Biology subjects

Scott, M.

Publications and source records attributed to Scott, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Particle size determines mucociliary transport mechanisms in normal and cystic fibrosis airways

A wide spectrum of microparticles is inhaled with each breath, deposited on airway surfaces, entrapped in the mucus, and removed by mucociliary transport (MCT). However, the influence of particle size on MCT remains largely unknown. Here, we investigated the MCT of microparticles with a trachea-on-a-chip method that integrates a micro-machined device with a trachea explant from newborn pigs. This method preserves airway structures for mucus secretion and cilia beating (e.g., airway surface epithelia and submucosal glands), maintains physiological air-liquid-interface on the airway surface, and allows tracks motion of microparticles with high resolution. Using this method, we found that, in normal airways, 6 {micro}m polystyrene particles clear rapidly, whereas 102 {micro}m particles clear slower and require mucus strands for motion. In cystic fibrosis (CF) airways, MCT of microparticles reduces, but particle size-dependence persists. Methacholine increases particle motion in normal airways, but not in CF airways. These findings suggest two distinct MCT processes, in which large particles rely on mucus strands for clearance, small particles can be cleared independent of mucus strands, and CF disrupts both. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/735890v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@3e3026org.highwire.dtl.DTLVardef@cb11fdorg.highwire.dtl.DTLVardef@a28a3org.highwire.dtl.DTLVardef@f1f1a9_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

bioengineering↗

bioRxiv2025

Measuring partner synchrony during salsa dancing and its relationship to changes in psychosocial domains

BackgroundDance is a promising rehabilitation adjunct but understanding the mechanisms through which dance improves physical and psychosocial well-being is necessary for implementation. This study investigated the feasibility of a measure of one possible mechanism: partner synchrony. Secondary objectives were to examine the relationships between partner synchrony, instructor ratings, and changes in psychosocial variables. MethodsParticipants wore an Inertial Measurement Unit (IMU) sensor during a salsa class that was video recorded. Partner synchrony was quantified with correlations of x, y, and z-axis acceleration between dancing pairs. Psychosocial variables were measured pre- and post-class. Salsa instructors rated partner synchrony from video recordings. Feasibility parameters included percentage of participants with data collected and sensor comfort. Pre-post changes were analyzed with Wilcoxon ranked tests and relationships were analyzed with Spearman correlations. ResultsData was collected for 23/24 (96%) participants and 17/24 (81%) reported the sensor was comfortable. All psychosocial variables improved from pre- to post-class. Partner synchrony was significantly associated with instructor ratings and change in positive and negative affect. ConclusionsAn IMU-based measure of dance partner synchrony is feasible, associated with ratings by dance instructors and related to changes in mood. The partner synchrony measure can be used to advance our understanding of dance as a therapeutic tool after its reliability is investigated.

neuroscience↗

bioRxiv2025

A mouse model of PTEN Hamartoma Tumour Syndrome reveals that loss of the nuclear function of PTEN drives macrocephaly, lymphoid overgrowth, and late-onset cancer

PTEN Hamartoma Tumour Syndrome (PHTS) is a rare disorder characterized by germline heterozygous mutations in the PTEN tumour suppressor gene, leading to multi-organ/tissue overgrowth, autism spectrum disorder and increased cancer risk. PHTS individuals display heterogeneity in phenotypes, which has been linked in part to the diverse genetic alterations in the PTEN gene and the multifaceted functions of this protein. Indeed, while PTEN primarily functions as a PIP3 lipid phosphatase in the cytosol, regulating PI3K/AKT signalling, a pathway commonly deregulated in cancer, it also plays crucial roles in maintaining chromosomal stability through nuclear activities such as double strand (ds) DNA damage repair. Recent studies have identified a subset of missense PHTS variants that cause nuclear exclusion of PTEN, impairing its nuclear functions. Here, we present our findings from one such pathogenic variant, PTEN-R173C, frequently found in PHTS and somatic cancers. Using cell biological and mouse modelling approaches, we show that PTEN-R173C has higher PIP3 phosphatase activity than wild-type PTEN, resulting in effective regulation of canonical PI3K/AKT signalling. However, PTEN-R173C is unstable and excluded from the nucleus. Aligning with their near normal PI3K/AKT signalling, Pten+/R173Cmice display a low incidence of solid tumours compared to Pten+/-mice. Pten+/R173C mice also exhibit lymphoid hyperplasia and macrocephaly which correlates with compromised nuclear functions of PTEN-R173C. That nuclear functions are compromised is demonstrated by reduced dsDNA damage repair in Pten+/R173Cmice. Integrating PHTS patient data with findings from our mouse model, our study indicates that nuclear dysfunction of pathogenic PTEN variants is a key factor in predicting the onset of the different PHTS-associated phenotypes. We speculate that late-onset cancer in individuals with nuclear-excluded PTEN results from genetic alterations unrelated to PTEN itself, facilitated by impaired PTEN-mediated dsDNA damage repair.

