Tissue specificity: Z-scores are calculated for each gene and each tissue and then they are binned based on quantiles of a perfect normal distribution. We compute the tissue specificity of a target as the number of standard deviations from the mean of the log RNA expression of the target across the available tissues. A target is considered to be tissue specific if the z-score is greater than 0.674 (or the 75th percentile of a perfect normal distribution). We remove data for under-expressed targets before the z-score calculation. This allows us to extract the tissues for which a gene is specific, defined as the expression value being above the 75th z-score percentile - in practice, anything in bin 2 or above.