The rudolph  mutation was recovered in another ENU mutagenesis screen in the Beier Lab (Stottmann et al., Genetics, 2011). Positional cloning identified an intronic mutation creating a hypomorphic allele of the gene hydroxysteroid (17-beta) dehydrogenase 7 (Hsd17b7; Stottmann et al., PLoS Genetics, 2011). Further studies of the rudolph mutation demonstrated for the first time in a genetic, in vivo, animal model a requirement for sterol metabolism in proper Sonic Hedgehog  intracellular signal transduction. The rudolph  mutants have a striking defect in tissue organization throughout the CNS which is not due to dysregulation of the Shh  pathway. Current efforts in the lab are aimed at understanding the molecular mechanisms underlying this defect. This will contribute to a greater understanding of the role of cholesterol metabolism in cortical development.