PT  - JOURNAL ARTICLE
AU  - Il-Youp Kwak
AU  - Candace R. Moore
AU  - Edgar P. Spalding
AU  - Karl W. Broman
TI  - Mapping quantitative trait loci underlying function-valued traits using functional principal component analysis and multi-trait mapping
AID  - 10.1101/025577
DP  - 2015 Jan 01
TA  - bioRxiv
PG  - 025577
4099  - http://biorxiv.org/content/early/2015/08/26/025577.short
4100  - http://biorxiv.org/content/early/2015/08/26/025577.full
AB  - We previously proposed a simple regression-based method to map quantitative trait loci underlying function-valued phenotypes. In order to better handle the case of noisy phenotype measurements and accommodate the correlation structure among time points, we propose an alternative approach that maintains much of the simplicity and speed of the regression-based method. We overcome noisy measurements by replacing the observed data with a smooth approximation. We then apply functional principal component analysis, replacing the smoothed phenotype data with a small number of principal components. Quantitative trait locus mapping is applied to these dimension-reduced data, either with a multi-trait method or by considering the traits individually and then taking the average or maximum LOD score across traits. We apply these approaches to root gravitropism data on Arabidopsis recombinant inbred lines and further investigate their performance in computer simulations. Our methods have been implemented in the R package, funqtl.