Biology subjects

Longo, F.

Publications and source records attributed to Longo, F..

12 recordsLinked to original sources

bioRxiv2026

Primary Hyperparathyroidism Reveals Limited Adipose Remodeling in Human

BackgroundPreclinical models implicate the parathyroid hormone/parathyroid-hormone-related protein (PTH/PTHrP)-PTH1 receptor (PTH1R) axis in adipocyte lipolysis, adipose browning, and energy wasting. Whether this catabolic program is reproduced in vivo in humans remains unresolved. Primary hyperparathyroidism (PHPT), a condition of chronic endogenous PTH excess, provides a clinically relevant model to test the translational relevance of this pathway. MethodsWe combined population-scale analyses with a prospective human intervention study. PTH/PTH1R associations with body composition were evaluated in the UK Biobank and compared with PTH dynamics in cancer-associated cachexia using TRACERx proteomic data. In parallel, patients with PHPT were assessed before and after parathyroidectomy and compared with matched surgical controls. Biochemical parameters, circulating adipocytokines, DXA- and BIA-derived body composition, histology, UCP1 immunohistochemistry, and supraclavicular adipose tissue transcriptomic and proteomic profiles were integrated, with external validation in an independent supraclavicular adipose dataset. ResultsIn the UK Biobank, apparent positive associations between circulating PTH/PTH1R signals and fat or lean mass were markedly attenuated after matching for age, sex, and BMI, arguing against a disease-specific adiposity effect of PHPT. In TRACERx, circulating PTH did not increase across BMI-adjusted weight-loss grades. In the prospective cohort, parathyroidectomy normalized PTH, calcium, and phosphate but did not induce coherent changes in glucose metabolism, lipid profile, inflammatory markers, body weight, fat mass, lean mass, or thermogenic adipose signatures. Supraclavicular adipose histology, UCP1 staining, RNA-seq, proteomics, pathway analysis, and external dataset reanalysis converged on the absence of browning or thermogenic activation. By contrast, PHPT was associated with a selective adipose-related secretory phenotype: adiponectin, adipsin, and retinol-binding protein 4 were reversible after surgery, whereas lipocalin- 2 and thrombospondin-1 remained elevated. ConclusionsChronic endogenous PTH excess is not sufficient to induce a detectable thermogenic or energy- dissipating adipose program in humans under basal clinical conditions. These findings challenge direct extrapolation from rodent PTH/PTHrP models and reposition the human PTH-adipose axis as a selective secretory and remodeling pathway rather than a dominant driver of adipose browning or wasting. HighlightsO_LIPHPT provides an in vivo human model of chronic endogenous PTH excess. C_LIO_LIPTH/PTH1R associations with body composition are lost after stringent confounder control. C_LIO_LIParathyroidectomy normalizes mineral metabolism without inducing adipose browning or wasting. C_LIO_LISupraclavicular adipose histology, UCP1 staining, transcriptomics, and proteomics show no thermogenic activation. C_LIO_LIPHPT unmasks a selective adipose-related secretory signature with reversible and persistent components. C_LI

physiology↗

bioRxiv2023

A small-molecule TrkB ligand improves dendritic spine phenotypes and atypical behaviors in female Rett syndrome mice

