Structure and topography of the synaptic V-ATPase-synaptophysin complex.

Synaptic vesicles are organelles with a precisely defined protein and lipid composition1,2, yet the molecular mechanisms for the biogenesis of synaptic vesicles are mainly unknown. Here, we discovered a well-defined interface between the synaptic vesicle V-ATPase and synaptophysin by in situ cryo-electron tomography and single particle cryo-electron microscopy of functional synaptic vesicles isolated from mouse brains3. The synaptic vesicle V-ATPase is an ATP-dependent proton pump that establishes the protein gradient across the synaptic vesicle, which in turn drives the uptake of neurotransmitters4,5. Synaptophysin6 and its paralogs synaptoporin7 and synaptogyrin8 belong to a family of abundant synaptic vesicle proteins whose function is still unclear. We performed structural and functional studies of synaptophysin knockout mice, confirming the identity of synaptophysin as an interaction partner with the V-ATPase. Although there is little change in the conformation of the V-ATPase upon interaction with synaptophysin, the presence of synaptophysin in synaptic vesicles profoundly affects the copy number of V-ATPases. This effect on the topography of synaptic vesicles suggests that synaptophysin assists in their biogenesis. In support of this model, we observed that synaptophysin knockout mice exhibit severe seizure susceptibility, suggesting an imbalance of neurotransmitter release as a physiological consequence of the absence of synaptophysin.

Dose-dependent reduction of somatic expansions but not Htt aggregates by di-valent siRNA-mediated silencing of MSH3 in HdhQ111 mice.

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by CAG trinucleotide repeat expansions in exon 1 of the HTT gene. In addition to germline CAG expansions, somatic repeat expansions in neurons also contribute to HD pathogenesis. The DNA mismatch repair gene, MSH3, identified as a genetic modifier of HD onset and progression, promotes somatic CAG expansions, and thus presents a potential therapeutic target. However, what extent of MSH3 protein reduction is needed to attenuate somatic CAG expansions and elicit therapeutic benefits in HD disease models is less clear. In our study, we employed potent di-siRNAs to silence mouse Msh3 mRNA expression in a dose-dependent manner in HdhQ111/+ mice and correlated somatic Htt CAG instability with MSH3 protein levels from simultaneously isolated DNA and protein after siRNA treatment. Our results reveal a linear correlation with a proportionality constant of ~ 1 between the prevention of somatic Htt CAG expansions and MSH3 protein expression in vivo, supporting MSH3 as a rate-limiting step in somatic expansions. Intriguingly, despite a 75% reduction in MSH3 protein levels, striatal nuclear HTT aggregates remained unchanged. We also note that evidence for nuclear Msh3 mRNA that is inaccessible to RNA interference was found, and that MSH6 protein in the striatum was upregulated following MSH3 knockdown in HdhQ111/+ mice. These results provide important clues to address critical questions for the development of therapeutic molecules targeting MSH3 as a potential therapeutic target for HD.

Personality correlates of dispositional forgiveness: a direct comparison of interpersonal and self-forgiveness using common transgression scenarios.

Although the personality correlates of dispositional interpersonal forgiveness (forgiveness of others) have been well characterized, those of dispositional self-forgiveness are less well understood. Moreover, when the personality correlates are examined for both types of forgiveness, the comparison has been based on participants' self-report ratings on questionnaires. The current study sought to address these gaps in the literature by adopting a scenario-based approach, which has been used less frequently, especially in self-forgiveness research. A total of 160 participants read six fictional scenarios, each describing a severe transgression, from the perspective of the transgressor (self-forgiveness, n = 78) or the victim (interpersonal forgiveness, n = 82) of the transgression, and then responded to several items assessing different facets of forgiveness (avoidance, revenge, and benevolence). Participants' personality (Big Five) and explanatory style were also assessed. Consistent with prior literature, agreeableness and neuroticism generally predicted different facets of interpersonal forgiveness. These two personality traits also predicted facets of self-forgiveness, but, additionally, conscientiousness and one's tendency to internalize failure (the personal component of explanatory style) uniquely predicted self-forgiveness, especially avoidance motivations. These results point to both similarities and differences in the personality correlates of interpersonal and self-forgiveness. As a secondary, more exploratory aim, the current study compared the results from our scenario-based assessment of forgiveness to those based on a commonly used questionnaire, the Other and Self subscales of the Heartland Forgiveness Scale (HFS). As expected, the Other subscale of the HFS were associated with levels of interpersonal forgiveness assessed with our transgression scenarios, but, surprisingly, the HFS Self subscale was more strongly related to interpersonal than self-forgivess assessed with scenarios. Moreover, the Self subscale was not associated with levels of self-forgiveness assessed with transgression scenarios, except for avoidance motivations. These results suggest that scenario-based and questionnaire-based methods may capture different facts of forgiveness and cannot be used interchangeably, especially for the assessment of self-forgiveness. More generally, the current study illustrates the importance of conducting direct within-study comparisons of interpersonal and self-forgiveness as well as of different assessment methods to better understand the similarities and differences between the two types of forgiveness.