The Affymetrix M430 database was used to identify sequence variants affecting the expression of Cd14 via eQTL mapping. The gene that codes for Cd14 is located at 36.88 Mb on chromosome 18. Simple interval mapping found a significant eQTL with a likelihood ratio statistics (LRS) of 18.2 on chromosome 18 at the Cd14 gene location (Fig 2). Composite interval mapping revealed no secondary loci modulating Cd14 expression levels. This indicates that Cd14 is cis-regulated, meaning that a sequence variant affecting its expression is located within or near the Cd14 gene itself. Using new open access sequence data resources at GeneNetwork, we identified 3 SNPs in Cd14 between the BXD parental strains. All three SNPs are located in the coding region, one of which is a synonymous SNP, and the other two nonsynonymous SNPs, indicating that there has been a change in the coded protein (Table 2). At least one of these SNPs is responsible for Cd14 expression differences in BXD mice.
