Learning the biochemical basis of axonal guidance: using Caenorhabditis elegans as a model

Aim: Experimental models are a powerful aid in visualizing molecular phenomena. This work reports how the worm Caenorhabditis elegans (C. elegans) can be effectively explored for students to learn how molecular cues dramatically condition axonal guidance and define nervous system structure and behavior at the organism level. Summary of work: A loosely oriented observational activity preceded detailed discussions on molecules implied in axonal migration. C. elegans mutants were used to introduce second-year medical students to the deleterious effects of gene malfunctioning in neuron response to extracellular biochemical cues and to establish links between molecular function, nervous system structure, and animal behavior. Students observed C. elegans cultures and associated animal behavior alterations with the lack of function of specific axon guidance molecules (the soluble cue netrin/UNC-6 or two receptors, DCC/UNC-40 and UNC-5H). Microscopical observations of these strains, in combination with pan-neuronal GFP expression, allowed optimal visualization of severely affected neurons. Once the list of mutated genes in each strain was displayed, students could also relate abnormal patterns in axon migration/ventral and dorsal nerve cord neuron formation in C. elegans with mutated molecular components homologous to those in humans. Summary of results: Students rated the importance and effectiveness of the activity very highly. Ninety-three percent found it helpful to grasp human axonal migration, and all students were surprised with the power of the model in helping to visualize the phenomenon.This work has been funded by National funds, through the Foundation for Science and Technology (FCT)—project UIDB/50026/2020 and UIDP/50026/2020 and by the projects, NORTE01-0145-FEDER-000039 and NORTE-01-0145-FEDER-085468, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work has been also funded by ICVS Scientific Microscopy Platform, member of the national infrastructure PPBI—Portuguese Platform of Bioimaging (PPBI-POCI-01-0145-FEDER-022122). Additionally, C.V. and D.V.C. were supported by the FCT individual fellowships 2022.11176.BD and SFRH/BD/147826/2019, respectively

Aripiprazole offsets mutant ATXN3-induced motor dysfunction by targeting dopamine D2 and serotonin 1A and 2A receptors in C. elegans

The atypical antipsychotic aripiprazole is a Food and Drug Administration-approved drug for the treatment of psychotic, mood, and other psychiatric disorders. Previous drug discovery efforts pinpointed aripiprazole as an effective suppressor of Machado–Joseph disease (MJD) pathogenesis, as its administration resulted in a reduced abundance and aggregation of mutant Ataxin-3 (ATXN3) proteins. Dopamine partial agonism and functional selectivity have been proposed as the main pharmacological mechanism of action of aripiprazole in the treatment of psychosis; however, this mechanism remains to be determined in the context of MJD. Here, we focus on confirming the efficacy of aripiprazole to reduce motor dysfunction in vivo, using a Caenorhabditis elegans (C. elegans) model of MJD, and on unveiling the drug targets required for its positive action against mutant ATXN3 pathogenesis. We employed pharmacogenetics and pharmacological approaches to identify which dopamine and serotonin receptors are critical for aripiprazole-mediated improvements in motor function. We demonstrated that dopamine D2-like and serotonin 5-HT1A and 5-HT2A receptors play important roles in this process. Our findings strengthen the relevance of dopaminergic and serotoninergic signaling modulation against mutant ATXN3-mediated pathogenesis. The identification of aripiprazole’s cellular targets, relevant for MJD and perhaps other neurodegenerative diseases, may pave the way for prospective drug discovery and development campaigns aiming to improve the features of this prototypical compound and reduce side effects not negligible in the case of aripiprazole.This work was funded by FEDER through the Competitiveness Internationalization Operational Program (POCI) and by National funds through the Foundation for Science and Technology (FCT), under the scope of the project POCI-01-0145-FEDER-0 31987, NORTE-01-0145-FEDER-000013, and NORTE-01-0145-FEDER-000023, supported by the Northern Portugal Regional Operational Program (NORTE 2020), under the Portugal 2020 Partnership Agreement through the European Regional Development Fund (ERDF) and by ICVS Scientific Microscopy Platform, member of the national infrastructure PPBI—Portuguese Platform of Bioimaging (PPBI-POCI-01-0145-FEDER-022122; by National funds through the Foundation for Science and Technology (FCT)—project UIDB/50026/2020 and UIDP/50026/2020). Additionally, this project was supported by the National Ataxia Foundation (NAF). A.J., J.P.-S., D.V.-C., and J.D.S. were supported by the FCT individual fellowships SFRH/BD/76613/2011, PD/BDE/127834/2016, SFRH/BD/147826/2019, and PD/BD/128074/2016, respectively