Sonic hedgehog regulates the growth and patterning of the cerebellum

The molecular bases of brain development and CNS malignancies remain poorly understood. Here we show that Sonic hedgehog (Shh) signaling controls the development of the cerebellum at multiple levels. SHH is produced by Purkin je neurons, it is required for the proliferation of granule neuron precurso rs and it induces the differentiation of Bergmann glia. Blocking SHH functi on in vivo results in deficient granule neuron and Bergmann glia differenti ation as well as in abnormal Purkinje neuron development. Thus, our finding s provide a molecular model for the growth and patterning of the cerebellum by SHH through the coordination of the development of cortical cerebellar cell types. In addition, they provide a cellular context for medulloblastom as, childhood cancers of the cerebellum.