Biology subjects

Fioravante, D.

Publications and source records attributed to Fioravante, D..

6 recordsLinked to original sources

bioRxiv2026

Precocious maturation and Purkinje cell dysfunction in the mouse Chd8 haploinsufficient cerebellum

The cerebellum plays an emerging, but understudied, role in neurodevelopmental disorders (NDDs). Mutations in CHD8 cause a monogenic NDD (CHD8-NDD) characterized by autism and other manifestations, and prior work in Chd8 mutant mice reported cerebellar abnormalities, raising the possibility of cerebellar contribution to CHD8-NDD. To comprehensively characterize the impact of Chd8 haploinsufficiency on cerebellar development and function, we profiled the postnatal day 12 (P12) cerebellum of germline Chd8+/- mice using transcriptomic, morphological, and electrophysiological approaches. Gross cerebellar morphology was unaffected, but single-nucleus RNA sequencing revealed transcriptomic signatures of pathophysiology across cell types, including accelerated maturation of molecular layer interneurons and granule cells, and altered myelination state of oligodendrocytes. Purkinje cells (PCs) showed the strongest transcriptomic burden of any cell type and, consistent with this, exhibited altered morphology and electrophysiological properties. Bulk RNA sequencing confirmed that transcriptomic pathology persists into adulthood, indicating lasting impacts on both neuronal and glial gene expression. Together, these results capture cell-type-specific cerebellar perturbations associated with Chd8 haploinsufficiency and support the cerebellum as a relevant site of pathology in CHD8-NDD.

neuroscience↗

bioRxiv2026

Viral Strategies for In Vivo Optogenetic Stimulation of Purkinje Cell Terminals and Electrophysiological Characterization of Downstream Cerebellar Nuclear Activity in Mice

The cerebellar cortex regulates motor and cognitive function through its sole output neurons, the Purkinje cells (PCs), which inhibit downstream targets, yet precise manipulation of PC activity in vivo remains technically challenging. Here, we describe two viral strategies with differing cell-type specificities for in vivo optogenetic control of PCs and functional assessment of neural activity in downstream target regions. Specifically, we detail strategies for expression of the fast channelrhodopsin ChETA in PCs that enable light-evoked activation of PC axonal terminals in medial deep cerebellar nuclei (mDCN), and demonstrate light-evoked modulation of mDCN neural activity using in vivo extracellular electrophysiology. This protocol provides a reproducible and adaptable framework for cell-type-specific manipulation and functional characterization of cerebellar circuits, with broad applicability to studies of cerebellar physiology, motor and nonmotor behavior, learning and disease.

neuroscience↗

bioRxiv2022

Novel cerebello-amygdala connections provide missing link between cerebellum and limbic system

The cerebellum is emerging as a powerful regulator of cognitive and affective processing and memory in both humans and animals and has been implicated in affective disorders. How the cerebellum supports affective function remains poorly understood. The short-latency (just a few ms) functional connections that were identified between the cerebellum and amygdala -a structure crucial for the processing of emotion and valence-more than 4 decades ago raise the exciting, yet untested, possibility that a cerebellum-amygdala pathway communicates information important for emotion. The major hurdle in rigorously testing this possibility is the lack of knowledge about the anatomy and functional connectivity of this pathway. Our initial anatomical tracing studies in mice excluded the existence of a direct monosynaptic pathway between cerebellum and amygdala. Using transneuronal tracing techniques, we have identified a novel disynaptic pathway that connects the cerebellar output nuclei to the basolateral amygdala. This pathway recruits the understudied intralaminar thalamus as a node. Using ex vivo optophysiology and super-resolution microscopy, we provide the first evidence for the functionality of the pathway, thus offering a missing mechanistic link between the cerebellum and amygdala. This discovery provides a connectivity blueprint between the cerebellum and a key structure of the limbic system. As such, it is the requisite first step toward obtaining new knowledge about cerebellar function in emotion, thus fundamentally advancing understanding of the neurobiology of emotion, which is perturbed in mental and autism spectrum disorders.

