Publications by authors named "Chandrasegaran S"

Deoxyribonucleic acid triplexes have potential roles in a range of biological processes involving gene and transcriptional regulation. A major challenge in exploiting the formation of these higher-order structures to target genes is their low stability, which is dependent on many factors including the length and composition of bases in the sequence. Here, different DNA base modifications have been explored, primarily using native mass spectrometry, in efforts to enable stronger binding between the triplex forming oligonucleotide (TFO) and duplex target sites.

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Cellular senescence is known to drive age-related pathology through the senescence-associated secretory phenotype (SASP). However, it also plays important physiological roles such as cancer suppression, embryogenesis and wound healing. Wound healing is a tightly regulated process which when disrupted results in conditions such as fibrosis and chronic wounds.

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Article Synopsis
  • The text discusses the complete process of creating a synthetic chromosome that is 404,963 base pairs long, including its synthesis, assembly, debugging, and characterization.
  • The authors resolved a bug in a crucial gene affecting telomerase function, resulting in a strain showing fitness similar to wild-type.
  • They combined chromosome transfer methods, like chromoduction and conditional centromere destabilization, for efficient substitution of chromosomes, while observing interactions between the synthetic and wild-type chromosomes that hint at gene dosage compensation.
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Article Synopsis
  • Gaucher disease (GD) is a genetic disorder caused by mutations in the GBA gene that affects macrophage function.
  • CRISPR gene editing was used to correct the GBA mutation in stem cells, producing cell lines with different genetic variations (homozygous and heterozygous).
  • The corrected macrophages demonstrated improved functions, indicating that GD mutations impact their ability to fight infections, and research suggests that having GD may offer some protection against tuberculosis.
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The ageing process is highly complex involving multiple processes operating at different biological levels. Systems Biology presents an approach using integrative computational and laboratory study that allows us to address such complexity. The approach relies on the computational analysis of knowledge and data to generate predictive models that may be validated with further laboratory experimentation.

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Visual data storytelling is gaining importance as a means of presenting data-driven information or analysis results, especially to the general public. This has resulted in design principles being proposed for data-driven storytelling, and new authoring tools being created to aid such storytelling. However, data analysts typically lack sufficient background in design and storytelling to make effective use of these principles and authoring tools.

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Alzheimer's disease is a neurodegenerative disorder that is caused by the accumulation of beta-amyloid plaques in the brain. Currently, there is no definitive cure available to treat Alzheimer's disease. The available medication in the market has the ability to only slow down its progression.

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Motivation: The analysis of longitudinal datasets and construction of gene regulatory networks (GRNs) provide a valuable means to disentangle the complexity of microRNA (miRNA)-mRNA interactions. However, there are no computational tools that can integrate, conduct functional analysis and generate detailed networks from longitudinal miRNA-mRNA datasets.

Results: We present TimiRGeN, an R package that uses time point-based differential expression results to identify miRNA-mRNA interactions influencing signaling pathways of interest.

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Dynamic networks-networks that change over time-can be categorized into two types: offline dynamic networks, where all states of the network are known, and online dynamic networks, where only the past states of the network are known. Research on staging animated transitions in dynamic networks has focused more on offline data, where rendering strategies can take into account past and future states of the network. Rendering online dynamic networks is a more challenging problem since it requires a balance between timeliness for monitoring tasks-so that the animations do not lag too far behind the events-and clarity for comprehension tasks-to minimize simultaneous changes that may be difficult to follow.

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Targeted genome editing with programmable nucleases has revolutionized biomedical research. The ability to make site-specific modifications to the human genome, has invoked a paradigm shift in gene therapy. Using gene editing technologies, the sequence in the human genome can now be precisely engineered to achieve a therapeutic effect.

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The rapid rise in technologies for data collection has created an unmatched opportunity to advance the use of data-rich tools for lifecycle decision-making. However, the usefulness of these technologies is limited by the ability to translate lifecycle data into actionable insights for human decision-makers. This is especially true in the case of sustainable lifecycle design (SLD), as the assessment of environmental impacts, and the feasibility of making corresponding design changes, often relies on human expertise and intuition.

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We describe complete design of a synthetic eukaryotic genome, Sc2.0, a highly modified genome reduced in size by nearly 8%, with 1.1 megabases of the synthetic genome deleted, inserted, or altered.

