Data from: House mouse Slx and Sly CNV and expression data

<p>A remarkable gene copy number (CN) arms race system has recently been described in laboratory mice, where <em>Slx;Slxl1</em> and <em>Sly</em> genes compete over transmission by altering fertilisation success of X and Y chromosome-bearing sperm, respectively. Here, we focus on this system in nature, where natural selection can counter CN/gene product escalation. Our model is house mouse subspecies hybridising in Europe. In some regions, Y chromosomes of the Eastern subspecies have introgressed onto Western genomic backgrounds, accompanied by sex ratio distortion in favour of males, consistent with the inbred-lines suggested mechanism: overabundance of SLY protein expressed by invading Y chromosomes. We take <em>Slx</em> as representative of the X side of this arms race and measure <em>Slx|Sly</em> CN and expression across an 'Invasion' transect where Ys introgress and a 'Control' transect with negligible introgression. Since we found similar <em>Slx|Sly</em> ratios in both transects, <em>SLY</em> overabundance is unlikely to explain the introgression. However, <em>Slx</em> CN is relatively low in the introgression area, suggesting <em>Slx</em> is less able to combat <em>Sly</em> effects here. Further, deterministic changes in <em>Slx;Sly</em> expression proportions versus CN proportions suggest standing variation for trans regulation of <em>Slx|Sly</em> is being co-opted in nature where their arms race reduces population fitness.</p>