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Ruchert JM, Brady MM, McMahan S, Lacey KJ, Latta LC, Sekelsky J, Stoffregen EP. Blm helicase facilitates rapid replication of repetitive DNA sequences in early Drosophila development. Genetics 2021; 220:6407149. [PMID: 34849849 DOI: 10.1093/genetics/iyab169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/18/2021] [Indexed: 11/12/2022] Open
Abstract
The absence of functional BLM DNA helicase, a member of the RecQ family of helicases, is responsible for the rare human disorder Bloom Syndrome, which results in developmental abnormalities, DNA repair defects, genomic instability, and a predisposition to cancer. In Drosophila melanogaster, the orthologous Blm protein is essential during early development when the embryo is under the control of maternal gene products. We show that lack of functional maternal Blm during the syncytial cell cycles of Drosophila embryonic development results in severe nuclear defects and lethality. Amongst the small fraction of embryos from Blm mutant mothers that survive to adulthood, a prominent sex-bias favors the class that inherits less repetitive DNA content, which serves as an endogenous source of replication stress. This selection against repetitive DNA content reflects a role for Blm in facilitating replication through repetitive sequences during the rapid S-phases of syncytial cell cycles. During these syncytial cycles, Blm is not required for complex DNA double-strand break repair; however, the progeny sex-bias resulting from the absence of maternal Blm is exacerbated by repetitive DNA sequences and by the slowing of replication fork progression, suggesting that the essential role for Blm during this stage is to manage replication fork stress brought about by impediments to fork progression. Additionally, our data suggest that Blm is only required to manage this replication stress during embryonic development, and likely only during the early, rapid syncytial cell cycles, and not at later developmental stages. These results provide novel insights into Blm function throughout development.
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Affiliation(s)
- Jolee M Ruchert
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Morgan M Brady
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Susan McMahan
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Karly J Lacey
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Leigh C Latta
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Jeff Sekelsky
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.,Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Eric P Stoffregen
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.,SPIRE Postdoctoral Fellowship Program, University of North Carolina, Chapel Hill, NC 27599, USA
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Matinyan N, Karkhanis MS, Gonzalez Y, Jain A, Saltzman A, Malovannaya A, Sarrion-Perdigones A, Dierick HA, Venken KJT. Multiplexed drug-based selection and counterselection genetic manipulations in Drosophila. Cell Rep 2021; 36:109700. [PMID: 34525356 PMCID: PMC8480232 DOI: 10.1016/j.celrep.2021.109700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 06/10/2021] [Accepted: 08/20/2021] [Indexed: 01/27/2023] Open
Abstract
The power of Drosophila melanogaster as a model system relies on tractable germline genetic manipulations. Despite Drosophila's expansive genetics toolbox, such manipulations are still accomplished one change at a time and depend predominantly on phenotypic screening. We describe a drug-based genetic platform consisting of four selection and two counterselection markers, eliminating the need to screen for modified progeny. These markers work reliably individually or in combination to produce specific genetic outcomes. We demonstrate three example applications of multiplexed drug-based genetics by generating (1) transgenic animals, expressing both components of binary overexpression systems in a single transgenesis step; (2) dual selectable and counterselectable balancer chromosomes; and (3) selectable, fluorescently tagged P[acman] bacterial artificial chromosome (BAC) strains. We perform immunoprecipitation followed by proteomic analysis on one tagged BAC line, demonstrating our platform's applicability to biological discovery. Lastly, we provide a plasmid library resource to facilitate custom transgene design and technology transfer to other model systems.
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Affiliation(s)
- Nick Matinyan
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Integrative Molecular Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Mansi S Karkhanis
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yezabel Gonzalez
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Antrix Jain
- Advanced Technology Cores, Mass Spectrometry Proteomics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Alexander Saltzman
- Advanced Technology Cores, Mass Spectrometry Proteomics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Anna Malovannaya
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Advanced Technology Cores, Mass Spectrometry Proteomics, Baylor College of Medicine, Houston, TX 77030, USA; Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Alejandro Sarrion-Perdigones
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Herman A Dierick
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Koen J T Venken
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA; Integrative Molecular Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA; Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA; Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX 77030, USA; McNair Medical Institute at The Robert and Janice McNair Foundation, Baylor College of Medicine, Houston, TX 77030, USA.
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Kandul NP, Liu J, Hsu AD, Hay BA, Akbari OS. A drug-inducible sex-separation technique for insects. Nat Commun 2020; 11:2106. [PMID: 32355156 PMCID: PMC7193620 DOI: 10.1038/s41467-020-16020-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/07/2020] [Indexed: 11/16/2022] Open
Abstract
Here, we describe a drug-inducible genetic system for insect sex-separation that demonstrates proof-of-principle for positive sex selection in D. melanogaster. The system exploits the toxicity of commonly used broad-spectrum antibiotics geneticin and puromycin to kill the non-rescued sex. Sex-specific rescue is achieved by inserting sex-specific introns into the coding sequences of antibiotic-resistance genes. When raised on geneticin-supplemented food, the sex-sorter line establishes 100% positive selection for female progeny, while the food supplemented with puromycin positively selects 100% male progeny. Since the described system exploits conserved sex-specific splicing mechanisms and reagents, it has the potential to be adaptable to other insect species of medical and agricultural importance.
