Biology subjects

Reed, M. L.

Publications and source records attributed to Reed, M. L..

6 recordsLinked to original sources

bioRxiv2026

Expression and Engineering of Conductive Cytochrome Nanowires

Electrically conductive protein nanowires produced by metal-reducing bacteria have attracted interest as sustainable electronic materials, but their study and engineering have been limited by difficulties in expression, purification, and genetic manipulation. Here we establish Shewanella oneidensis as a heterologous host for production of Geobacter sulfurreducens OmcZ nanowires and progress a complementary in vitro assembly strategy that yields highly pure nanowire preparations. This platform enabled systematic engineering of OmcZ, revealing extensive tolerance to sequence variation and faciliating the design of enhanced-conductivity variants. Guided by comparative analysis of environmental OmcZ homologs, we generated a chimeric nanowire, OmcZ+, that exhibited a [~]3.5-fold increase in bulk conductivity while retaining the overall structure of the parent nanowire. Cryo-electron microscopy revealed unexpected architectural plasticity in OmcZ+ wires, including non-linear dendritic and pentameric assemblies mediated by the solvent-exposed heme VII, suggesting previously unrecognized modes of cytochrome nanowire organization. Incorporation of engineered OmcZ variants into water evaporation-induced electricity generators produced power densities up to [~]25.3 W cm-{superscript 2} and enabled high-performance operation in saline environments, including seawater and human sweat. Together, these results establish a versatile platform for the production, structural analysis, and engineering of cytochrome nanowires, providing a foundation for the development of programmable biological electronic materials.

bioengineering↗

bioRxiv2026

Single-cell chromatin profiling reveals dynamic regulatory logic and enhancer elements in brain and retina development

Cell type identity in the nervous system is encoded within cis-regulatory landscapes that integrate transcription factor activity with chromatin accessibility. However, how these regulatory programs are organized and remodeled during post-embryonic neural development is poorly understood. We generate a temporally resolved single-cell chromatin accessibility atlas of [~]95,000 zebrafish brain and retina nuclei spanning larval, juvenile, and adult stages. We define 212 discrete chromatin states and uncover widespread, cell type-specific chromatin reorganization across development. By integrating with transcriptomic data, we link motif accessibility to transcription factor expression and identify regulatory programs that are either maintained or reconfigured during post-embryonic development of each neural cell type. Leveraging this atlas, we systematically identify and functionally validate candidate enhancers in vivo. Focusing on the slc1a3b locus in radial glia, we define evolutionarily conserved, compact enhancer modules that act combinatorially to drive gene expression. Together, these findings provide a systems-level framework for decoding neural regulatory logic and enable functional dissection of conserved cis-regulatory programs in the vertebrate nervous system.

developmental biology↗

bioRxiv2023

Rolling the evolutionary dice: Neisseria commensals as proxies for elucidating the underpinnings of antibiotic resistance mechanisms and evolution in human pathogens

Species within the genus Neisseria are especially adept at sharing adaptive allelic variation across species boundaries, with commensal species repeatedly transferring resistance to their pathogenic relative N. gonorrhoeae. However, resistance in commensal Neisseria is infrequently characterized at both the phenotypic and genotypic levels, limiting our ability to predict novel and potentially transferable resistance mechanisms that ultimately may become important clinically. Unique evolutionary starting places of each Neisseria species will have distinct genomic backgrounds, which may ultimately control the fate of evolving populations in response to selection, as epistatic and additive interactions may coerce lineages along divergent evolutionary trajectories. However alternatively, similar genetic content present across species due to shared ancestry may constrain the adaptive solutions that exist. Thus, identifying the paths to resistance across commensals may aid in characterizing the Neisseria resistome - or the reservoir of alleles within the genus, as well as its depth. Here, we use in vitro evolution of four commensal species to investigate the potential for and repeatability of resistance evolution to two antimicrobials, the macrolide azithromycin and the {beta}-lactam penicillin. After 20 days of selection, commensals evolved elevated minimum inhibitory concentrations (MICs) to penicillin and azithromycin in 11/16 and 12/16 cases respectively. Almost all cases of resistance emergence converged on mutations within ribosomal components or the mtrRCDE efflux pump for azithromycin-based selection, and mtrRCDE or penA for penicillin selection; thus, supporting constrained adaptive solutions despite divergent evolutionary starting points across the genus for these particular drugs. However, continuing to explore the paths to resistance across different experimental conditions and genomic backgrounds, which could shunt evolution down alternative evolutionary trajectories, will ultimately flesh out the full Neisseria resistome.

microbiology↗

bioRxiv2023

ATOMDANCE: interpretable kernel-based learning for denoising functional and evolutionary comparisons of protein dynamics