genetics↗

bioRxiv2024

Morning Engagement of Hepatic Insulin Receptors Improves Afternoon Hepatic Glucose Disposal and Storage

Glucose tolerance improves significantly upon consuming a second, identical meal later in the day (second meal phenomenon). We previously established that morning hyperinsulinemia primes the liver for increased afternoon hepatic glucose uptake (HGU). Although the route of insulin delivery is an important determinant of the mechanisms by which insulin regulates liver glucose metabolism (direct hepatic vs indirect insulin action), it is not known if insulins delivery route affects the second meal response. To determine whether morning peripheral insulin delivery (as occurs clinically (subcutaneous)) can enhance afternoon HGU, conscious dogs were treated in the morning with insulin delivered via the portal vein, or peripherally (leg vein), while glucose was infused to maintain euglycemia. Consequently, arterial insulin levels increased similarly in both groups, but relative hepatic insulin deficiency occurred when insulin was delivered peripherally. In the afternoon, all animals were challenged with the same hyperinsulinemic-hyperglycemic clamp to simulate identical postprandial-like conditions. The substantial enhancement of HGU in the afternoon caused by morning portal vein insulin delivery was lost when insulin was delivered peripherally. This indicates that morning insulin does not cause the second meal phenomenon via its indirect actions on the liver, but rather through direct activation of hepatic insulin signaling. Article HighlightsO_LIMorning insulin delivery primes the liver for increased hepatic glucose uptake (HGU) later in the day, but the mechanism (direct hepatic and/or indirect insulin action) remains unclear. C_LIO_LIThis study compared insulin infusion via physiologic (hepatic portal vein) and clinical (peripheral) routes to assess their impact on afternoon hepatic glucose disposal. C_LIO_LIMorning peripheral insulin delivery failed to induce a significant enhancing effect on afternoon HGU and glycogen storage, unlike morning hepatic portal vein insulin delivery, which did. C_LIO_LIThese findings highlight the importance of achieving appropriate hepatic insulin exposure in the morning to effectively prime the liver for efficient glucose disposal. C_LI

physiology↗

bioRxiv2024

Exercise Evokes Retained Motor Performance without Neuroprotection in a Mouse Model of Parkinson's Disease

Exercise has been extensively studied in Parkinsons Disease, with a particular focus on the potential for neuroprotection that has been demonstrated in animal models. While this preclinical work has provided insight into the underlying molecular mechanisms, it has not addressed the neurophysiological changes during exercise. Here, first, we tested for neuroprotective effects of adaptive wheel running exercise in the 6-hydroxydopamine mouse model of Parkinsons disease, assessing for dopaminergic cell preservation. Finding none, despite running performance that equaled the pre-parkinsonian state, we probed the neurophysiology of running exercise as a transient state of high motor function amidst an unameliorated Parkinsonian lesion. Exercise was associated with characteristic, excitatory changes in the dopamine-depleted substantia nigra, which could be suppressed along with running itself by dopamine receptor blockade. Going forward, the functional state evoked by exercise merits further study, as it has parallels in human disease and may represent an optimal physiologic target for neuromodulation.

neuroscience↗

bioRxiv2024

Human melanoma cell lines that possess wild-type BRAF alleles but are dependent on ERBB4 and ERBB2

