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Neurexins are highly-spliced transmembrane cell adhesion molecules that bind an array of partners via their extracellular domains. However, much less is known about the signaling pathways downstream of neurexin’s largely-invariant intracellular domain. C. elegans contains a single neurexin gene that we have previously shown is required for presynaptic assembly and stabilization. To gain insight into the signaling pathways mediating neurexin’s presynaptic functions, we employed a proximity ligation method, endogenously tagging neurexin’s intracellular domain with the promiscuous biotin ligase TurboID, allowing us to isolate adjacent biotinylated proteins by streptavidin pull-down and mass spectrometry. We compared our experimental strain to a control strain in which neurexin, endogenously tagged with TurboID, was dispersed from presynaptic active zones by the deletion of its C-terminal PDZ-binding motif. Using this approach we identified both known and novel intracellular interactors of neurexin, including active zone scaffolds, actin-binding proteins (including almost every member of the Arp2/3 complex), signaling molecules, and mediators of RNA trafficking, protein synthesis and degradation, among others. Characterization of mutants for candidate neurexin interactors revealed that they recapitulate aspects of thenrx-1mutant phenotype, suggesting they may be involved in neurexin signaling. Finally, to investigate a possible role for neurexin in local actin assembly, we endogenously tagged its intracellular domain with actin depolymerizing and sequestering peptides (DeActs), and found that this led to defects in active zone assembly.

Mesodiencephalic dopamine (mDA) neurons play a wide range of brain functions. Distinct subtypes of mDA neurons regulate these functions but the molecular mechanisms that drive the mDA circuit formation are largely unknown. Here we show that autophagy, the main recycling cellular pathway, is present in the growth cones of developing mDA neurons and its level changes dynamically in response to guidance cues. To characterize the role of autophagy in mDA axon growth/guidance, we knocked-out (KO) essential autophagy genes (Atg12, Atg5) in mice mDA neurons. Autophagy deficient mDA axons exhibit axonal swellings and decreased branching both in vitro and in vivo, likely due to aberrant microtubule looping. Strikingly, deletion of autophagy-related genes, blunted completely the response of mDA neurons to chemo-repulsive and chemo-attractive guidance cues. Our data demonstrate that autophagy plays a central role in regulating mDA neurons development, orchestrating axonal growth and guidance.

α-synuclein (α-syn) aggregation into insoluble deposits, referred to as Lewy bodies (LBs) is the paramount pathological hallmark of Parkinson’s disease and related α-synucleinopathies. However, how these aggregates affect neuronal homeostasis leading to neurodegeneration remains elusive. This gap in knowledge is mainly due to the lack of proper cellular and animal models to undertake such investigations. We have addressed this by developing a light-inducible protein aggregation (LIPA) system that allows for real-time induction of α-syn inclusions formation with remarkable spatial and temporal resolution in both cell culture and in vivo paradigms. We report that LIPA-induced aggregates auto-perpetuate for several days after transient light induction, and faithfully mimic several authentic features of LBs in vivo and in cell culture. Moreover, optogenetically induced α-syn aggregation in mouse midbrains compromised the nigrostriatal transmission and induced a significant dopaminergic neuronal loss and behavioural impairment. Our system provides a novel, dependable and invaluable tool by which to generate, visualize and dissect the role of protein aggregates in neurodegeneration.

Significance Degeneration of midbrain dopamine neurons is the main pathological hallmark of Parkinson’s disease. Identifying transcriptional programs that maintain these neurons in the adult brain will help us understand their specific vulnerability. Here, we show that the survival of dopaminergic neurons requires the ongoing action of LIM-homeodomain transcription factors Lmx1a and Lmx1b. We discovered an Lmx1a/b-dependent pathway maintaining mitochondrial functions in midbrain dopaminergic neurons. Accordingly, ablation of Lmx1a/b results in impaired respiratory chain activity, increased oxidative stress, and mitochondrial DNA damage and causes Lewy neurite-like pathology. Importantly, deletion of Lmx1a/b links metabolic impairment, α-synuclein inclusions, and progressive neuronal loss. Modulation of this pathway opens new strategies to slow down or prevent the death of vulnerable neurons in Parkinson’s disease.

This study investigates the Drosophilidae species associated to fruiting bodies of fungi in forested and anthropized environments of the Atlantic Rain Forest Biome, in south and southeastern Brazil. We collected samples of imagoes flying over and emerging from fruiting bodies of species of five fungi families, in six collection sites. We obtained 18 samples, from which emerged 910 drosophilids of 31 species from the genera Drosophila Fallen, 1823, Hirtodrosophila Duda, 1923, Leucophenga Mik, 1886, Mycodrosophila Oldenberg, 1914, Scaptomyza Hardy, 1849, Zaprionus Coquillett, 1901 and Zygothrica Wiedemann, 1830. The Drosophila species collected on fungi, as well as Zaprionus indianus Gupta, 1970, had previously been recorded colonizing fruits, demonstrating their versatility in resource use. Most of these species belong to the immigrans-tripunctata radiation of Drosophila. Our records expands the mycophagous habit (feeding or breeding on fungi) to almost all species groups of this radiation in the Neotropical region, even those supposed to be exclusively frugivorous. Assemblages associated to fungi of forested areas were more heterogeneous in terms of species composition, while those associated to fungi of anthropized areas were more homogeneous. The drosophilids from anthropized areas were also more versatile in resource use. Foi realizado um estudo das espécies de Drosophilidae associadas aos corpos de frutificação de fungos em ambientes florestais e antrópicos no Bioma Mata Atlântica, no sul e sudeste do Brasil. Foram realizadas coletas de adultos sobrevoando e emergindo de corpos de frutificação de espécies de fungos de cinco famílias, em seis pontos de coleta. Foram obtidas 18 amostras, onde foram coletados 910 indivíduos de 31 espécies, pertencentes aos gêneros Drosophila Fallen, 1823, Hirtodrosophila Duda, 1923, Leucophenga Mik, 1886, Mycodrosophila Oldenberg, 1914, Scaptomyza Hardy, 1849, Zaprionus Coquillett, 1901 e Zygothrica Wiedemann, 1830. As espécies de Drosophila coletadas, assim como Zaprionus indianus Gupta, 1970, já haviam sido registradas em frutos, evidenciando sua versatilidade na utilização dos recursos. A maioria destas espécies pertence à radiação immigrans-tripunctata de Drosophila. Em espécies desta radiação que habitam regiões temperadas, a micofagia é amplamente difundida; nossos registros (de sítios de alimentação e oviposição em fungos) expandem este hábito para quase todos os grupos de espécies desta radiação na região Neotropical, mesmo aquelas que se supunham ser exclusivamente frugívoras. As assembléias colonizadoras dos corpos de frutificação variaram entre as espécies de fungos e com o tipo de ambiente em que eles se desenvolviam, onde as espécies de drosofilídeos generalistas utilizam os fungos em ambientes mais degradados.