Using C. elegans to decipher the cellular and molecular mechanisms underlying neurodevelopmental disorders

Prova tipográfica (uncorrected proof)Neurodevelopmental disorders such as epilepsy, intellectual disability (ID), and autism spectrum disorders (ASDs) occur in over 2 % of the population, as the result of genetic mutations, environmental factors, or combination of both. In the last years, use of large-scale genomic techniques allowed important advances in the identification of genes/loci associated with these disorders. Nevertheless, following association of novel genes with a given disease, interpretation of findings is often difficult due to lack of information on gene function and effect of a given mutation in the corresponding protein. This brings the need to validate genetic associations from a functional perspective in model systems in a relatively fast but effective manner. In this context, the small nematode, Caenorhabditis elegans, presents a good compromise between the simplicity of cell models and the complexity of rodent nervous systems. In this article, we review the features that make C. elegans a good model for the study of neurodevelopmental diseases. We discuss its nervous system architecture and function as well as the molecular basis of behaviors that seem important in the context of different neurodevelopmental disorders. We review methodologies used to assess memory, learning, and social behavior as well as susceptibility to seizures in this organism. We will also discuss technological progresses applied in C. elegans neurobiology research, such as use of microfluidics and optogenetic tools. Finally, we will present some interesting examples of the functional analysis of genes associated with human neurodevelopmental disorders and how we can move from genes to therapies using this simple model organism.The authors would like to acknowledge Fundação para a Ciência e Tecnologia (FCT) (PTDC/SAU-GMG/112577/2009). AJR and CB are recipients of FCT fellowships: SFRH/BPD/33611/2009 and SFRH/BPD/74452/2010, respectively

Acute Versus Chronic Loss of Mammalian Azi1/Cep131 Results in Distinct Ciliary Phenotypes

Defects in cilium and centrosome function result in a spectrum of clinically-related disorders, known as ciliopathies. However, the complex molecular composition of these structures confounds functional dissection of what any individual gene product is doing under normal and disease conditions. As part of an siRNA screen for genes involved in mammalian ciliogenesis, we and others have identified the conserved centrosomal protein Azi1/Cep131 as required for cilia formation, supporting previous Danio rerio and Drosophila melanogaster mutant studies. Acute loss of Azi1 by knock-down in mouse fibroblasts leads to a robust reduction in ciliogenesis, which we rescue by expressing siRNA-resistant Azi1-GFP. Localisation studies show Azi1 localises to centriolar satellites, and traffics along microtubules becoming enriched around the basal body. Azi1 also localises to the transition zone, a structure important for regulating traffic into the ciliary compartment. To study the requirement of Azi1 during development and tissue homeostasis, Azi1 null mice were generated (Azi1(Gt/Gt)). Surprisingly, Azi1(Gt/Gt) MEFs have no discernible ciliary phenotype and moreover are resistant to Azi1 siRNA knock-down, demonstrating that a compensation mechanism exists to allow ciliogenesis to proceed despite the lack of Azi1. Cilia throughout Azi1 null mice are functionally normal, as embryonic patterning and adult homeostasis are grossly unaffected. However, in the highly specialised sperm flagella, the loss of Azi1 is not compensated, leading to striking microtubule-based trafficking defects in both the manchette and the flagella, resulting in male infertility. Our analysis of Azi1 knock-down (acute loss) versus gene deletion (chronic loss) suggests that Azi1 plays a conserved, but non-essential trafficking role in ciliogenesis. Importantly, our in vivo analysis reveals Azi1 mediates novel trafficking functions necessary for flagellogenesis. Our study highlights the importance of both acute removal of a protein, in addition to mouse knock-out studies, when functionally characterising candidates for human disease

Computer-delivered social norm message increases pain tolerance.

BackgroundFew experimental studies have been conducted on social determinants of pain tolerance.PurposeThis study tests a brief, computer-delivered social norm message for increasing pain tolerance.MethodsHealthy young adults (N = 260; 44 % Caucasian; 27 % Hispanic) were randomly assigned into a 2 (social norm) × 2 (challenge) cold pressor study, stratified by gender. They received standard instructions or standard instructions plus a message that contained artificially elevated information about typical performance of others.ResultsThose receiving a social norm message displayed significantly higher pain tolerance, F(1, 255) = 26.95, p < .001, η p (2)  = .10 and pain threshold F(1, 244) = 9.81, p = .002, η p (2)  = .04, but comparable pain intensity, p > .05. There were no interactions between condition and gender on any outcome variables, p > .05.ConclusionsSocial norms can significantly increase pain tolerance, even with a brief verbal message delivered by a video

Computer-delivered social norm message increases pain tolerance.