Metastatic skin cutaneous melanomas that contain wild-type BRAF alleles typically possess an activating mutation in a RAS allele or a loss-of-function mutation in an NF1 allele ("BRAF-WT&RAS/NF1-mutant melanomas"). Nonetheless, these tumors remain a significant clinical challenge; they are resistant to MEK and BRAF inhibitors, their response to immune checkpoint inhibitors is less robust than the response of BRAF mutant melanomas to these agents, and additional validated targets for therapeutic intervention have yet to be identified. Previous work from our laboratory has demonstrated that ERBB4 is required for the proliferation of the IPC-298, MEL-JUSO, MeWo, and SK-MEL-2 BRAF-WT&RAS/NF1-mutant melanoma cell lines. Surprisingly, the synthetic constitutively dimerized and active Q646C ERBB4 mutant allele appears to strongly inhibits the proliferation of BRAF-WT&RAS/NF1- mutant melanoma cell lines. Given that we have also previously demonstrated that ERBB4-ERBB2 and ERBB4-EGFR heterodimers are more potent drivers of proliferation than are ERBB4 homodimers, here we begin to test the hypothesis that ERBB4 heterodimers drive the proliferation of BRAF-WT&RAS/NF1-mutant melanoma cell lines. Here we demonstrate that the kinase-deficient (dominant-negative) ERBB2 K753A mutant allele inhibits the clonogenic proliferation of the IPC-298, MEL-JUSO, and MeWo ERBB4-dependent, BRAF-WT&RAS/NF1-mutant melanoma cell lines. Moreover, the kinase-deficient (dominant-negative) EGFR K721A mutant allele inhibits the clonogenic proliferation of the MeWo cell line, but not the IPC-298 or MEL-JUSO cell lines. Finally, the clonogenic proliferation of the SK-MEL-2 ERBB4-dependent, BRAF-WT&RAS/NF1-mutant melanoma cell line is unaffected by the ERBB2 K753A or EGFR K721A dominant-negative mutant alleles. We discuss these findings in the context of our hypothesis that ERBB4 heterodimers drive the proliferation of BRAF-WT&RAS/NF1-mutant melanoma cell lines.

cancer biology↗

bioRxiv2024

Retrospective Analysis of the Effects of BWF Interdisciplinary Postdoctoral to Faculty Transition Awards on Future Funding Success

Established by the Burroughs Wellcome Fund (BWF) in 2001, the Career Award at the Scientific Interface (CASI) is a career development award for scientists with doctoral training in the physical/mathematical/computational sciences or engineering conducting postdoctoral research in the biological sciences. The goal of the program is to support early career scientists interested in pursuing an independent research career with an interdisciplinary focus. In order to assess the benefit of the CASI award on recipients, the authors undertook a retrospective analysis of the funding data for CASI recipients to evaluate success against matching cohorts. These cohorts included applicants who succeeded to the final interview stage but were ultimately unsuccessful (interviewed), applicants who submitted proposals but did not make it to the final interview stage (proposal declined), and a randomly selected dataset of researchers from a comparable program, the highly competitive Pathway to Independence Award (K99/R00) from the National Institutes of Health (NIH). The results indicate that CASI recipients outperformed unsuccessful applicants and their K99/R00 counterparts in federal grant rates and overall grant dollars. The authors conclusion affirms that the CASI mechanism and BWF support successfully achieve the objective of invigorating the careers of young investigators, resulting in tangible downstream long-term effects.

scientific communication and education↗

bioRxiv2024

Duration of Morning Hyperinsulinemia is Key to the Enhancement of Hepatic Glucose Uptake and Glycogen Storage Later in the Day