Comparative methods in molecular biology and molecular evolution rely exclusively upon the analysis of DNA sequence and protein structure, both static forms of information. However, it is widely accepted that protein function results from changes in dynamic machine-like motions induced by molecular interactions, a type of data for which comparative methods of analysis are challenged by the large fraction of protein motion created by random thermal noise in the surrounding solvent. Here, we introduce ATOMDANCE, a suite of statistical and kernel-based machine learning tools designed for comparing and denoising functional states of protein motion captured in time-series from molecular dynamics simulations. ATOMDANCE employs interpretable Gaussian kernel functions to compute site-wise maximum mean discrepancy (MMD) between learned features of motion representing two functional, malfunctional or evolutionary protein states (e.g. bound vs. unbound, wild-type vs. mutant). ATOMDANCE derives empirical p-values identifying functional similarity/difference in dynamics at each amino acid site on the protein. ATOMDANCE also employs MMD to contextually analyze potential random amino-acid replacements thus allowing for a site-wise test of neutral vs. non-neutral evolution in the divergence of dynamic function in protein homologs. Lastly, ATOMDANCE also employs mixed-model ANOVA combined with graph network community detection to identify functional shifts in protein regions that exhibit time-coordinated dynamics or resonance of motion across sites. Here, we demonstrate the utility of the software for identifying key sites involved in dynamic responses during functional binding interactions involving DNA, small molecule drugs, and virus-host recognition. We also demonstrate its utility in understanding dynamic resonance changes occurring during the allosteric activation of a pathogenic protease. ATOMDANCE offers a user-friendly interface and only requires an input structure, topology and trajectory files for each of the two proteins being compared (i.e .pdb, .prmtop, and .nc). A separate interface for generating molecular dynamics simulations via open-source tools is also offered. Lay Audience Summary - ATOMDANCE is a suite of software pipelines controlled by a single user interface and designed to comprehensively simulate, calculate and compare protein motions between two functional or evolutionary states while controlling for random noise. It is useful for finding amino acid sites on a given protein that are important in binding other proteins, DNA, or drugs/toxins. It can also be used to assess the effect of genetic mutation on protein motion, and identifies regions of sites on proteins that tend to move together or resonate as a whole unit or community.

biophysics↗

bioRxiv2022

Local translation provides the asymmetric distribution of CaMKII required for associative memory formation

How compartment-specific local proteomes are generated and maintained is inadequately understood, particularly in neurons, which display extreme asymmetries. Here we show that local enrichment of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in axons of Drosophila mushroom body neurons is necessary for cellular plasticity and associative memory formation. Enrichment is achieved via enhanced axoplasmic translation of CaMKII mRNA, through a mechanism requiring the RNA-binding protein Mub and a 23-base Mub-recognition element in the CaMKII 3UTR. Perturbation of either dramatically reduces axonal, but not somatic, CaMKII protein without altering the distribution or amount of mRNA in vivo and both are necessary and sufficient to enhance axonal translation of reporter mRNA. Together, these data identify elevated levels of translation of an evenly distributed mRNA as a novel strategy for generating subcellular biochemical asymmetries. They further demonstrate the importance of distributional asymmetry in the computational and biological functions of neurons.

neuroscience↗

bioRxiv2022

Pairing-dependent plasticity in a dissected fly brain is input-specific and requires synaptic CaMKII enrichment and nighttime sleep

In Drosophila, in vivo functional imaging studies revealed that associative memory formation is coupled to a cascade of neural plasticity events in distinct compartments of the mushroom body (MB). In-depth investigation of the circuit dynamics, however, will require an ex vivo model that faithfully mirrors these events to allow direct manipulations of circuit elements that are inaccessible in the intact fly. The current ex vivo models have been able to reproduce the fundamental plasticity of aversive short-term memory, a potentiation of the MB intrinsic neurons (Kenyon cells; KCs) responses after artificial learning ex vivo. However, this potentiation showed different localization and encoding properties from those reported in vivo and failed to generate the previously reported suppression plasticity in the mushroom body output neurons (MBONs). Here, we develop an ex vivo model using the female Drosophila brain that recapitulates behaviorally evoked plasticity in the KCs and MBONs. We demonstrate that this plasticity accurately localizes to the MB 3 compartment and is encoded by a coincidence between KCs activation and dopaminergic input. The formed plasticity is input-specific, requiring pairing of the conditioned stimulus (CS) and unconditioned stimulus (US) pathways; hence we name it pairing-dependent plasticity (PDP). PDP formation requires an intact CaMKII gene and is blocked by previous-night sleep deprivation but is rescued by rebound sleep. In conclusion, we show that our ex vivo preparation recapitulates behavioral and imaging results from intact animals and can provide new insights into mechanisms of memory formation at the level of molecules, circuits, and brain state. Significance StatementThe mammalian ex vivo LTP model enabled in-depth investigation of the hippocampal memory circuit. We develop a parallel model to study the Drosophila mushroom body (MB) memory circuit. Pairing activation of the conditioned stimulus and unconditioned stimulus pathways in dissected brains induces a potentiation pairing-dependent plasticity (PDP) in the axons of {beta} Kenyon cells and a suppression PDP in the dendrites of their postsynaptic MB output neurons, localized in the MB 3 compartment. This PDP is input-specific and requires the 3 untranslated region of CaMKII. Interestingly, ex vivo PDP carries information about the animals experience before dissection; brains from sleep deprived animals fail to form PDP while those from animals who recovered 2 hours of their lost sleep form PDP.

neuroscience↗