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in methyl-CpG-binding protein-2 (MECP2), encoding a transcriptional regulator of many genes, including brain-derived neurotrophic factor (Bdnf). BDNF mRNA and protein levels are lower in RTT autopsy brains and in multiple brain regions of Mecp2-deficient mice, and experimentally increasing BDNF levels improve atypical phenotypes in Mecp2 mutant mice. Due to the low blood-brain barrier permeability of BDNF itself, we tested the effects of a brain penetrant, small molecule ligand of its TrkB receptors. Applied in vitro, LM22A-4 increased dendritic spine density in pyramidal neurons in cultured hippocampal slices from postnatal day (P) 7 male Mecp2 knockout (KO) mice as much as recombinant BDNF, and both effects were prevented by the TrkB receptor inhibitors K-252a and ANA-12. Consistent with its partial agonist activity, LM22A-4 did not affect spine density in CA1 pyramidal neurons in slice cultures from male wildtype (WT) mice, where typical BDNF levels outcompete its binding to TrkB. To identify neurons of known genotypes in the mosaic brain of female Mecp2 heterozygous (HET) mice, we treated 4-6-month-old female MeCP2-GFP WT and HET mice with peripheral injections of LM22A-4 for 4 weeks. Surprisingly, mutant neurons lacking MeCP2-GFP showed dendritic spine volumes comparable to that in WT controls, while MeCP2-GFP-expressing neurons showed larger spines, similar to the phenotype we described in symptomatic male Mecp2 KO mice where all neurons lack MeCP2. Consistent with this non-cell-autonomous mechanism, a 4-week systemic treatment with LM22A-4 had an effect only in MeCP2-GFP-expressing neurons in female Mecp2 HET mice, bringing dendritic spine volumes down to WT control levels, and without affecting spines of MeCP2-GFP-lacking neurons. At the behavioral level, we found that female Mecp2 HET mice engaged in aggressive behaviors significantly more than WT controls, which were reduced to WT levels by a 4-week systemic treatment with LM22A-4. Altogether, these data revealed differences in dendritic spine size and altered behaviors in Mecp2 HET mice, in addition to provide support to the potential usefulness of BDNF-related therapeutic approaches such as the partial TrkB agonist LM22A-4.

neuroscience↗

bioRxiv2022

Cell type-specific disruption of cortico-striatal circuitry drive repetitive patterns of behaviour in fragile X syndrome model mice

Individuals with fragile X syndrome (FXS) are frequently diagnosed with autism spectrum disorder (ASD), including increased risk for restricted and repetitive behaviours (RRBs). Consistent with observations in humans, FXS model mice display distinct RRBs and hyperactivity that are consistent with dysfunctional cortico-striatal circuits, an area relatively unexplored in FXS. Using a multidisciplinary approach, we dissected the contribution of two populations of striatal medium spiny neurons (SPNs) in the expression of RRBs in FXS model mice. We found that dysregulated protein synthesis at cortico-striatal synapses is a molecular culprit of the synaptic and ASD-associated motor phenotypes displayed by FXS model mice. Cell-type-specific translational profiling of the FXS mouse striatum revealed differentially translated mRNAs, providing critical information concerning potential therapeutic targets. Our findings represent the first evidence of a cell-type specific impact of the loss of FMRP on translation and the sequence of neuronal events in the striatum that drive RRBs in FXS. HighlightsDysregulated striatal protein synthesis underlies altered synaptic plasticity and RRBs displayed by FXS model mice FXS model mice exhibit cell type-specific molecular, morphological, and synaptic changes in the dorsolateral striatum Selective deletion of Fmr1 from dSNPs in mice alters translation and causes repetitive behavior TRAP-Seq indicates that there is altered binding of >120 mRNAs to ribosomes in dSNPs of Fmr1 KO mice G-protein signaling (RGS) 4 translation is significantly reduced in dSPNs in FXS model mice Treatment of FXS model mice with VU0152100, a positive allosteric modulator of the M4 muscarinic receptor that is upstream of RGS4, can reverse RRBs

neuroscience↗

bioRxiv2022

Myeloid deficiency of the intrinsic clock protein Bmal1 accelerates cognitive aging by disrupting microglial synaptic pruning

Aging is associated with loss of circadian immune responses and circadian gene transcription in peripheral macrophages. Microglia, the resident macrophages of the brain, also show diurnal rhythmicity in regulating local immune responses and synaptic remodeling. To investigate the interaction between aging and microglial circadian rhythmicity, we examined mice deficient in the core clock transcription factor, BMAL1. Aging Cd11bcre;Bmallox/lox mice demonstrated accelerated cognitive decline in association with suppressed hippocampal long-term potentiation and increases in immature dendritic spines. C1q deposition at synapses and synaptic engulfment were significantly decreased in aging Bmal1-deficient microglia, suggesting that BMAL1 plays a role in regulating synaptic pruning in aging. In addition to accelerated age-associated hippocampal deficits, Cd11bcre;Bmallox/lox mice also showed deficits in the sleep-wake cycle with increased wakefulness across light and dark phases. These results highlight an essential role of microglial BMAL1 in maintenance of synapse homeostasis in the aging brain. Significance StatementThis study demonstrates that myeloid deficiency of the circadian clock gene Bmal1 disrupts microglial synaptic pruning in the hippocampus, accelerates age-associated cognitive decline, and disrupts the sleep-wake cycle.

