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Targeted assembly of ectopic kinetochores to induce chromosome-specific segmental aneuploidies

ABSTRACT: Cancer cells display persistent underlying chromosomal instability, with individual tumour types intriguingly exhibiting characteristic subsets of whole, and sub-chromosomal aneuploidies. Few methods to induce specific aneuploidies at will exist, hampering investigation of functional consequences of recurrent aneuploidies, as well as the acute consequences of specific chromosome mis-segregation. We therefore investigated the possibility of sabotaging the mitotic segregation of specific chromosomes using nuclease-dead CRISPR-Cas9 (dCas9) as a cargo carrier to specific genomic loci. We recruited the kinetochore-nucleating domain of centromere protein CENP-T to assemble ectopic kinetochores either near the centromere of chromosome 9, or the telomere of chromosome 1. Ectopic kinetochore assembly led to increased chromosome instability and partial aneuploidy of the target chromosomes, providing the potential to induce specific chromosome mis-segregation events in a range of cell types. We also provide an analysis of putative endogenous repeats that could support ectopic kinetochore formation. Overall, our findings provide new insights into ectopic kinetochore biology, and represent an important step towards investigating the role of specific aneuploidy and chromosome mis segregation events in diseases associated with aneuploidy.

SUBMITTER: Dr. Laura Tovini

PROVIDER: S-SCDT-10_15252-EMBJ_2022111587 | biostudies-other |

REPOSITORIES: biostudies-other

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Targeted assembly of ectopic kinetochores to induce chromosome-specific segmental aneuploidies.

Project description:Cancer cells display persistent underlying chromosomal instability, with individual tumour types intriguingly exhibiting characteristic subsets of whole, and subchromosomal aneuploidies. Few methods to induce specific aneuploidies will exist, hampering investigation of functional consequences of recurrent aneuploidies, as well as the acute consequences of specific chromosome mis-segregation. We therefore investigated the possibility of sabotaging the mitotic segregation of specific chromosomes using nuclease-dead CRISPR-Cas9 (dCas9) as a cargo carrier to specific genomic loci. We recruited the kinetochore-nucleating domain of centromere protein CENP-T to assemble ectopic kinetochores either near the centromere of chromosome 9, or the telomere of chromosome 1. Ectopic kinetochore assembly led to increased chromosome instability and partial aneuploidy of the target chromosomes, providing the potential to induce specific chromosome mis-segregation events in a range of cell types. We also provide an analysis of putative endogenous repeats that could support ectopic kinetochore formation. Overall, our findings provide new insights into ectopic kinetochore biology and represent an important step towards investigating the role of specific aneuploidy and chromosome mis-segregation events in diseases associated with aneuploidy.

| S-EPMC10183824 | biostudies-literature

Targeted assembly of ectopic kinetochores to induce chromosome-specific segmental aneuploidies

Project description:Targeted assembly of ectopic kinetochores to induce chromosome-specific segmental aneuploidies

| PRJEB59859 | ENA

Mislocalization of the Drosophila centromere-specific histone CID promotes formation of functional ectopic kinetochores.

Project description:The centromere-specific histone variant CENP-A (CID in Drosophila) is a structural and functional foundation for kinetochore formation and chromosome segregation. Here, we show that overexpressed CID is mislocalized into normally noncentromeric regions in Drosophila tissue culture cells and animals. Analysis of mitoses in living and fixed cells reveals that mitotic delays, anaphase bridges, chromosome fragmentation, and cell and organismal lethality are all direct consequences of CID mislocalization. In addition, proteins that are normally restricted to endogenous kinetochores assemble at a subset of ectopic CID incorporation regions. The presence of microtubule motors and binding proteins, spindle attachments, and aberrant chromosome morphologies demonstrate that these ectopic kinetochores are functional. We conclude that CID mislocalization promotes formation of ectopic centromeres and multicentric chromosomes, which causes chromosome missegregation, aneuploidy, and growth defects. Thus, CENP-A mislocalization is one possible mechanism for genome instability during cancer progression, as well as centromere plasticity during evolution.

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Increased prevalence of sex chromosome aneuploidies in specific language impairment and dyslexia.

