Biology subjects

Di Giaimo, R.

Publications and source records attributed to Di Giaimo, R..

6 recordsLinked to original sources

bioRxiv2024

Intrinsic and extrinsic mechanisms alter neural cell fate specification in EPM1 Epilepsy

The extracellular milieu, including extracellular vesicles (EVs), plays a pivotal role in brain development by regulating neural processes such as proliferation, differentiation, and migration. In this study, we sought to elucidate the pathogenesis of progressive myoclonus epilepsy type 1 (EPM1), a disease caused by mutations in the CSTB gene, using cerebral organoids (COs) derived from EPM1 patient cells. The results demonstrate that EPM1 COs display increased electrophysiological activity and a disrupted excitatory/inhibitory balance. Single-cell RNA sequencing (scRNA-seq) analysis of ventral EPM1-Cos revealed an abnormal specification of progenitor fate, with a shift toward dorsal neuron identities at the expense of inhibitory interneurons. In addition, pathological alterations in EV biogenesis and cargo were identified, including aberrant Sonic Hedgehog (SHH) signaling, which may disrupt cortical patterning. These findings suggest that both intrinsic progenitor identity shifts and extrinsic EV-mediated signaling contribute to EPM1 pathology. Our study highlights potential therapeutic strategies mediated by EVs as a novel approach to mitigate disease progression.

neuroscience↗

bioRxiv2024

Neuronal Hyperactivity in Neurons Derived from Individuals with Grey Matter Heterotopia

Periventricular heterotopia (PH), a common form of grey matter heterotopia associated with developmental delay and drug-resistant seizures, poses a challenge in understanding its neurophysiological basis. Human cerebral organoids (hCOs) derived from patients with causative mutations in FAT4 or DCHS1 mimic PH features. However, neuronal activity in these 3D models has not yet been invetigated. Here, silicon probe recordings revealed exaggerated spontaneous spike activity in FAT4 and DCHS1 hCOs, suggesting functional changes in neuronal networks. Transcriptome and proteome analyses identified changes in gene ontology terms associated with neuronal morphology and synaptic function. Furthermore, patch-clamp recordings revealed a decreased spike threshold specifically in DCHS1 neurons, likely due to increased somatic voltage-gated sodium channels. Morphological reconstructions and immunostainings revealed greater morphological complexity of PH neurons and synaptic alterations contributing to hyperactivity, with morphological rescue observed in DCHS1 neurons by wild-type DCHS1 expression. Overall, we provide new comprehensive insights into the cellular changes underlying symptoms of grey matter heterotopia.

neuroscience↗

bioRxiv2023

Extracellular vesicle-mediated trafficking of developmental cues is altered during human brain disease

Cellular crosstalk is an essential process influenced by numerous factors including secreted vesicles that transfer nucleic acids, lipids, and proteins between cells. Extracellular vesicles (EVs) have been the center of many studies focusing on neuron-to-neuron communication, but the role of EVs in progenitor-to-neuron and -astrocyte communication and whether EVs display cell-type-specific features for cellular crosstalk during neurogenesis is unknown. Here, using human-derived cerebral organoids, neural progenitors, neurons, and astrocytes, we found that many proteins coded by genes associated with neurodevelopmental disorders are transported via EVs. Thus, we characterized the protein content of EVs and showed their cell type-specific dynamics and function during brain development. Changes in the physiological crosstalk between cells can lead to neurodevelopmental disorders. EVs from patients with epilepsy were found altered in composition and function. Alterations in the intracellular and extracellular compartments highlighted a clear dysregulation of protein trafficking. This study sheds new light on the biology of EVs during brain development and neurodevelopmental disorders. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=185 SRC="FIGDIR/small/546646v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1dad15aorg.highwire.dtl.DTLVardef@e699ccorg.highwire.dtl.DTLVardef@17b371borg.highwire.dtl.DTLVardef@5efa7b_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract(left) EV uptake mechanism varies depending on the receiving cell type; NPCs transport neuron EVs (nEVs) and astrocyte EVs (aEVs) to the nucleus, astrocytes localize progenitor EVs (pEVs) to the cytoplasm, and neurons retain pEVs and aEVs along the plasma membrane. (right) Cerebral organoids (COs) from progressive Myoclonus Epilepsy Type I (EPM1) patients release EVs lacking key proteins in neurodevelopment and proteins necessary for EV biogenesis and release. Illustration created using BioRender.

developmental biology↗

bioRxiv2022

Extrinsic regulation of interneuron specification and migration

The imbalance between excitatory and inhibitory neurons in the human brain might lead to neurodevelopmental and neuropsychiatric disorders including cortical malformations, epilepsy, and autism spectrum disorders. We propose that the extracellular environment regulates interneuron differentiation and migration during development, ultimately affecting the excitatory/inhibitory balance. Using ventral cerebral organoids and dorso-ventral cerebral assembloids with mutations in the extracellular matrix gene LGALS3BP, we show that the composition of the extracellular environment regulates the molecular differentiation of neurons, resulting in alterations in migratory dynamics. To investigate how the extracellular environment affects neuronal specification and migration, we characterized the protein content of extracellular vesicles from cerebral organoids carrying a mutation in LGALS3BP, previously identified in individuals with cortical malformations and neuropsychiatric disorders. These results revealed differences in protein composition. Interestingly, proteins associated with cell-fate decision, neuronal migration and extracellular matrix composition were altered in mutant extracellular vesicles. Moreover, we show that treatment with extracellular vesicles changes the transcriptomic profile in neural progenitor cells. Our results indicate that neuronal molecular differentiation is regulated by factors released into the extracellular environment.

developmental biology↗

bioRxiv2022

Tripartite extended amygdala - basal ganglia CRH circuit drives arousal and avoidance behaviour

An adaptive stress response involves various mediators and circuits orchestrating a complex interplay of physiological, emotional and behavioural adjustments. We identified a population of corticotropin-releasing hormone (CRH) neurons in the lateral part of the interstitial nucleus of the anterior commissure (IPACL) - a subdivision of the extended amygdala, which exclusively innervate the substantia nigra (SN). Specific stimulation of this circuit elicits arousal and avoidance behaviour contingent on CRH receptor 1 (CRHR1) located at axon terminals in the SN, which originate from external globus pallidus (GPe) neurons. The neuronal activity prompting the observed behaviour is shaped by IPACLCRH and GPeCRHR1 neurons coalescing in the SN. These results delineate a novel tripartite CRH circuit functionally connecting extended amygdala and basal ganglia nuclei to drive arousal and avoidance behaviour. One-Sentence SummaryBrain centres involved in emotional and motor control are connected through a stress peptide promoting arousal and avoidance behaviour

neuroscience↗

bioRxiv2020

Cell-type specific impact of glucocorticoid receptor activation on the developing brain

A fine-tuned balance of glucocorticoid receptor (GR) activation is essential for organ formation, with disturbances influencing health outcomes. Excess GR-activation in utero has been linked to brain-related negative outcomes, with unclear underlying mechanisms, especially regarding cell-type specific effects. To address this, we used an in vitro model of fetal human brain, induced pluripotent-stem-cell-derived cerebral organoids, and mapped GR-activation effects using single-cell transcriptomics across development. Interestingly, neurons showed targeted regulation of differentiation- and maturation-related transcripts, suggesting a delay of these processes upon GR-activation. Uniquely in neurons, differentially-expressed transcripts were significantly enriched for genes associated with behavior-related phenotypes and disorders. This suggests that aberrant GR-activation could impact proper neuronal maturation, leading to increased disease susceptibility, through neurodevelopmental processes at the interface of genetic susceptibility and environmental exposure.

neuroscience↗