The second meal phenomenon refers to the improvement in glucose tolerance seen following a second identical meal. We previously showed that 4 hours of morning hyperinsulinemia, but not hyperglycemia, enhanced hepatic glucose uptake (HGU) and glycogen storage during an afternoon hyperinsulinemic-hyperglycemic (HIHG) clamp. Our current aim was to determine if the duration or pattern of morning hyperinsulinemia is important for the afternoon response to a HIHG clamp. To determine this, we administered the same total amount of insulin either over 2h in the first (Ins2h-A) or second (Ins2h-B) half of the morning, or over the entire 4h (Ins4h) of the morning. In the 4h afternoon period, all three groups had 4x-basal insulin, 2x-basal glycemia, and portal glucose infusion to expose the liver to the primary postprandial regulators of hepatic glucose metabolism. During the afternoon clamp, there was a marked increase in HGU and hepatic glycogen synthesis in the Ins4h group compared to the Ins2h-A and Ins2h-B groups, despite matched hepatic glucose loads and total insulin infusion rates. Thus, the longer duration (Ins4h) of lower hyperinsulinemia in the morning seems to be the key to much greater liver glucose uptake during the afternoon clamp. New and noteworthyMorning insulin exposure primes the liver for increased hepatic glucose uptake and glycogen storage during a subsequent hyperinsulinemic-hyperglycemic clamp. This study addressed whether the pattern and/or duration of insulin delivery in the morning influences insulins ensuing priming effect. We found that despite receiving equal total doses of insulin in the morning, a prolonged, lower rate of morning insulin delivery improved afternoon liver glucose metabolism more effectively than a shorter, higher rate of delivery.

physiology↗

bioRxiv2024

Four centuries of commercial whaling eroded 11,000 years of population stability in bowhead whales

The bowhead whale, an Arctic endemic, was heavily overexploited during commercial whaling between the 16th-20th centuries1. Current climate warming, with Arctic amplification of average global temperatures, poses a new threat to the species2. Assessing the vulnerability of bowhead whales to near-future predictions of climate change remains challenging, due to lacking data on population dynamics prior to commercial whaling and responses to past climatic change. Here, we integrate palaeogenomics and stable isotope ({delta}13C and{delta} 15N) analysis of 201 bowhead whale fossils from the Atlantic Arctic with palaeoclimate and ecological modelling based on 823 radiocarbon dated fossils, 151 of which are new to this study. We find long-term resilience of bowhead whales to Holocene environmental perturbations, with no obvious changes in genetic diversity or population structure, despite large environmental shifts and centuries of whaling by Indigenous peoples prior to commercial harvests. Leveraging our empirical data, we simulated a time-series model to quantify population losses associated with commercial whaling. Our results indicate that commercial exploitation induced population subdivision and losses of genetic diversity that are yet to be fully realised; declines in genetic diversity will continue, even without future population size reductions, compromising the species resilience to near-future predictions of Arctic warming.

evolutionary biology↗

bioRxiv2024

Elucidating the sustainability of 700 years of Inuvialuit beluga whale hunting in the Mackenzie River Delta, Northwest Territories, Canada

Beluga whales play a critical role in the subsistence economies and cultural heritage of Indigenous communities across the Arctic, yet the effects of Indigenous hunting on beluga whales remains unknown. Here, we integrate paleogenomics and stable{delta} 13C and{delta} 15N isotope analysis to investigate 700 years of beluga subsistence hunting in the Mackenzie Delta area of northwestern Canada. Genetic identification of the zooarchaeological remains, which based on radiocarbon dating span three time periods (1290-1440 CE; 1450-1650 CE; 1800-1870 CE), indicate shifts across time in the sex ratio of the harvested belugas. The equal number of females and males harvested in 1450-1650 CE versus more males harvested in the two other time periods may reflect changes in hunting practices or temporal shifts in beluga availability. We find temporal shifts and sex-based differences in {delta}13C of the harvested belugas across time, suggesting historical adaptability in the foraging ecology of the whales. Although we uncovered novel mitochondrial diversity in the Mackenzie Delta belugas, we found no changes in nuclear genomic diversity nor any substructuring across time. Our findings indicate the genomic stability and continuity of the Mackenzie Delta beluga population across the 700 years surveyed, indicating the impact of Inuvialuit subsistence harvests on the genetic diversity of contemporary beluga individuals has been negligible. Significance StatementSince colonizing the Mackenzie Delta in northwestern Canada [~]1200 CE, Inuvialuit have been heavily reliant on belugas for their livelihoods and cultural heritage. However, little is known of the impact of centuries of sustained Inuvialuit subsistence hunting on the beluga population inhabiting the Mackenzie Delta. Using palaeogenomic and stable isotope analysis of zooarchaeological remains, and comparing the findings with contemporary data, we investigate temporal changes in beluga diversity, structuring, and foraging ecology. We show Inuvialuit harvests had a negligible impact on the genetic diversity of contemporary Mackenzie belugas, and highlight the applicability of combining genomic sexing and isotope analysis of zooarchaeological remains for advancing our understanding of past hunting practices and faunal ecologies.

