Mosaic-variegated aneuploidy syndrome mutation or haploinsufficiency in Cep57 impairs tumor suppression
Khaled Aziz, … , David J. Katzmann, Jan M. van Deursen
Khaled Aziz, … , David J. Katzmann, Jan M. van Deursen
Published July 23, 2018
Citation Information: J Clin Invest. 2018;128(8):3517-3534. https://doi.org/10.1172/JCI120316.
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Research Article Cell biology Oncology

Mosaic-variegated aneuploidy syndrome mutation or haploinsufficiency in Cep57 impairs tumor suppression

Abstract

A homozygous truncating frameshift mutation in CEP57 (CEP57T/T) has been identified in a subset of mosaic-variegated aneuploidy (MVA) patients; however, the physiological roles of the centrosome-associated protein CEP57 that contribute to disease are unknown. To investigate these, we have generated a mouse model mimicking this disease mutation. Cep57T/T mice died within 24 hours after birth with short, curly tails and severely impaired vertebral ossification. Osteoblasts in lumbosacral vertebrae of Cep57T/T mice were deficient for Fgf2, a Cep57 binding partner implicated in diverse biological processes, including bone formation. Furthermore, a broad spectrum of tissues of Cep57T/T mice had severe aneuploidy at birth, consistent with the MVA patient phenotype. Cep57T/T mouse embryonic fibroblasts and patient-derived skin fibroblasts failed to undergo centrosome maturation in G2 phase, causing premature centriole disjunction, centrosome amplification, aberrant spindle formation, and high rates of chromosome missegregation. Mice heterozygous for the truncating frameshift mutation or a Cep57-null allele were overtly indistinguishable from WT mice despite reduced Cep57 protein levels, yet prone to aneuploidization and cancer, with tumors lacking evidence for loss of heterozygosity. This study identifies Cep57 as a haploinsufficient tumor suppressor with biologically diverse roles in centrosome maturation and Fgf2-mediated bone formation.

Authors

Khaled Aziz, Cynthia J. Sieben, Karthik B. Jeganathan, Masakazu Hamada, Brian A. Davies, Raul O. Fierro Velasco, Nazneen Rahman, David J. Katzmann, Jan M. van Deursen

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Figure 7

Cep57 truncation leads to aberrant spindles that missegregate chromosomes.

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Cep57 truncation leads to aberrant spindles that missegregate chromosome...
(A) Representative images of metaphase microtubule configurations and intensity in MEFs. Right: Quantification of spindle abnormalities. (B) Quantification of spindle intensities as seen in A. (C) Quantification of spindle α-tubulin intensity in human fibroblasts of indicated genotypes. (D) Microtubule regrowth assay on Cep57-insufficient cells. Left: Images of mitotic MEFs of the indicated genotypes placed on ice for 40 minutes and stained for α- and γ-tubulin after the indicated recovery times at 37°C. Right: Quantification of α-tubulin signals in MEFs of the indicated genotypes. (E) Measurement of metaphase plate width in MEFs of indicated genotypes/subgroups. (F) Percentage of cells undergoing indicated chromosome missegregation error determined by live-cell imaging on MEFs expressing H2B-mRFP. (G) Percentage of cells observed to form micronuclei after a chromosome missegregation event, per analyses performed in E. (H) Percentage of P5 MEFs with abnormal number of chromosomes counted on metaphase spreads. Polyploid cells were excluded. Analyses in A, B, and D were performed on at least 3 independent lines per genotype (20 cells per line). Analysis in C was performed on 1 cell line per genotype (20 cells analyzed per line). The experiment was repeated 3 times. Analyses in E and F were performed on at least 3 independent lines per genotype (at least 25 cells per line). Analysis in G was performed on at least 3 lines per genotype (50 cells per line). Data in A–H represent the mean ± SEM. Statistical significance in A, E, and H was determined using 1-way ANOVA followed by Tukey’s multiple-comparisons test. Statistical significance in C, D, F, and G was determined using a 2-tailed unpaired t test, and in B using a 1-tailed unpaired t test. *P < 0.05, **P < 0.01, ***P < 0.001. Scale bars: 5 μm.