FLRT proteins act as guidance cues for migrating cortical interneurons

The establishment of functional neuronal connectivity starts during development and depends on neuronal migration and the correct positioning of newborn neurons which integrate into specific layers of the cortex. The fibronectin and leucine-rich family of transmembrane proteins (FLRT) have evolved as new regulators of several aspects during nervous system development, including neuronal migration. This work is focused on the study of in vivo FLRTs involvement in the tangential migration of interneurons. For this, we have analyzed nervous system specific knockout animals for FLRT2 and FLRT3, single mutants as well as the double mutants The simultaneous suppression of FLRT2 and FLRT3, resulted in the appearance of several defects related to interneuron migration. Finally, was addressed the intracellular mechanisms involved in FLRT function and was assessed the relationship between FLRT3 and the Rho GTPase Rnd3. The results suggest a possible functional interaction between FLRTs and Rnds in the central nervous system.L’establiment de les connectivitats neuronals a l’escorça en desenvolupament depèn de la migració i del correcte posicionament de les noves neurones que integren específicament les diferents capes corticals. Les proteïnes transmembrana riques en fibronectina i leucina (FLRT) han estat identificades com a nous reguladors de diversos aspectes en el desenvolupament del sistema nerviós, incloent la migració neuronal. El present treball de tesi està centrat en l’estudi in vivo de la implicació dels FLRTs en la migració tangencial de les interneurones. Amb aquest propòsit, hem analitzat animals knockout de FLRT2 i FLRT3, específics de sistema nerviós, com a mutants simples i també, com a dobles mutants. La supressió simultània de FLRT2 i FLRT3, produeix diversos defectes relacionats amb la migració de les interneurones. Finalment, es van abordar els mecanismes intracel•lulars implicats en la funció de FLRT, descrivint la relació entre FLRT3 i RhoGTPase Rnd3. Això suggereix una interacció funcional entre els FLRTs i els Rnds en el sistema nerviós.El establecimiento de las conectividad neuronal comienza durante el desarrollo y depende de la migración neuronal y del correcto posicionamiento de las nuevas neuronas, las cuales se integran dentro de capas específicas de la corteza. Las proteínas transmembrana ricas en fibronectina y leucina (FLRT) han evolucionado como nuevos reguladores de varios aspectos durante el desarrollo del sistema nervioso, incluyendo la migración neuronal. Este trabajo se centra en el estudio de la implicación in vivo de FLRTs en la migración tangencial de las interneuronas. Para ello, hemos analizado animales knockout (KO) específicos del sistema nervioso para FLRT2 y FLRT3, simples mutantes y dobles KOs (DKO). La supresión simultánea de FLRT2 y FLRT3, resultó en la aparición de varios defectos relacionados con la migración de las interneuronas. Por último, se abordaron los mecanismos intracelulares implicados en la función de FLRT y se evaluó la relación entre FLRT3 y Rho GTPase Rnd3. Los resultados sugieren una posible interacción funcional entre FLRTs y Rnds en este sistema

FLRT2 and FLRT3 Cooperate in Maintaining the Tangential Migratory Streams of Cortical Interneurons during Development

Neuron migration is a hallmark of nervous system development that allows gathering of neurons from different origins for assembling of functional neuronal circuits. Cortical inhibitory interneurons arise in the ventral telencephalon and migrate tangentially forming three transient migratory streams in the cortex before reaching the final laminar destination. Although migration defects lead to the disruption of inhibitory circuits and are linked to aspects of psychiatric disorders such as autism and schizophrenia, the molecular mechanisms controlling cortical interneuron development and final layer positioning are incompletely understood. Here, we show that mouse embryos with a double deletion of FLRT2 and FLRT3 genes encoding cell adhesion molecules exhibit an abnormal distribution of interneurons within the streams during development, which in turn, affect the layering of somatostatin+ interneurons postnatally. Mechanistically, FLRT2 and FLRT3 proteins act in a noncell-autonomous manner, possibly through a repulsive mechanism. In support of such a conclusion, double knockouts deficient in the repulsive receptors for FLRTs, Unc5B and Unc5D, also display interneuron defects during development, similar to the FLRT2/FLRT3 mutants. Moreover, FLRT proteins are chemorepellent ligands for developing interneurons in vitro, an effect that is in part dependent on FLRT-Unc5 interaction. Together, we propose that FLRTs act through Unc5 receptors to control cortical interneuron distribution in a mechanism that involves cell repulsion.This work was supported by grants from the Spanish Ministry of Science and Innovation (BFU2010-1805, BFU2013-48563-P, and PGC2018-101910-B-I00 to J.E. and BES-2014-067618 to P.M.-O.), FP7-PEOPLE-2011-CIG (PCIG9-GA-2011-293980 to J.E.), the Max-Planck Society (R.K.), and the Jade Plus Fellowship Program 2011–2014 (C.F.). We thank Tristan Rodríguez (Sox1-Cre line) and Anne Eichmann (Unc5Blx line) for the transgenic mice; Michèle Studer for the vasointestinal peptide probe; Eve Seuntjens and Veronique van den Berghe for scientific discussion; Inmaculada Segura for reading the manuscript; Serafí Cambray, Alex Espinós, Ma José Menal, Inma Montoliu, Montse Ortega, Noel Pérez, Sònia Rius, Marc Tarrés, and the University of Lleida Scientific and Technical Services for technical assistance, and the University of Lleida animal house staff facility for animal care

proBDNF is modified by advanced glycation end products in Alzheimer’s disease and causes neuronal apoptosis by inducing p75 neurotrophin receptor processing