genomics↗

bioRxiv2024

Leucine Rich Repeat Kinase 2 is not required for lysozyme expression in intestinal Paneth cells

Genetic variants in Leucine-rich Repeat Kinase 2 (LRRK2) gene have been linked to Parkinsons disease (PD) and are also associated with inflammatory bowel diseases (IBD), specifically Crohns disease (CD), a transmural inflammation that can affect the entire length of the gastrointestinal tract and is commonly seen in the ileum1. In ileal CD, defects in specialized intestinal epithelial cells known as Paneth cells are believed to drive disease pathogenesis2,3. Paneth cells contribute to mucosal defense by secreting antimicrobial peptides including lysozyme and to the maintenance of intestinal stem cells by secreting growth factors. A previous article published by Zhang et al4 in Nature Immunology identified a key role for LRRK2 in selective sorting and secretion of lysozyme in Paneth cells. However, after extended analyses, we find that LRRK2 is not required for lysozyme expression in the murine gut and is not expressed in either murine or human Paneth cells.

physiology↗

bioRxiv2023

Proteome partitioning constraints on long-term laboratory evolution

Adaptive laboratory evolution experiments provide a controlled context in which the dynamics of selection and adaptation can be followed in real-time at the single-nucleotide level1. And yet this precision introduces hundreds of degrees-of-freedom as genetic changes accrue in parallel lineages over generations2. On short timescales, physiological constraints have been leveraged to provide a coarse-grained view of bacterial gene expression characterized by a small set of phenomenological parameters3-5. Here, we ask whether this same framework, operating at a level between genotype and fitness, informs physiological changes that occur on evolutionary timescales. Using Lenskis Ara-1 lineage adapted to growth in glucose minimal medium6, we find that the proteome is substantially remodeled over 40 000 generations. We apply our existing quantitative proteomics analysis to partition hundreds of expressed proteins into six sectors with shared metabolic function and physiological response4. To accommodate the increased growth rates in the evolved strains, expression of metabolic enzymes undergoes sector-specific adaptation to enable increased fluxes. We find that catabolic proteins adapt by increasing the total enzyme abundance, whereas anabolic and glycolytic proteins exhibit decreased free-enzyme pools. We propose that flux-dependent regulation7 and substrate saturation8 can account for the sector-specific remodeling.

microbiology↗

bioRxiv2023

A Ray of Light Against Age Related Neurodegeneration

Mitochondrial function declines with age and many pathological processes of neurodegenerative diseases stem from this dysfunction when mitochondria fail to produce the necessary energy required. Photobiomodulation (PBM), long-wavelength light therapy, has been shown to rescue mitochondrial function in animal models and improve human health, but clinical uptake is limited due to uncertainty around efficacy and the mechanisms responsible. Through combined theoretical Monte Carlo light modelling and practical 31P Magnetisation Transfer Magnetic Resonance Spectroscopy (MT-MRS) we quantify the effects of 670 nm PBM treatment on healthy aging brains. 31P MT-MRS revealed a significant increase in the rate of ATP flux after PBM in a sample of older adults. Light modelling shows 1% absorption in grey matter and confirms absorption peaks at 670 and 820 nm. Our study provides evidence of PBM therapeutic efficacy and strengthens confidence in PBM as an acceptable healthcare technology to improve mitochondrial function and human health.

