HGNC Approved Gene Symbol: CEP63
Cytogenetic location: 3q22.2 Genomic coordinates (GRCh38) : 3:134,485,724-134,782,559 (from NCBI)
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
|---|---|---|---|---|
| 3q22.2 | ?Seckel syndrome 6 | 614728 | Autosomal recessive | 3 |
CEP63 is a subunit of the centrosome, the major microtubule-organizing center of animal cells. The centrosome influences cell shape, polarity, and motility, and it has a crucial function in cell division (summary by Andersen et al., 2003).
By mass spectrometric analysis of centrosomes purified from the KE-37 human lymphoblastic cell line, followed by database analysis, Andersen et al. (2003) identified CEP63. The deduced protein contains 6 coiled-coil domains and has a calculated molecular mass of 63.4 kD. Fluorescence-tagged CEP63 associated with centrosomes in transfected U2OS cells, and salt extraction experiments suggested that CEP63 is a core centrosomal protein.
Loffler et al. (2011) stated that there are 4 major splice variants of CEP63, as well as several minor variants. These 4 major variants encode proteins with 309 identical N-terminal amino acids and unique C termini. Quantitative RT-PCR showed that CEP63 variant 3, which encodes a 496-amino acid protein, was the most abundant CEP63 variant in BJ human fibroblasts and U2OS human osteosarcoma cells. Immunohistochemical analysis of several human cell lines showed that endogenous CEP63 localized exclusively to centrosomes throughout the cell cycle. Western blot analysis detected prominent CEP63 bands at apparent molecular masses of 63 and 58 kD, corresponding to isoforms 2 and 3, respectively.
Using PCR, Sir et al. (2011) found variable expression of all 4 CEP63 splice variants in adult and fetal brain and HeLa cell cDNA libraries. The deduced full-length CEP63 protein, which corresponds to CEP63 isoform 1 reported by Loffler et al. (2011), contains 703 amino acids and has 6 predicted coiled-coil domains. Super-resolution microscopy revealed that CEP63 colocalized with the centrosome duplication factor CEP152 (613529) in a discrete ring around the proximal end of the parental centriole in avian and human cell lines.
Sir et al. (2011) determined that the CEP63 gene contains 16 exons. It has a single CpG island, and the translational start site is in exon 3.
Hartz (2012) mapped the CEP63 gene to chromosome 3q22.2 based on an alignment of the CEP63 sequence (GenBank AK023448) with the genomic sequence (GRCh37).
Using small interfering RNA, time-lapse video microscopy, and immunohistochemical analysis, Loffler et al. (2011) found that knockdown of CEP63 in U2OS cells resulted in loss of CDK1 (116940) localization at centrosomes, causing mitotic skipping, cell enlargement, and polyploidization. Conversely, overexpression of fluorescence-tagged CEP63 in U2OS cells resulted in centrosome amplification during interphase. Coimmunoprecipitation analysis and protein pull-down assays revealed direct interaction between CEP63 isoform 3 and CDK1. Deletion analysis revealed that the N-terminal 290 amino acids of CEP63, which are present in all 4 major CEP63 isoforms, were required for centrosomal localization and centrosome amplification. By examining CEP63 mRNA expression in 244 human neuroblastomas, Loffler et al. (2011) found a correlation between high CEP63 expression and advanced stage of the disease. In culture, CEP63 expression impaired the DNA damage response to replication stress.
Sir et al. (2011) found that knockout of Cep63 in DT40 chicken B lymphocytes resulted in mitotic spindle defects, including monopolar and multipolar spindles. Cep63-knockout cells did not become depleted of centrosomes, suggesting that CEP63 is not a core centriole assembly factor. Several protein interaction assays revealed that the C-terminal part of full-length CEP63 bound CEP152 in HeLa and DT40 cells. Centrosomal localization of Cep152 was disrupted in cycling Cep63-knockout DT40 cells, and overexpression of human CEP152 restored centriole numbers and reversed the mitotic spindle phenotype of Cep63-knockout cells. Sir et al. (2011) concluded that CEP63 is required for centrosomal localization of CEP152 and for centrosome duplication.
Using the centriolar satellite protein CEP63 as bait in a proximity interaction assay, Firat-Karalar et al. (2014) identified KIAA0753 (617112) and CCDC14 (617147). Coimmunoprecipitation analysis confirmed that KIAA0753 and CCDC14 interacted with CEP63 in HEK293T cells. Knockdown of KIAA0753 via small interfering RNA reduced CEP63 localization at centrosomes and inhibited centriole duplication in cycling U2OS cells. In contrast, knockdown of CCDC14 significantly increased CEP63 content at centrosomes and increased the number of cycling cells with more than 4 centrioles. Firat-Karalar et al. (2014) concluded that, during the cell cycle, KIAA0753 and CCDC14 positively and negative regulate centriole duplication, respectively, by regulating CEP63 levels at the centrosome.
In 3 female cousins from a consanguineous Pakistani family with microcephaly and short stature mapping to chromosome 3q22 (Seckel syndrome-6; 614728), Sir et al. (2011) sequenced 3 candidate genes and identified homozygosity for a nonsense mutation in the CEP63 gene (614724.0001). Centrosomal colocalization of CEP63 and CEP152 was found to be disrupted in CEP63-deficient patient cells.
In 3 female cousins from a consanguineous Pakistani family with microcephaly and short stature (SCKL6; 614728), Sir et al. (2011) identified homozygosity for a 129G-A transition in exon 4 of the CEP63 gene, resulting in a trp43-to-ter (W43X) substitution. CEP63-deficient patient-derived cells showed disruption of the normal pattern of colocalization of CEP63 and CEP152 (613529) in a discrete ring around the proximal end of the parent centriole.
Andersen, J. S., Wilkinson, C. J., Mayor, T., Mortensen, P., Nigg, E. A., Mann, M. Proteomic characterization of the human centrosome by protein correlation profiling. Nature 426: 570-574, 2003. [PubMed: 14654843] [Full Text: https://doi.org/10.1038/nature02166]
Firat-Karalar, E., Rauniyar, N., Yates, J. R., III, Stearns, T. Proximity interactions among centrosome components identify regulators of centriole duplication. Curr. Biol. 24: 664-670, 2014. [PubMed: 24613305] [Full Text: https://doi.org/10.1016/j.cub.2014.01.067]
Hartz, P. A. Personal Communication. Baltimore, Md. 7/17/2012.
Loffler, H., Fechter, A., Matuszewska, M., Saffrich, R., Mistrik, M., Marhold, J., Hornung, C., Westermann, F., Bartek, J., Kramer, A. Cep63 recruits Cdk1 to the centrosome: implications for regulation of mitotic entry, centrosome amplification, and genome maintenance. Cancer Res. 71: 2129-2139, 2011. [PubMed: 21406398] [Full Text: https://doi.org/10.1158/0008-5472.CAN-10-2684]
Sir, J.-H., Barr, A. R., Nicholas, A. K., Carvalho, O. P., Khurshid, M., Sossick, A., Reichelt, S., D'Santos, C., Woods, C. G., Gergely, F. A primary microcephaly protein complex forms a ring around parental centrioles. Nature Genet. 43: 1147-1153, 2011. [PubMed: 21983783] [Full Text: https://doi.org/10.1038/ng.971]