Alzheimer disease (AD) is a complex pathology related to multiple causes including oxidative stress. Brain-derived neurotrophic factor (BDNF) is a neutrotrophic factor essential for the survival and differentiation of neurons and is considered a key target in the pathophysiology of various neurodegenerative diseases, as for example AD. Contrarily to BDNF, the precursor form of BDNF (proBDNF) induces apoptosis through the specific interaction with p75 and its co-receptor, Sortilin. We used hippocampal tissue and cerebrospinal fluid from AD patients and controls. to study the localization and the levels of proBDNF, p75 and Sortilin as well as the post-traduccional modifications of proBDNF induced by Radical Oxygen Species, by immunofluorescence and Western blot. Differentiation and survival were assessed on differentiated mouse hippocampal neurons derived from postnatal neural stem cells from WT animals or from the transgenic AD animal model APP/PS1ΔE9, based on mutations of familiar AD. In AD patients we observe a significative increase of proBDNF and Sortilin expression and a significative increase of the ratio proBDNF/BDNF in their cerebrospinal fluid compared to controls. In addition, the proBDNF of AD patients is modified by ROS-derived advanced glycation end products, which prevent the processing of the proBDNF to the mature BDNF, leading to an increase of pathogenicity and a decrease of trophic effects. The cerebrospinal fluid from AD patients, but not from controls, induces apoptosis in differentiated hippocampal neurons mainly by the action of AGE-modified proBDNF present in the cerebrospinal fluid of the patients. This effect is triggered by the activation and processing of p75 that stimulate the internalization of the intracellular domain (ICD) within the nucleus causing apoptosis. Induction of apoptosis and p75 ICD internalization by AD patients-derived proBDNF is further enhanced in neuron cultures from the AD model expressing the APP/PS1ΔE9 transgene. Our results indicate the importance of proBDNF neurotoxic signaling in AD pathology essentially by three mechanisms: i) by an increase of proBDNF stability due to ROS-induced post-traductional modifications; ii) by the increase of expression of the p75 co-receptor, Sortilin and iii) by the increase of the basal levels of p75 processing found in AD

Immuno-toxicological Evaluation of the Adjuvant Formulations for Experimental Anti-meningococcal Vaccines without Aluminium Hydroxide

International audienceThe proteoliposomes and cochleates are used as adjuvants for vaccines since they are potent immune stimulators. However, the hyper stimulation of the immune system provoked by adjuvants can cause immunetoxicological side effects. The present study was carried out to evaluate the toxic and immuno-toxicological effects of new adjuvants for anti-meningococci vaccines based on neo-proteoliposomes (nPL) and neocochleates (nCh), in Balb/c mice that were administered doses of 15 µg each, over periods of 14 days through intramuscular route and three inoculations with the same doses through intranasal route, every 7 days. The Scanning and Transmission Electron Microscopy showed that the nPL and nCh had nanometric dimensions and their normal peculiar forms. The experimental formulations did not provoke general toxiceffects in the tested animals, which tended to the progressive normal growing of this species, that did not statistically differ from the control ones. The studies of pathologic anatomy in inoculation organs and sites did not reveal modifications that can indicate toxicity and there was no sign of hepatic damage. The structural observations found in the spleen and lymphatic nodes showed the physiological development ofthe immune response, which was normal in all cases showing the restitution of the stimulation signs. The relative weight values of the spleen were within the standard range. These results showed that the nPL and nCh elaborated as adjuvants for vaccines did not show any evident induction of general toxic or particular immune-toxicologicl effects

Remote induction of cellular immune response in mice by anti-meningococcal nanocochleates - nanoproteoliposomes

International audienceNew adjuvant formulations, based on proteoliposomes b40 nm and cochleates b100 nm, without Al(OH)3 adjuvant, were evaluated regarding their ability to generate Th1 immune response through a Delayed -Type Hypersensitivity Test, at the mouse model, by using a Neisseria meningitidis B protein complex as antigen. The formulations were administered by intramuscular (IM) (2 inoculations - at baseline and after 14 days) and intranasal (IN) (3 inoculations at 7 days) immunization pathways. All IM immunized groups were able to induce similar response to these formulations as well as to VA-MENGOC-BC® vaccine - containing Al(OH)3 adjuvant (used as positive control of the trial). In all groups, the induced inflammation (IP) rate was statistically higher than in the negative control group (CN) (p b 0.05). Immunogenicity, measured by HSR and CD4+ lymphocyte increase was equivalent to the control vaccine and most important, granuloma reactogenicity at the site of injection was eliminated, fact demonstrated by histological study. All groups of animals immunized by IN route showed HSR reactions and statistically significant differences with respect to the CN group. However, IP values were lower, with statistical differences (p b 0.05) for the same adjuvant formulation IM administered, except the AIF2-nCh formulation that generated statistically similar induction (p N 0.05) by both immunization pathways, suggesting it to be the best candidate for the next IN trial. Proteoliposome and cochleate formulations tested were able to mount potent Th-1 immune response, equivalent to the original vaccine formulation, with the advantage of less reactogenicity in the site of the injection, caused by the toxicity of Al(OH)3 adjuvant gel