The two halves of the human brain are connected by several so called commissures. These crossing tracts link structures of the right and the left cerebral hemisphere, mediating coordination and ensuring transfer of information between them. Scientists now report in Nature Genetics that autosomal recessive mutations in the DCC gene that have an inactivating effect on the gene cause a congenital syndrome in which these crossing pathways between the two hemispheres are either absent or structurally altered. Affected individuals show, among others, intellectual disability and horizontal gaze palsy. Scoliosis may also be associated. Interestingly, a second study published in the same issue of Nature Genetics describes that autosomal dominant DCC mutations can result in isolated agenesis of the largest commissure of the brain, the corpus callosum, without manifestation of intellectual disability. The two studies demonstrate in an impressive manner that the axon-guidance receptor encoded by DCC plays an essential role in the anatomical network between the two cerebral hemispheres and that different functional disturbances in this receptor give rise to varying problems in their interconnection.