Plays a role as a marker and a regulator of neuronal differentiation; Up-regulated by a variety of neurogenic signals; such as retinoic acid; epidermal growth factor/EGF and NGFB/nerve growth factor. Induces apoptosis; growth arrest and the expression of cyclin-dependent kinase inhibitor CDKN1B. Plays a role as a tumor repressor and inhibits cell growth and tumorigenicity of medulloblastoma (MDB). Acts as probable substrate-specific adapter for a BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex towards HDAC1. Functions as antagonist of the Hedgehog pathway on cell proliferation and differentiation by affecting the nuclear transfer of transcription factor GLI1; thus maintaining cerebellar granule cells in undifferentiated state; this effect probably occurs via HDAC1 down-regulation; keeping GLI1 acetylated and inactive. When knock-down; Hedgehog antagonism is impaired and proliferation of granule cells is sustained. Activates the caspase cascade.