A new Caenorhabditis elegans model to study copper toxicity in Wilson disease.

Wilson disease (WD) is caused by mutations in the ATP7B gene that encodes a copper (Cu) transporting ATPase whose trafficking from the Golgi to endo-lysosomal compartments drives sequestration of excess Cu and its further excretion from hepatocytes into the bile. Loss of ATP7B function leads to toxic Cu overload in the liver and subsequently in the brain, causing fatal hepatic and neurological abnormalities. The limitations of existing WD therapies call for the development of new therapeutic approaches, which require an amenable animal model system for screening and validation of drugs and molecular targets. To achieve this objective, we generated a mutant Caenorhabditis elegans strain with a substitution of a conserved histidine (H828Q) in the ATP7B ortholog cua-1 corresponding to the most common ATP7B variant (H1069Q) that causes WD. cua-1 mutant animals exhibited very poor resistance to Cu compared to the wild-type strain. This manifested in a strong delay in larval development, a shorter lifespan, impaired motility, oxidative stress pathway activation, and mitochondrial damage. In addition, morphological analysis revealed several neuronal abnormalities in cua-1 mutant animals exposed to Cu. Further investigation suggested that mutant CUA-1 is retained and degraded in the endoplasmic reticulum, similarly to human ATP7B-H1069Q. As a consequence, the mutant protein does not allow animals to counteract Cu toxicity. Notably, pharmacological correctors of ATP7B-H1069Q reduced Cu toxicity in cua-1 mutants indicating that similar pathogenic molecular pathways might be activated by the H/Q substitution and, therefore, targeted for rescue of ATP7B/CUA-1 function. Taken together, our findings suggest that the newly generated cua-1 mutant strain represents an excellent model for Cu toxicity studies in WD.

Enteric neurons increase maternal food intake during reproduction.

Reproduction induces increased food intake across females of many animal species1-4, providing a physiologically relevant paradigm for the exploration of appetite regulation. Here, by examining the diversity of enteric neurons in Drosophila melanogaster, we identify a key role for gut-innervating neurons with sex- and reproductive state-specific activity in sustaining the increased food intake of mothers during reproduction. Steroid and enteroendocrine hormones functionally remodel these neurons, which leads to the release of their neuropeptide onto the muscles of the crop-a stomach-like organ-after mating. Neuropeptide release changes the dynamics of crop enlargement, resulting in increased food intake, and preventing the post-mating remodelling of enteric neurons reduces both reproductive hyperphagia and reproductive fitness. The plasticity of enteric neurons is therefore key to reproductive success. Our findings provide a mechanism to attain the positive energy balance that sustains gestation, dysregulation of which could contribute to infertility or weight gain.

Bi-allelic loss-of-function variants in PPFIBP1 cause a neurodevelopmental disorder with microcephaly, epilepsy, and periventricular calcifications.

PPFIBP1 encodes for the liprin-ß1 protein, which has been shown to play a role in neuronal outgrowth and synapse formation in Drosophila melanogaster. By exome and genome sequencing, we detected nine ultra-rare homozygous loss-of-function variants in 16 individuals from 12 unrelated families. The individuals presented with moderate to profound developmental delay, often refractory early-onset epilepsy, and progressive microcephaly. Further common clinical findings included muscular hyper- and hypotonia, spasticity, failure to thrive and short stature, feeding difficulties, impaired vision, and congenital heart defects. Neuroimaging revealed abnormalities of brain morphology with leukoencephalopathy, ventriculomegaly, cortical abnormalities, and intracranial periventricular calcifications as major features. In a fetus with intracranial calcifications, we identified a rare homozygous missense variant that by structural analysis was predicted to disturb the topology of the SAM domain region that is essential for protein-protein interaction. For further insight into the effects of PPFIBP1 loss of function, we performed automated behavioral phenotyping of a Caenorhabditis elegans PPFIBP1/hlb-1 knockout model, which revealed defects in spontaneous and light-induced behavior and confirmed resistance to the acetylcholinesterase inhibitor aldicarb, suggesting a defect in the neuronal presynaptic zone. In conclusion, we establish bi-allelic loss-of-function variants in PPFIBP1 as a cause of an autosomal recessive severe neurodevelopmental disorder with early-onset epilepsy, microcephaly, and periventricular calcifications.

RTN2 deficiency results in an autosomal recessive distal motor neuropathy with lower limb spasticity.

