1
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Biggs BW, de Paz AM, Bhan NJ, Cybulski TR, Church GM, Tyo KEJ. Engineering Ca 2+-Dependent DNA Polymerase Activity. ACS Synth Biol 2023; 12:3301-3311. [PMID: 37856140 DOI: 10.1021/acssynbio.3c00302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
Advancements in synthetic biology have provided new opportunities in biosensing, with applications ranging from genetic programming to diagnostics. Next generation biosensors aim to expand the number of accessible environments for measurements, increase the number of measurable phenomena, and improve the quality of the measurement. To this end, an emerging area in the field has been the integration of DNA as an information storage medium within biosensor outputs, leveraging nucleic acids to record the biosensor state over time. However, slow signal transduction steps, due to the time scales of transcription and translation, bottleneck many sensing-DNA recording approaches. DNA polymerases (DNAPs) have been proposed as a solution to the signal transduction problem by operating as both the sensor and responder, but there is presently a lack of DNAPs with functional sensitivity to many desirable target ligands. Here, we engineer components of the Pol δ replicative polymerase complex of Saccharomyces cerevisiae to sense and respond to Ca2+, a metal cofactor relevant to numerous biological phenomena. Through domain insertion and binding site grafting to Pol δ subunits, we demonstrate functional allosteric sensitivity to Ca2+. Together, this work provides an important foundation for future efforts in the development of DNAP-based biosensors.
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Affiliation(s)
- Bradley W Biggs
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Alexandra M de Paz
- Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Namita J Bhan
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Thaddeus R Cybulski
- Interdepartmental Neuroscience Program, Northwestern University, Chicago, Illinois 60611, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - George M Church
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Keith E J Tyo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
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2
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Lin D, Li X, Moult E, Park P, Tang B, Shen H, Grimm JB, Falco N, Jia BZ, Baker D, Lavis LD, Cohen AE. Time-tagged ticker tapes for intracellular recordings. Nat Biotechnol 2023; 41:631-639. [PMID: 36593408 PMCID: PMC10192119 DOI: 10.1038/s41587-022-01524-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 09/22/2022] [Indexed: 01/03/2023]
Abstract
Recording transcriptional histories of a cell would enable deeper understanding of cellular developmental trajectories and responses to external perturbations. Here we describe an engineered protein fiber that incorporates diverse fluorescent marks during its growth to store a ticker tape-like history. An embedded HaloTag reporter incorporates user-supplied dyes, leading to colored stripes that map the growth of each individual fiber to wall clock time. A co-expressed eGFP tag driven by a promoter of interest records a history of transcriptional activation. High-resolution multi-spectral imaging on fixed samples reads the cellular histories, and interpolation of eGFP marks relative to HaloTag timestamps provides accurate absolute timing. We demonstrate recordings of doxycycline-induced transcription in HEK cells and cFos promoter activation in cultured neurons, with a single-cell absolute accuracy of 30-40 minutes over a 12-hour recording. The protein-based ticker tape design we present here could be generalized to achieve massively parallel single-cell recordings of diverse physiological modalities.
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Affiliation(s)
- Dingchang Lin
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, USA.
| | - Xiuyuan Li
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Eric Moult
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Pojeong Park
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Benjamin Tang
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Hao Shen
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Jonathan B Grimm
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Natalie Falco
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Bill Z Jia
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - David Baker
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Adam E Cohen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
- Department of Physics, Harvard University, Cambridge, MA, USA.
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3
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Abstract
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Molecular circuits
capable of processing temporal information are
essential for complex decision making in response to both the presence
and history of a molecular environment. A particular type of temporal
information that has been recognized to be important is the relative
timing of signals. Here we demonstrate the strategy of temporal memory
combined with logic computation in DNA strand-displacement circuits
capable of making decisions based on specific combinations of inputs
as well as their relative timing. The circuit encodes the timing information
on inputs in a set of memory strands, which allows for the construction
of logic gates that act on current and historical signals. We show
that mismatches can be employed to reduce the complexity of circuit
design and that shortening specific toeholds can be useful for improving
the robustness of circuit behavior. We also show that a detailed model
can provide critical insights for guiding certain aspects of experimental
investigations that an abstract model cannot. We envision that the
design principles explored in this study can be generalized to more
complex temporal logic circuits and incorporated into other types
of circuit architectures, including DNA-based neural networks, enabling
the implementation of timing-dependent learning rules and opening
up new opportunities for embedding intelligent behaviors into artificial
molecular machines.
