bioRxiv Subject Collection: Neuroscience's Journal
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Saturday, February 22nd, 2025
| Time |
Event |
| 2:17a |
FMRP Regulates Neuronal RNA Granules Containing Stalled Ribosomes, Not Where Ribosomes Stall
Local protein synthesis is a crucial process that maintains synaptic proteostasis. A large percentage of mRNAs translated in developing neurons are associated with stalled ribosomes. FMRP, the protein lost in Fragile X syndrome, is highly enriched in RNA granules that contain stalled ribosomes. Previous examination of ribosome protected fragments (RPFs) from stalled neuronal ribosomes has identified motifs that match those found in mRNAs associated with FMRP, as recognized by FMRP cross-linking immunoprecipitation (CLIP) (Anadolu et al, 2023, Journal of Neuroscience doi: 10.1523/JNEUROSCI.1002-22.2023). To investigate whether FMRP recognition of these sequences is important for determining where ribosomes are stalled on mRNAs, we examined stalled ribosomes RPFs isolated from P5 mice of both sexes lacking the FMRP protein. We found that the loss of FMRP had no effect on the proteins associated with neuronal stalled ribosomes, the structure of the ribosomes, or the stalling sites (locations where RPFs accumulated). However, we observed a significant decrease in the amount of mRNAs previously shown to be associated with FMRP by CLIP in stalled ribosomes. Additionally, the number of neuronal RNA granules containing stalled ribosomes, as assayed by ribopuromycylation in distal neurites, decreased. Unlike neuronal RNA granules in WT neurons, the remaining distal neuronal RNA granules were resistant to reactivation by stimuli that induce mGLuR-LTD. These results highlight important roles of FMRP in regulating neuronal RNA granules that contain stalled ribosomes, though it does not influence where ribosomes are stalled and is not directly involved in stalled ribosome formation. | | 4:37a |
Environmentally Relevant Lead Exposure Alters Cell Morphology and Expression of Neural Hallmarks During SH-SY5Y Neuronal Differentiation
Lead (Pb) continues to be a public health burden, in the US and around the world, and yet the effects of historical and current exposure levels on neurogenesis are not fully understood. Here we examine the effects of a range of environmentally relevant Pb concentrations (0.16uM, 1.26uM, and 10uM Pb) relative to control on neural differentiation in the SH-SY5Y cell model. Pb exposure began on Day 5 and continued throughout differentiation at Day 18. We assessed morphological measures related to neurogenesis at several time points during this process, including the expression of proteins key in neural differentiation (B-tubulin III and GAP43), cell number and size, as well as the development of neurites. The bulk of detectable changes occurred with 10uM Pb exposure, most notably that of B-tubulin III and GAP43 expression. Effects with the 0.16uM and 1.26uM Pb exposure conditions increased as differentiation progressed, with significant reductions in cell and nuclear size as well as the number and length of neural projections by Day 18. Best benchmark concentration (BMC) analysis revealed many of these metrics to be susceptible to levels of Pb at or below historically relevant levels. This work highlights the disruption of neurite formation and protein expression as potential new mechanisms by which environmentally relevant Pb exposure impacts neurogenesis and morphology and perturb cognitive health throughout the life course. | | 4:37a |
In vitro cellular phenotypes of cortical neurons from R255X MECP2 knock-in mice are improved by either expression of wildtype MeCP2 or read-through with G418
Approximately 60% of individuals with Rett syndrome (RTT) carry a nonsense variant in the MECP2 gene; thus, there is an unmet need to identify novel nonsense suppression compound(s) that can restore full length MeCP2 protein levels and function. Here, we characterized neuronal phenotypes in cultured cortical neurons from newborn knock-in mice harboring the MECP2 R255X variant. After 2 weeks in vitro, R255X mutant neurons showed smaller cell bodies, shorter dendrites, fewer dendritic branches, and a lower density of excitatory synapses when compared to wildtype (WT) neurons. Transduction of AAV9-MeCP2-GFP in R255X mutant neurons made these cellular phenotypes similar to those in WT neurons, including soma size, dendritic length and branching, and excitatory synapse density. As proof of principle for the potential clinical use of read-through compounds, cultured R255X mutant neurons treated with the aminoglycoside G418 for 72h in vitro showed cell body size and excitatory synapse density similar to WT neurons. We expect these combined approaches will identify effective compounds to suppress translation termination at a premature termination codon, which can be moved to further preclinical functional and behavioral studies in R255X MECP2 knock-in mice. | | 7:54a |