neuroscience↗

bioRxiv2021

Astrocytes derived from ASD patients alter behavior and destabilize neuronal activity through aberrant Ca2+ signaling

The cellular mechanisms of Autism Spectrum Disorder (ASD) are poorly understood. Cumulative evidence suggests that abnormal synapse function underlies many features of this disease. Astrocytes play in several key neuronal processes, including the formation of synapses and the modulation of synaptic plasticity. Astrocyte abnormalities have also been identified in the postmortem brain tissue of ASD patients. However, it remains unclear whether astrocyte pathology plays a mechanistic role in ASD, as opposed to a compensatory response. To address this, we strategically combined stem cell culturing with transplantation techniques to determine disease specific properties inherent to patient derived astrocytes. We demonstrate that ASD astrocytes induce repetitive behavior as well as impair memory and long-term potentiation when transplanted into the healthy mouse brain. These in vivo phenotypes were accompanied by reduced neuronal network activity and spine density caused by ASD astrocytes in hippocampal neurons in vitro. Transplanted ASD astrocytes also exhibit exaggerated Ca2+ fluctuations in chimeric brains. Genetic modulation of evoked Ca2+ responses in ASD astrocytes modulates behavior and neuronal activity deficits. Thus, we determine that ASD patient astrocytes are sufficient to induce repetitive behavior as well as cognitive deficit, suggesting a previously unrecognized primary role for astrocytes in ASD.

neuroscience↗

bioRxiv2021

Sacsin cotranslational degradation causes autosomal recessive spastic ataxia of Charlevoix-Saguenay

Autosomal recessive spastic ataxia of Charlevoix-Saguenay is caused by more than 200 different mutations in the SACS gene encoding sacsin, a huge multimodular protein of unknown function. ARSACS phenotypic spectrum is highly variable. Previous studies correlated the nature and position of SACS mutations with age of onset or disease severity, though the effects on protein stability were not considered. In this study, we explain mechanistically the lack of genotype-phenotype correlation in ARSACS, with important consequences for disease diagnosis and treatment. We found that sacsin is almost absent in ARSACS fibroblasts, regardless of the nature of the mutation. We did not detect sacsin in patients with truncating mutations, while we found it strikingly reduced or absent also in compound heterozygotes carrying diverse missense mutations. We excluded SACS mRNA decay, defective translation, or faster post-translational degradation as causes of protein reduction. Conversely, we demonstrated that nascent mutant sacsin protein undergoes preemptive cotranslational degradation, emerging as a novel cause of a human disease. Based on these findings, sacsin levels should be included in the diagnostic algorithm for ARSACS.

genetics↗

bioRxiv2020

Correction of eIF2-dependent defects in brain protein synthesis, synaptic plasticity, and memory in mouse models of Alzheimer's disease

Neuronal protein synthesis is essential for long-term memory consolidation. Conversely, dysregulation of protein synthesis has been implicated in a number of neurodegenerative disorders, including Alzheimers disease (AD). Several types of cellular stress trigger the activation of protein kinases that converge on the phosphorylation of eukaryotic translation initiation factor 2 (eIF2-P). This leads to attenuation of cap-dependent mRNA translation, a component of the integrated stress response (ISR). We show that AD brains exhibit increased eIF2-P and reduced eIF2B, key components of the eIF2 translation initiation complex. We further demonstrate that attenuating the ISR with the small molecule compound ISRIB (ISR Inhibitor) rescues hippocampal protein synthesis and corrects impaired synaptic plasticity and memory in mouse models of AD. Our findings suggest that attenuating eIF2-P-mediated translational inhibition may comprise an effective approach to alleviate cognitive decline in AD.

neuroscience↗

bioRxiv2020

Improved neurocognitive performance in FIV infected cats following treatment with the p75 neurotrophin receptor ligand LM11A-31

