Biology subjects

De Leonibus, E.

Publications and source records attributed to De Leonibus, E..

6 recordsLinked to original sources

bioRxiv2025

Functional specialization of the hippocampus along its dorso-ventral axis: from span to supraspan in working memory capacity

Working memory (WM) is characterized by a limited capacity or span, beyond which performance deteriorates, the supraspan condition. Human neuropsychology and neuroimaging studies have implicated the medial temporal lobe (MTL), including the hippocampus (HPC), in WM particularly when memory load exceeds span, yet no animal model has been established to investigate supraspan mechanisms. Here, we present a novel rodent model of supraspan memory and examine the distinct roles of dorsal and ventral HPC. Using selective NMDA lesions in mice combined with object recognition tasks and a modified radial arm maze (RAM), we manipulated memory load and strategy constraints to assess span and supraspan performance. Dorsal HPC lesions impaired object memory span, while ventral lesions spared this ability. In the RAM, span performance (number of correct arm visits before the first error) was unaffected by either lesion under allocentric conditions. However, once animals exceeded span, following the first error, here defined as the supraspan condition, both dorsal and ventral lesions caused catastrophic disorientation and error escalation. Under free-choice conditions, ventral HPC lesions selectively reduced the occurrence of trials with no errors in the first 5 choices, increased errors overall, and disrupted sequential egocentric strategies. Together, these results demonstrate that supraspan performance can be modeled in rodents, revealing a dorsal contribution to object memory under high load, a ventral contribution to egocentric spatial strategies, and a shared hippocampal role in supraspan memory performance. This paradigm provides a translational framework for investigating supraspan deficits observed in MTL patients and Alzheimers disease.

neuroscience↗

bioRxiv2024

Tbx1 haploinsufficiency causes brain metabolic and behavioral anomalies in adult mice which are corrected by vitamin B12 treatment

IntroductionThe brain-related phenotypes observed in 22q11.2 deletion syndrome (22q11.2DS) are highly variable and their origin is poorly understood. Changes in brain metabolism may cause or contribute to the phenotypes, given that many of the deleted genes (approx. 10%) are implicated in metabolic processes, but this is currently unknown. It is clearly important to address this knowledge gap, but in humans, the primary material required for studying brain metabolism is inaccessible. For this reason, we sought to address the issue using two mouse models of 22q11.2DS. MethodsWe used three independent approaches to investigate brain metabolism in young adult mice, namely, mass spectrometry, nuclear magnetic resonance spectroscopy and transcriptomics. We selected to study primarily Tbx1 single gene mutants because it is the primary candidate disease gene. We then confirmed key findings in the multi-gene deletion mutant Df1/+. ResultsWe found that Tbx1 mutants have alterations of specific brain metabolites, including methylmalonic acid, which is highly brain-toxic, as well as a more general metabolomic imbalance. We provide transcriptomic evidence of an interaction genotype-vB12 treatment, and behavioural evidence of a response to vB12 treatment, which rescued some of the behavioural anomaly observed in Tbx1 mutants. We conclude that Tbx1 haploinsufficiency causes extensive brain metabolic anomalies, which are partially responsive to vB12 treatment. We suggest that alterations of glutamine-glutamate metabolism and fatty acid metabolism are key components of the metabolic phenotype in these mutants.

genetics↗

bioRxiv2022

Reactive microglia and cytokine release entails microtubule remodeling from acentrosomal to centrosomal arrays

Microglia reactivity entails a large-scale remodeling of cellular geometry, but the role of the microtubule cytoskeleton during these changes remains unexplored. Here we show that reactive proinflammatory microglia provide a heretofore unique example of microtubule reorganization from a non-centrosomal array of parallel and stable microtubules to a radial array of more dynamic microtubules. While in the homeostatic state microglia nucleate microtubules at Golgi outposts, proinflammatory signaling induces recruitment of nucleating material nearby the centrosome and inhibition of centrosomal maturation enhances NLRP3 inflammasome activation and secretion of IL-1{beta}. Our results demonstrate that a hallmark of microglia reactivity is a striking remodeling of the microtubule cytoskeleton and suggest that pericentrosomal microtubule nucleation may serve as a distinct marker of microglia activation as well as a novel target to modulate cytokine-mediated inflammatory responses in chronic disease and tissue injury.