Disentangling value, arousal and valence systems in approach-avoidance behaviors in humans using functional magnetic resonance imaging
Appetitive and aversive stimuli evoke approach and avoidance behaviors essential for survival and well-being. While affective processing has been extensively examined in terms of arousal and valence, the extent to which value processing is independent from arousal and valence processing in naturalistic contexts remains unclear. We addressed this gap using a naturalistic approach-avoidance task. Ninety-one human participants underwent functional MRI scanning while engaging in approach-avoidance tasks involving two levels of threat (mild or aversive electrical stimulation) and reward (monetary gains). We estimated effect sizes (Cohen's D) across subjects for increasing levels of threat, reward and arousal; for valence (negative vs positive); and for valence-arousal interactions. Effect sizes for threat and reward were strongly positively correlated across brain voxels (r = 0.82), suggesting a strong influence of a shared factor. Spatial independent component analysis decomposed these effect sizes into two independent latent factors, one that represented arousal processing and another that exhibited characteristics of value processing. Importantly, we predicted that valence-arousal interaction effects would increase with latent value effects across voxels, since both valence and arousal contribute to our overall valuation process. We indeed found this to be true. Furthermore, sizable latent value effects were observed in dorsolateral prefrontal cortex, fusiform gyrus and middle temporal gyrus, areas also involved in attention and executive control. Thus, our findings revealed a value system in the human brain that could operate independently of arousal and valence systems during naturalistic approach-avoidance behaviors, providing new insights into the neural mechanisms of affective processing. | | 7:54a |
The impact of testosterone on paraventricular nucleus gene expression in male and female spontaneously hypertensive rats
Background: Hypertension is a polygenic, complex disease that impacts men and women differently; whilst the incidence of high blood pressure (BP) is roughly equal over a lifetime, men typically are at higher risk of developing the disease earlier in life, before 50 years of age. There is adequate evidence that the brain is critical for the BP setpoint. The paraventricular nucleus (PVN) of the hypothalamus is an integrative structure that can influence not only neurohumoral responses to blood pressure changes, but also sympathetic drive. Here we manipulate the androgenic status of both male and female spontaneously hypertensive rats (SHRs) to determine how this changes gene expression within the PVN of these animals. Methods: SHR (8-weeks old) were either sham-operated or orchiectomized, whereas all females were oophorectomized, half of which received 10mg testosterone propionate subcutaneously. Mean arterial pressure (MAP) and testosterone (T) were measured by carotid cannulation and ELISA respectively. Sequencing was performed on hand-punched PVN sections and subjected to robust bioinformatic analysis. Results: in total, 6,571 differentially regulated genes (DRGs) are regulated in the PVN of male and female rats. High T (endogenous or replaced) correlates with higher MAP in both sexes. Orchidectomy-induced T depletion resulted in the significant regulation of 2,104 genes, involved in thousands of biological roles, including ones related to hormone and sex-hormone signalling. In the female SHR, testosterone replacement in oophorectomized animals induced the regulation of 1,727 genes, sharing many biological functions with those in the high T males. We validated key genes by qPCR to determine false discovery rate. Conclusions: T status in hypertensive rats correlates with MAP, and consistent changes in PVN transcriptome | | 7:54a |
A Myosin Nanomotor Essential for Stereocilia Maintenance Expands the Etiology of Hereditary Hearing Loss DFNB3
