The mef2ca transcriptional target dlx5a is differentially regulated between low- and high-penetrance strains and is required for normal craniofacial development in unselected strains.
(A) Head expression of dlx5a was quantified by RT-qPCR in full-sibling mef2ca mutant and wild-type embryos from low- and high-penetrance strains at 28 and 48 hpf. Expression levels for all conditions were normalized to mef2ca wild types at 28 hpf. Asterisks at 28 hpf mark significantly different expression levels between mef2ca mutants compared with mef2ca wild types within each strain. Asterisks at 48 hpf mark significantly different expression levels between low- and high-penetrance strains within each mef2ca genotype (T-test at alpha = 0.05), error bars are standard deviation. (B) Heterozygous dlx5aj1073Gt adults from an unselected background were intercrossed, 6 dpf offspring were fixed and stained with Alcian Blue (cartilage) and Alizarin Red (bone). Stained skeletons were genotyped, and flat mounts were imaged. Arrows mark ectopic cartilage nubbins, caret indicates jaw-joint fusion. Scale bar: 50 μm. (C) Penetrance scores for phenotypes associated with dlx5a heterozygotes and mutants in an unselected background. Asterisk indicates significance at alpha = 0.05 Fisher’s exact test compared with dlx5a+/+. (D) Head expression of dlx5a was quantified by RT-qPCR in full-sibling dlx5a wild-type and mutant embryos at 28 hpf. Expression in dlx5a mutants was normalized to wild-type sibling expression levels (black line). Asterisk marks expression level significantly different in dlx5a mutants compared with dlx5a wild types (T-test at alpha = 0.05). Error bars are standard deviation.