oligodendrogliomas are the second most common malignant brain tumor in adults . these tumors often contain a chromosomal abnormality involving a pericentromeric fusion of chromosomes 1 and 19 , resulting in losses of the entire short arm of the former and the long arm of the latter . to identify the molecular genetic basis for this alteration , we performed exomic sequencing of seven anaplastic oligodendrogliomas with chromosome 1p and 19q losses . among other changes , we found that that cic on chromosome 19q was somatically mutated in six of the seven cases and that fubp1 binding protein ) on chromosome 1p was somatically mutated in two of the seven cases . examination of 27 additional oligodendrogliomas revealed 12 and 3 more tumors with mutations of cic and fubp1 , respectively , 58 % of which were predicted to result in truncations of the encoded proteins . these results suggest a critical role for these genes in the biology and pathology of oligodendrocytes .