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Affiliation(s)
- Anna P Lapteva
- Bioengineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Namita Sarraf
- Bioengineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Lulu Qian
- Bioengineering, California Institute of Technology, Pasadena, California 91125, United States.,Computer Science, California Institute of Technology, Pasadena, California 91125, United States
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4
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Akhlaghpour H. An RNA-Based Theory of Natural Universal Computation. J Theor Biol 2021; 537:110984. [PMID: 34979104 DOI: 10.1016/j.jtbi.2021.110984] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 09/30/2021] [Accepted: 12/07/2021] [Indexed: 12/15/2022]
Abstract
Life is confronted with computation problems in a variety of domains including animal behavior, single-cell behavior, and embryonic development. Yet we currently do not know of a naturally existing biological system that is capable of universal computation, i.e., Turing-equivalent in scope. Generic finite-dimensional dynamical systems (which encompass most models of neural networks, intracellular signaling cascades, and gene regulatory networks) fall short of universal computation, but are assumed to be capable of explaining cognition and development. I present a class of models that bridge two concepts from distant fields: combinatory logic (or, equivalently, lambda calculus) and RNA molecular biology. A set of basic RNA editing rules can make it possible to compute any computable function with identical algorithmic complexity to that of Turing machines. The models do not assume extraordinarily complex molecular machinery or any processes that radically differ from what we already know to occur in cells. Distinct independent enzymes can mediate each of the rules and RNA molecules solve the problem of parenthesis matching through their secondary structure. In the most plausible of these models all of the editing rules can be implemented with merely cleavage and ligation operations at fixed positions relative to predefined motifs. This demonstrates that universal computation is well within the reach of molecular biology. It is therefore reasonable to assume that life has evolved - or possibly began with - a universal computer that yet remains to be discovered. The variety of seemingly unrelated computational problems across many scales can potentially be solved using the same RNA-based computation system. Experimental validation of this theory may immensely impact our understanding of memory, cognition, development, disease, evolution, and the early stages of life.
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Affiliation(s)
- Hessameddin Akhlaghpour
- Laboratory of Integrative Brain Function, The Rockefeller University, New York, NY, 10065, USA
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5
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Bhan N, Callisto A, Strutz J, Glaser J, Kalhor R, Boyden ES, Church G, Kording K, Tyo KEJ. Recording Temporal Signals with Minutes Resolution Using Enzymatic DNA Synthesis. J Am Chem Soc 2021; 143:16630-16640. [PMID: 34591459 DOI: 10.1021/jacs.1c07331] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Employing DNA as a high-density data storage medium has paved the way for next-generation digital storage and biosensing technologies. However, the multipart architecture of current DNA-based recording techniques renders them inherently slow and incapable of recording fluctuating signals with subhour frequencies. To address this limitation, we developed a simplified system employing a single enzyme, terminal deoxynucleotidyl transferase (TdT), to transduce environmental signals into DNA. TdT adds nucleotides to the 3'-ends of single-stranded DNA (ssDNA) in a template-independent manner, selecting bases according to inherent preferences and environmental conditions. By characterizing TdT nucleotide selectivity under different conditions, we show that TdT can encode various physiologically relevant signals such as Co2+, Ca2+, and Zn2+ concentrations and temperature changes in vitro. Further, by considering the average rate of nucleotide incorporation, we show that the resulting ssDNA functions as a molecular ticker tape. With this method we accurately encode a temporal record of fluctuations in Co2+ concentration to within 1 min over a 60 min period. Finally, we engineer TdT to allosterically turn off in the presence of a physiologically relevant concentration of calcium. We use this engineered TdT in concert with a reference TdT to develop a two-polymerase system capable of recording a single-step change in the Ca2+ signal to within 1 min over a 60 min period. This work expands the repertoire of DNA-based recording techniques by developing a novel DNA synthesis-based system that can record temporal environmental signals into DNA with a resolution of minutes.