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Affiliation(s)
- Nikolay P Kandul
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92092, USA
| | - Junru Liu
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92092, USA
| | - Alexander D Hsu
- Division of Biology and Biological Engineering, MC 156-29, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Bruce A Hay
- Division of Biology and Biological Engineering, MC 156-29, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Omar S Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92092, USA.
- Division of Biology and Biological Engineering, MC 156-29, California Institute of Technology, Pasadena, CA, 91125, USA.
- Tata Institute for Genetics and Society-UCSD, La Jolla, CA, USA.
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Abstract
The physical connections established by recombination are normally sufficient to ensure proper chromosome segregation during female Meiosis I. However, nonexchange chromosomes (such as the Muller F element or "dot" chromosome in D. melanogaster) can still segregate accurately because they remain connected by heterochromatic tethers. A recent study examined female meiosis in the closely related species D. melanogaster and D. simulans, and found a nearly twofold difference in the mean distance the obligately nonexchange dot chromosomes were separated during Prometaphase. That study proposed two speculative hypotheses for this difference, the first being the amount of heterochromatin in each species, and the second being the species' differing tolerance for common inversions in natural populations. We tested these hypotheses by examining female meiosis in 12 additional Drosophila species. While neither hypothesis had significant support, we did see 10-fold variation in dot chromosome sizes, and fivefold variation in the frequency of chromosomes out on the spindle, which were both significantly correlated with chromosome separation distances. In addition to demonstrating that heterochromatin abundance changes chromosome behavior, this implies that the duration of Prometaphase chromosome movements must be proportional to the size of the F element in these species. Additionally, we examined D. willistoni, a species that lacks a free dot chromosome. We observed that chromosomes still moved out on the meiotic spindle, and the F element was always positioned closest to the spindle poles. This result is consistent with models where one role of the dot chromosomes is to help organize the meiotic spindle.
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The Drosophila Dot Chromosome: Where Genes Flourish Amidst Repeats. Genetics 2019; 210:757-772. [PMID: 30401762 PMCID: PMC6218221 DOI: 10.1534/genetics.118.301146] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/17/2018] [Indexed: 11/18/2022] Open
Abstract
The F element of the Drosophila karyotype (the fourth chromosome in Drosophila melanogaster) is often referred to as the "dot chromosome" because of its appearance in a metaphase chromosome spread. This chromosome is distinct from other Drosophila autosomes in possessing both a high level of repetitious sequences (in particular, remnants of transposable elements) and a gene density similar to that found in the other chromosome arms, ∼80 genes distributed throughout its 1.3-Mb "long arm." The dot chromosome is notorious for its lack of recombination and is often neglected as a consequence. This and other features suggest that the F element is packaged as heterochromatin throughout. F element genes have distinct characteristics (e.g, low codon bias, and larger size due both to larger introns and an increased number of exons), but exhibit expression levels comparable to genes found in euchromatin. Mapping experiments show the presence of appropriate chromatin modifications for the formation of DNaseI hypersensitive sites and transcript initiation at the 5' ends of active genes, but, in most cases, high levels of heterochromatin proteins are observed over the body of these genes. These various features raise many interesting questions about the relationships of chromatin structures with gene and chromosome function. The apparent evolution of the F element as an autosome from an ancestral sex chromosome also raises intriguing questions. The findings argue that the F element is a unique chromosome that occupies its own space in the nucleus. Further study of the F element should provide new insights into chromosome structure and function.
