice
Figure 4
Analysis of cellular proteins in mammary tissue.
Panel A: SDS-polyacrylamide gel analysis of total protein extracts derived from lactating mammary tissue of wild-type [+/+], heterozygous [+/−] and homozygous [−/−] α-casein deficient mice. Proteins were separated on a 10% gel and stained with Coomassie Blue. The sizes of the protein molecular weight markers (New England Biolabs, broad range protein marker) are indicated as are the positions of the β-casein and γ-casein proteins (arrows). The grp78/BiP and grp94 proteins and the breakdown products of the β-casein and γ-casein proteins are marked by arrowheads. Panel B: Western blot analysis of milk derived from wild-type [+/+], heterozygous [+/−] and homozygous [−/−] α-casein deficient mice. The β-casein protein was detected using a goat-anti β-casein antiserum. Panel C: Western blot analysis of milk derived from wild-type [+/+], heterozygous [+/−] and homozygous [−/−] α-casein deficient mice (9, 31 and 55). The grp78/BiP protein was detected using a goat-anti grp78 antiserum. Panel D: Correlation of gene expression in wild type [+/+], heterozygous [+/−] and α-casein deficient mice [−/−] using quantitative PCR. The results for the genes encoding the ER proteins BiP/grp78, PDIA6, grp94 and REDD1 were correlated with the expression of the reference gene β-actin. Quantification was done in 3 [+/+], 5 [+/−] and 5 [−/−] mice. Statistical analysis using one-way ANOVA demonstrates that the expression increases for BiP, grp94 and PDIA6 observed in α-casein deficient mice with respect to both wild-type and heterozygous mice occur with p<0.05. For comparisons against wild-type mice in a one-way ANOVA p<0.05 is indicated by *, p<0.01 by **, and p<0.001 by ***.