Figure 1.

Tissue-specific repression of housekeeping genes. (A) Frequency distribution of the sum score for islets (green) and liver (brown) as baseline. Sum score numbers are calculated genewise and are the addition of the number of pairwise t-tests where expression in baseline is significantly lower (−1) or higher (+1) as compared to the other tissues. Liver- and islet-specific genes reside in the category with the highest possible sum score (right), whereas genes of which expression is specifically repressed in islets and liver are found in the category with the lowest possible sum score (left). (B) Strategy to identify genes that are selectively repressed in one tissue, based on mRNA profiling of 21 mouse tissues. Expression of a gene in a baseline tissue was compared to expression of that gene in all other tissues. When significantly lower compared to all other tissues, this gene was termed repressed in that tissue. This procedure was applied to all genes and repeated for all tissues in the panel. Statistical testing methods are described in Methods. (C) Pie-chart distribution of the number of specifically repressed genes in tissues. (D) Significant associations of specifically repressed genes (in all tissues) with molecular and cellular functions. The Benjamini-Hochberg-corrected P-value threshold of 0.05 is indicated by a dashed line.