| 1. |
- Calvigioni, Daniela
(författare)
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Molecular determinants of endocannabinoid-mediated brain development
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The enchanting process of brain development entails a fragile and finite time window, throughout which biochemical imbalances and external insults can potentially affect developing neuronal circuits. Within the numerous exquisitely orchestrated events taking place in the foetal brain, axonal pathfinding is of paramount importance. If aberrant, axonal outgrowth can lead to errors in synaptogenesis and impaired connectivity, with potential long-lasting behavioural phenotypes. Despite the prominent role of endocannabinoids (eCBs) in axonal guidance, the molecular determinants of eCB-mediated axonal regulation remain largely unexplored. Aiming to interrogate the eCB machinery in less explored subcortical territories, study I investigates the role of the eCB system and its underlying components in foetal cholinergic projection neurons. Prenatal manipulation of cannabinoid receptor 1 (CB1R) permanently reshaped septo-hippocampal cholinergic projections. Nerve growth factor (NGF) was identified as an upstream molecule capable of regulating 2-arachydonoylglycerol (2-AG) via monoacylglycerol lipase (MAGL) degradation. The compartmentalization of each eCB machinery component along extending neurites is therefore crucial. However, axonal pathfinding takes place within the extracellular matrix, migrating glia and developing oligodendrocytes, generating a convoluted scenario where each growth cone interacts with multiple guidance proteins. Cannabinoid receptor 2 (CB2R)-expressing oligodendrocytes are introduced in study II as an additional player able to drive aberrant callosal axons spread upon supra-physiological 2-AG levels. Excess 2-AG engaged CB2R-mediated premature proliferation of oligodendrocyte end-feet. The interaction between the oligodendrocyte-derived chemorepellant molecule Slit2 and its receptor roundabout 1 (Robo1) on corticofugal axonal ends induced errant CB1R-expressing corticofugal axon pathfinding. In addition to being an endogenous receptor of eCBs, CB1R is also a target for the principal psychoactive compound of cannabis, ∆9-tetrahydrocannabinol (THC). In study III we undertook an unbiased proteomics screening of the embryonic cortical plate following maternal THC exposure. Superior Cervical Ganglion 10 (SCG10), a microtubule-binding protein present in extending growth cones, was identified as a direct molecular target of THC. Thus, microtubule dynamics represent a novel target of prenatal THC exposure, whose impairment promotes axonal defects and long-lasting synaptic connectivity impairment. Cholecystokinin (Cck)-containing interneurons, due to their high expression of CB1Rs and early appearance in the developing cortex, are likely targets of in utero eCB imbalances. Taking advantage of the recent CckBAC/DsRed mouse line in study IV we achieved a systematic anatomical and physiological characterization of Cck-CB1R-expressing cells from embryonic day (E)10.5 to adulthood. In sum, multiple upstream and downstream molecular components of the eCBs system were assessed over the course of this thesis investigation, within both physiological brain development and upon maternal cannabis exposure.
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| 2. |
- Malenczyk, Katarzyna, et al.
(författare)
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Fetal endocannabinoids orchestrate the organization of pancreatic islet microarchitecture
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:45, s. E6185-E6194
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Tidskriftsartikel (refereegranskat)abstract
- Endocannabinoids are implicated in the control of glucose utilization and energy homeostasis by orchestrating pancreatic hormone release. Moreover, in some cell niches, endocannabinoids regulate cell proliferation, fate determination, and migration. Nevertheless, endocannabinoid contributions to the development of the endocrine pancreas remain unknown. Here, we show that α cells produce the endocannabinoid 2-arachidonoylglycerol (2-AG) in mouse fetuses and human pancreatic islets, which primes the recruitment of β cells by CB1 cannabinoid receptor (CB1R) engagement. Using subtractive pharmacology, we extend these findings to anandamide, a promiscuous endocannabinoid/endovanilloid ligand, which impacts both the determination of islet size by cell proliferation and α/β cell sorting by differential activation of transient receptor potential cation channel subfamily V member 1 (TRPV1) and CB1Rs. Accordingly, genetic disruption of TRPV1 channels increases islet size whereas CB1R knockout augments cellular heterogeneity and favors insulin over glucagon release. Dietary enrichment in ω-3 fatty acids during pregnancy and lactation in mice, which permanently reduces endocannabinoid levels in the offspring, phenocopies CB1R(-/-) islet microstructure and improves coordinated hormone secretion. Overall, our data mechanistically link endocannabinoids to cell proliferation and sorting during pancreatic islet formation, as well as to life-long programming of hormonal determinants of glucose homeostasis.
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| 3. |
- Romanov, Roman A., et al.
(författare)
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Molecular interrogation of hypothalamic organization reveals distinct dopamine neuronal subtypes
- 2017
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Ingår i: Nature Neuroscience. - : Nature Publishing Group. - 1097-6256 .- 1546-1726. ; 20:2, s. 176-188
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Tidskriftsartikel (refereegranskat)abstract
- The hypothalamus contains the highest diversity of neurons in the brain. Many of these neurons can co-release neurotransmitters and neuropeptides in a use-dependent manner. Investigators have hitherto relied on candidate protein-based tools to correlate behavioral, endocrine and gender traits with hypothalamic neuron identity. Here we map neuronal identities in the hypothalamus by single-cell RNA sequencing. We distinguished 62 neuronal subtypes producing glutamatergic, dopaminergic or GABAergic markers for synaptic neurotransmission and harboring the ability to engage in task-dependent neurotransmitter switching. We identified dopamine neurons that uniquely coexpress the Onecut3 and Nmur2 genes, and placed these in the periventricular nucleus with many synaptic afferents arising from neuromedin S+ neurons of the suprachiasmatic nucleus. These neuroendocrine dopamine cells may contribute to the dopaminergic inhibition of prolactin secretion diurnally, as their neuromedin S+ inputs originate from neurons expressing Per2 and Per3 and their tyrosine hydroxylase phosphorylation is regulated in a circadian fashion. Overall, our catalog of neuronal subclasses provides new understanding of. hypothalamic organization and function.
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| 4. |
- Weglage, Moritz, et al.
(författare)
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Complete representation of action space and value in all dorsal striatal pathways
- 2021
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 36:4
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Tidskriftsartikel (refereegranskat)abstract
- The dorsal striatum plays a central role in the selection, execution, and evaluation of actions. An emerging model attributes action selection to the matrix and evaluation to the striosome compartment. Here, we use large-scale cell-type-specific calcium imaging to determine the activity of striatal projection neurons (SPNs) during motor and decision behaviors in the three major outputs of the dorsomedial striatum: Oprm1+ striosome versus D1+ direct and A2A+ indirect pathway SPNs. We find that Oprm1+ SPNs show complex tunings to simple movements and value-guided actions, which are conserved across many sessions in a single task but remap between contexts. During decision making, the SPN tuning profiles form a complete representation in which sequential SPN activity jointly encodes task progress and value. We propose that the three major output pathways in the dorsomedial striatum share a similarly complete representation of the entire action space, including task- and phase-specific signals of action value and choice.
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