Global changes in miRNA and mRNA expression. (a) Hierarchical clustering of time points based on the relative log2 expression of 102 detected miRNAs. (b) miRNAs and mRNAs exhibit reduced overall expression during lactation and early involution time points. Black dots correspond to independent biological replicates. Median values for each time point are connected by a solid black line. (Top) miRNA expression. Normalised log2 median fluorescence intensity (MFI) values (see Methods) were averaged for each sample by taking the arithmetic mean. (Middle) mRNA expression. The background corrected Illumina probe level data were transformed by taking logs (base 2) but no between sample normalisation was performed. Non-normalised log2 intensities were averaged for each sample by taking the arithmetic mean. (Bottom) Mass of total RNA extracted from whole mammary glands, and equally sized partial glands for lactation and involution time points.