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Affiliation(s)
- Namita Bhan
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Mitolab, Cambridge, Massachusetts 02139, United States
| | - Alec Callisto
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Jonathan Strutz
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Joshua Glaser
- Center for Theoretical Neuroscience, Columbia University, New York, New York 10027, United States
| | - Reza Kalhor
- Department of Biomedical Engineering, Center for Epigenetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, United States
| | - Edward S Boyden
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.,McGovern Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.,Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - George Church
- Department of Biomedical Engineering, Center for Epigenetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, United States
| | - Konrad Kording
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Keith E J Tyo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
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6
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Loveless TB, Grotts JH, Schechter MW, Forouzmand E, Carlson CK, Agahi BS, Liang G, Ficht M, Liu B, Xie X, Liu CC. Lineage tracing and analog recording in mammalian cells by single-site DNA writing. Nat Chem Biol 2021; 17:739-747. [PMID: 33753928 PMCID: PMC8891441 DOI: 10.1038/s41589-021-00769-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 02/09/2021] [Indexed: 01/31/2023]
Abstract
Studying cellular and developmental processes in complex multicellular organisms can require the non-destructive observation of thousands to billions of cells deep within an animal. DNA recorders address the staggering difficulty of this task by converting transient cellular experiences into mutations at defined genomic sites that can be sequenced later in high throughput. However, existing recorders act primarily by erasing DNA. This is problematic because, in the limit of progressive erasure, no record remains. We present a DNA recorder called CHYRON (Cell History Recording by Ordered Insertion) that acts primarily by writing new DNA through the repeated insertion of random nucleotides at a single locus in temporal order. To achieve in vivo DNA writing, CHYRON combines Cas9, a homing guide RNA and the template-independent DNA polymerase terminal deoxynucleotidyl transferase. We successfully applied CHYRON as an evolving lineage tracer and as a recorder of user-selected cellular stimuli.
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Affiliation(s)
- Theresa B Loveless
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
- NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, Irvine, CA, USA
| | - Joseph H Grotts
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Mason W Schechter
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Elmira Forouzmand
- Department of Computer Science, University of California, Irvine, Irvine, CA, USA
| | - Courtney K Carlson
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Bijan S Agahi
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Guohao Liang
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Michelle Ficht
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Beide Liu
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Xiaohui Xie
- Department of Computer Science, University of California, Irvine, Irvine, CA, USA
| | - Chang C Liu
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA.
- NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, Irvine, CA, USA.
- Department of Chemistry, University of California, Irvine, Irvine, CA, USA.
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, USA.
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, USA.
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7
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Guitchounts G, Cox D. 64-Channel Carbon Fiber Electrode Arrays for Chronic Electrophysiology. Sci Rep 2020; 10:3830. [PMID: 32123283 PMCID: PMC7052209 DOI: 10.1038/s41598-020-60873-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 02/17/2020] [Indexed: 12/11/2022] Open
Abstract
A chief goal in neuroscience is to understand how neuronal activity relates to behavior, perception, and cognition. However, monitoring neuronal activity over long periods of time is technically challenging, and limited, in part, by the invasive nature of recording tools. While electrodes allow for recording in freely-behaving animals, they tend to be bulky and stiff, causing damage to the tissue they are implanted in. One solution to this invasiveness problem may be probes that are small enough to fly under the immune system's radar. Carbon fiber (CF) electrodes are thinner and more flexible than typical metal or silicon electrodes, but the arrays described in previous reports had low channel counts and required time-consuming manual assembly. Here we report the design of an expanded-channel-count carbon fiber electrode array (CFEA) as well as a method for fast preparation of the recording sites using acid etching and electroplating with PEDOT-TFB, and demonstrate the ability of the 64-channel CFEA to record from rat visual cortex. We include designs for interfacing the system with micro-drives or flex-PCB cables for recording from multiple brain regions, as well as a facilitated method for coating CFs with the insulator Parylene-C. High-channel-count CFEAs may thus be an alternative to traditional microwire-based electrodes and a practical tool for exploring the neural code.
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Affiliation(s)
- Grigori Guitchounts
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, 02138, USA.
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA.
- Program in Neuroscience, Harvard University, Cambridge, Massachusetts, 02138, USA.
| | - David Cox
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, 02138, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, 02138, USA
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8
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Abstract
Molecular data storage is an attractive alternative for dense and durable information storage, which is sorely needed to deal with the growing gap between information production and the ability to store data. DNA is a clear example of effective archival data storage in molecular form. In this Review, we provide an overview of the process, the state of the art in this area and challenges for mainstream adoption. We also survey the field of in vivo molecular memory systems that record and store information within the DNA of living cells, which, together with in vitro DNA data storage, lie at the growing intersection of computer systems and biotechnology.
