Figure 2.

X overexpression in F₁ hybrid male testes is associated with a musculus^PWK introgression on the proximal X. (A) Sex chromosome genotypes and mean X overexpression in experimental males. X introgression genotypes are numbered 1–7; regions of uncertainty between domesticus^LEWES (open) and musculus^PWK (solid) recombination break points on the X are shown shaded; all genoytpes share the same F₁ autosomal background. Expression was normalized relative to beta-actin, Acrv1, and Protamine 1 (ΔC_T); mean ΔΔC_T is the difference in expression between experimental genotypes and the fertile F₁, averaged across the 12 X-linked genes indicated on the left side. Error bars are +1 SE. Tests for significant differences between experimental genotypes and control were performed on ΔC_T values with ANOVA followed by Dunnett post hoc tests, (*) P < 0.01, (***) P < 0.0001. (B) Overexpression of individual X-linked genes does not require a musculus^PWK allele. Data are presented as genotype means (±1 SE) for six representative genes. Sex chromosome genotypes are shown on the x-axis. Solid bars denote the musculus^PWK allele at a given locus; open bars denote the domesticus^LEWES allele. Significance was tested as in 2A, (*) P ≤ 0.05, (**) P ≤ 0.001. See also Figure S2.