Papel del gen Mash1 en la determinación de la Eminencia Ganglionar Medial

"LOS GANGLIOS DE LA BASE SON UN CONJUNTO DE ESTRUCTURAS CON LA FUNCIÓN DE RECIBIR INFORMACIO¿N DE DIVERSAS ESTRUCTURAS COMO LA CORTEZA CEREBRAL, EL TÁLAMO, LOS NÚCLEOS SUBTALÁMICOS Y LA SUSTANCIA NEGRA, INTEGRARLA Y ENVIAR UNA SEÑAL EN FORMA DE RESPUESTA DE VUELTA A DICHAS ESTRUCTURAS. CON ESTO SE CONSIGUEN FUNCIONES IMPORTANTES COMO EL CONTROL MOTOR Y ALGUNAS FUNCIONES COGNITIVAS. ESTO HACE QUE ALTERACIONES EN ESTE COMPLEJO CAUSEN DIFERENTES TRASTORNOS COMO EL COREA, EL HEMIBALISMO O EL PARKINSON. POR TANTO, EL ESTUDIO DEL DESARROLLO, ESPECIFICACIÓN Y FUNCIONAMIENTO DE LOS GANGLIOS BASALES, MEDIANTE EL ESTUDIO DE LOS GENES INVOLUCRADOS, ES VITAL PARA PODER CREAR TÉCNICAS DE DETECCIÓN Y/O ALGÚN TIPO DE TRATAMIENTO. EN ESTE TRABAJO, EL OBJETIVO FUE ESTUDIAR EL PAPEL DEL GEN MASH1EN LA FORMACIO¿N DE LOS GANGLIOS BASALES. ESTE GEN ES UN FACTOR DE TRANSCRIPCIO¿N EXPRESADO DURANTE EL DESARROLLO DEL SISTEMA NERVIOSO CENTRAL. PARA ELLO, SE EMPLEÓ UN MUTANTE DE PÉRDIDA DE FUNCIÓN DE MASH1 Y SE ESTUDIO¿ LA POBLACIÓN DE NEURONAS GABAÉRGICAS DE LA EMINENCIA GANGLIONAR MEDIAL, A PARTIR DE LA CUAL SE DESARROLLA, EN EMBRIONES SILVESTRES EL GLOBO PÁLIDO, UNA DE LAS ESTRUCTURAS QUE CONFORMAN LOS GANGLIOS BASALES. SE CONCLUYÓ QUE EL GEN MASH1 PARTICIPA EN LA DIFERENCIACIÓN DE NEUROBLASTOS HACIA NEURONAS GABAE¿RGICAS INHIBITORIAS. SIN EMBARGO, NO ES EL U¿NICO GEN QUE CUMPLE ESTA FUNCIO¿N, PUES HAY MA¿S GENES INDUCIENDO CASCADAS QUE FAVORECEN ESTA DIFERENCIACIÓN. EL MUTANTE MASH1-/- NO ES CAPAZ DE ESPECIFICAR BIEN LA EMINENCIA GANGLIONAR MEDIAL, POR LO QUE EL GLOBO PÁLIDO NO SE LLEGA A FORMAR. ADEMÁS, LA PÉRDIDA DE FUNCIO¿N DE ESTE GEN AFECTA A LA TRAYECTORIA DE LAS FIBRAS TALAMOCORTICALES, YA QUE ESTA DEPENDE DE LA CORRECTA ESPECIFICACIÓN DE ESTA EMINENCIA GANGLIONAR MEDIAL.""THE BASAL GANGLIA ARE A GROUP OF STRUCTURES, WHICH RECEIVE INFORMATION OF DISTINCT STRUCTURES SUCH AS THE CEREBRAL CORTEX, THE THALAMUS, SUBTHALAMIC NUCLEUS AND THE SUBSTANTIA NIGRA. THE COMPLEX PROCESSES THE INFORMATION, GENERATES A RESPONSE AND SENDS IT BACK TO THE STRUCTURES; PLAYING AN IMPORTANT ROLE IN MOTOR CONTROL AND SOME COGNITIVE FUNCTIONS. ALTERATION OF THESE STRUCTURES CAN CAUSE DIFFERENT DISORDERS LIKE CHOREA, PARKINSON¿S DISEASE AND HEMIBALLISMUS. SO THAT, THE STUDY OF DEVELOPMENT, SPECIFICATION AND FUNCTIONING OF THE BASAL GANGLIA AND THE IMPLICATED GENS, COULD BE USEFUL FOR THE DEVELOPMENT OF DIAGNOSIS TECHNIQUES AND DIFFERENT TREATMENTS. THE OBJECTIVE OF THE PRESENT STUDY WAS TO CLARIFY THE FUNCTION OF THE GEN MASH1 IN THE FORMATION OF BASAL GANGLIA. THIS GEN IS A TRANSCRIPTIONAL FACTOR EXPRESSED DURING THE DEVELOPMENT OF THE CENTRAL NERVOUS SYSTEM. FOR THAT PURPOSE, A MUTANT WITH LACK FUNCTION OF MASH1 WAS USED AND THE POPULATION OF GABAERGIC NEURONS IN THE MEDIAL GANGLIONIC EMINENCE WAS STUDIED. GLOBUS PALLIDUS, A COMPONENT OF BASAL GANGLIA IS GENERATED FROM THIS REGION, THE MEDIAL GANGLIONIC EMINENCE. THIS STUDY CONCLUDES THAT THE GEN MASH1 IS INVOLVED IN THE DIFFERENTIATION OF NEUROBLAST IN GABAERGIC INHIBITORY NEURONS. HOWEVER, MASH1 IS NOT THE ONLY ONE GEN IMPLICATED IN THIS PROCESS, THERE ARE OTHER GENS INDUCTING THIS DIFFERENTIATION. MASH1-/- MUTANT IS NOT CAPABLE OF SPECIFY THE MEDIAL GANGLIONIC EMINENCE, SO THAT, GLOBUS PALLIDUS IS NOT FORMED. IN ADDITION, THE LACK IF THIS GENE FUNCTION HAS AN EFFECT IN THE THALAMOCORTICAL FIBERS TRAJECTORY BECAUSE IT DEPENDS ON THE CORRECT SPECIFICATION OF THE MEDIAL GANGLIONIC EMINENCE.

