Neural mechanisms underlying reduced nocifensive sensitivity in autism-associated Shank3 mutant dogs
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PTN activity in quiescent neural stem cells mediates Shank3 overexpression-induced manic behavior
Mania is a complex psychiatric disease characterized by hyperactivity, elevated mood and reduced anxiety. Despite extensive studies on the mechanism of the manic episodes, the molecular targets that control manic pathogenesis remain largely unclear. Here, through single-cell RNA sequencing (scRNA-seq) analysis, we show aberrant adult neurogenesis due to increased numbers of quiescent neural stem cells (qNSC) in a manic mouse model with Shank3 overexpression. Particularly, we found that the excessive Pleiotrophin (PTN), released by dysregulated qNSCs, is a key factor contributing to the manic-like phenotypes in Shank3-overexpressing mouse models. Pharmacological and molecular inhibition of PTN in qNSCs rescued aberrant neurogenesis and effectively alleviated the manic-like social deficits observed in Shank3-overexpressing mice. Taken together, our findings present an approach for modulating PTN activity in qNSCs, proposing it as a promising therapeutic target for manic development.
Shank3 modulates Rpl3 expression and protein synthesis via mGlu5: implications for Phelan McDermid syndrome
Mutations or deletions in the SHANK3 gene have been identified in up to 1% of autism spectrum disorder cases and are considered the primary cause of neuropsychiatric symptoms in Phelan McDermid syndrome (PMS). While synaptic dysfunctions have been extensively documented in the absence of Shank3, other mechanisms through which Shank3 may regulate neuronal functions remain unclear. In this study, we report that the ribosomal protein Rpl3 and overall protein synthesis are downregulated in the cortex and striatum of Shank3 knockout (KO) mice and in neurons differentiated from human-induced pluripotent stem cells (hiPSCs) derived from a PMS patient. Moreover, restoring Rpl3 expression in the striatum of Shank3 KO mice was sufficient to rescue protein synthesis and mitigate excessive grooming, suggesting that the behavioral alterations observed in Shank3 KO mice might be, at least in part, caused by Rpl3 downregulation and consequent impaired protein synthesis. Furthermore, we demonstrated that chronic inhibition of mGlu5 is sufficient to reduce Rpl3 expression, which in turn impairs global protein synthesis. Consequently, chronic treatment with VU0409551, a potent and selective mGlu5 positive allosteric modulator, rescues Rpl3 expression and the resulting reduction in protein synthesis, leading to long-lasting improvements in behavioral deficits in Shank3 KO mice Altogether, we propose a new role for Shank3 in modulating Rpl3 protein expression, ribosomal function, and protein synthesis by downregulating mGlu5 receptor activity.
Oxytocin improves maternal licking behavior deficits in autism-associated Shank3 mutant dogs
Impaired social interaction and repetitive behavior are key features observed in individuals with autism spectrum disorder (ASD). SHANK3 is a high-confidence ASD risk gene that encodes an abundant scaffolding protein in the postsynaptic density. In wild-type (WT) domestic dogs, maternal behaviors such as licking and nursing (largely milk feeding) of puppies are most commonly observed. To address whether SHANK3 plays a role in social behaviors especially maternal behaviors, we analyzed Shank3 mutant dogs generated by CRISPR/Cas9 methodology. We found that Shank3 mutant dams exhibited a fewer and shorter licking behavior, as well as reduced nursing frequency when compared with WT dams. Additionally, a significant decrease in blood oxytocin (OXT) concentration was detected in Shank3 mutant dams. We thus conducted a vehicle-controlled experiment to examine whether a two-week intranasal OXT treatment, initiated on the 8th postpartum day, could rescue the maternal licking deficits in Shank3 mutant dams. We found that the decreased licking behavior in Shank3 mutant dams was significantly attenuated both acutely and chronically by OXT treatment. The rescue effect of OXT implicates an oxytocinergic contribution to the maternal defects in Shank3 mutant dams, suggesting a potential therapeutic strategy for SHANK3-associated ASD.
LmCen−/− based vaccine is protective against canine visceral leishmaniasis following three natural exposures in Tunisia
Dogs are the main reservoir host of Leishmania infantum, etiological agent of zoonotic visceral leishmaniasis (ZVL). An effective vaccine against Canine Visceral Leishmaniasis (CVL) will help the control and elimination of ZVL. In this study, we evaluated in dogs the safety, immunogenicity, and efficacy of a live attenuated Leishmania major Centrin gene-deleted (LmCen−/−) as a vaccine. Two doses (106 or 107) of LmCen−/− vaccine were administered intradermally in a prime-boost regimen. Both vaccine doses induced equally high level of IgG anti-Leishmania and exhibited strong antigen-specific cellular responses with IFN-γ production by CD4 + T cells one-month post-immunization. A second cohort of dogs was vaccinated with 106 LmCen−/− parasites one month prior to their transfer to a CVL endemic focus in Northern Tunisia for exposure to sand fly bites during three successive transmission seasons. Dogs were exposed to bite from naturally infected sandflies for 3–5 months per year. Our results showed that only 1/11 vaccinated dogs became PCR positive for Leishmania and developed clinical signs of CVL. In contrast, 4/11 unvaccinated dogs were tested PCR positive for Leishmania and displayed oligosymptomatic CVL, demonstrating that immunization with LmCen−/− vaccine confers long-term protection with an efficacy of 82.5% against CVL in natural transmission settings.
Polygenic scores for autism are associated with reduced neurite density in adults and children from the general population
Genetic variants linked to autism are thought to change cognition and behaviour by altering the structure and function of the brain. Although a substantial body of literature has identified structural brain differences in autism, it is unknown whether autism-associated common genetic variants are linked to changes in cortical macro- and micro-structure. We investigated this using neuroimaging and genetic data from adults (UK Biobank, N = 31,748) and children (ABCD, N = 4928). Using polygenic scores and genetic correlations we observe a robust negative association between common variants for autism and a magnetic resonance imaging derived phenotype for neurite density (intracellular volume fraction) in the general population. This result is consistent across both children and adults, in both the cortex and in white matter tracts, and confirmed using polygenic scores and genetic correlations. There were no sex differences in this association. Mendelian randomisation analyses provide no evidence for a causal relationship between autism and intracellular volume fraction, although this should be revisited using better powered instruments. Overall, this study provides evidence for shared common variant genetics between autism and cortical neurite density.
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