Compilation of meta-analysis results. (a) Functional classification of genetic modifiers and their enrichments represented by p-values. (b) (Left) Correlation analysis of modifiers and non-modifiers between diseases. Pairwise correlations (Matthew’s correlation coefficient) are represented by a color matrix ranging from −1 (inverse correlation, red), via 0 (no correlation, yellow), to 1 (high correlation, green). (Right) Modifiers in SCA3 and ADTau were further analyzed to see which functional categories are enriched among these genetic modifiers. (c) List of genes identified as modifiers of several diseases in D. melanogaster. Red and grey denote the number of diseases in which a gene is identified as a modifier and non-modifier, respectively (see Additional file 1: Figure S7 for full list). (d) List of disease-specific genetic modifiers. The same color annotation as in (c) is used here (see Additional file 1: Figure S8 for full list). (e) Enrichment analysis results of HD modifiers in D. melanogaster and PD modifiers in C. elegans with respect to the mode of action of the modifiers. Tox, toxicity modifiers; Agg, aggregation modifiers; Both, aggregation and toxicity modifiers. (f) Identification of modifiers and non-modifiers depending on the length of the polyQ stretch in HD models in D. melanogaster. Each line refers to one gene and each green dot refers to one experiment with a specific length of the polyQ stretch. If dots are in the purple and green region, it means the gene has been identified as a non-modifier and modifier, respectively. See Additional file 1 for details of meta-analysis.