HIV rapidly infects the central nervous system (CNS) and establishes a persistent viral reservoir within microglia, perivascular macrophages and astrocytes. Inefficient control of CNS viral replication by antiretroviral therapy results in chronic inflammation and progressive cognitive decline in up to 50% of infected individuals with no effective treatment options. Neurotrophin based therapies have excellent potential to stabilize and repair the nervous system. A novel non-peptide ligand, LM11A-31, that targets the p75 neurotrophin receptor (p75NTR) has been identified as a small bioavailable molecule capable of strong neuroprotection with minimal side effects. To evaluate the neuroprotective effects of LM11A-31 in a natural infection model, we treated cats chronically infected with feline immunodeficiency virus (FIV) with 13 mg/kg LM11A-31 twice daily over a period of 10 weeks and assessed effects on cognitive functions, open field behaviors, activity, sensory thresholds, plasma FIV, cerebrospinal fluid (CSF) FIV, peripheral blood mononuclear cell provirus, CD4 and CD8 cell counts and general physiology. Between 12 and 18 months post-inoculation, cats began to show signs of neural dysfunction in T maze testing and novel object recognition, which were prevented by LM11A-31 treatment. Anxiety-like behavior was reduced in the open field and no changes were seen in sensory thresholds. Systemic FIV titers were unaffected but treated cats exhibited a log drop in CSF FIV titers. No significant adverse effects were observed under all conditions. The data indicate that LM11A-31 is likely to be a potent adjunctive treatment for the control of neurodegeneration in HIV infected individuals. Author SummaryThere are no effective treatments to halt the progression of most neurodegenerative diseases including HIV-associated neurodegeneration. Neurotrophins have the potential to provide strong neuroprotection but it has been difficult to develop usable interventions. A new drug, LM11A-31, that targets the p75 neurotrophin receptor has been developed that provides potent neuroprotection, is orally bioavailable and has the potential to prevent disease progression. The current studies were designed to evaluate the effects of the compound in an animal model of active HIV infection in preparation for a human clinical trial. Treatment of chronically infected animals with LM11A-31 normalized deficits in T maze performance, novel object recognition and open field behavior with no measurable adverse effects. Potential adverse effects associated with natural neurotrophins such as changes in sensory perception and increased systemic viral burden were not observed. A decrease in CSF FIV titers and a slight improvement in the CD4:CD8 ratio suggested that LM11A-31 may have beneficial effects beyond the anticipated neuroprotective effects. These findings are similar to beneficial effects seen in other animal models of neurodegeneration and CNS injury and support the use of LM11A-31 as an adjunctive neuroprotective agent for the treatment of HIV infected individuals.

neuroscience↗

bioRxiv2020

Genetic removal of p70 S6K1 corrects coding sequence length-dependent alterations in mRNA translation in fragile X syndrome mice

Loss of the fragile X mental retardation protein (FMRP) causes fragile X syndrome (FXS). FMRP is widely thought to repress protein synthesis, but its translational targets and modes of control remain in dispute. We previously showed that genetic removal of p70 S6 kinase 1 (S6K1) corrects altered protein synthesis as well as synaptic and behavioral phenotypes in FXS mice. In this study, we examined the gene-specificity of altered mRNA translation in FXS and the mechanism of rescue with genetic reduction of S6K1 by carrying out ribosome profiling and RNA-Seq on cortical lysates from wild-type, FXS, S6K1 knockout, and double knockout mice. We observed reduced ribosome footprint abundance in the majority of differentially translated genes in the cortices of FXS mice. We used molecular assays to discover evidence that the reduction in ribosome footprint abundance reflects an increased rate of ribosome translocation, which is captured as a decrease in the number of translating ribosomes at steady state, and is normalized by inhibition of S6K1. We also found that genetic removal of S6K1 prevented a positive-to-negative gradation of alterations in translation efficiencies (RF/mRNA) with coding sequence length across mRNAs in FXS mouse cortices. Our findings reveal the identities of dysregulated mRNAs and a molecular mechanism by which reduction of S6K1 prevents altered translation in FXS.

neuroscience↗

bioRxiv2020

Genetic reduction of PERK-eIF2α signaling in dopaminergic neurons drives cognitive and age-dependent motor dysfunction