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Genome engineering with programmable nucleases depends on cellular responses to a targeted double-strand break (DSB). The first truly targetable reagents were the zinc finger nucleases (ZFNs) showing that arbitrary DNA sequences could be addressed for cleavage by protein engineering, ushering in the breakthrough in genome manipulation. ZFNs resulted from basic research on zinc finger proteins and the FokI restriction enzyme (which revealed a bipartite structure with a separable DNA-binding domain and a non-specific cleavage domain).

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Advances in DNA synthesis and assembly methods over the past decade have made it possible to construct genome-size fragments from oligonucleotides. Early work focused on synthesis of small viral genomes, followed by hierarchical synthesis of wild-type bacterial genomes and subsequently on transplantation of synthesized bacterial genomes into closely related recipient strains. More recently, a synthetic designer version of yeast Saccharomyces cerevisiae chromosome III has been generated, with numerous changes from the wild-type sequence without having an impact on cell fitness and phenotype, suggesting plasticity of the yeast genome.

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Generation and precise genetic correction of patient-derived hiPSCs have great potential in regenerative medicine. Such targeted genetic manipulations can now be achieved using gene-editing nucleases. Here, we report generation of cystic fibrosis (CF) and Gaucher's disease (GD) hiPSCs respectively from CF (homozygous for CFTRΔF508 mutation) and Type II GD [homozygous for β-glucocerebrosidase (GBA) 1448T>C mutation] patient fibroblasts, using CCR5- specific TALENs.

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Rapid advances in DNA synthesis techniques have made it possible to engineer viruses, biochemical pathways and assemble bacterial genomes. Here, we report the synthesis of a functional 272,871-base pair designer eukaryotic chromosome, synIII, which is based on the 316,617-base pair native Saccharomyces cerevisiae chromosome III. Changes to synIII include TAG/TAA stop-codon replacements, deletion of subtelomeric regions, introns, transfer RNAs, transposons, and silent mating loci as well as insertion of loxPsym sites to enable genome scrambling.

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RNA-guided genome engineering based on the type II prokaryotic CRISPR/Cas system provides an efficient and versatile method for targeted manipulation of mammalian genomes.

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Zinc finger nucleases (ZFNs) have become powerful tools to deliver a targeted double-strand break at a pre-determined chromosomal locus in order to insert an exogenous transgene by homology-directed repair. ZFN-mediated gene targeting was used to generate both single-allele chemokine (C-C motif) receptor 5 (CCR5)-modified human induced pluripotent stem cells (hiPSCs) and biallele CCR5-modified hiPSCs from human lung fibroblasts (IMR90 cells) and human primary cord blood mononuclear cells (CBMNCs) by site-specific insertion of stem cell transcription factor genes flanked by LoxP sites into the endogenous CCR5 locus. The Oct4 and Sox2 reprogramming factors, in combination with valproic acid, induced reprogramming of human lung fibroblasts to form CCR5-modified hiPSCs, while 5 factors, Oct4/Sox2/Klf4/Lin28/Nanog, induced reprogramming of CBMNCs.

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Build-a-Genome is an intensive laboratory course at Johns Hopkins University that introduces undergraduates to the burgeoning field of synthetic biology. In addition to lectures that provide a comprehensive overview of the field, the course contains a unique laboratory component in which the students contribute to an actual, ongoing project to construct the first synthetic eukaryotic cell, a yeast cell composed of man-made parts. In doing so, the students acquire basic molecular biology skills and gain a truly "graduate student-like experience" in which they take ownership of their projects, troubleshoot their own experiments, present at frequent laboratory meetings, and are given 24-h access to the laboratory, albeit with all the guidance they will need to complete their projects during the semester.

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As described in a different chapter in this volume, the uracil-specific excision reaction (USER) fusion method can be used to assemble multiple small DNA fragments (∼0.75-kb size) into larger 3-kb DNA segments both in vitro and in vivo (in Escherichia coli). However, in order to assemble an entire synthetic yeast genome (Sc2.

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Recent advances in DNA synthesis technology make it possible to design and synthesize DNA fragments of several kb in size. However, the process of assembling the smaller DNA fragments into a larger DNA segment is still a cumbersome process. In this chapter, we describe the use of the uracil specific excision reaction (USER)-mediated approach for rapid and efficient assembly of multiple DNA fragments both in vitro and in vivo (using Escherichia coli).

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Recent advances in DNA synthesis technology have enabled the construction of novel genetic pathways and genomic elements, furthering our understanding of system-level phenomena. The ability to synthesize large segments of DNA allows the engineering of pathways and genomes according to arbitrary sets of design principles. Here we describe a synthetic yeast genome project, Sc2.

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