Biology subjects

McMahon, G.

Publications and source records attributed to McMahon, G..

7 recordsLinked to original sources

bioRxiv2025

4D mitochondrial network assumes distinct and predictive phenotypes through human lung and intestinal epithelial development

Mitochondria form a dynamic three-dimensional network within the cell that exhibits a wide range of morphologies and behaviors. Depending on cell state, cell type, and cell fate, a cells mitochondrial phenotype might range from relatively isolated mitochondrial segments to complex branching networks, and from stationary mitochondria to highly motile structures. While isolated mitochondrial phenotypes have been described for a subset of cell states, types, and fates, an integrated map of how mitochondrial phenotypes change over the full course of tissue development has so far been lacking. Here, we identify the mitochondrial phenotypes that appear throughout the course of lung and intestinal epithelial development from stem cells to differentiated tissue. Using human stem cell-derived intestinal and branching lung organoids that mimic developing human organs as model systems, we extract and analyze key mitochondrial biophysical phenotypes in human development. To achieve this, we employ lattice light-sheet microscopy (LLSM), which enables high-resolution, 4D (x, y, z, time) imaging of mitochondria in organoid tissues with minimal damage to the sample. We image at key developmental time points from stem cell differentiation into mature organoid tissue. For data processing, we utilize the MitoGraph and MitoTNT software packages along with our developed custom computational tools. These tools allow for automated 4D organoid to single cell image processing and quantitative 4D single cell mitochondrial temporal network tracking. This work represents the first 4D high spatiotemporal-resolution quantification of live human organoid tissues at the single-cell level through development. We identified distinct mitochondrial phenotypes unique to each organoid type and found correlations between mitochondrial phenotypes, cellular age, and cell type. Furthermore, we demonstrate that mitochondrial network characteristics can predict both organoid type and cell age. Our findings reveal fundamental aspects of mitochondrial biology that were previously unobservable, offering new insights into cell-type-specific mitochondrial dynamics and enabling new findings in relevant human model systems. We believe that our findings and methods will be essential for advancing 4D cell biology, providing a powerful framework for characterizing organelles in organoid tissues.

cell biology↗

bioRxiv2024

Engineered Nanotopographies Induce Transient Openings in the Nuclear Membrane

Materials with engineered nano-scale surface topographies, such as nanopillars, nanoneedles, and nanowires, mimic natural structures like viral spike proteins, enabling them to bypass biological barriers like the plasma membrane. These properties have led to applications in nanoelectronics for intracellular sensing and drug delivery platforms, some of which are already in clinical trials. Here, we present evidence that nanotopographic materials can induce transient openings in the nuclear membranes of various cell types without penetrating the cells, breaching the nucleo-cytoplasmic barrier and allowing uncontrolled molecular exchange across the nuclear membrane. These openings, induced by nanoscale curvature, are temporary and repaired through ESCRT-mediated mechanisms. Our findings suggest a potential for nano topographic materials for direct nuclear sensing and delivery, holding promise for improving the delivery, efficiency, and safety of therapeutic agents to the nucleus.

bioengineering↗

bioRxiv2024

LiveLattice: Real-time visualization of tilted light-sheet microscopy data using a memory-efficient transformation algorithm

Light-sheet fluorescence microscopy (LSFM), a prominent fluorescence microscopy technique, offers enhanced temporal resolution for imaging biological samples in four dimensions (4D; x, y, z, time). Some of the most recent implementations, including inverted selective plane illumination microscopy (iSPIM) and lattice light-sheet microscopy (LLSM), rely on a tilting of the sample plane with respect to the light sheet of 30-45 degrees to ease sample preparation. Data from such tilted-sample-plane LSFMs require subsequent deskewing and rotation for proper visualization and analysis. Such transformations currently demand substantial memory allocation. This poses computational challenges, especially with large datasets. The consequence is long processing times compared to data acquisition times, which currently limits the ability for live-viewing the data as it is being captured by the microscope. To enable the fast preprocessing of large light-sheet microscopy datasets without significant hardware demand, we have developed WH-Transform, a novel GPU-accelerated memory-efficient algorithm that integrates deskewing and rotation into a single transformation, significantly reducing memory requirements and reducing the preprocessing run time by at least 10-fold for large image stacks. Benchmarked against conventional methods and existing software, our approach demonstrates linear scalability. Processing large 3D stacks of up to 15 GB is now possible within one minute using a single GPU with 24 GB of memory. Applied to 4D LLSM datasets of human hepatocytes, human lung organoid tissue, and human brain organoid tissue, our method outperforms alternatives, providing rapid, accurate preprocessing within seconds. Importantly, such processing speeds now allow visualization of the raw microscope data stream in real time, significantly improving the usability of LLSM in biology. In summary, this advancement holds transformative potential for light-sheet microscopy, enabling real-time, on-the-fly data processing, visualization, and analysis on standard workstations, thereby revolutionizing biological imaging applications for LLSM, SPIM and similar light microscopes.

cell biology↗

bioRxiv2024

Subcellular visualization of the distribution of atmospheric dinitrogen fixed by Gluconacetobacter diazotrophicus bacteria in maize