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Affiliation(s)
- Luis Ceze
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA.
| | - Jeff Nivala
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
| | - Karin Strauss
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, WA, USA.,Microsoft Research, Redmond, WA, USA
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9
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El-Atab N, Shaikh SF, Hussain MM. Nano-scale transistors for interfacing with brain: design criteria, progress and prospect. NANOTECHNOLOGY 2019; 30:442001. [PMID: 31342924 DOI: 10.1088/1361-6528/ab3534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
According to the World Health Organization, one quarter of the world's population suffers from various neurological disorders ranging from depression to Alzheimer's disease. Thus, understanding the operation mechanism of the brain enables us to help those who are suffering from these diseases. In addition, recent clinical medicine employs electronic brain implants, despite the fact of being invasive, to treat disorders ranging from severe coronary conditions to traumatic injuries. As a result, the deaf could hear, the blind could see, and the paralyzed could control robotic arms and legs. Due to the requirement of high data management capability with a power consumption as low as possible, designing nanoscale transistors as essential I/O electronics is a complex task. Herein, we review the essential design criteria for such nanoscale transistors, progress and prospect for implantable brain-machine-interface electronics. This article also discusses their technological challenges for practical implementation.
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Affiliation(s)
- Nazek El-Atab
- MMH Labs, Computer Electrical Mathematical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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10
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Abstract
Measuring biological data across time and space is critical for understanding complex biological processes and for various biosurveillance applications. However, such data are often inaccessible or difficult to directly obtain. Less invasive, more robust and higher-throughput biological recording tools are needed to profile cells and their environments. DNA-based cellular recording is an emerging and powerful framework for tracking intracellular and extracellular biological events over time across living cells and populations. Here, we review and assess DNA recorders that utilize CRISPR nucleases, integrases and base-editing strategies, as well as recombinase and polymerase-based methods. Quantitative characterization, modelling and evaluation of these DNA-recording modalities can guide their design and implementation for specific application areas.
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Affiliation(s)
- Ravi U Sheth
- Department of Systems Biology, Columbia University Medical Center, New York, NY, USA
- Integrated Program in Cellular, Molecular and Biomedical Studies, Columbia University, New York, NY, USA
| | - Harris H Wang
- Department of Systems Biology, Columbia University Medical Center, New York, NY, USA.
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA.
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11
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Kebschull JM, Zador AM. Cellular barcoding: lineage tracing, screening and beyond. Nat Methods 2018; 15:871-879. [PMID: 30377352 DOI: 10.1038/s41592-018-0185-x] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 09/26/2018] [Indexed: 01/14/2023]
Abstract
Cellular barcoding is a technique in which individual cells are labeled with unique nucleic acid sequences, termed barcodes, so that they can be tracked through space and time. Cellular barcoding can be used to track millions of cells in parallel, and thus is an efficient approach for investigating heterogeneous populations of cells. Over the past 25 years, cellular barcoding has been used for fate mapping, lineage tracing and high-throughput screening, and has led to important insights into developmental biology and gene function. Driven by plummeting sequencing costs and the power of synthetic biology, barcoding is now expanding beyond traditional applications and into diverse fields such as neuroanatomy and the recording of cellular activity. In this review, we discuss the fundamental principles of cellular barcoding, including the underlying mathematics, and its applications in both new and established fields.
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Affiliation(s)
- Justus M Kebschull
- Watson School of Biological Sciences, Cold Spring Harbor, NY, USA.,Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
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12
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Abstract
The central dogma processes of DNA replication, transcription, and translation are responsible for the maintenance and expression of every gene in an organism. An orthogonal central dogma may insulate genetic programs from host regulation and allow expansion in the roles of these processes within the cell.
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Affiliation(s)
- Chang C. Liu
- Department of Biomedical Engineering, University of California, Irvine, California, USA
- Department of Chemistry, University of California, Irvine, California, USA
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, USA
| | - Michael C. Jewett
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Jason W. Chin
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
- Department of Chemistry, Cambridge University, Cambridge, UK
| | - Chris A. Voigt
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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13
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Lissek T. Interfacing Neural Network Components and Nucleic Acids. Front Bioeng Biotechnol 2017; 5:53. [PMID: 29255707 PMCID: PMC5722975 DOI: 10.3389/fbioe.2017.00053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 08/14/2017] [Indexed: 11/24/2022] Open
Abstract
Translating neural activity into nucleic acid modifications in a controlled manner harbors unique advantages for basic neurobiology and bioengineering. It would allow for a new generation of biological computers that store output in ultra-compact and long-lived DNA and enable the investigation of animal nervous systems at unprecedented scales. Furthermore, by exploiting the ability of DNA to precisely influence neuronal activity and structure, it could be possible to more effectively create cellular therapy approaches for psychiatric diseases that are currently difficult to treat.