Heterozygous RTN2 variants have been previously identified in a limited cohort of families affected by autosomal dominant spastic paraplegia (SPG12-OMIM:604805) with a variable age of onset. Nevertheless, the definitive validity of SPG12 remains to be confidently confirmed due to the scarcity of supporting evidence. In this study, we identified and validated seven novel or ultra-rare homozygous loss-of-function RTN2 variants in 14 individuals from seven consanguineous families with distal hereditary motor neuropathy (dHMN) using exome, genome and Sanger sequencing coupled with deep-phenotyping. All affected individuals (seven males and seven females, aged 9-50 years) exhibited weakness in the distal upper and lower limbs, lower limb spasticity and hyperreflexia, with onset in the first decade of life. Nerve conduction studies revealed axonal motor neuropathy with neurogenic changes in the electromyography. Despite a slowly progressive disease course, all patients remained ambulatory over a mean disease duration of 19.71 ± 13.70 years. Characterization of Caenorhabditis elegans RTN2 homologous loss-of-function variants demonstrated morphological and behavioural differences compared with the parental strain. Treatment of the mutant with an endoplasmic/sarcoplasmic reticulum Ca2+ reuptake inhibitor (2,5-di-tert-butylhydroquinone) rescued key phenotypic differences, suggesting a potential therapeutic benefit for RTN2-disorder. Despite RTN2 being an endoplasmic reticulum (ER)-resident membrane shaping protein, our analysis of patient fibroblast cells did not find significant alterations in ER structure or the response to ER stress. Our findings delineate a distinct form of autosomal recessive dHMN with pyramidal features associated with RTN2 deficiency. This phenotype shares similarities with SIGMAR1-related dHMN and Silver-like syndromes, providing valuable insights into the clinical spectrum and potential therapeutic strategies for RTN2-related dHMN.

Tissue-specific isoforms of the single C. elegans Ryanodine receptor gene unc-68 control specific functions.

Ryanodine receptors (RyR) are essential regulators of cellular calcium homeostasis and signaling. Vertebrate genomes contain multiple RyR gene isoforms, expressed in different tissues and executing different functions. In contrast, invertebrate genomes contain a single RyR-encoding gene and it has long been proposed that different transcripts generated by alternative splicing may diversify their functions. Here, we analyze the expression and function of alternative exons in the C. elegans RyR gene unc-68. We show that specific isoform subsets are created via alternative promoters and via alternative splicing in unc-68 Divergent Region 2 (DR2), which actually corresponds to a region of high sequence variability across vertebrate isoforms. The expression of specific unc-68 alternative exons is enriched in different tissues, such as in body wall muscle, neurons and pharyngeal muscle. In order to infer the function of specific alternative promoters and alternative exons of unc-68, we selectively deleted them by CRISPR/Cas9 genome editing. We evaluated pharyngeal function, as well as locomotor function in swimming and crawling with high-content computer-assisted postural and behavioral analysis. Our data provide a comprehensive map of the pleiotropic impact of isoform-specific mutations and highlight that tissue-specific unc-68 isoforms fulfill distinct functions. As a whole, our work clarifies how the C. elegans single RyR gene unc-68 can fulfill multiple tasks through tissue-specific isoforms, and provide a solid foundation to further develop C. elegans as a model to study RyR channel functions and malfunctions.

Grit is associated with psychological health among older sexual minority men.

Objectives: Studies have shown that grit-defined as perseverance and passion for achieving one's long-term goals-is associated with improved health outcomes, including lower levels of psychological distress. However, the psychometric properties of the original Grit Scale (Grit-O Scale) has not been validated among sexual minority men (SMM). The present study aimed to validate the Grit-O Scale among a sample of older SMM and assess the relationships between the Grit-O Scale factors and symptoms of psychological distress.Method: We used data from a single visit of participants in the Multicenter AIDS Cohort Study (MACS) Healthy Aging longitudinal study. The sample included 981 older SMM (mean age = 61, SD = 8.5) with and without HIV. We conducted confirmatory factor analysis (CFA) to identify the two factors of the Grit-O Scale: consistency of interest and perseverance of effort. We also conducted a latent profile analysis (LPA) to identify distinct profiles of psychological distress from self-reported scales of depression, anxiety, and perceived stress.Results:The Grit-O Scale showed acceptable reliability estimates for the items with Cronbach's alpha reliability coefficients ranging from 0.77 to 0.82. The CFA identified the two factors of the Grit-O Scale with acceptable model fit (root mean square error of approximation = 0.058 [95% CI = 0.050, 0.067], comparative fit index = 0.95, Tucker-Lewis Index = 0.93, standardized root mean square residual = 0.07). The LPA yielded three mutually exclusive profiles of psychological distress (profile 1: low stress, anxiety, and depression; profile 2: high stress and depression and low anxiety; and profile 3: high stress, anxiety, and depression). In adjusted multinominal logistic regression analysis, we found that both higher levels of consistency of interest and perseverance of effort factors of the Grit-O Scale were significantly associated with decreased odds of being in profiles 2 and 3 compared with being in profile 1.Conclusion: Our findings support the use of the Grit-O Scale among older SMM. Grit factors could explain variability in the negative psychological symptoms among older SMM and warrant further investigation.Supplemental data for this article is available online at http://dx.doi.org/10.1080/13607863.2022.2032594.