Neuronal tangential migration from Nkx2.1-positive hypothalamus

During the development of the central nervous system, the immature neurons suffer different migration processes. It is well known that Nkx2.1-positive ventricular layer give rise to critical tangential migrations into different regions of the developing forebrain. Our aim was to study this phenomenon in the hypothalamic region. With this purpose, we used a transgenic mouse line that expresses the tdTomato reporter driven by the promotor of Nkx2.1. Analysing the Nkx2.1-positive derivatives at E18.5, we found neural contributions to the prethalamic region, mainly in the zona incerta and in the mes-diencephalic tegmental region. We studied the developing hypothalamus along the embryonic period. From E10.5 we detected that the Nkx2.1 expression domain was narrower than the reporter distribution. Therefore, the Nkx2.1 expression fades in a great number of the early-born neurons from the Nkx2.1-positive territory. At the most caudal positive part, we detected a thin stream of positive neurons migrating caudally into the mes-diencephalic tegmental region using time-lapse experiments on open neural tube explants. Late in development, we found a second migratory stream into the prethalamic territory. All these tangentially migrated neurons developed a gabaergic phenotype. In summary, we have described the contribution of interneurons from the Nkx2.1-positive hypothalamic territory into two different rostrocaudal territories: the mes-diencephalic reticular formation through a caudal tangential migration and the prethalamic zona incerta complex through a dorsocaudal tangential migratio

Multiple parallel cell lineages in the developing mammalian cerebral cortex

Cortical neurogenesis follows a simple lineage: apical radial glia cells (RGCs) generate basal progenitors, and these produce neurons. How this occurs in species with expanded germinal zones and a folded cortex, such as human, remains unclear. We used single-cell RNA sequencing from individual cortical germinal zones in ferret and barcoded lineage tracking to determine the molecular diversity of progenitor cells and their lineages. We identified multiple RGC classes that initiate parallel lineages, converging onto a common class of newborn neuron. Parallel RGC classes and transcriptomic trajectories were repeated across germinal zones and conserved in ferret and human, but not in mouse. Neurons followed parallel differentiation trajectories in the gyrus and sulcus, with different expressions of human cortical malformation genes. Progenitor cell lineage multiplicity is conserved in the folded mammalian cerebral cortex.This work was supported by ERC-AdG grant Neurocentro-885382 to M.G. and by Spanish State Research Agency grants SAF2015-69168-R, PGC2018-102172-B, and PDI2021-125618NB and “Severo Ochoa” Programme for Centers of Excellence in R&D (CEX-2021-00165-S) to V.B. Additional support was provided by Spanish State Research Agency FPI contract (BES-2016-077737) to L.D.-V.-A., “JdC incorporación” fellowship (IJC2020-044653-I) to V.F., and by Fundación Tatiana Pérez de Guzmán el Bueno fellowship to A.P.-C.With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX-2021-00165-S).Peer reviewe

Properties of the epileptiform activity in the cingulate cortex of a mouse model of LIS1 dysfunction

