Biology subjects

Morton, K.

Publications and source records attributed to Morton, K..

7 recordsLinked to original sources

bioRxiv2025

Specialized high-capacity mitochondria fuel cell invasion

Cell invasion through basement membrane (BM) is energetically intensive, and how an invading cell produces high ATP levels to power invasion is understudied. By generating 20 endogenously tagged mitochondrial proteins, we identified a specialized mitochondrial subpopulation within the C. elegans anchor cell (AC) that localizes to the BM breaching site and generates elevated ATP to fuel invasion. These ETC-enriched high-capacity mitochondria are compositionally unique, harboring increased protein import machinery and dense cristae enriched with ETC components. High-capacity mitochondria emerge at the time of AC specification and depend on the AC pro-invasive transcriptional program. Finally, we show that netrin signaling through a Src kinase directs microtubule polarization, which facilitates metaxin adaptor complex dependent ETC-enriched mitochondrial trafficking to the AC invasive front. Our studies reveal that an invasive cell produces high ATP by generating and localizing high-capacity mitochondria. This might be common strategy used by other cells to meet energy demanding processes.

cell biology↗

bioRxiv2025

Mitophagy at the oocyte-to-zygote transition promotes species immortality

The quality of inherited mitochondria determines embryonic viability1, metabolic health during adulthood and future generation endurance. The oocyte is the source of all zygotic mitochondria2, and mitochondrial health is under strict developmental regulation during early oogenesis3-5. Yet, fully developed oocytes exhibit the presence of deleterious mitochondrial DNA (mtDNA)6,7 and mitochondrial dysfunction from high levels of endogenous reactive oxygen species8 and exogenous toxicants9. How fully developed oocytes prevent transmission of damaged mitochondria to the zygotes is unknown. Here we discover that the onset of oocyte-to-zygote transition (OZT) developmentally triggers a robust and rapid mitophagy event that we term mitophagy at OZT (MOZT). We show that MOZT requires mitochondrial fragmentation, activation of the macroautophagy system and the mitophagy receptor FUNDC1, but not the prevalent mitophagy factors PINK1 and BNIP3. Oocytes upregulate expression of FUNDC1 in response to diverse mitochondrial insults, including mtDNA mutations and damage, uncoupling stress, and mitochondrial dysfunction, thereby promoting selection against damaged mitochondria. Loss of MOZT leads to increased inheritance of deleterious mtDNA and impaired bioenergetic health in the progeny, resulting in diminished embryonic viability and the extinction of descendent populations. Our findings reveal FUNDC1-mediated MOZT as a mechanism that preserves mitochondrial health during the mother-to-offspring transmission and promotes species continuity. These results may explain how mature oocytes from many species harboring mutant mtDNA give rise to healthy embryos with reduced deleterious mtDNA.

cell biology↗

bioRxiv2024

Acute nicotine vapor normalizes sensorimotor gating and reduces locomotor activity deficits in HIV-1 transgenic rats

RationaleDespite improved life expectancy of people with HIV (PWH), HIV-associated neurocognitive impairment (NCI) persists, alongside deficits in sensorimotor gating and neuroinflammation. PWH exhibit high smoking rates, possibly due to neuroprotective, anti-inflammatory, and cognitive-enhancing effects of nicotine, suggesting potential self-medication. ObjectivesHere, we tested the effects of acute nicotine vapor exposure on translatable measures of sensorimotor gating and exploratory behavior in the HIV-1 transgenic (HIV-1Tg) rat model of HIV. MethodsMale and female HIV-1Tg and F344 control rats (n=57) were exposed to acute nicotine or vehicle vapor. Sensorimotor gating was assessed using prepulse inhibition (PPI) of the acoustic startle response, and exploratory behavior was evaluated using the behavioral pattern monitor (BPM). ResultsVehicle-treated HIV-1Tg rats exhibited PPI deficits at low prepulse intensities compared to F344 controls, as seen previously. No PPI deficits were observed in nicotine-treated HIV-1Tg rats, however. HIV-1Tg rats were hypoactive in the BPM relative to controls, whilst nicotine vapor increased activity and exploratory behavior across genotypes. Cotinine analyses confirmed comparable levels of the primary metabolite of nicotine across genotypes. ConclusionsPrevious findings of PPI deficits in HIV-1Tg rats were replicated and, importantly, attenuated by acute nicotine vapor. Evidence for similar cotinine levels suggest a nicotine-specific effect in HIV-1Tg rats. HIV-1Tg rats had reduced exploratory behavior compared to controls, attenuated by acute nicotine vapor. Therefore, acute nicotine may be beneficial for remediating sensorimotor and locomotor activity deficits in PWH. Future studies should determine the long-term effects of nicotine vapor on similar HIV/NCI-relevant behaviors.

