RT Journal Article SR Electronic T1 Association mapping reveals the role of mutation-selection balance in the maintenance of genomic variation for gene expression JF bioRxiv FD Cold Spring Harbor Laboratory SP 015743 DO 10.1101/015743 A1 Emily B. Josephs A1 Young Wha Lee A1 John R. Stinchcombe A1 Stephen I. Wright YR 2015 UL http://biorxiv.org/content/early/2015/02/26/015743.abstract AB The evolutionary forces that maintain genetic variation for quantitative traits within populations remain unknown. One hypothesis suggests that variation is maintained by a balance between new mutations and their removal by selection and drift. Theory predicts that this mutation-selection balance will result in an excess of low-frequency variants and a negative correlation between minor allele frequency and selection coefficients. Here, we test these predictions using the genetic loci associated with total expression variation (‘eQTLs’) and allele-specific expression variation (‘aseQTLs’) mapped within a single population of the plant Capsella grandiflora. In addition to finding eQTLs and aseQTLs for a large fraction of genes, we show that alleles at these loci are rarer than expected and exhibit a negative correlation between effect size and frequency. Overall, our results show that mutation-selection balance is the dominant contributor to genomic variation for expression within a single, outcrossing population.