Dysfunction of the LIS1 gene causes lissencephaly, a drastic neurological disorder characterized by a deep disruption of the cortical structure. We aim to uncover alterations of the cortical neuronal networks related with the propagation of epileptiform activity in the Lis1/sLis1 mouse, a model lacking the LisH domain in heterozygosis. We did extracellular field-potential and intracellular recordings in brain slices of the anterior cingulate cortex (ACC) or the retrosplenial cortex (RSC) to study epileptiform activity evoked in the presence of bicuculline (10 µM), a blocker of GABAA receptors. The sensitivity to bicuculline of the generation of epileptiform discharges was similar in wild type (WT) and Lis1/sLis1 cortex (EC50 1.99 and 2.24 µM, respectively). In the Lis1/sLis1 cortex, we observed a decreased frequency of the oscillatory post-discharges of the epileptiform events; also, the propagation of epileptiform events along layer 2/3 was slower in the Lis1/sLis1 cortex (WT 47.69 ± 2.16 mm/s, n = 25; Lis1/sLis1 37.34 ± 2.43 mm/s, n = 15; p = 0.004). The intrinsic electrophysiological properties of layer 2/3 pyramidal neurons were similar in WT and Lis1/sLis1 cortex, but the frequency of the spontaneous EPSCs was lower and their peak amplitude higher in Lis1/sLis1 pyramidal neurons. Finally, the propagation of epileptiform activity was differently affected by AMPA receptor blockers: CNQX had a larger effect in both ACC and RSC while GYKI53655 had a larger effect only in the ACC in the WT and Lis1/sLis1 cortex. All these changes indicate that the dysfunction of the LIS1 gene causes abnormalities in the properties of epileptiform discharges and in their propagation along the layer 2/3 in the anterior cingulate cortex and in the restrosplenial cortex.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO/AEI/FEDER, UE; grant numbers SAF2017-83702-R, PID2020-118171RB-I00), Spanish State Research Agency, through the “Programa Severo Ochoa” for Centers of Excellence in R&D (grant number SEV-2017-0723), and Generalitat Valenciana (program Prometeo II, grant number 2018/041).Peer reviewe

Neuronal tangential migration from Nkx2.1-positive hypothalamus

During the development of the central nervous system, the immature neurons suffer different migration processes. It is well known that Nkx2.1-positive ventricular layer give rise to critical tangential migrations into different regions of the developing forebrain. Our aim was to study this phenomenon in the hypothalamic region. With this purpose, we used a transgenic mouse line that expresses the tdTomato reporter driven by the promotor of Nkx2.1. Analysing the Nkx2.1-positive derivatives at E18.5, we found neural contributions to the prethalamic region, mainly in the zona incerta and in the mes-diencephalic tegmental region. We studied the developing hypothalamus along the embryonic period. From E10.5 we detected that the Nkx2.1 expression domain was narrower than the reporter distribution. Therefore, the Nkx2.1 expression fades in a great number of the early-born neurons from the Nkx2.1-positive territory. At the most caudal positive part, we detected a thin stream of positive neurons migrating caudally into the mes-diencephalic tegmental region using time-lapse experiments on open neural tube explants. Late in development, we found a second migratory stream into the prethalamic territory. All these tangentially migrated neurons developed a gabaergic phenotype. In summary, we have described the contribution of interneurons from the Nkx2.1-positive hypothalamic territory into two different rostrocaudal territories: the mes-diencephalic reticular formation through a caudal tangential migration and the prethalamic zona incerta complex through a dorsocaudal tangential migration.Work supported by MINECO/AEI/FEDER (BFU2013-48230) to E. Puelles and D. Echevarría; MINECO/AEI/FEDER (SAF2017-83702-R), GVA (PROMETEO/2018/041), ISCIII (“RD16/001/0010”), co-funded by ERDF/ESF, “Investing in your future”, and FTPGB (FTPGB18/SM) to S. Martinez; MECD (FPU16/03853) to V. Company.Peer reviewe

