HeritSeq – model based heritability scores for high-throughput sequencing data

Heritability of a phenotypic or molecular trait measures the proportion of variance that is attributable to genotypic variance. It is an important concept in breeding and genetics. Few methods are available for calculating heritability for traits derived from high-throughput sequencing.

University of Colorado researchers have developed several statistical models and different methods to compute and test a heritability measure for such data based on linear and generalized linear mixed effects models. They also provide methodology for hypothesis testing and interval estimation. Their analyses show that, among the methods, the negative binomial mixed model (NB-fit), compound Poisson mixed model (CP-fit), and the variance stabilizing transformed linear mixed model (VST) outperform the voom-transformed linear mixed model (voom). NB-fit and VST appear to be more robust than CP-fit for estimating and testing the heritability scores, while NB-fit is the most computationally expensive. CP-fit performed best in terms of the coverage of the confidence intervals. In addition, the researchers applied the methods to both microRNA (miRNA) and messenger RNA (mRNA) sequencing datasets from a recombinant inbred mouse panel. They show that miRNA and mRNA expression can be a highly heritable molecular trait in mouse, and that some top heritable features coincide with expression quantitative trait loci.

Sequencing read examples for a a top heritable miRNA and b a top heritable mRNA features. Each boxplot summarizes the reads for one strain and they are sorted by strain mean in an increasing order. The color of the boxes have no special significance. The estimated VPC scores are reported in the top left tables

The models and methods these researchers investigated are applicable and extendable to sequencing experiments where some biological replicates are available and the environmental variation is properly controlled. The CP-fit approach for assessing heritability was implemented for the first time to their knowledge. All the methods presented, as well as the generation of simulated sequencing data under either negative binomial or compound Poisson mixed models, are provided in the R package HeritSeq.

Availability – The package HeritSeq is available on CRAN (https://CRAN.R-project.org/package=HeritSeq)