Fine mapping of complex traits have often yielded multiple constituent loci within a QTL interval [87],[88]. Our mapping analyses of expression traits also show that multiple gene variants, rather than one master regulatory gene, cause the aggregation of expression QTLs in Qrr1. Subgroups of genes with tight coexpression can be dissected from the dense cluster of QTLs. Most notable is the strong trans-regulatory effect of Qrr1d on genes involved in amino acid metabolism and translation, including a host of ARS transcripts. However, there are limits to our ability to dissect Qrr1, and genes associated with protein degradation and RNA metabolism map throughout the region. In part this may be due to inadequate mapping resolution, but it may also reflect clusters of functionally related loci and genes [89]. At this stage we are also unable to discern whether there is a single or multiple QTLs within Qrr1d. While it is likely that a single QTL modulates the expression of the ARS, there may be additional gene variants in Qrr1d that modulate other transcripts involved in translation and RNA metabolism. With increased resolving power it may be possible to further subdivide transcripts that map to Qrr1p and Qrr1d into smaller functional modules.