Cochlear hair cells transduce sound using stereocilia, and disruption to these delicate mechanosensors is a significant cause of hearing loss. Stereocilia architecture is dependent upon the nanomotor myosin 15. A short isoform (MYO15A-2) drives stereocilia development by delivering an elongation-promoting complex (EC) to stereocilia tips, and an alternatively spliced long isoform (MYO15A-1) tunes postnatal size in shorter stereocilia, which possess mechanosensitive ion channels. Disruption of these functions causes two distinct stereocilia pathologies, which underly human autosomal recessive non-syndromic hearing loss DFNB3. Here, we characterize a new isoform, MYO15A-3, that increases expression in postnatal hair cells as the developmental MYO15A-2 isoform wanes reciprocally. We show the critical EC complex is initially delivered by MYO15A-2, followed by a postnatal handover to MYO15A-3, which continues to deliver the EC. In a Myo15a-3 mutant mouse, stereocilia develop normally with correct EC targeting, but lack the EC postnatally and do not maintain their adult architecture, leading to progressive hearing loss. We conclude MYO15A-3 delivers the EC in postnatal hair cells and that the EC and MYO15A-3 are both required to maintain stereocilia integrity. Our results add to the spectrum of stereocilia pathology underlying DFNB3 hearing loss and reveal new molecular mechanisms necessary for resilient hearing during adult life. | | 9:02a |
DMC-BrainMap - an open-source, end-to-end tool for multi-feature brain mapping across species
A central goal of current neuroscience research is to understand how behavior emerges from neuronal circuit activity. For this, cellular and circuit components in intact brains need to be identified and studied using e.g. viral tracing, electrophysiology, imaging, activity perturbations, and behavior. A commonality of these approaches is the need to establish the anatomical locations of both experimental parameters (e.g. recording/injection sites) and circuit components (e.g. cell bodies/projections). The development of standardized coordinate systems, i.e. reference brain atlases, has proven essential for reproducible, cross-laboratory mapping of anatomical data. However, the process of mapping, analyzing, and visualizing anatomical data remains challenging, especially for users lacking programming expertise. Here, we introduce DMC-BrainMap, an open-source napari plugin designed as a user-friendly tool for streamlined processing and whole-brain analysis of anatomical data. The working principle and core functionalities include all steps after image acquisition, i.e., preprocessing of images, registration of images to a reference atlas, segmentation of different anatomical features, and data analysis/visualization. DMC-BrainMap can be applied to histological data obtained from a variety of model organisms at different developmental stages, including mouse, rat, and zebrafish. We demonstrate the utility of DMC-BrainMap by mapping and quantifying cell bodies, axonal densities, injection sites as well as placement of optical fibers and Neuropixels probes. Further, we show how spatial transcriptomics data can be integrated into the DMC-BrainMap workflow. By eliminating the need for programming by the user, DMC-BrainMap provides an easy-to-use tool for increased rigor, reproducibility, and data sharing in neuroscientific research involving animal models. | | 11:46a |
Reward-based prosocial choices in mice
Prosocial behaviors, actions that benefit others, are an essential part of the social life of humans and other animals, by promoting bonding and cohesion among individuals and groups. Here we present a new behavioural paradigm to assess prosociality in food foraging contexts in laboratory mice, based in our paradigm previously developed for rats. In this task, the decision-maker can choose between two options, one that will only provide rewards to itself (selfish choice) or one that will reward both itself and its cagemate (prosocial choice). Our work reveals that prosocial choices in male mice are not widespread and are only observed in a small proportion of animals. Using detailed analysis of behavior, we describe that recipients of help express different social cues in prosocial and selfish trials, but decision makers do not take them into account to guide their choices. Furthermore, we assess how the level of individual training and the physical layout of the paradigm might affect the performance in this social task. Only those mice with increased social attention (16% of the animals) display prosocial preferences, suggesting these to be rooted in similar behavioural factors and social interactions that we previously described in other work with rats. |
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