No abstract

The G protein-coupled cannabinoid receptors type 1 (CB1R) and type 2 (CB2R), and their endocannabinoid (eCBs) ligands, have been implicated in several aspects of brain wiring during development. Here we aim to assess whether interfering with CB1R affects development, neuritogenesis and pathfinding of GnRH and AgRP neurons, forebrain neurons that control respectively reproduction and appetite. We pharmacologically and genetically interfered with CB1R in zebrafish strains with fluorescently labeled GnRH3 and the AgRP1 neurons. By applying CB1R antagonists we observed a reduced number of GnRH3 neurons, fiber misrouting and altered fasciculation. Similar phenotypes were observed by CB1R knockdown. Interfering with CB1R also resulted in a reduced number, misrouting and poor fasciculation of the AgRP1 neuron’s axonal projections. Using a bioinformatic approach followed by qPCR validation, we have attempted to link CB1R functions with known guidance and fasciculation proteins. The search identified stathmin-2, a protein controlling microtubule dynamics, previously demonstrated to be coexpressed with CB1R and now shown to be downregulated upon interference with CB1R in zebrafish. Together, these results raise the likely possibility that embryonic exposure to low doses of CB1R-interfering compounds could impact on the development of the neuroendocrine systems controlling sexual maturation, reproduction and food intake.

Forebrain GABAergic neurons, the main inhibitory type of neuron in the cortex and hippocampus, represent a highly heterogeneous cell population that has been implicated in the predisposition to epilepsy and the onset of seizure. Earlier attempts to restore inhibition and reduce seizure in animal models of epilepsy have been carried out using embryonic basal forebrain tissue as source of immature GABAergic progenitors in cell-based therapies, with promising results. For therapeutic strategies this approach appears unrealistic, while the use of pluripotent stem cells to obtain immature GABAergic neurons opens new and promising avenues. Research on neural stem cells and pluripotent stem cells has greatly advanced and protocols have been established to effi ciently direct progenitor cells to differentiate towards the GABAergic lineage. However, being highly heterogeneous, these neurons are diffi cult to be fully represented in vitro. Better knowledge on the expressed gene profi les, at single cell level, and the differentiation trajectory of these neurons will consent a more precise monitoring of the differentiation steps. Here we review the current literature about how to obtain and characterize genuine inhibitory neurons, how these can be grafted in animal models (and one day possibly in human) and which diseases could potentially be targeted and the effi ciency of therapeutic outcome. The main obstacles that need to be overcome are: a) choice of an appropriate animal model, b) availability of human cells prone to GABA differentiation, c) the full representation of all IN subtypes, their proportions and their physiological activities, d) how to monitor them on the long-term after transplant.

No abstract

The impairment of development/migration of hypothalamic gonadotropin-releasing hormone (GnRH) neurons is the main cause of Kallmann's syndrome (KS), an inherited disorder characterized by hypogonadism, anosmia, and other developmental defects. Olfactorin is an extracellular matrix protein encoded by the UMODL1 (uromodulin-like 1) gene expressed in the mouse olfactory region along the migratory route of GnRH neurons. It shares a combination of WAP and FNIII repeats, expressed in complementary domains, with anosmin-1, the product of the ANOS1 gene, identified as the causative of KS. In the present study, we have investigated the effects of olfactorin in vitro and in vivo models. The results show that olfactorin exerts an anosmin-1-like strong chemoattractant effect on mouse-immortalized GnRH neurons (GN11 cells) through the activation of the FGFR and MAPK pathways. In silico analysis of olfactorin and anosmin-1 reveals a satisfactory similarity at the N-terminal region for the overall arrangement of corresponding WAP and FNIII domains and marked similarities between WAP domains’ binding modes of interaction with the resolved FGFR1–FGF2 complex. Finally, in vivo experiments show that the down-modulation of the zebrafish z-umodl1 gene (orthologous of UMODL1) in both GnRH3:GFP and omp2k:gap-CFPrw034 transgenic zebrafish strains leads to a clear disorganization and altered fasciculation of the neurites of GnRH3:GFP neurons crossing at the anterior commissure and a significant increase in olfactory CFP + fibers with altered trajectory. Thus, our study shows olfactorin as an additional factor involved in the development of olfactory and GnRH systems and proposes UMODL1 as a gene worthy of diagnostic investigation in KS.