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Eliminating both canonical and short-patch mismatch repair in Drosophila melanogaster suggests a new meiotic recombination model. PLoS Genet 2014; 10:e1004583. [PMID: 25188408 PMCID: PMC4154643 DOI: 10.1371/journal.pgen.1004583] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 07/08/2014] [Indexed: 01/31/2023] Open
Abstract
In most meiotic systems, recombination is essential to form connections between homologs that ensure their accurate segregation from one another. Meiotic recombination is initiated by DNA double-strand breaks that are repaired using the homologous chromosome as a template. Studies of recombination in budding yeast have led to a model in which most early repair intermediates are disassembled to produce noncrossovers. Selected repair events are stabilized so they can proceed to form double-Holliday junction (dHJ) intermediates, which are subsequently resolved into crossovers. This model is supported in yeast by physical isolation of recombination intermediates, but the extent to which it pertains to animals is unknown. We sought to test this model in Drosophila melanogaster by analyzing patterns of heteroduplex DNA (hDNA) in recombination products. Previous attempts to do this have relied on knocking out the canonical mismatch repair (MMR) pathway, but in both yeast and Drosophila the resulting recombination products are complex and difficult to interpret. We show that, in Drosophila, this complexity results from a secondary, short-patch MMR pathway that requires nucleotide excision repair. Knocking out both canonical and short-patch MMR reveals hDNA patterns that reveal that many noncrossovers arise after both ends of the break have engaged with the homolog. Patterns of hDNA in crossovers could be explained by biased resolution of a dHJ; however, considering the noncrossover and crossover results together suggests a model in which a two-end engagement intermediate with unligated HJs can be disassembled by a helicase to a produce noncrossover or nicked by a nuclease to produce a crossover. While some aspects of this model are similar to the model from budding yeast, production of both noncrossovers and crossovers from a single, late intermediate is a fundamental difference that has important implications for crossover control. During meiosis, breaks are introduced into the DNA, then repaired to give either crossovers between homologous chromosomes (these help to ensure correct segregation of these chromosomes from one another), or non-crossover products. Meiotic break repair mechanisms have been best studied in budding yeast, leading to detailed molecular models. Technical limitations have prevented directly testing these models in multi-cellular organisms. One approach that has been tried is to map segments of DNA that are mismatched, since different models predict different arrangements. Mismatches are usually repaired quickly, so analyzing these patterns requires eliminating mismatch repair processes. Although others have knocked out the primary mismatch repair system, we have now, for the first time in an animal, identified the secondary repair pathway and eliminated it and the primary pathway simultaneously. We then analyzed mismatches produced during meiosis. Though the results can be fit to the most popular current model from yeast, if some modifications are made, we also consider a simpler model that incorporates elements of the current model and of earlier models.
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Double-strand break repair assays determine pathway choice and structure of gene conversion events in Drosophila melanogaster. G3-GENES GENOMES GENETICS 2014; 4:425-32. [PMID: 24368780 PMCID: PMC3962482 DOI: 10.1534/g3.113.010074] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Double-strand breaks (DSBs) must be accurately and efficiently repaired to maintain genome integrity. Depending on the organism receiving the break, the genomic location of the DSB, and the cell-cycle phase in which it occurs, a DSB can be repaired by homologous recombination (HR), nonhomologous end-joining (NHEJ), or single-strand annealing (SSA). Two novel DSB repair assays were developed to determine the contributions of these repair pathways and to finely resolve repair event structures in Drosophila melanogaster. Rad51-dependent homologous recombination is the preferred DSB repair pathway in mitotically dividing cells, and the pathway choice between HR and SSA occurs after end resection and before Rad51-dependent strand invasion. HR events are associated with long gene conversion tracts and are both bidirectional and unidirectional, consistent with repair via the synthesis-dependent strand annealing pathway. Additionally, HR between diverged sequences is suppressed in Drosophila, similar to levels reported in human cells. Junction analyses of rare NHEJ events reveal that canonical NHEJ is utilized in this system.
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Fresnedo-Ramírez J, Martínez-García PJ, Parfitt DE, Crisosto CH, Gradziel TM. Heterogeneity in the entire genome for three genotypes of peach [Prunus persica (L.) Batsch] as distinguished from sequence analysis of genomic variants. BMC Genomics 2013; 14:750. [PMID: 24182359 PMCID: PMC4046826 DOI: 10.1186/1471-2164-14-750] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 10/19/2013] [Indexed: 12/22/2022] Open
Abstract
Background Peach [Prunus persica (L.) Batsch] is an economically important fruit crop that has become a genetic-genomic model for all Prunus species in the family Rosaceae. A doubled haploid reference genome sequence length of 227.3 Mb, a narrow genetic base contrasted by a wide phenotypic variability, the generation of cultivars through hybridization with subsequent clonal propagation, and the current accessibility of many founder genotypes, as well as the pedigree of modern commercial cultivars make peach a model for the study of inter-cultivar genomic heterogeneity and its shaping by artificial selection. Results The quantitative genomic differences among the three genotypes studied as genomic variants, included small variants (SNPs and InDels) and structural variants (SV) (duplications, inversions and translocations). The heirloom cultivar 'Georgia Belle’ and an almond by peach introgression breeding line 'F8,1-42’ are more heterogeneous than is the modern cultivar 'Dr. Davis’ when compared to the peach reference genome ('Lovell’). A pair-wise comparison of consensus genome sequences with 'Lovell’ showed that 'F8,1-42’ and 'Georgia Belle’ were more divergent than were 'Dr. Davis’ and 'Lovell’. Conclusions A novel application of emerging bioinformatics tools to the analysis of ongoing genome sequencing project outputs has led to the identification of a range of genomic variants. Results can be used to delineate the genomic and phenotypic differences among peach genotypes. For crops such as fruit trees, the availability of old cultivars, breeding selections and their pedigrees, make them suitable models for the study of genome shaping by artificial selection. The findings from the study of such genomic variants can then elucidate the control of pomological traits and the characterization of metabolic pathways, thus facilitating the development of protocols for the improvement of Prunus crops. Electronic supplementary material The online version of this article (doi: 10.1186/1471-2164-14-750) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jonathan Fresnedo-Ramírez
- Department of Plant Sciences, University of California Davis, One Shields Ave, Davis, CA 95616, USA.
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