Longitudinal associations of relationship support and strain and internalized homophobia with mental health among middle-aged and older gay and bisexual men.

Objectives: Mental health concerns (e.g. depression, anxiety) that negatively impact gay, bisexual, and other men who have sex with men (GBMSM) persist over the life course and into old age, but less is known about potential contributors to GBMSM's mental health. Close relationships can be a source of risk or resilience from stress, exerting direct relationships on mental health, and may mediate well-established associations between minority stress and mental health. This study examined whether primary partner relationship support and strain were uniquely associated with, and mediated the association between internalized homophobia, and mental health among older GBMSM.Methods: GBMSM (N = 517, M age = 60) from the Multicenter AIDS Cohort Study, who were in primary relationships with men, provided self-report data at four timepoints. We used multilevel modeling to examine longitudinal associations among relationship support and strain and internalized homophobia with depression and anxiety.Results: Relationship strain, but not support, was positively associated with mental health concerns longitudinally. There was a significant, positive indirect effect of internalized homophobia on depression and anxiety through strain, but no support. Internalized homophobia was positively associated with relationship strain, which was positively associated with mental health symptoms longitudinally.Conclusions: Relationship strain was associated with depression and anxiety longitudinally among middle-aged and older GBMSM and mediated associations of internalized homophobia with mental health. The role of partner support warrants further investigation. Mental health interventions are critically needed for older GBMSM and, for partnered GBMSM, should include strategies for reducing relationship strain to foster well-being.

Behavioral fingerprints predict insecticide and anthelmintic mode of action.

Novel invertebrate-killing compounds are required in agriculture and medicine to overcome resistance to existing treatments. Because insecticides and anthelmintics are discovered in phenotypic screens, a crucial step in the discovery process is determining the mode of action of hits. Visible whole-organism symptoms are combined with molecular and physiological data to determine mode of action. However, manual symptomology is laborious and requires symptoms that are strong enough to see by eye. Here, we use high-throughput imaging and quantitative phenotyping to measure Caenorhabditis elegans behavioral responses to compounds and train a classifier that predicts mode of action with an accuracy of 88% for a set of ten common modes of action. We also classify compounds within each mode of action to discover substructure that is not captured in broad mode-of-action labels. High-throughput imaging and automated phenotyping could therefore accelerate mode-of-action discovery in invertebrate-targeting compound development and help to refine mode-of-action categories.

Biopsychosocial Health Outcomes and Experienced Intersectional Stigma in a Mixed HIV Serostatus Longitudinal Cohort of Aging Sexual Minority Men, United States, 2008‒2019.

Objectives. To determine whether intersectional stigma is longitudinally associated with biopsychosocial outcomes. Methods. We measured experienced intersectional stigma (EIS; ≥ 2 identity-related attributions) among sexual minority men (SMM) in the United States participating in the Multicenter AIDS Cohort Study. We assessed longitudinal associations between EIS (2008‒2009) and concurrent and future hypertension, diabetes, dyslipidemia, antiretroviral therapy adherence, HIV viremia, health care underutilization, and depression symptoms (2008‒2019). We conducted causal mediation to assess the contribution of intersectional stigma to the relationship between self-identified Black race and persistently uncontrolled outcomes. Results. The mean age (n = 1806) was 51.8 years (range = 22-84 years). Of participants, 23.1% self-identified as Black; 48.3% were living with HIV. Participants reporting EIS (30.8%) had higher odds of hypertension, dyslipidemia, diabetes, depression symptoms, health care underutilization, and suboptimal antiretroviral therapy adherence compared with participants who did not report EIS. EIS mediated the relationship between self-identified Black race and uncontrolled outcomes. Conclusions. Our findings demonstrate that EIS is a durable driver of biopsychosocial health outcomes over the life course. Public Health Implications. There is a critical need for interventions to reduce intersectional stigma, help SMM cope with intersectional stigma, and enact policies protecting minoritized people from discriminatory acts. (Am J Public Health. 2022;112(S4):S452-S462. https://doi.org/10.2105/AJPH.2022.306735).