neuroscience↗

bioRxiv2021

Short-term plasticity persists in the absence of PKC phosphorylation of Munc18-1

Post tetanic potentiation (PTP) is a form of short-term plasticity that lasts for tens of seconds following a burst of presynaptic activity. It has been proposed that PTP arises from protein kinase C (PKC) phosphorylation of Munc18-1, an SM (Sec1/Munc-18 like) family protein that is essential for release. To test this model, we made a knockin mouse in which all Munc18-1 PKC phosphorylation sites were eliminated through serine-to-alanine point mutations (Munc18-1 SA mice). Expression of Munc18-1 was not altered in Munc18-1SA mice, and there were no obvious behavioral phenotypes. At the hippocampal CA3 to CA1 synapse, and the granule cell parallel fiber to Purkinje cell (PF to PC) synapse, basal transmission was largely normal except for small decreases in paired-pulse facilitation that are consistent with a slight elevation in release probability. Phorbol esters that mimic activation of PKC by diacylglycerol still increased synaptic transmission in Munc18-1 SA mice. In Munc18-1 SA mice, 70% of PTP remained at CA3 to CA1 synapses, and the amplitude of PTP was not reduced at PF to PC synapses. These findings indicate that at both CA3 to CA1 and PF to PC synapses, phorbol esters and PTP enhance synaptic transmission primarily by mechanisms that are independent of PKC phosphorylation of Munc18-1. Significance StatementA leading mechanism for a prevalent form of short-term plasticity, post-tetanic potentiation (PTP), involves protein kinase C phosphorylation of Munc18-1. This study tests this mechanism by creating a knock in mouse in which Munc18-1 is replaced by a mutated form of Munc18-1 that cannot be phosphorylated. The main finding is that most PTP at hippocampal CA3 to CA1 synapses, or at cerebellar granule cell to Purkinje cell synapses does not rely on PKC phosphorylation of Munc18-1. Thus, mechanisms independent of PKC phosphorylation of Munc18-1 are important mediators of PTP.

neuroscience↗

bioRxiv2020

Cerebellar Activation Bidirectionally Regulates Nucleus Accumbens Shell and Core

Although the cerebellum is now recognized as part of a long-range brain network that serves limbic functions and motivated behavior, knowledge of cerebello-limbic connectivity is limited, and nothing is known about how the cerebellum connects functionally to the nucleus accumbens (NAc). Here, we report that stimulation of cerebellar nuclei in mice of both sexes modulates spiking activity in both NAc core and medial shell with fast excitation and slower, less synchronized inhibition. Fast responses would be well poised to support rapid communication of information critical to the control of motivated behavior, whereas slower responses may be suggestive of a regulatory function, such as gain control. Tracing experiments to chart cerebellar nuclei-NAc pathways identified disynaptic pathways that recruit the ventral tegmental area (VTA) and intralaminar thalamus (Centromedial and Parafascicular nuclei) as intermediary nodes. Optogenetic activation of cerebellar axons in each of these nodes was sufficient to evoke responses in both NAc core and medial shell, albeit with distinct, node-dependent properties. These pathways and the functional connectivity they support could underlie the role of the cerebellum in motivated behavior.

neuroscience↗

bioRxiv2020

High-frequency stimulation of ventral CA1 neurons reduces amygdala activity and inhibits fear

The hippocampus can be divided into distinct segments that make unique contributions to learning and memory. The dorsal hippocampus supports cognitive processes like spatial learning and navigation while the ventral hippocampus regulates emotional behaviors related to fear, anxiety and reward. In the current study, we determined how pyramidal cells in ventral CA1 respond to spatial cues and aversive stimulation during a context fear conditioning task. We also examined the effects of high and low frequency stimulation of these neurons on defensive behaviors. Similar to previous work in the dorsal hippocampus, we found that cells in ventral CA1 expressed high-levels of c-Fos in response to a novel spatial environment. Surprisingly, however, the number of activated neurons did not increase when the environment was subsequently paired with footshock. This was true even in the subpopulation of ventral CA1 pyramidal cells that send direct projections to the amygdala. When these cells were stimulated at high-frequencies (20-Hz), we observed feedforward inhibition of basal amygdala neurons and impaired expression of context fear. In contrast, low-frequency stimulation (4-Hz) did not inhibit principal cells in the amygdala and produced a slight increase in fear generalization. Similar results have been reported in dorsal CA1. Therefore, despite the clear differences between the dorsal and ventral hippocampus, CA1 neurons in each segment appear to make similar contributions to context fear conditioning.

neuroscience↗