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Affiliation(s)
- Thomas Lissek
- Department of Neurobiology, Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany
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14
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Increased Processivity, Misincorporation, and Nucleotide Incorporation Efficiency in Sulfolobus solfataricus Dpo4 Thumb Domain Mutants. Appl Environ Microbiol 2017; 83:AEM.01013-17. [PMID: 28710267 DOI: 10.1128/aem.01013-17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/04/2017] [Indexed: 01/21/2023] Open
Abstract
The present study aimed to increase the processivity of Sulfolobus solfataricus DNA polymerase Dpo4. Protein engineering and bioinformatics were used to compile a library of potential Dpo4 mutation sites. Ten potential mutants were identified and constructed. A primer extension assay was used to evaluate the processivity of Dpo4 mutants. Thumb (A181D) and finger (E63K) domain mutants showed a processivity of 20 and 19 nucleotides (nt), respectively. A little finger domain mutant (I248Y) exhibited a processivity of 17 nt, only 1 nt more than wild-type Dpo4. Furthermore, the A181D mutant showed lower fidelity and higher nucleotide incorporation efficiency (4.74 × 10-4 s-1 μM-1) than E63K and I248Y mutants. When tasked with bypassing damage, the A181D mutant exhibited a 3.81-fold and 2.62-fold higher catalytic efficiency (kcat/Km ) at incorporating dCTP and dATP, respectively, than wild-type Dpo4. It also showed a 55% and 91.5% higher catalytic efficiency when moving beyond the damaged 8-oxoG:C and 8-oxoG:A base pairs, respectively, compared to wild-type Dpo4. Protein engineering and bioinformatics methods can effectively increase the processivity and translesion synthesis ability of Dpo4.IMPORTANCE DNA polymerases with poor fidelity can be exploited to store data and record changes in response to the intracellular environment. Sulfolobus solfataricus Dpo4 is such an enzyme, although its use is hindered by its low processivity. In this work, we used a bioinformatics and protein engineering approach to generate Dpo4 mutants with improved processivity. We identified the Dpo4 thumb domain as the most relevant in controlling processivity.
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15
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DNA binding strength increases the processivity and activity of a Y-Family DNA polymerase. Sci Rep 2017; 7:4756. [PMID: 28684739 PMCID: PMC5500549 DOI: 10.1038/s41598-017-02578-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 04/12/2017] [Indexed: 11/09/2022] Open
Abstract
DNA polymerase (pol) processivity, i.e., the bases a polymerase extends before falling off the DNA, and activity are important for copying difficult DNA sequences, including simple repeats. Y-family pols would be appealing for copying difficult DNA and incorporating non-natural dNTPs, due to their low fidelity and loose active site, but are limited by poor processivity and activity. In this study, the binding between Dbh and DNA was investigated to better understand how to rationally design enhanced processivity in a Y-family pol. Guided by structural simulation, a fused pol Sdbh with non-specific dsDNA binding protein Sso7d in the N-terminus was designed. This modification increased in vitro processivity 4-fold as compared to the wild-type Dbh. Additionally, bioinformatics was used to identify amino acid mutations that would increase stabilization of Dbh bound to DNA. The variant SdbhM76I further improved the processivity of Dbh by 10 fold. The variant SdbhKSKIP241–245RVRKS showed higher activity than Dbh on the incorporation of dCTP (correct) and dATP (incorrect) opposite the G (normal) or 8-oxoG(damaged) template base. These results demonstrate the capability to rationally design increases in pol processivity and catalytic efficiency through computational DNA binding predictions and the addition of non-specific DNA binding domains.
