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

Data availability: The datasets used for this study are: 1) For the mitotic chromosome analyses: (Ohta et al., 2010) 2) For the neuroblastoma patients, data sets are available at https://hgserver1.amc.nl/cgi-bin/r2 Imaging and quantification datasets are available upon request from the corresponding authors and will be shared via Figshare.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 partialdis organisation of the chromosome periphery with partial alterations in the localisation 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 includeCCDC86/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.The Vagnarelli lab is supported by the Wellcome Trust Investigator award 210742/Z/18/Z (Chromatin Re-Organisation at the Transition from Mitosis to G1: How Phospho-Switches Regulate the Process in Space and Time) to Paola Vagnarelli. The study on MYC (Figure 5) was supported by Kidscan PhD studentship awarded to PV. The Ohta lab is supported by Research Foundation for the Electrotechnology of Chubu (grant number R-01227) to SO. Work in the Earnshaw laboratory is funded by Wellcome, from whom WCE holds a Principal Research Fellowship (grant no. 107022)