Fig. 3.

ENU-based suppressor screen in a mousemodel of NEB-related NM. Schematic of dominant suppressor screen. Heterozygous male Neb mutant (Neb^Δ55/+) mice were treated with ENU (90 mg/kg weekly for 3 weeks), then allowed to recover for up to 8 weeks, then tested for fertility by mating with female WT CD-1 animals. Fertile males were then mated on a rotating schedule with heterozygous Neb mutant (Neb^Δ55/+) females. The resulting generation one (G1) offspring were monitored daily starting from birth. A subset of live-born pups exhibited an obvious phenotype consistent with the reported Neb phenotype. These animals all died by P7. Animals surviving beyond this point were monitored daily, and then genotyped by age 3 weeks. No animals surviving to 3 weeks had the Neb mutant genotype (Neb^Δ55/Δ55). 14 G1 heterozygous mice unexpectedly had weakness (heterozygous mice are typically normal). However, upon inheritance testing the motor dysfunction phenotypes did not segregate with the heterozygous genotype. Of note, there was non-significant (P=0.0582) skewing of numbers of wild-type versus heterozygous mice, potentially indicating that some heterozygous mice had a second Neb mutation in trans that resulted in a perinatal lethal phenotype similar to that of Neb^Δ55 homozygotes.