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16
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Cybulski TR, Boyden ES, Church GM, Tyo KEJ, Kording KP. Nucleotide-time alignment for molecular recorders. PLoS Comput Biol 2017; 13:e1005483. [PMID: 28459860 PMCID: PMC5432193 DOI: 10.1371/journal.pcbi.1005483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 05/15/2017] [Accepted: 03/24/2017] [Indexed: 11/18/2022] Open
Abstract
Using a DNA polymerase to record intracellular calcium levels has been proposed as a novel neural recording technique, promising massive-scale, single-cell resolution monitoring of large portions of the brain. This technique relies on local storage of neural activity in strands of DNA, followed by offline analysis of that DNA. In simple implementations of this scheme, the time when each nucleotide was written cannot be determined directly by post-hoc DNA sequencing; the timing data must be estimated instead. Here, we use a Dynamic Time Warping-based algorithm to perform this estimation, exploiting correlations between neural activity and observed experimental variables to translate DNA-based signals to an estimate of neural activity over time. This algorithm improves the parallelizability of traditional Dynamic Time Warping, allowing several-fold increases in computation speed. The algorithm also provides a solution to several critical problems with the molecular recording paradigm: determining recording start times and coping with DNA polymerase pausing. The algorithm can generally locate DNA-based records to within <10% of a recording window, allowing for the estimation of unobserved incorporation times and latent neural tunings. We apply our technique to an in silico motor control neuroscience experiment, using the algorithm to estimate both timings of DNA-based data and the directional tuning of motor cortical cells during a center-out reaching task. We also use this algorithm to explore the impact of polymerase characteristics on system performance, determining the precision of a molecular recorder as a function of its kinetic and error-generating properties. We find useful ranges of properties for DNA polymerase-based recorders, providing guidance for future protein engineering attempts. This work demonstrates a useful general extension to dynamic alignment algorithms, as well as direct applications of that extension toward the development of molecular recorders, providing a necessary stepping stone for future biological work.
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Affiliation(s)
- Thaddeus R. Cybulski
- Department of Physical Medicine and Rehabilitation, Rehabilitation Institute of Chicago, Northwestern University, Chicago, Illinois, United States of America
- * E-mail:
| | - Edward S. Boyden
- Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- McGovern Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - George M. Church
- Biophysics Program, Harvard University, Boston, Massachusetts, United States of America
- Wyss Institute, Harvard University, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Harvard University, Boston, Massachusetts, United States of America
| | - Keith E. J. Tyo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States of America
| | - Konrad P. Kording
- Department of Physical Medicine and Rehabilitation, Rehabilitation Institute of Chicago, Northwestern University, Chicago, Illinois, United States of America
- Department of Physiology, Northwestern University, Chicago, Illinois, United States of America
- Department of Applied Mathematics, Northwestern University, Evanston, Illinois, United States of America
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Treweek JB, Gradinaru V. Extracting structural and functional features of widely distributed biological circuits with single cell resolution via tissue clearing and delivery vectors. Curr Opin Biotechnol 2016; 40:193-207. [PMID: 27393829 DOI: 10.1016/j.copbio.2016.03.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 03/10/2016] [Accepted: 03/15/2016] [Indexed: 12/13/2022]
Abstract
The scientific community has learned a great deal from imaging small and naturally transparent organisms such as nematodes and zebrafish. The consequences of genetic mutations on their organ development and survival can be visualized easily and with high-throughput at the organism-wide scale. In contrast, three-dimensional information is less accessible in mammalian subjects because the heterogeneity of light-scattering tissue elements renders their organs opaque. Likewise, genetically labeling desired circuits across mammalian bodies is prohibitively slow and costly via the transgenic route. Emerging breakthroughs in viral vector engineering, genome editing tools, and tissue clearing can render larger opaque organisms genetically tractable and transparent for whole-organ cell phenotyping, tract tracing and imaging at depth.
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Affiliation(s)
- Jennifer Brooke Treweek
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Viviana Gradinaru
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA.
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18
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Puzzle Imaging: Using Large-Scale Dimensionality Reduction Algorithms for Localization. PLoS One 2015; 10:e0131593. [PMID: 26192446 PMCID: PMC4507868 DOI: 10.1371/journal.pone.0131593] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 06/02/2015] [Indexed: 01/06/2023] Open
Abstract
Current high-resolution imaging techniques require an intact sample that preserves spatial relationships. We here present a novel approach, "puzzle imaging," that allows imaging a spatially scrambled sample. This technique takes many spatially disordered samples, and then pieces them back together using local properties embedded within the sample. We show that puzzle imaging can efficiently produce high-resolution images using dimensionality reduction algorithms. We demonstrate the theoretical capabilities of puzzle imaging in three biological scenarios, showing that (1) relatively precise 3-dimensional brain imaging is possible; (2) the physical structure of a neural network can often be recovered based only on the neural connectivity matrix; and (3) a chemical map could be reproduced using bacteria with chemosensitive DNA and conjugative transfer. The ability to reconstruct scrambled images promises to enable imaging based on DNA sequencing of homogenized tissue samples.
