Biology subjects

De Sanctis, C.

Publications and source records attributed to De Sanctis, C..

3 recordsLinked to original sources

bioRxiv2022

MicroRNA-218 instructs proper assembly of hippocampal networks

The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. A key aspect of this developmental program is mediated at the post-transcriptional level by microRNAs (miRNAs). Deletion of neuronal enriched miRNAs induces strong developmental phenotypes, and multiple reports have found altered levels of miRNAs in patients with neurodevelopmental disorders. However, cellular and molecular mechanisms used by miRNAs to instruct proper brain development remain largely unexplored. Here, through multiple screens, we identified miR-218 as a critical regulator of hippocampal assembly in mice. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons and GABAergic inhibitory interneurons. Transient inhibition of miR-218 in early life results in an adult brain with heightened network activity and a predisposition to seizures. We used RNA-seq and FACS-seq (fluorescence-activated cell sorting followed by RNA-seq) to identify global and cell type-specific changes in gene expression in the absence of miR-218 and narrow down which altered developmental processes would lead to long-term network instability. We find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Finally, conditional knockout of miR-218 in interneurons, but not pyramidal neurons is sufficient to recapitulate the effects on long-term stability. Taken together, the data suggest that miR-218 orchestrates hippocampal network assembly to produce a stable network in the adult, primarily by regulating interneuron function in early postnatal life.

neuroscience↗

bioRxiv2021

Stabilization of spine Synaptopodin by mGluR1 is required for mGluR-LTD

Dendritic spines, actin-rich protrusions forming the postsynaptic sites of excitatory synapses, undergo activity-dependent molecular and structural remodeling. Activation of group 1 metabotropic glutamate receptors - mGluR1 and mGluR5 - by synaptic or pharmacological stimulation, induces LTD but whether this is accompanied with spine elimination remains unresolved. A subset of telencephalic mushroom spines contains the spine apparatus (SA), an enigmatic organelle composed of stacks of smooth endoplasmic reticulum, whose formation depends on the expression of the actin-bundling protein Synaptopodin. Allocation of Synaptopodin to spines appears governed by cell-intrinsic mechanisms as the relative frequency of spines harboring Synaptopodin is conserved in vivo and in vitro. Here we show that expression of Synaptopodin/SA in spines is required for induction of mGluR-LTD at Schaffer collateral-CA1 synapses. Post-mGluR-LTD, mushroom spines lacking Synaptopodin/SA are selectively lost whereas spines harboring it are preserved, a process dependent on activation of mGluR1 but not mGluR5. Mechanistically, we find that mGluR1 supports physical retention of Synaptopodin within excitatory spine synapses during LTD while triggering lysosome-dependent degradation of the protein residing in dendritic shafts. Together, these results reveal a cellular mechanism, dependent on mGluR1, which enables selective preservation of stronger spines containing Synaptopodin/SA while eliminating weaker ones and potentially countering spurious strengthening by de novo recruitment of Synaptopodin. Overall our results identify spines with Synaptopodin/SA as the locus of mGluR-LTD and underscore the importance of the molecular microanatomy of spines in synaptic plasticity.

neuroscience↗

bioRxiv2020

The G protein-Coupled Metabotropic Glutamate Receptor 1 controls neuronal macroautophagy

Autophagy is an evolutionarily conserved, highly regulated catabolic process critical to neuronal homeostasis, function and survival throughout organismal lifespan. However, the external factors and signals that control autophagy in neurons are still poorly understood. Here we report that the G protein-coupled metabotropic glutamate receptor 1 (mGlu1) contributes to control basal autophagy in the brain. Autophagy is upregulated in the brain of adult mGlu1 knockout mice and genetic deletion or pharmacological inhibition of native mGlu1 receptors enhances autophagy flux in neurons. The evolutionarily conserved adaptor protein FEZ1, identified by a genome-wide screen as mGlu1 receptor interacting partner, was found to participate in the regulation of neuronal autophagy and to be required for repression of autophagy flux by the mGlu1 receptor. Furthermore, FEZ1 appears to enable association of mGlu1 with Ulk1, a core component of the autophagy pathway. Thus, we propose that the mGlu1 receptor contributes to restrain constitutive autophagy in neurons.

neuroscience↗