Project description:AimSex chromosome aneuploidies increase the risk of spoken or written language disorders but individuals with specific language impairment (SLI) or dyslexia do not routinely undergo cytogenetic analysis. We assess the frequency of sex chromosome aneuploidies in individuals with language impairment or dyslexia.MethodGenome-wide single nucleotide polymorphism genotyping was performed in three sample sets: a clinical cohort of individuals with speech and language deficits (87 probands: 61 males, 26 females; age range 4 to 23 years), a replication cohort of individuals with SLI, from both clinical and epidemiological samples (209 probands: 139 males, 70 females; age range 4 to 17 years), and a set of individuals with dyslexia (314 probands: 224 males, 90 females; age range 7 to 18 years).ResultsIn the clinical language-impaired cohort, three abnormal karyotypic results were identified in probands (proband yield 3.4%). In the SLI replication cohort, six abnormalities were identified providing a consistent proband yield (2.9%). In the sample of individuals with dyslexia, two sex chromosome aneuploidies were found giving a lower proband yield of 0.6%. In total, two XYY, four XXY (Klinefelter syndrome), three XXX, one XO (Turner syndrome), and one unresolved karyotype were identified.InterpretationThe frequency of sex chromosome aneuploidies within each of the three cohorts was increased over the expected population frequency (approximately 0.25%) suggesting that genetic testing may prove worthwhile for individuals with language and literacy problems and normal non-verbal IQ. Early detection of these aneuploidies can provide information and direct the appropriate management for individuals.

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Buffering of segmental and chromosomal aneuploidies in Drosophila melanogaster.

Project description:Chromosomal instability, which involves the deletion and duplication of chromosomes or chromosome parts, is a common feature of cancers, and deficiency screens are commonly used to detect genes involved in various biological pathways. However, despite their importance, the effects of deficiencies, duplications, and chromosome losses on the regulation of whole chromosomes and large chromosome domains are largely unknown. Therefore, to explore these effects, we examined expression patterns of genes in several Drosophila deficiency hemizygotes and a duplication hemizygote using microarrays. The results indicate that genes expressed in deficiency hemizygotes are significantly buffered, and that the buffering effect is general rather than being mainly mediated by feedback regulation of individual genes. In addition, differentially expressed genes in haploid condition appear to be generally more strongly buffered than ubiquitously expressed genes in haploid condition, but, among genes present in triploid condition, ubiquitously expressed genes are generally more strongly buffered than differentially expressed genes. Furthermore, we show that the 4th chromosome is compensated in response to dose differences. Our results suggest general mechanisms have evolved that stimulate or repress gene expression of aneuploid regions as appropriate, and on the 4th chromosome of Drosophila this compensation is mediated by Painting of Fourth (POF).

| S-EPMC2668767 | biostudies-literature

Adaptation to spindle assembly checkpoint inhibition through the selection of specific aneuploidies.

Project description:Both the presence of an abnormal complement of chromosomes (aneuploidy) and an increased frequency of chromosome missegregation (chromosomal instability) are hallmarks of cancer. Analyses of cancer genome data have identified certain aneuploidy patterns in tumors; however, the bases behind their selection are largely unexplored. By establishing time-resolved long-term adaptation protocols, we found that human cells adapt to persistent spindle assembly checkpoint (SAC) inhibition by acquiring specific chromosome arm gains and losses. Independently adapted populations converge on complex karyotypes, which over time are refined to contain ever smaller chromosomal changes. Of note, the frequencies of chromosome arm gains in adapted cells correlate with those detected in cancers, suggesting that our cellular adaptation approach recapitulates selective traits that dictate the selection of aneuploidies frequently observed across many cancer types. We further engineered specific aneuploidies to determine the genetic basis behind the observed karyotype patterns. These experiments demonstrated that the adapted and engineered aneuploid cell lines limit CIN by extending mitotic duration. Heterozygous deletions of key SAC and APC/C genes recapitulated the rescue phenotypes of the monosomic chromosomes. We conclude that aneuploidy-induced gene dosage imbalances of individual mitotic regulators are sufficient for altering mitotic timing to reduce CIN.

| S-EPMC10111865 | biostudies-literature

The impact of monosomies, trisomies and segmental aneuploidies on chromosomal stability.