Multidimensional phenotyping predicts lifespan and quantifies health in Caenorhabditis elegans.

Ageing affects a wide range of phenotypes at all scales, but an objective measure of ageing remains challenging, even in simple model organisms. To measure the ageing process, we characterized the sequence of alterations of multiple phenotypes at organismal scale. Hundreds of morphological, postural, and behavioral features were extracted from high-resolution videos. Out of the 1019 features extracted, 896 are ageing biomarkers, defined as those that show a significant correlation with relative age (age divided by lifespan). We used support vector regression to predict age, remaining life and lifespan of individual C. elegans. The quality of these predictions (age R2 = 0.79; remaining life R2 = 0.77; lifespan R2 = 0.72) increased with the number of features added to the model, supporting the use of multiple features to quantify ageing. We quantified the rate of ageing as how quickly animals moved through a phenotypic space; we quantified health decline as the slope of the declining predicted remaining life. In both ageing dimensions, we found that short lived-animals aged faster than long-lived animals. In our conditions, for isogenic wild-type worms, the health decline of the individuals was scaled to their lifespan without significant deviation from the average for short- or long-lived animals.

Self-perception of aging among HIV-positive and HIV-negative participants in the Multicenter AIDS Cohort Study.

Self-perception of aging is an important predictor of quality of life. Therefore, we sought to examine self-perceptions of aging (age discrepancy and aging satisfaction) between HIV-positive and HIV-negative men in the Multicenter AIDS Cohort Study (MACS). We included 835 HIV-negative and 784 HIV-positive men aged 50 years and older who had completed a survey about age discrepancy and aging satisfaction from the "Attitude toward own aging" subscale of the Philadelphia Geriatric Center Morale scale. Multinomial generalized logit models were generated to assess self-perception of aging by HIV-status. Most of the participants self-identified as white, former smokers, and had completed high school. HIV-positive individuals reported higher prevalence of comorbidities than HIV-negative individuals. After adjusting for covariates, positive age discrepancy (older subjective age) was positively associated with being HIV-positive and having less than a high school education, depressive symptoms, diabetes, and medium and low aging satisfaction. Low aging satisfaction was associated with being a current and former smoker and having depressive symptoms, diabetes, and no age and positive age discrepancy. Being black had decreased odds of low aging satisfaction. These findings should inform health care professionals to promote positive views of aging in the assessment and management of HIV, depression, and diabetes.

Glassy worm-like micelles in solvent and shear mediated shape transitions.

The glassiness of polymer melts is generally considered to be suppressed by small dimensions, added solvent, and heat. Here, we suggest that glassiness persists at the nanoscale in worm-like micelles composed of amphiphilic diblock copolymers of poly(ethylene oxide)-polystyrene (PS). The glassiness of these worms is indicated by a lack of fluorescence recovery after photobleaching as well as micron-length rigid segments separated by hinges. The coarse-grained molecular dynamics studies probe the dynamics of the PS in these glassy worms. Addition of an organic solvent promotes a transition from hinged to fully flexible worms and to spheres or vesicles. Simulation demonstrates two populations of organic solvent in the core of the micelle-a solvent 'pool' in the micelle core and a second population that accumulates at the interface between the core and the corona. The stable heterogeneity of the residual solvent could explain the unusual hinged rigidity, but solvent removal during shear-extension could be more effective and yield - as observed - nearly straight worms without hinges.

Predicting path from undulations for C. elegans using linear and nonlinear resistive force theory.

A basic issue in the physics of behaviour is the mechanical relationship between an animal and its surroundings. The model nematode C. elegans provides an excellent platform to explore this relationship due to its anatomical simplicity. Nonetheless, the physics of nematode crawling, in which the worm undulates its body to move on a wet surface, is not completely understood and the mathematical models often used to describe this phenomenon are empirical. We confirm that linear resistive force theory, one such empirical model, is effective at predicting a worm's path from its sequence of body postures for forward crawling, reversing, and turning and for a broad range of different behavioural phenotypes observed in mutant worms. Worms recently isolated from the wild have a higher effective drag anisotropy than the laboratory-adapted strain N2 and most mutant strains. This means the wild isolates crawl with less surface slip, perhaps reflecting more efficient gaits. The drag anisotropies required to fit the observed locomotion data (70 ± 28 for the wild isolates) are significantly larger than the values measured by directly dragging worms along agar surfaces (3-10 in Rabets et al (2014 Biophys. J. 107 1980-7)). A proposed nonlinear extension of the resistive force theory model also provides accurate predictions, but does not resolve the discrepancy between the parameters required to achieve good path prediction and the experimentally measured parameters. We confirm that linear resistive force theory provides a good effective model of worm crawling that can be used in applications such as whole-animal simulations and advanced tracking algorithms, but that the nature of the physical interaction between worms and their most commonly studied laboratory substrate remains unresolved.

