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Using transient nondisjunction to generate disomic strains of yeast

ABSTRACT: Background. Most methods for constructing aneuploid yeast strains that have gained a specific chromosome rely on spontaneous failures of cell division fidelity. In Saccharomyces cerevisiae, extra chromosomes can be obtained when errors in meiosis or mitosis lead to nondisjunction, or when nuclear breakdown occurs in heterokaryons. We describe a strategy for constructing N+1 disomes that does not require such spontaneous failures. The method combines two well-characterized genetic tools: a conditional centromere that transiently blocks disjunction of one specific chromosome, and a duplication marker assay that identifies disomes among daughter cells. To test the strategy, we targeted chromosomes III, IV, and VI for duplication. Results. The centromere of each target chromosome was replaced by a conditional centromere that can be blocked by growth in galactose, and ura3::HIS3, a duplication marker. Transient exposure to galactose induced the appearance of colonies carrying duplicated markers for chromosomes III or IV, but not VI. Microarray-based comparative genomic hybridization (CGH) confirmed that disomic strains carrying extra chromosome III or IV were generated. Chromosome VI contains several genes known to be deleterious when overexpressed, including the beta-tubulin gene TUB2. To test whether a tubulin stoichiometry imbalance prevents viability in cells carrying an extra chromosome VI, we supplied the parent strain with extra copies of the alpha-tubulin gene TUB1, then induced nondisjunction. Galactose-dependent chromosome VI disomes were produced, as revealed by CGH. Some chromosome VI disomes also carried extra, unselected copies of additional chromosomes. Conclusions. This method causes efficient nondisjunction of a targeted chromosome and allows resulting disomic cells to be identified and maintained. We used the method to test the role of tubulin imbalance in the apparent lethality of disomic chromosome VI. Our results indicate that a tubulin imbalance is necessary for disomic VI lethality, but it may not be the only dosage-dependent effect. Keywords: comparative genomic hybridization, CGH

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE14377 | GEO | 2009/01/13

SECONDARY ACCESSION(S): PRJNA111423

REPOSITORIES: GEO

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Project description:Background. Most methods for constructing aneuploid yeast strains that have gained a specific chromosome rely on spontaneous failures of cell division fidelity. In Saccharomyces cerevisiae, extra chromosomes can be obtained when errors in meiosis or mitosis lead to nondisjunction, or when nuclear breakdown occurs in heterokaryons. We describe a strategy for constructing N+1 disomes that does not require such spontaneous failures. The method combines two well-characterized genetic tools: a conditional centromere that transiently blocks disjunction of one specific chromosome, and a duplication marker assay that identifies disomes among daughter cells. To test the strategy, we targeted chromosomes III, IV, and VI for duplication. Results. The centromere of each target chromosome was replaced by a conditional centromere that can be blocked by growth in galactose, and ura3::HIS3, a duplication marker. Transient exposure to galactose induced the appearance of colonies carrying duplicated markers for chromosomes III or IV, but not VI. Microarray-based comparative genomic hybridization (CGH) confirmed that disomic strains carrying extra chromosome III or IV were generated. Chromosome VI contains several genes known to be deleterious when overexpressed, including the beta-tubulin gene TUB2. To test whether a tubulin stoichiometry imbalance prevents viability in cells carrying an extra chromosome VI, we supplied the parent strain with extra copies of the alpha-tubulin gene TUB1, then induced nondisjunction. Galactose-dependent chromosome VI disomes were produced, as revealed by CGH. Some chromosome VI disomes also carried extra, unselected copies of additional chromosomes. Conclusions. This method causes efficient nondisjunction of a targeted chromosome and allows resulting disomic cells to be identified and maintained. We used the method to test the role of tubulin imbalance in the apparent lethality of disomic chromosome VI. Our results indicate that a tubulin imbalance is necessary for disomic VI lethality, but it may not be the only dosage-dependent effect. Keywords: comparative genomic hybridization, CGH Candidate disomes (Ura+His+) were compared to their euploid parents by CGH. 27 candidate strains were examined with 27 arrays. 4 candidates targeted chromosome III (3 induced, 1 spontaneous), 14 candidates targeted chromosome IV (8 induced, 6 spontaneous), and 9 candidates targeted chromosome VI (all induced).

