Figure 7. Cdh11 is a key target of the Bhlhb5/Prdm8 repressor complex.

A) Affymetrix microarray-based gene profiling identifies Cdh11 as a gene that is significantly upregulated in the dorsal telencephalon of Bhlhb5^−/− mice (FDR < 0.05) from E13.5 – E17.5. Data are mean +/− SEM of biological replicates, with WT in black and Bhlhb5^−/− in red, as indicated. B) Cdh11 mRNA is also upregulated in the dorsal telencephalon of Prdm8^−/− mice relative to WT littermates at E14.5, as shown by qPCR. Data are normalized to WT and are presented as mean +/− SEM of biological replicates. * indicates significant difference relative to controls (p < 0.05, t-test). C–D) Cdh11 protein is upregulated in the dorsal telencephalon of Bhlhb5^−/− mice. Sagittal sections from mice of the indicated genotype at E16.5 were stained with antibodies to Cdh11. Note the high Cdh11 expression in the axons of corticofugal fibers in the internal capsule (white arrows). Boxed insets are enlarged in D, which also shows the corresponding immunostaining with antibodies to Bhlhb5. E) Sagittal schematic of the brain illustrating the path of the corticospinal tract. Regions I and II (gray) indicate the location of sections in the coronal plane that were used to quantify the area of the corticospinal tract in Bhlhb5^−/− mice and Bhlhb5^−/−; Cdh11^−/− double mutant mice (F). F) Quantification of the axon area in regions I and II. Relative to WT mice, there is a dramatic loss of axon area in the Bhlhb5^−/− mice (black bars) and this loss is partially rescued in Bhlhb5^−/−;Cdh11^−/− double mutant mice (red bars). Five pairs of adult littermate mice were analyzed. * indicates significant (p < 0.05, t-test). G) Representative images showing the corticospinal tract stained with PKCγ in WT, Cdh11^−/−, Bhlhb5^−/−, and Bhlhb5^−/−;Cdh11^−/− mice. Matched cervical sections (corresponding to region II) from adult littermate mice are shown. The corticospinal tract is almost absent in the cervical spinal cord of Bhlhb5^−/− mice but a partial rescue is seen in Bhlhb5;Cdh11^−/− double mutant mice. The loss of Cdh11 alone has no effect on the formation of the corticospinal tract. H) Bhlhb5 mutant mice develop skin lesions by ~ 6 weeks of age. The onset of skin lesions is significantly delayed to ~13 weeks in Bhlhb5^−/−; Cdh11^−/− double mutant mice. n = 12 littermate pars; * indicates significant difference (p < 0.05, t-test.)