neuroscience↗

bioRxiv2022

Functional characterization of a PHF8 processed pseudogene in the mouse genome

The majority of pseudogenes are generated when an RNA transcript is reverse-transcribed and integrated into the genome at a new location. Pseudogenes are often considered as an imperfect and silent copy of a functional gene because of the accumulation of numerous mutations in their sequence. Here we report the presence of PHF8-ps, a PHF8 retrotransposed pseudogene in the mouse genome, which has no disruptions in its coding sequence. We showed that this pseudogene was specifically transcribed in testis and can produce a Phf8-ps protein in vivo. As Phf8-ps protein has a well-conserved JmjC domain, we characterized its enzymatic activity and showed that Phf8-ps did not have the intrinsic capability to demethylate H3K9me2 in vitro compared to the parental Phf8 protein. Surprisingly, Phf8-ps did not localize in the nucleus like Phf8 but rather was mostly located at the cytoplasm. Finally, our proteomic analysis of Phf8-ps associated proteins revealed that Phf8-ps interacted with mitochondrial proteins but also with prefoldin subunits (PFDN proteins) that deliver unfolded proteins to the cytosolic chaperonin complex implicated the folding of cytosolic proteins. Together, our findings highlighted Phf8-ps as a new pseudogene-derived protein with distinct molecular functions from Phf8.

biochemistry↗

bioRxiv2022

Impact of Holocene environmental change on the evolutionary ecology of an Arctic top predator

The Arctic is among the most climatically sensitive environments on Earth, and the disappearance of multiyear sea-ice in the Arctic Ocean is predicted within decades. As apex predators, polar bears are sentinel species for addressing the impact of environmental variability on Arctic marine ecosystems. By integrating genomics, isotopic analysis, morphometrics, and ecological modelling, we investigate how Holocene environmental changes affected the evolutionary ecology of polar bears around Greenland. We show that throughout the last [~]11,000 years, Greenlandic polar bears have been heavily influenced by changes in sea-surface temperature (SST) and sea-ice cover. Most notable are major reductions in effective population size at the beginning of the Holocene and during the Holocene Thermal Maximum [~]6 kya, which coincide with increases in annual mean SST, reduction in sea-ice covers, declines in suitable habitat, and shifts in suitable habitat northwards. Furthermore, we show how individuals sampled from west and east Greenland are genetically, morphologically, and ecologically distinct. We find bears sampled in west Greenland to be larger, more genetically diverse and have diets dominated by ringed seals, whereas bears from east Greenland are smaller and less diverse with more varied diets, putatively driven by regional biotic differences. Taken together, we provide novel insights into the vulnerability of polar bears to environmental change, and how the Arctic marine ecosystem plays a vital role in shaping the evolutionary and ecological trajectories of its inhabitants. TeaserMultivariate investigations of the environments role in the evolutionary ecology of Greenlandic polar bears.

evolutionary biology↗

bioRxiv2022

Polyploidy, regular patterning of genome copies, and unusual control of DNA partitioning in the Lyme disease spirochete

Borrelia burgdorferi, the tick-transmitted spirochete agent of Lyme disease, has a highly segmented genome with a linear chromosome and various linear or circular plasmids. Here, by imaging several chromosomal loci and 16 distinct plasmids, we show that B. burgdorferi is polyploid during growth in culture and that the number of genome copies decreases during stationary phase. B. burgdorferi is also polyploid inside fed ticks and chromosome copies are regularly spaced along the spirochetes length in both growing cultures and ticks. This patterning involves the conserved DNA partitioning protein ParA whose localization is controlled by a potentially phage-derived protein, ParZ, instead of its usual partner ParB. ParZ binds its own coding region and acts as a centromere-binding protein. While ParA works with ParZ, ParB controls the localization of the condensin, SMC. Together, the ParA/ParZ and ParB/SMC pairs ensure faithful chromosome inheritance. Our findings underscore the plasticity of cellular functions, even those as fundamental as chromosome segregation.

microbiology↗

bioRxiv2022

Integrated Regulation of Dopaminergic and Epigenetic Effectors of Neuroprotection in Parkinson's Disease Models

