Oligodendrogliomas (ODG) are brain tumours with distinct genetic hallmarks, including 1p/19q chromosomal co-deletion and IDH1/2 mutation. The gene encoding Capicua (CIC), on chr19q13.2, has been identified as mutated in ODGs with 1p/19q loss and IDH1/2 mutation, a rare genetic signature. Mutation of the retained 19q CIC allele is likely functionally important, but its contribution to ODG biology is unknown. To characterize the temporal and spatial expression of CIC in the normal mouse cerebrum, I examined CIC expression throughout development. CIC is expressed at a time and place in development in which it may influence cortical progenitors. To determine if CIC loss affects proliferation or differentiation of neural progenitors, CIC biologic functions were examined using loss-of-function approaches in vitro and in vivo. CIC loss was increased proliferation and cell growth, and effected progenitor differentiation and migration. Thus, my data supports a role for CIC in regulating processes in neural progenitors that are relevant to cancer.