Wnt1 role in the development of the habenula and the fasciculus retroflexus

Wnt1 is one of the morphogenes that controls the specification and differentiation of neuronal populations in the developing central nervous system. The habenula is a diencephalic neuronal complex located in the most dorsal aspect of the thalamic prosomere. This diencephalic neuronal population is involved in the limbic system and its malfunction is related with several psychiatric disorders. Our aim is to elucidate the Wnt1 role in the habenula and its main efferent tract, the fasciculus retroflexus, development. In order to achieve these objectives, we analyzed these structures development in a Wnt1 lack of function mouse model. The habenula was generated in our model, but it presented an enlarged volume. This alteration was due to an increment in habenular neuroblasts proliferation rate. The fasciculus retroflexus also presented a wider and disorganized distribution and a disturbed final trajectory toward its target. The mid-hindbrain territories that the tract must cross were miss-differentiated in our model. The specification of the habenula is Wnt1 independent. Nevertheless, it controls its precursors proliferation rate. Wnt1 expressed in the isthmic organizer is vital to induce the midbrain and rostral hindbrain territories. The alteration of these areas is responsible for the fasciculus retroflexus axons misroute.This work was supported by the MINECO/AEI/FEDER (BFU2013-48230) to EP and DE; MINECO/AEI/FEDER (SAF2017-83702-R; PID2020-118171RB-I00), GVA (PROME TEO/2018/041), ISCIII (“RD16/001/0010”), co-funded by the ERDF/ESF, “Investing in your future,” and FTPGB (FTPGB18/SM) to SM; MECD (FPU16/03853) to VC. The Institute of Neurosciences is a “Centre of Excellence Severo Ochoa (SEV-2017-0723)”.Peer reviewe

Adhesion molecule Amigo2 is involved in the fasciculation process of the fasciculus retroflexus

[Background] The fasciculus retroflexus is the prominent efferent pathway from the habenular complex. Medial habenular axons form a core packet whereas lateral habenular axons course in a surrounding shell. Both groups of fibers share the same initial pathway but differ in the final segment of the tract, supposedly regulated by surface molecules. The gene Amigo2 codes for a membrane adhesion molecule with an immunoglobulin-like domain 2 and is selectively expressed in the medial habenula. We present it as a candidate for controlling the fasciculation behavior of medial habenula axons.[Results] First, we studied the development of the habenular efferents in an Amigo2 lack of function mouse model. The fasciculus retroflexus showed a variable defasciculation phenotype. Gain of function experiments allowed us to generate a more condensed tract and rescued the Amigo2 knock-out phenotype. Changes in Amigo2 function did not alter the course of habenular fibers.[Conclusion] We have demonstrated that Amigo2 plays a subtle role in the fasciculation of the fasciculus retroflexus.Fundación Tatiana Pérez de Guzmán el Bueno, Grant/Award Number: FTPGB18/SM; Generalitat Valenciana, Grant/Award Number: PROMETEO/2018/041; Instituto de Salud Carlos III, Grant/Award Number: RD16/001/0010; Ministerio de Educación, Cultura y Deporte, Grant/Award Number: FPU16/03853; Secretaría de Estado de Investigación, Desarrollo e Innovación, Grant/Award Numbers: BFU2013-48230, SAF2017-83702-R, SEV-2017-0723.Peer reviewe

Gestational exposure to sodium valproate disrupts fasciculation of the mesotelencephalic dopaminergic tract, with a selective reduction of dopaminergic output from the ventral tegmental area

Gestational exposure to valproic acid (VPA) is known to cause behavioral deficits of sociability, matching similar alterations in human autism spectrum disorder (ASD). Available data are scarce on the neuromorphological changes in VPA-exposed animals. Here, we focused on alterations of the dopaminergic system, which is implicated in motivation and reward, with relevance to social cohesion. Whole brains from 7-day-old mice born to mothers given a single injection of VPA (400 mg/kg b.wt.) on E13.5 were immunostained against tyrosine hydroxylase (TH). They were scanned using the iDISCO method with a laser light-sheet microscope, and the reconstructed images were analyzed in 3D for quantitative morphometry. A marked reduction of mesotelencephalic (MT) axonal fascicles together with a widening of the MT tract were observed in VPA treated mice, while other major brain tracts appeared anatomically intact. We also found a reduction in the abundance of dopaminergic ventral tegmental (VTA) neurons, accompanied by diminished tissue level of DA in ventrobasal telencephalic regions (including the nucleus accumbens (NAc), olfactory tubercle, BST, substantia innominata). Such a reduction of DA was not observed in the non-limbic caudate-putamen. Conversely, the abundance of TH+ cells in the substantia nigra (SN) was increased, presumably due to a compensatory mechanism or to an altered distribution of TH+ neurons occupying the SN and the VTA. The findings suggest that defasciculation of the MT tract and neuronal loss in VTA, followed by diminished dopaminergic input to the ventrobasal telencephalon at a critical time point of embryonic development (E13-E14) may hinder the patterning of certain brain centers underlying decision making and sociability.This work was supported by the Spanish Ministry of Science and Innovation grant: Federación Española de Enfermedades Raras (FEDER) SAF2014-59347-C2-1-R, Severo Ochoa Excellence Project SEV-2013-0317; ISCIII: Red TERCEL RD12/0019/0024 and CIBERSAM; GVA: PROMETEO II/2014/014, as well as the Excellence in Higher Education Program of Hungary.Peer reviewe