Congenic dissection of a major QTL for methamphetamine sensitivity implicates epistasis

We identified a congenic mouse with an introgressed region from the A/J donor inbred strain on an inbred C57BL/6J background that showed a reduced locomotor stimulant response to methamphetamine. We conducted microarray analysis of the striatum from drug-naive female and male mice that were 6-9 weeks old. The congenic region is on chromosome 11 and spans approximately 84-96 Mb. There were two groups of mice used in the analysis: B6 control mice versus congenic mice. Congenic mice were collapsed across heterozygous and homozygous genotypes. All mice are on a C57BL/6J background. Congenic mice differ only on chromosome 11 where they contain the introgressed A/J alleles from 84-96 Mb. 14 C57BL/6J wildtype mice and 14 B6.A/J congenic mice (84-96 Mb region from A/J strain) were examined for gene expression differences using striatal tissue (left and right punches pooled). All mice were drug-naïve and were 6-9 weeks old at the time of sacrifice.