Cis-regulation
Trans-regulation 5
Objective: pathway reconstruction
Identify candidate causal genes within the eQTL confidence interval around a marker by (partial) gene expression correlation analysis
Target gene Genome with potential candidate genes
Target gene Marker
Target gene Bootstrap confidence interval
Target gene Significant correlation with target gene
Target gene Significant correlation with target gene
Correlation Partial correlation
direct interaction common regulator indirect interaction co-regulation Distinguish between direct and indirect interactions A and B have a low partial correlation
Target gene Significant correlation with target gene Method of Bing and Hoeschele
Target gene Keep only the strongest correlation, if significant Method of Bing and Hoeschele
Target gene Compute 1 st -order partial correlations Method of Bing and Hoeschele
Target gene Keep only the strongest partial correlation, if significant Method of Bing and Hoeschele
Target gene Compute 2 nd –order partial correlations Method of Bing and Hoeschele
Target gene Discard 2 nd -order partial correlation if not significant Method of Bing and Hoeschele
Target gene Resulting network Method of Bing and Hoeschele
Network reconstruction, part 1 For each gene included in the gene list of an eQTL confidence interval compute correlation coefficient with the gene expression profile of the gene affected by the eQTL. Test for significant departure from zero via a t- test with Bonferroni correction (threshold p- value: 0.05/n, n: number of genes in the eQTL confidence interval) If significant: Identify the gene with the most significant correlation coefficient Gene 1.
Network reconstruction, part 2 Compute first-order partial correlation coefficients between the other genes and the gene affected by the eQTL, conditional on Gene 1. Test for significant departure from zero via a t-test with Bonferroni correction (threshold p-value: 0.05/(n-1), n: number of genes in the eQTL confidence interval). If significant: Identify the gene with the most significant partial correlation coefficient Gene 2.
Network reconstruction, part 3 Compute second-order partial correlation coefficients between the other genes and the gene affected by the eQTL, conditional on Genes 1 & 2. Test for significant departure from zero via a t-test with Bonferroni correction (threshold p-value: 0.05/(n-2), n: number of genes in the eQTL confidence interval). If significant: Identify the gene with the most significant partial correlation coefficient Gene 3. And so on …
Shortcomings Iterative, heuristic piecemeal approach No conditioning on the whole system, but on a set of pre-selected genes
Friedman et al. (2000), J. Comp. Biol. 7, Marriage between graph theory and probability theory
Hyperparameter β trades off data versus prior knowledge KEGG pathway Microarray data β Bayesian analysis: integration of prior knowledge
Hyperparameter β trades off data versus prior knowledge KEGG pathway Microarray data β small
Hyperparameter β trades off data versus prior knowledge KEGG pathway Microarray data β large
Input: Learn: MCMC
Protein signalling network from the literature
Predicted network