cell biology↗

bioRxiv2021

Mirtazapine treatment in a young female mouse model of Rett syndrome identifies time windows for the rescue of early phenotypes during development

Rett Syndrome (RTT) is a rare X-linked neurodevelopmental disorder, mainly caused by mutations in the MECP2 gene. Reduction in monoamine levels in RTT patients and mouse models suggested the possibility to rescue clinical phenotypes through antidepressants. Accordingly, we tested mirtazapine (MTZ), a noradrenergic and specific-serotonergic tetracyclic antidepressant (NaSSA). In previous studies, we showed high tolerability and significant positive effects of MTZ in male Mecp21m1.1Bird-knock-out mice, adult female Mecp2tm1.1Bird-heterozygous (Mecp2+/-) mice, and adult female RTT patients. However, it remained to explore MTZ efficacy in female Mecp2+/- mice at young ages. As RTT-like phenotypes in young Mecp2+/- mice have been less investigated, we carried out a behavioural characterization to analyze Mecp2+/- mice in "early adolescence" (6 weeks) and "late adolescence/young adulthood" (11 weeks) and identified several progressive phenotypes. Then, we evaluated the effects of either a 15- or a 30-day MTZ treatment on body weight and impaired motor behaviours in 11-week-old Mecp2+/- mice. Finally, since defective cortical development is a hallmark of RTT, we performed a histological study on the maturation of perineuronal nets (PNNs) and parvalbuminergic (PV) neurons in the primary motor cortex. The 30-day MTZ treatment was more effective than the shorter 15-day treatment, leading to the significant rescue of body weight, hindlimb clasping and motor learning in the accelerating rotarod test. Behavioral improvement was associated with normalized PV immunoreactivity levels and PNN thickness. These results support the use of MTZ as a new potential treatment for adolescent girls affected by RTT and suggest a possible mechanism of action.

neuroscience↗

bioRxiv2021

Thalamo-hippocampal pathway regulates incidental memory load: insights from sex differences

Incidental memory can be challenged by increasing either the retention delay or the memory load. The dorsal hippocampus (dHP) appears to help with both consolidation from short-term (STM) to long-term memory (LTM), and higher memory loads, but the mechanism is not fully understood. Here we find that female mice, despite having the same STM capacity of 6 objects and higher resistance to distraction in our different object recognition task (DOT), when tested over 1h or 24h delays appear to transfer to LTM only 4 objects, whereas male mice have an STM capacity of 6 objects in this task. In male mice the dHP shows greater activation (as measured by c-Fos expression), whereas female mice show greater activation of the ventral midline thalamus (VMT). Optogenetic inhibition of the VMT-dHP pathway during off-line memory consolidation enables 6-object LTM retention in females, while chemogenetic VMT-activation impairs it in males. Thus, removing or enhancing sub-cortical inhibitory control over the hippocampus, leads to differences in incidental memory. One Sentence SummaryThe sex-dependent recruitment of a subcortical pathway regulates how many items are spontaneously memorized in mice.

neuroscience↗

bioRxiv2019

α-synuclein in the retina leads to degeneration of dopamine amacrine cells impairing vision

Introduction-synuclein aggregates have been identified in the retina of Parkinsons disease patients associated to vision impairment. In this study, we sought to determine the effects of -synuclein overexpression on the survival and function of dopaminergic (DA) amacrine cells in the retina.\n\nMethodsAdult mice were intravitreally injected with an adeno-associated viral (AAV) vector to overexpress human wild-type -synuclein in the inner retina. Following systemic injections of levodopa (L-DOPA), retinal responses and visual acuity driven behavior were measured by electroretinography (ERG) and water maze task, respectively. Amacrine cells and ganglion cells were counted at 1, 2 and 3 months post-injection.\n\nResults-synuclein led to an early loss of DA cells, which was associated with the decrease of light-adapted ERG responses and visual acuity. Systemic injections of L-DOPA rescued these retinal and visual abnormalities.\n\nConclusionsThe data show that -synuclein affects dopamine neurons in the retina. The approach provides a novel accessible mode of modeling the underlying mechanisms implicated in synucleinophaties pathogenesis and for testing novel treatments.

neuroscience↗