Project description:Aneuploidy and chromosomal instability are both commonly found in cancer. Chromosomal instability leads to karyotype heterogeneity in tumors and is associated with therapy resistance, metastasis and poor prognosis. It has been hypothesized that aneuploidy per se is sufficient to drive CIN, however due to limited models and heterogenous results, it has remained controversial which aspects of aneuploidy can drive CIN. In this study we systematically tested the impact of different types of aneuploidies on the induction of CIN. We generated a plethora of isogenic aneuploid clones harboring whole chromosome or segmental aneuploidies in human p53-deficient RPE-1 cells. We observed increased segregation errors in cells harboring trisomies that strongly correlated to the number of gained genes. Strikingly, we found that clones harboring only monosomies do not induce a CIN phenotype. Finally, we found that an initial chromosome breakage event and subsequent fusion can instigate breakage-fusion-bridge cycles. By investigating the impact of monosomies, trisomies and segmental aneuploidies on chromosomal instability we further deciphered the complex relationship between aneuploidy and CIN.

| S-EPMC9249180 | biostudies-literature

Buffering of segmental and chromosomal aneuploidies in Drosophila melanogaster

Project description:Chromosomal instability which involves deletion and duplication of chromosomes or chromosome parts is a common feature of cancers, and deficiency screens are commonly used as a method to find genes involved in different biological pathways. Still, how gene expression from whole chromosomes or large chromosomal domains is affected by deficiencies, duplications or chromosome loss is largely unknown. Using expression microarrays of deficiency hemizygotes and a duplication hemizygote we show that expressed genes are significantly buffered when present in a deficiency hemizygote and that the buffering effect is general and not mainly caused by feedback regulation of individual genes. Differentially expressed genes are in general better buffered than ubiquitously expressed genes when present in one copy. When present in three copies, differentially expressed genes are in general less buffered than ubiquitously expressed genes. Furthermore, we show that the 4th chromosome is compensated in response to dose differences. Our results suggest that general mechanisms exist to stimulate and to repress gene expression of aneuploidy regions and on the 4th chromosome this compensation is mediated by POF (Painting of Fourth). Keywords: dose response

2009-03-30 | GSE14517 | GEO

Segmental duplication as potential biomarkers for non-invasive prenatal testing of aneuploidies.

Project description:BackgroundSegmental duplication (SD) regions are distinct targets for aneuploidy detection owing to the virtual elimination of amplification bias. The difficulty of searching SD sequences for assay design has hampered their applications.MethodsWe developed a computational program, ChAPDes, which integrates SD searching, refinement, and design of specific PCR primer/probe sets in a pipeline to remove most of the manual work. The generated primer/probe sets were first tested in a multiplex multicolour melting curve analysis for the detection of five common aneuploidies. The primer/probe sets were then tested in a digital PCR assay for the detection of trisomy 21. Finally, a digital PCR protocol was established to quantify maternal plasma DNA sequences for the non-invasive prenatal detection of fetal trisomy 21.FindingsChAPDes could output 21,772 candidate primer/probe sets for trisomy 13, 18, 21 and sex chromosome aneuploidies within 2 working days. Clinical evaluation of the multiplex multicolour melting curve analysis involving 463 fetal genomic DNA samples revealed a sensitivity of 100% and specificity of 99.64% in comparison with the reference methods. Using the established digital PCR protocol, we correctly identified two trisomy 21 fetuses and thirteen euploid foetuses from the maternal plasma samples.InterpretationThe combination of ChAPDes with digital PCR detection could facilitate the use of SD as potential biomarkers for the non-invasive prenatal testing of fetal chromosomal aneuploidies.FundingNone.

| S-EPMC8374395 | biostudies-literature

An ectopic human XIST gene can induce chromosome inactivation in postdifferentiation human HT-1080 cells.

Project description:It has been believed that XIST RNA requires a discrete window in early development to initiate the series of chromatin-remodeling events that form the heterochromatic inactive X chromosome. Here we investigate four adult male HT-1080 fibrosarcoma cell lines expressing ectopic human XIST and demonstrate that these postdifferentiation cells can undergo chromosomal inactivation outside of any normal developmental context. All four clonal lines inactivated the transgene-containing autosome to varying degrees and with variable stability. One clone in particular consistently localized the ectopic XIST RNA to a discrete chromosome territory that exhibited striking hallmarks of inactivation, including long-range transcriptional inactivation. Results suggest that some postdifferentiation cell lines are capable of de novo chromosomal inactivation; however, long-term retention of autosomal inactivation was less common, which suggests that autosomal inactivation may confer a selective disadvantage. These results have fundamental significance for understanding genomic programming in early development.

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