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19
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Marblestone AH, Zamft BM, Maguire YG, Shapiro MG, Cybulski TR, Glaser JI, Amodei D, Stranges PB, Kalhor R, Dalrymple DA, Seo D, Alon E, Maharbiz MM, Carmena JM, Rabaey JM, Boyden ES, Church GM, Kording KP. Physical principles for scalable neural recording. Front Comput Neurosci 2013; 7:137. [PMID: 24187539 PMCID: PMC3807567 DOI: 10.3389/fncom.2013.00137] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 09/23/2013] [Indexed: 12/20/2022] Open
Abstract
Simultaneously measuring the activities of all neurons in a mammalian brain at millisecond resolution is a challenge beyond the limits of existing techniques in neuroscience. Entirely new approaches may be required, motivating an analysis of the fundamental physical constraints on the problem. We outline the physical principles governing brain activity mapping using optical, electrical, magnetic resonance, and molecular modalities of neural recording. Focusing on the mouse brain, we analyze the scalability of each method, concentrating on the limitations imposed by spatiotemporal resolution, energy dissipation, and volume displacement. Based on this analysis, all existing approaches require orders of magnitude improvement in key parameters. Electrical recording is limited by the low multiplexing capacity of electrodes and their lack of intrinsic spatial resolution, optical methods are constrained by the scattering of visible light in brain tissue, magnetic resonance is hindered by the diffusion and relaxation timescales of water protons, and the implementation of molecular recording is complicated by the stochastic kinetics of enzymes. Understanding the physical limits of brain activity mapping may provide insight into opportunities for novel solutions. For example, unconventional methods for delivering electrodes may enable unprecedented numbers of recording sites, embedded optical devices could allow optical detectors to be placed within a few scattering lengths of the measured neurons, and new classes of molecularly engineered sensors might obviate cumbersome hardware architectures. We also study the physics of powering and communicating with microscale devices embedded in brain tissue and find that, while radio-frequency electromagnetic data transmission suffers from a severe power-bandwidth tradeoff, communication via infrared light or ultrasound may allow high data rates due to the possibility of spatial multiplexing. The use of embedded local recording and wireless data transmission would only be viable, however, given major improvements to the power efficiency of microelectronic devices.
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Affiliation(s)
- Adam H. Marblestone
- Biophysics Program, Harvard UniversityBoston, MA, USA
- Wyss Institute for Biologically Inspired Engineering at Harvard UniversityBoston, MA, USA
| | | | - Yael G. Maguire
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
- Plum Labs LLCCambridge, MA, USA
| | - Mikhail G. Shapiro
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadena, CA, USA
| | | | - Joshua I. Glaser
- Interdepartmental Neuroscience Program, Northwestern UniversityChicago, IL, USA
| | - Dario Amodei
- Department of Radiology, Stanford UniversityPalo Alto, CA, USA
| | | | - Reza Kalhor
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
| | - David A. Dalrymple
- Biophysics Program, Harvard UniversityBoston, MA, USA
- NemaloadSan Francisco, CA, USA
- Media Laboratory, Massachusetts Institute of TechnologyCambridge, MA, USA
| | - Dongjin Seo
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Elad Alon
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Michel M. Maharbiz
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Jose M. Carmena
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
- Helen Wills Neuroscience Institute, University of California at BerkeleyBerkeley, CA, USA
| | - Jan M. Rabaey
- Department of Electrical Engineering and Computer Sciences, University of California at BerkeleyBerkeley, CA, USA
| | - Edward S. Boyden
- Media Laboratory, Massachusetts Institute of TechnologyCambridge, MA, USA
- Departments of Brain and Cognitive Sciences and Biological Engineering, Massachusetts Institute of TechnologyCambridge, MA, USA
| | - George M. Church
- Biophysics Program, Harvard UniversityBoston, MA, USA
- Wyss Institute for Biologically Inspired Engineering at Harvard UniversityBoston, MA, USA
- Department of Genetics, Harvard Medical SchoolBoston, MA, USA
| | - Konrad P. Kording
- Departments of Physical Medicine and Rehabilitation and of Physiology, Northwestern University Feinberg School of MedicineChicago, IL, USA
- Sensory Motor Performance Program, The Rehabilitation Institute of ChicagoChicago, IL, USA
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