Project description:Purpose:To dissect the mechanisms underlying altered gene expression in aneuploids, we measured transcript abundance in colonies of haploid yeast strain F45 and derived strains, including strains disomic for chromosomes XV and XVI, using RNA-seq. F45 colonies display complex “fluffy” morphologies, while the disomic colonies are smooth, resembling laboratory strains Methods: RNA-seq analysis was carried out on RNA isolated from fully developed S. cerevisiae colonies, grown on solid medium for four days, either in triplicate or quadruplicate. Stranded, paired-end sequencing was carried out in two batches. In the first batch 2x51 bp sequencing was carried out on an Illumina Hiseq2000 and in the second batch 2x75 bp sequencing was carried out on an Illumina NextSeq. Readpairs were aligned using Bowtie2 (version 2.1.0)with the parameters [-N 1 -I 50 -X 450 -p 6 --reorder -x -S] and allowing 1 mismatch per read. Differential transcription was detected and quantified using EdgeR (v. 3.6.8) Results: Our two disomes displayed similar transcriptional profiles, a phenomenon not driven by their shared smooth colony morphology nor specified purely by the karyotype. Surprisingly, the environmental stress response (ESR) was induced in euploid F45, relative to the two disomes, rather than vice-versa. We also identified genes whose expression reflected a non-linear interaction between the copy number of a transcriptional regulatory gene on chromosome XVI, DIG1, and the copy number of other chromosome XVI genes. DIG1 and the remaining chromosome XVI genes also demonstrated distinct contributions to the effect of the chromosome XVI disome on ESR gene expression. Conclusions: Expression changes in aneuploids reflect a mixture of effects shared between different aneuploidies, including stress responses, and effects unique to perturbing the copy number of particular chromosomes, including non-linear copy number interactions between genes. The balance between these two phenomena is likely to be genotype and environment specific.

Project description:Inflammatory leiomyosarcoma (ILMS) is a soft tissue tumor that morphologically resembles conventional leiomyosarcoma (LMS) admixed with a prominent inflammatory infiltrate. Genetic data on ILMS are still limited but have suggested that this entity is characterized by hyperhaploidy (24-34 chromosomes). This low chromosome number is otherwise uncommon in neoplasia and has been found only in 0.2-0.3% of cytogenetically investigated tumors. Here, three ILMS were investigated using cytogenetic, SNP array and global gene expression analyses. All cases displayed a hyperhaploid origin. Combined with previously reported cases, hyperhaploidy has been found in six of seven cytogenetically investigated ILMS. The copy number distribution of individual chromosomes is clearly nonrandom; the hyperhaploid clones of all six cases displayed disomy for chromosomes 5 and 20, and two copies of chromosomes 18, 21 and 22 were also common. All chromosomes identified as disomic showed a biparental origin by SNP array analysis; whether this is of pathogenetic importance is not known. Compared with conventional LMS, ILMS had a distinct gene expression signature. Furthermore, the number of chromosome copies correlated well with gene expression levels, a finding which has not previously been reported for hyperhaploid tumors. Genes on disomic chromosomes showed higher expression levels in ILMS compared to LMS and disomic chromosomes showed higher average gene expression levels than monosomic chromosomes. Taken together, our findings suggest that disomy for some chromosomes, notably 5 and 20, as well as distorted gene expression balance achieved through massive loss of other chromosomes are essential for the development of ILMS. Tumor DNA was hybridized onto Illumina Human CNV370-Quad v3_C (case 1) and Illumina Human CNV370 v1_C (cases 2 and 3) BeadChips, containing ~370,000 markers, following standard protocols supplied by the manufacturer (Illumina). Data analysis was performed using the GenomeStudio software (Illumina), detecting imbalances by visual inspection.

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Using transient nondisjunction to generate disomic strains of yeast

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