CCDC86/Cyclon is a novel Ki-67 interacting protein important for cell division

The chromosome periphery is a network of proteins and RNAs that coats the outer surface of mitotic chromosomes. Despite the identification of new components, the functions of this complex compartment are poorly characterised. In this study we identified a novel chromosome periphery-associated protein CCDC86/cyclon. Using a combination of RNAi (RNA interference), microscopy and biochemistry, we studied the functions of CCDC86/cyclon in mitosis. CCDC86/cyclon depletion resulted in partial disorganisation of the chromosome periphery with partial alterations in the localization of Ki-67 and Nucleolin and the formation of abnormal cytoplasmic aggregates. Furthermore, CCDC86/cyclon-depleted cells displayed errors in chromosome alignment, altered spindle length and increased apoptosis. These results suggest that, within the chromosome periphery, different subcomplexes that include CCDC86/cyclon, Nucleolin and B23 are required for mitotic spindle regulation and correct kinetochore-microtubule attachments, thus contributing to chromosome segregation in mitosis. Moreover, we have identified CCDC86/cyclon as a MYC-N regulated gene whose expression levels represent a powerful marker for prognostic outcomes in neuroblastoma. Summary statement Here we report the identification of CCDC86/cyclon as novel component of the perichromosomal layer. CCDC86 is important for chromosome segregation and represents a strong prognostic marker for neuroblastoma patients.