ZIC1 and medulloblastoma: Indeed, overexpression of ZIC1 constructs in mouse granule neuron progenitor (GNPs) cells (the cell of origin for SHH medulloblastoma)10,12 results in increased cellular proliferation, which was more pronounced with the SHH medulloblastoma ZIC1 mutants as compared to WT ZIC1 or G4 medulloblastoma ZIC1 mutants (Fig. 8a,b).