# AffiXcan AffiXcan is an R package that includes a set of functions to train and to apply statistical models to estimate the **GReX** (genetically regulated expression). To use AffiXcan please refer to the [Bioconductor](https://bioconductor.org/packages/AffiXcan) webpage. ## Background Understanding and predicting how genetic variation influences gene expression in cells and tissues is of great interest in modern biological and medical sciences. The present methods to estimate the genetic contribution to gene expression do not take into account functional information in identifying _expression quantitative trait loci_ (eQTL), i.e. those genetic variants that contribute to explaining the variation of gene expression. Relying on SNPs as predictors allows to make significant models of gene expression only for those genes for which SNPs with a fairly good effect size exist, but this condition is not satisfied for the majority of genes, despite their expression having a non-zero heritability (h²). To address this issue, new, different strategies to analyze genetic variability of regulatory regions and their influence on transcription are needed. ## General features __AffiXcan__ (total binding AFFInity-eXpression sCANner) implements a functional approach based on the [TBA](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0143627) (Total Binding Affinity) score to make statistical models of gene expression, being able to make significant predictions on genes for which SNPs with strong effect size are absent. Furthermore, such a functional approach allows to make mechanistic interpretations in terms of transcription factors binding events that drive differential transcriptional expression. These features are of considerable importance for eQTL discovery and to improve the capability to estimate a **GReX** (genetically regulated expression) for a greater number of genes, at the same time giving insights on the possible molecular mechanisms that are involved in differential expression of genes.