A database of Caenorhabditis elegans behavioral phenotypes.

Using low-cost automated tracking microscopes, we have generated a behavioral database for 305 Caenorhabditis elegans strains, including 76 mutants with no previously described phenotype. The growing database currently consists of 9,203 short videos segmented to extract behavior and morphology features, and these videos and feature data are available online for further analysis. The database also includes summary statistics for 702 measures with statistical comparisons to wild-type controls so that phenotypes can be identified and understood by users.

Reconciling Epidemiology and Social Justice in the Public Health Discourse Around the Sexual Networks of Black Men Who Have Sex With Men.

Several studies have implicated the sexual networks of Black men who have sex with men (MSM) as facilitating disproportionally high rates of new HIV infections within this community. Although structural disparities place these networks at heightened risk for infection, HIV prevention science continues to describe networks as the cause for HIV disparities, rather than an effect of structures that pattern infection. We explore the historical relationship between public health and Black MSM, arguing that the current articulation of Black MSM networks is too often incomplete and counterproductive. Public health can offer a counternarrative that reconciles epidemiology with the social justice that informs our discipline, and that is required for an effective response to the epidemic among Black MSM.

Changes in Postural Syntax Characterize Sensory Modulation and Natural Variation of C. elegans Locomotion.

Locomotion is driven by shape changes coordinated by the nervous system through time; thus, enumerating an animal's complete repertoire of shape transitions would provide a basis for a comprehensive understanding of locomotor behaviour. Here we introduce a discrete representation of behaviour in the nematode C. elegans. At each point in time, the worm's posture is approximated by its closest matching template from a set of 90 postures and locomotion is represented as sequences of postures. The frequency distribution of postural sequences is heavy-tailed with a core of frequent behaviours and a much larger set of rarely used behaviours. Responses to optogenetic and environmental stimuli can be quantified as changes in postural syntax: worms show different preferences for different sequences of postures drawn from the same set of templates. A discrete representation of behaviour will enable the use of methods developed for other kinds of discrete data in bioinformatics and language processing to be harnessed for the study of behaviour.

A dictionary of behavioral motifs reveals clusters of genes affecting Caenorhabditis elegans locomotion.

Visible phenotypes based on locomotion and posture have played a critical role in understanding the molecular basis of behavior and development in Caenorhabditis elegans and other model organisms. However, it is not known whether these human-defined features capture the most important aspects of behavior for phenotypic comparison or whether they are sufficient to discover new behaviors. Here we show that four basic shapes, or eigenworms, previously described for wild-type worms, also capture mutant shapes, and that this representation can be used to build a dictionary of repetitive behavioral motifs in an unbiased way. By measuring the distance between each individual's behavior and the elements in the motif dictionary, we create a fingerprint that can be used to compare mutants to wild type and to each other. This analysis has revealed phenotypes not previously detected by real-time observation and has allowed clustering of mutants into related groups. Behavioral motifs provide a compact and intuitive representation of behavioral phenotypes.

Advance Care Planning Among Sexual Minority Men: Sociodemographic, Health Care, and Health Status Predictors.

Objectives: Advance care planning (ACP) specifies decision-making surrogates and preferences for serious illness or end-of-life medical care. ACP research has largely neglected sexual minority men (SMM), a population that experiences disparities in health care and health status. Methods: We examined formal and informal ACP among SMM ages 40+ in the Multicenter AIDS Cohort Study (N = 1,071). Results: For informal ACP (50%), younger SMM and men with past cardiovascular events had greater odds of planning; single men had lower odds of planning. For formal ACP (39%), SMM with greater socioeconomic status had greater odds of planning; SMM who were younger, of racial/ethnic minority identities, who were single or in a relationship without legal protections, and who lacked a primary care home had lower odds of planning. Discussion: Findings warrant further exploration of both informal and formal planning. More equitable, culturally-humble engagement of SMM may facilitate access, uptake, and person-centered planning.