[PDF][PDF] OUTRIDER: a statistical method for detecting aberrantly expressed genes in RNA sequencing data

F Brechtmann, C Mertes, A Matusevičiūtė… - The American Journal of …, 2018 - cell.com
F Brechtmann, C Mertes, A Matusevičiūtė, VA Yépez, Ž Avsec, M Herzog, DM Bader
The American Journal of Human Genetics, 2018cell.com
RNA sequencing (RNA-seq) is gaining popularity as a complementary assay to genome
sequencing for precisely identifying the molecular causes of rare disorders. A powerful
approach is to identify aberrant gene expression levels as potential pathogenic events.
However, existing methods for detecting aberrant read counts in RNA-seq data either lack
assessments of statistical significance, so that establishing cutoffs is arbitrary, or rely on
subjective manual corrections for confounders. Here, we describe OUTRIDER (Outlier in …
RNA sequencing (RNA-seq) is gaining popularity as a complementary assay to genome sequencing for precisely identifying the molecular causes of rare disorders. A powerful approach is to identify aberrant gene expression levels as potential pathogenic events. However, existing methods for detecting aberrant read counts in RNA-seq data either lack assessments of statistical significance, so that establishing cutoffs is arbitrary, or rely on subjective manual corrections for confounders. Here, we describe OUTRIDER (Outlier in RNA-Seq Finder), an algorithm developed to address these issues. The algorithm uses an autoencoder to model read-count expectations according to the gene covariation resulting from technical, environmental, or common genetic variations. Given these expectations, the RNA-seq read counts are assumed to follow a negative binomial distribution with a gene-specific dispersion. Outliers are then identified as read counts that significantly deviate from this distribution. The model is automatically fitted to achieve the best recall of artificially corrupted data. Precision-recall analyses using simulated outlier read counts demonstrated the importance of controlling for covariation and significance-based thresholds. OUTRIDER is open source and includes functions for filtering out genes not expressed in a dataset, for identifying outlier samples with too many aberrantly expressed genes, and for detecting aberrant gene expression on the basis of false-discovery-rate-adjusted p values. Overall, OUTRIDER provides an end-to-end solution for identifying aberrantly expressed genes and is suitable for use by rare-disease diagnostic platforms.
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