Mosaic-variegated aneuploidy syndrome mutation or haploinsufficiency in Cep57 impairs tumor suppression
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
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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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 6

Cep57 controls the timing of centriole disengagement in mitosis.

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Cep57 controls the timing of centriole disengagement in mitosis. (A) Rep...
(A) Representative images of MEFs labeled for centrin 2 to measure intercentriolar distance. Scale bar: 5 μm. (B) Dot plot of metaphase intercentriolar distance measurements in MEFs of indicated genotypes. Twelve data points for Cep57T/T are outside the range shown. (C) Dot plot of metaphase intercentriolar distance measurements in human fibroblasts of indicated genotypes. One data point (CEP57T/T) is outside the range shown. (D) Dot plot of metaphase intercentriolar distance measurements in WT MEFs transduced with indicated shRNAs. (E) Quantification of the percentage of cells with centrosome amplification after knockdown using indicated shRNAs. Analyses in B, D, and E were performed on at least 3 independent lines per genotype (20 cells per line). Analysis in C was performed on 1 line per genotype (at least 20 cells per line). The experiment was repeated 3 times. Data in E represent the mean ± SEM. Statistical significance in B was determined using 1-way ANOVA followed by Tukey’s multiple-comparisons test. Statistical significance in C–E was determined using a 2-tailed unpaired t test. *P < 0.05, **P < 0.01, ***P < 0.001.