Whole exome sequencing of Parkinsons disease (PD) patient DNA identified single-nucleotide polymorphisms (SNPs) in the TNK2 gene. Although TNK2 encodes a non-receptor tyrosine kinase that has been shown to prevent the endocytosis of the dopamine reuptake transporter (DAT), a causal role for TNK2 in PD remains unresolved. We postulated that specific recessive mutations in patients resulted in aberrant or prolonged overactivity as a consequence of failed negative regulation by an E3 ubiquitin ligase, NEDD4. Interestingly, the sole Caenorhabditis elegans ortholog of TNK2, termed SID-3, is an established mediator of epigenetic gene silencing and systemic RNA interference facilitated by the SID-1 dsRNA transporter. While SID-3 had no prior association to dopamine neurotransmission in C. elegans, we hypothesized that TNK2/SID-3 represented a node of integrated dopaminergic and epigenetic signaling essential to neuronal homeostasis. Using genetic and chemical modifiers, including a TNK2 inhibitor (AIM-100) and NEDD4 activator (NAB2), in bioassays for dopamine uptake or RNAi in dopaminergic neurons of C. elegans, we determined that sid-3 mutants displayed neuroprotection from 6-hydroxydopamine (6-OHDA) exposure, as did wildtype animals treated with AIM-100 or NAB2. Additionally, NAB2 treatment of rat primary neurons correlated with a reduction of TNK2 levels and the attenuation of 6-OHDA neurotoxicity. Notably, CRISPR-modified nematodes engineered with genomic mutations in sid-3 analogous to PD patient-associated SNPs in TNK2 circumvented the resistance to RNAi characteristic of SID-3 dysfunction and furthermore exhibited enhanced susceptibility to neurodegeneration. This study describes a molecular etiology for PD whereby dysfunctional cellular dynamics, dopaminergic, and epigenetic signaling intersect to cause neurodegeneration. Significance StatementThe progressive loss of dopamine neurons is a pathological hallmark of Parkinsons disease (PD). Distinctions between resilience or susceptibility to neurodegeneration in PD are a combined consequence of genetic predisposition and environmental factors, the latter often manifesting as changes in gene expression that are coordinately controlled by small RNA molecules. This research reveals a functional convergence of proteins that modulate uptake of both dopamine and small RNAs, as a regulatory intersection for the integrated control of dopamine neuron health. Analysis of PD-patient mutations in the central protein associated with this functional interface further illustrated the clinical significance of this regulatory mechanism, as well as its potential for therapeutic intervention to prevent neurodegeneration through the fine-tuning of dopamine levels.

neuroscience↗

bioRxiv2021

Evolutionarily conserved genetic interactions between nphp-4 and bbs-5 mutations exacerbate ciliopathy phenotypes

Primary cilia are sensory and signaling hubs with a protein composition that is distinct from the rest of the cell due to the barrier function of the transition zone (TZ) at the base of the cilium. Protein transport across the TZ is mediated in part by the BBSome, and mutations disrupting TZ and BBSome proteins cause human ciliopathy syndromes. Ciliopathies have phenotypic variability even among patients with identical genetic variants, suggesting a role for modifier loci. To identify potential ciliopathy modifiers, we performed a mutagenesis screen on nphp-4 mutant C. elegans and uncovered a novel allele of bbs-5. Nphp-4;bbs-5 double mutant worms have phenotypes not observed in either individual mutant strain. To test whether this genetic interaction is conserved, we also analyzed zebrafish and mice mutants. While Nphp4 mutant zebrafish appeared overtly normal, Bbs5 mutants exhibited scoliosis. When combined, Nphp4;Bbs5 double mutant zebrafish did not exhibit synergistic effects, but the lack of a phenotype in Nphp4 mutants makes interpreting these data difficult. In contrast, viable Nphp4;Bbs5 double mutant mice were not obtained and there were fewer mice than expected carrying three mutant alleles. Additionally, postnatal loss of Bbs5 in mice using a conditional allele compromised survival when combined with a Nphp4 allele. As cilia are formed in the double mutant mice, the exacerbated phenotype is likely a consequence of disrupted ciliary signaling. Collectively, these data support an evolutionarily conserved genetic interaction between Bbs5 and Nphp4 alleles that may contribute to the variability in ciliopathy phenotypes.

genetics↗