BackgroundFew experimental studies have been conducted on social determinants of pain tolerance.PurposeThis study tests a brief, computer-delivered social norm message for increasing pain tolerance.MethodsHealthy young adults (N = 260; 44 % Caucasian; 27 % Hispanic) were randomly assigned into a 2 (social norm) × 2 (challenge) cold pressor study, stratified by gender. They received standard instructions or standard instructions plus a message that contained artificially elevated information about typical performance of others.ResultsThose receiving a social norm message displayed significantly higher pain tolerance, F(1, 255) = 26.95, p < .001, η p (2)  = .10 and pain threshold F(1, 244) = 9.81, p = .002, η p (2)  = .04, but comparable pain intensity, p > .05. There were no interactions between condition and gender on any outcome variables, p > .05.ConclusionsSocial norms can significantly increase pain tolerance, even with a brief verbal message delivered by a video

Internet-based Advertising Claims and Consumer Reasons for Using Electronic Cigarettes by Device Type in the US.

ObjectivesImportant differences exist between closed-system and open-system e-cigarettes, but it is unknown whether online companies are marketing these devices differently and whether consumer reasons for using e-cigarettes vary by device type. This paper compares Internet-based advertising claims of closed- versus open-system products, and evaluates US consumers' reasons for using closed- versus open-system e-cigarettes.MethodsInternet sites selling exclusively closed (N = 130) or open (N = 129) e-cigarettes in December 2013-January 2014 were coded for advertising claims. Current users (≥18 years old) of exclusively closed or open e-cigarettes (N = 860) in a nationally representative online survey in February-March 2014 provided their main reason for using e-cigarettes.ResultsInternet sites that exclusively sold closed-system e-cigarettes were more likely to make cigarette-related claims such as e-cigarettes being healthier and cheaper than cigarettes (ps < .0001) compared to sites selling open systems. Many sites implied their products could help smokers quit. Exclusive users of both systems endorsed cessation as their top reason. Closed-system users were more likely to report their reason as "use where smoking is banned."ConclusionsAlthough promotion of e-cigarettes as cessation aids is prohibited, consumers of both systems endorsed smoking cessation as their top reason for using e-cigarettes

Effects of Marijuana Use on Smokers Switching to E-Cigarettes in a Randomized Clinical Trial.

IntroductionCo-use of tobacco and marijuana is common, and research suggests that marijuana use may be a barrier to smoking cessation. Research to date has not evaluated how marijuana use affects e-cigarette switching behaviors and related outcomes in a harm reduction trial.Aims and methodsThis secondary analysis includes African American (48%) and Latinx (52%) adult smokers randomized to the e-cigarette group (N = 114) of a harm reduction clinical trial from 2018 to 2019. Participants were provided JUUL e-cigarettes and encouraged to make an exclusive switch for 6 weeks. Our primary outcome was cigarettes smoked per week. Secondary health outcomes were e-cigarette substitution (calculated by measuring e-cigarette pod use), expired carbon monoxide (CO), and respiratory symptoms. Marijuana products were recorded at three timepoints and coded for combustion.ResultsMarijuana use during the study (n = 52, 46%) was not associated with week 6 cigarettes smoked or e-cigarette substitution, and combustible marijuana use was not associated with week 6 respiratory symptoms (ps > .05). After controlling for cigarettes smoked at week 6, combustible marijuana use was significantly associated with a 4.4 ppm increase in CO compared with no use of marijuana (p = .001).ConclusionsMarijuana use was not a barrier to switching to e-cigarettes in this 6-week trial. Marijuana use contributed to elevated CO, reflecting greater exposure to toxic combustion products, beyond the effects of cigarette smoking. Marijuana co-use may increase risk of adverse health outcomes and may be a confounding factor when using CO as an endpoint to bioverify exclusive e-cigarette use.ImplicationsThis is the first known study to examine the effects of marijuana use on smokers switching to e-cigarettes. Marijuana use was not a barrier to cigarette reduction in a 6-week randomized clinical trial. Marijuana use uniquely contributed to higher carbon monoxide among cigarette smokers, indicating greater exposure to toxic combustion products, which could increase risk of adverse health outcomes. Furthermore, combustible marijuana use may be a confounding factor when CO is used as an endpoint to bioverify exclusive e-cigarette use