Plants normally obtain the nitrogen required for growth through their roots, often after application of synthetic fertilizer to the soil, at great cost to the environment and climate. Inoculation of plant seeds with nitrogen-fixing bacteria is a promising alternative means of supplying plants the nitrogen they require in an environmentally friendly manner. When maize seeds inoculated with nitrogen-fixing Gluconacetobacter diazotrophicus (Gd) are grown for two weeks in a 15N2 air environment, nanoscale secondary ion mass spectrometry (NanoSIMS) imaging shows the distribution of fixed nitrogen with subcellular resolution, with the majority being incorporated heterogeneously into chloroplasts. Chloroplasts, as the chief energy source that drives plant growth via photosynthesis, are vital for healthy plant growth and these results help explain the observations of enhanced growth rates in plants containing this nitrogen fixing bacteria. The methodology provides a template upon which more powerful, correlative studies combining genomic and/or spatial transcriptomic methods may be based.

plant biology↗

bioRxiv2024

Variation in drug penetration does not account for the natural resistance of Mycobacterium abscessus biofilms to antibiotic

Mycobacterium abscessus, an inherently drug-resistant, opportunistic, nontuberculous mycobacterium (NTM) predominantly causes pulmonary infections in immunocompromised patients, notably those with cystic fibrosis. M. abscessus subspecies display distinct colony morphologies (rough and smooth), with the prevalent view that M. abscessus (smooth) is a persistent, biofilm-forming phenotype, whilst M. abscessus (rough) is unable to form biofilms. Biofilm formation contributes to persistent infections and exhibits increased antibiotic resistance. We used the chemical mapping technique, nanoscale secondary ion spectrometry (NanoSIMS), to investigate if variations in the biofilm morphology and antibiotic penetration account for the antibiotic susceptibility amongst M. abscessus subspecies, contributing to increased antimicrobial resistance (AMR) and potentially explaining the protracted treatment duration. The susceptibility to bedaquiline (BDQ) of M. abscessus grown as planktonic bacilli and biofilms was measured. The minimum biofilm eradication concentration (MBEC) of BDQ was 8-16 times higher (2-4{micro}g/ml) compared with the minimum inhibitory concentration (MIC) (0.25{micro}g/ml), indicating reduced efficacy against biofilms. Correlative imaging with electron microscopy revealed that M. abscessus (irrespective of the colony morphotype) formed biofilms and that BDQ treatment influenced biofilm morphology. We determined that M. abscessus morphotypes exhibit differential uptake of the antibiotic BDQ in biofilms. M. abscessus subsp. abscessus (smooth) biofilms exhibited the least uptake of BDQ, whereas M. abscessus subsp. bolletii biofilms showed the greatest antibiotic penetration. NanoSIMS analysis revealed no correlation between antibiotic penetration and drug efficacy within the biofilm. This challenges the previous assumption linking biofilm architecture to drug efficacy. Investigating other biofilm characteristics like antibiotic persistence could lead to enhanced treatment approaches. Significance StatementMycobacterium abscessus is an increasingly prevalent pathogen, most often causing lung infections in immunocompromised individuals. Their distinct morphotypes and biofilm-forming capabilities contribute to persistent infections, rendering them challenging to treat with increased antibiotic resistance. This research demonstrates that the antibiotic, bedaquiline exhibits significantly reduced efficacy against M. abscessus growing as a biofilm compared to planktonic growth, but that the efficiency of antibiotic penetration was not the main explanation for the different susceptibilities of MABC biofilms to treatment.

microbiology↗

bioRxiv2023

The first complete genome of the extinct European wild ass (Equus hemionus hydruntinus)

We present paleogenomes of three morphologically-unidentified Anatolian equids dating to the 1st millennium BCE, sequenced to coverages of 0.6-6.4X. Mitochondrial DNA haplotypes of the Anatolian individuals clustered with those of Equus hydruntinus (or Equus hemionus hydruntinus), the extinct European wild ass. The Anatolian wild ass whole genome profiles fall outside the genomic diversity of other extant and past Asiatic wild ass (E.hemionus) lineages. These observations strongly suggest that the three Anatolian wild asses represent E.hydruntinus, making them the latest recorded survivors of this lineage, about a millennium later than the latest observations in the zooarchaeological record. Comparative genomic analyses suggest that E.hydruntinus was a sister clade to all ancient and present-day E.hemionus lineages, representing an early split. We also find indication of gene flow between hydruntines and Middle Eastern wild asses. Analyses of genome-wide heterozygosity and runs of homozygosity reveal that the Anatolian wild ass population had severely lost genetic diversity by the mid-1st millennium BCE, a likely omen of its eventual demise.

genomics↗

bioRxiv2018

Genomic analysis of diet composition finds novel loci and associations with health and lifestyle

We conducted genome-wide association study (GWAS) meta-analyses of relative caloric intake from fat, protein, carbohydrates and sugar in over 235,000 individuals. We identified 21 approximately independent lead SNPs. Relative protein intake exhibits the strongest relationships with poor health, including positive genetic associations with obesity, type 2 diabetes, and heart disease (rg {approx} 0.15 - 0.5). Relative carbohydrate and sugar intake have negative genetic correlations with waist circumference, waist-hip ratio, and neighborhood poverty (|rg| {approx} 0.1 - 0.3). Overall, our results show that the relative intake of each macronutrient has a distinct genetic architecture and pattern of genetic correlations suggestive of health implications beyond caloric content.

genetics↗