An array of phenotypes in animal models of neurodegenerative disease have been shown to be reversed by neuronal inhibition of PERK, an eIF2 kinase that modulates the unfolded protein response (UPR). This suggests that targeting PERK therapeutically could be beneficial for treatment of human disease. Herein, using multiple genetic approaches we show that selective deletion of the PERK in mouse midbrain dopaminergic (DA) neurons results in multiple cognitive and age-dependent motor phenotypes. Conditional expression of phospho-mutant eIF2 in DA neurons recapitulated the phenotypes caused by deletion of PERK, consistent with a causal role of decreased eIF2 phosphorylation. In addition, deletion of PERK in DA neurons resulted in altered de novo translation, as well as age-dependent changes in axonal DA release and uptake in the striatum that mirror the pattern of motor changes observed. Taken together, our findings show that proper regulation of PERK-eIF2 signaling in DA neurons is required for normal cognitive and motor function across lifespan, and also highlight the need for caution in the proposed use of sustained PERK inhibition in neurons as a therapeutic strategy in the treatment of neurodegenerative disorders.

neuroscience↗

bioRxiv2019

Chemogenetic evidence that rapid neuronal de novo protein synthesis is required for consolidation of long-term memory

Translational control of memory processes is a tightly regulated process where the coordinated interaction and modulation of translation factors provides a permissive environment for protein synthesis during memory formation. Existing methods used to block translation lack the spatiotemporal precision to investigate cell-specific contributions to consolidation of long-term memories. Here, we have developed a novel chemogenetic mouse resource for cell type-specific and drug-inducible protein synthesis inhibition (ciPSI) that utilizes an engineered version of the catalytic kinase domain of dsRNA-activated protein (PKR). ciPSI allows rapid and reversible phosphorylation of eIF2 causing a block on general translation by 50% in vivo. Using this resource, we discovered that temporally structured pan-neuronal protein synthesis is required for consolidation of long-term auditory threat memory. Targeted protein synthesis inhibition in CamK2 expressing glutamatergic neurons in lateral amygdala (LA) impaired long-term memory, which was recovered with artificial chemogenetic reactivation at the cost of stimulus generalization. Conversely, genetically reducing phosphorylation of eIF2 in CamK2 positive neurons in LA enhanced memory strength, but was accompanied with reduced memory fidelity and behavior inflexibility. Our findings provide evidence for a finely tuned translation program during consolidation of long-term threat memories.

neuroscience↗

bioRxiv2018

Compartmentalized nonsense-mediated mRNA decay regulates synaptic plasticity and cognitive function via GluR1 signaling

Synaptic plasticity relies on new protein synthesis in dendrites that involves the selective translation of specific mRNAs. This requires a tight control of mRNA levels in dendrites. Consistently, RNA translation and degradation pathways have been recently linked to neurodevelopmental and neuropsychiatric diseases, suggesting a role for RNA regulation in synaptic plasticity and cognition. Despite being the only RNA regulatory pathway that is associated with multiple mental illnesses, the Nonsense-Mediated mRNA Decay (NMD) pathway presents an unexplored regulatory mechanism for synaptic function and plasticity. NMD is a highly conserved and selective RNA degradation pathway that exerts its function in a cell- and spatiotemporally-specific manner. Here, we show that neuron-specific disruption of NMD in adulthood attenuates learning, memory, hippocampal LTP, and potentiates perseverative/repetitive behavior. While it is known that local translation of specific mRNAs in dendrites enables synaptic plasticity, the tightly-controlled mechanisms that regulate local quantity of specific mRNAs remains poorly understood. We report that the NMD pathway operates within dendrites to regulate GluR1 surface levels. Specifically, NMD modulates the internalization of GluR1 and promotes its local synthesis in dendrites. We identified AMPK as a mechanistic substrate for NMD that contributes to the NMD-mediated regulation of GluR1 by limiting total GluR1 levels. These data establish that NMD regulates synaptic plasticity, cognition, and local protein synthesis in dendrites, providing fundamental insight into the neuron-specific function of NMD within the brain.

neuroscience↗