neuroscience↗

bioRxiv2024

Biomimetic fractal topography enhances podocyte maturation in vitro

Cells and tissues in their native environment are organized into intricate fractal structures, which are rarely recapitulated in their culture in vitro. The extent to which fractal patterns that resemble complex topography in vivo influence cell maturation, and the cellular responses to such shape stimulation remain inadequately elucidated. Yet, the application of fractal cues (topographical stimulation via self-similar patterns) as an external input may offer a much-needed solution to the challenge of improving the differentiated cell phenotype in vitro. Here, we established fractality in podocytes, branching highly differentiated kidney cells, and glomerulus structure. Biomimetic fractal patterns derived from glomerular histology were used to generate topographical (2.5-D) substrates for cell culture. Podocytes grown on fractal topography were found to express higher levels of functional markers and exhibit enhanced cell polarity. To track morphological complexities of differentiated podocytes, we employed a fluorescent labelling assay where labelled individual cells are tracked within otherwise optically silent confluent cell monolayer to reveal cell-cell interdigitation. RNAseq analysis suggests enhanced ECM deposition and remodeling in podocytes grown on fractal topography compared to flat surface or non-fractal microcurvature, mediated by YAP signaling. The incorporation of fractal topography into standard tissue culture well plates as demonstrated here may serve as a user-friendly bioengineered platform for high-fidelity cell culture.

bioengineering↗

bioRxiv2023

The effect of common paralytic agents used for fluorescence imaging on redox tone and ATP levels in Caenorhabditis elegans

One aspect of Caenorhabditis elegans that makes it a highly valuable model organism is the ease of use of in vivo genetic reporters, facilitated by its transparent cuticle and highly tractable genetics. Despite the rapid advancement of these technologies, worms must be paralyzed for most imaging applications, and few investigations have characterized the impacts of common chemical anesthetic methods on the parameters measured, in particular biochemical measurements such as cellular energetics and redox tone. Using two dynamic reporters, QUEEN-2m for relative ATP levels and reduction-oxidation sensitive GFP (roGFP) for redox tone, we assess the impact of commonly used chemical paralytics. We report that no chemical anesthetic is entirely effective at doses required for full paralysis without altering redox tone or ATP levels, though 100 mM 2,3-Butadione monoxime appears to be the least problematic. We also assess the use of cold shock, commonly used in combination with physical restraint methods, and find that cold shock does not alter either ATP levels or redox tone. In addition to informing which paralytics are most appropriate for research in these topics, we highlight the need for tailoring the use of anesthetics to different endpoints and experimental questions. Further, we reinforce the need for developing less disruptive paralytic methods for optimal imaging of dynamic in vivo reporters.

pharmacology and toxicology↗

bioRxiv2023

An unbiased, automated platform for scoring dopaminergic neurodegeneration in C. elegans

Caenorhabditis elegans (C. elegans) has served as a simple model organism to study dopaminergic neurodegeneration, as it enables quantitative analysis of cellular and sub-cellular morphologies in live animals. These isogenic nematodes have a rapid life cycle and transparent body, making high-throughput imaging and evaluation of fluorescently tagged neurons possible. However, the current state-of-the-art method for quantifying dopaminergic degeneration requires researchers to manually examine images and score dendrites into groups of varying levels of neurodegeneration severity, which is time consuming, subject to bias, and limited in data sensitivity. We aim to overcome the pitfalls of manual neuron scoring by developing an automated, unbiased image processing algorithm to quantify dopaminergic neurodegeneration in C. elegans. The algorithm can be used on images acquired with different microscopy setups and only requires two inputs: a maximum projection image of the four cephalic neurons in the C. elegans head and the pixel size of the users camera. We validate the platform by detecting and quantifying neurodegeneration in nematodes exposed to rotenone, cold shock, and 6-hydroxydopamine using 63x epifluorescence, 63x confocal, and 40x epifluorescence microscopy, respectively. Analysis of tubby mutant worms with altered fat storage showed that, contrary to our hypothesis, increased adiposity did not sensitize to stressor-induced neurodegeneration. We further verify the accuracy of the algorithm by comparing code-generated, categorical degeneration results with manually scored dendrites of the same experiments. The platform, which detects 19 different metrics of neurodegeneration, can provide comparative insight into how each exposure affects dopaminergic neurodegeneration patterns.

bioengineering↗

bioRxiv2022

On the origin and evolution of the mosquito male-determining factor Nix

The mosquito family Culicidae is divided into two subfamilies named the Culicinae and Anophelinae. Nix, the dominant male-determining factor, has only been found in the culicines Aedes aegypti and Ae. albopictus, two important arboviral vectors that belong to the subgenus Stegomyia. Here we performed sex-specific whole-genome sequencing and RNAseq of divergent mosquito species and explored additional male-inclusive datasets to investigate the distribution of Nix. Except for the Culex genus, Nix homologs were found in all species surveyed from the Culicinae subfamily, including 12 additional species from three highly divergent tribes comprising 4 genera, suggesting Nix originated at least 133-165 MYA. Heterologous expression of one of three divergent Nix ORFs in Ae. aegypti resulted in partial masculinization of genetic females as evidenced by morphology and doublesex splicing. It is not clear whether insufficient transgene expression or sequence divergence or both are responsible for the lack of phenotype for the other two. Phylogenetic analysis suggests Nix is related to femaleless (fle), a recently described intermediate sex-determining factor found exclusively in anopheline mosquitoes. Nix from all species has a conserved structure, including three RNA-recognition motifs (RRMs), as does fle. However, Nix has evolved at a much faster rate than fle. The RRM3 of both Nix and fle are related to the single RRM of a widely distributed and conserved splicing factor transformer-2 (tra2). RRM3-based phylogenetic analysis suggests this domain in Nix and fle may have evolved from tra2 in a common ancestor of mosquitoes. Our results provide insights into the evolution of sex-determination and homomorphic sex chromosomes in mosquitoes, and will inform broad applications of mosquito-control strategies based on manipulating sex ratios towards the non-biting males.

evolutionary biology↗