Cerebroespinal fluid control of neurogenesis induced by retinoic acid during early brain development

Producción CientíficaEmbryonic-cerebrospinal fluid (E-CSF) plays crucial roles in early brain development including the control of neurogenesis. Although FGF2 and lipoproteins present in the E-CSF have previously been shown to be involved in neurogenesis, the main factor triggering this process remains unknown. E-CSF contains all-trans-retinol and retinol-binding protein involved in the synthesis of retinoic acid (RA), a neurogenesis inducer. In early chick embryo brain, only the mesencephalic-rombencephalic isthmus (IsO) is able to synthesize RA. Here we show that in chick embryo brain development: (1) E-CSF helps to control RA synthesis in the IsO by means of the RBP and all-trans-retinol it contains; (2) E-CSF has retinoic acid activity, which suggests it may act as a diffusion pathway for RA; and (3) the influence of E-CSF on embryonic brain neurogenesis is to a large extent due to its involvement in RA synthesis. These data help to understand neurogenesis from neural progenitor cells2015-05-2

Functional measurements of [Ca2+] in the endoplasmic reticulum using a herpes virus to deliver targeted aequorin

Producción CientíficaChanges in the free calcium concentration of the endoplasmic reticulum ([Ca 2+],,) play a central role controlling cellular functions like contraction, secretion or neuronal signaling. We recently reported that recombinant aequorin targeted to the endoplasmic reticulum (ER) [Montero M., Brini M., Marsault R. et al. Monitoring dynamic changes in free Ca2+ concentration in the endoplasmic reticulum of intact cells. EMBO J 1995; 14: 5467-5475, Montero M., Barrero M.J., Alvarez J. [Ca2+] microdomains control agonist-induced Ca2+ release in intact cells. FASEB J 1997; 11: 881-8861 can be used to monitor selectively [Ca2+le, in intact HeLa cells. Here we have used a herpes simplex virus type 1 (HSV-1) based system to deliver targeted aequorin into a number of different cell types including both postmitotic primary cells (anterior pituitary cells, chromaffin cells and cerebellar neurons) and cell lines (HeLa, NIH3T3, GH, and PC12 cells). Functional studies showed that the steady state lumenal [Ca*+],, ranged from around 300 pM in granule cells to 800 ).rM in GH,cells. InsP,-coupled receptor stimulation with agonists like histamine (in HeLa, NIH3T3 and chromaffin cells), UTP and bradykinin (in PC12 cells) or thyrotropin-releasing hormone (TRH, in GH,cells) produced a very rapid decrease in lumenal [Ca’+],,. Caffeine caused a rapid Ca2+ depletion of the ER in chromaffin cells, but not in the other cell types. Depolarization by high K+ produced an immediate and reversible increase of [Ca2+lerin all the excitable cells (anterior pituitary, GH,, chromaffin cells and granule neurons). We conclude that delivery of recombinant aequorin to the ER using HSV amplicon provides the first direct quantitative and dynamic measurements of [Ca2+le, in several primary non-dividing cells

Role of interleukin 1B in the control of neuropithelial proliferation and differentiation of the spinal cord during development

Producción CientíficaInterleukin-1b (IL-1b) is an important trophic factor in the nervous system (NS). IL-1b is ubiquitously expressed from very early stages during the development of the amphibian NS and its action has been demonstrated in vitro on survival, proliferation and differ- entiation in mammalian embryos. In this report, we show that IL-1b is immunocytochemically expressed in embryonic spinal cord from early stages, both in rat (embryonic day 12) and in chicken (stage 17-HH), in neuroepithelial cells and nerve fibres, dorsal root ganglia, anterior and posterior roots of the spinal nerves, and in the fibres of these nerves. Our in vivo experiments on chick embryos, with micro- beads impregnated with IL-1b implanted laterally to the spinal cord at the level of the wing anlage, demonstrate that this cytokine pro- duces a statistically significant increase in nuclear incorporation of BrdU at the dorsal level and a reduction of this at the ventral level, whereas local immunoblocking with anti-IL-1b antibodies causes a dorsal reduction of BrdU incorporation and alters ventral differen- tiation. These data demonstrate that IL-1b plays a part in controlling proliferation and early differentiation during the development of the spinal cord in chick embryos

Chromaffin-cell stimulation triggers fast millimolar mitochondrial Ca2+ transients that modulate secretion

Producción CientíficaActivation of calcium-ion (Ca2+) channels on the plasma membrane and on intracellular Ca2+ stores, such as the endoplasmic reticulum, generates local transient increases in the cytosolic Ca2+ concentration that induce Ca2+ uptake by neighbouring mitochondria. Here, by using mitochondrially targeted aequorin proteins with different Ca2+ affinities, we show that half of the chromaffin-cell mitochondria exhibit surprisingly rapid millimolar Ca2+ transients upon stimulation of cells with acetylcholine, caffeine or high concentrations of potassium ions. Our results show a tight functional coupling of voltage-dependent Ca2+ channels on the plasma membrane, ryanodine receptors on the endoplasmic reticulum, and mitochondria. Cell stimulation generates localized Ca2+ transients, with Ca2+ concentrations above 20–40 mM, at these functional units. Protonophores abolish mitochondrial Ca2+ uptake and increase stimulated secretion of catecholamines by three- to fivefold. These results indicate that mitochondria modulate secretion by controlling the availability of Ca2+ for exocytosis.2015-03-1

Embryonic cerebrospinal fluid in brain development: neural progenitor control

Producción CientíficaDue to the effort of several research teams across the world, today we have a solid base of knowledge on the liquid contained in the brain cavities, its composition, and biological roles. Although the cerebrospinal fluid (CSF) is among the most relevant parts of the central nervous system from the physiological point of view, it seems that it is not a permanent and stable entity because its composition and biological properties evolve across life. So, we can talk about different CSFs during the vertebrate life span. In this review, we focus on the CSF in an interesting period, early in vertebrate development before the formation of the choroid plexus. This specific entity is called “embryonic CSF.” Based on the structure of the compartment, CSF composition, origin and circulation, and its interaction with neuroepithelial precursor cells (the target cells) we can conclude that embryonic CSF is different from the CSF in later developmental stages and from the adult CSF. This article presents arguments that support the singularity of the embryonic CSF, mainly focusing on its influence on neural precursor behavior during development and in adult life

FGF2 plays a key role in embryonic cerebrospinal fluid trophic properties over chick embryo neuroepithelial stem cells

Producción CientíficaDuring early stages of brain development, neuroepithelial stem cells undergo intense proliferation as neurogenesis begins. Fibroblast growth factor 2 (FGF2) has been involved in the regulation of these processes, and although it has been suggested that they work in an autocrine–paracrine mode, there is no general agreement on this because the behavior of neuroepithelial cells is not self-sufficient in explants cultured in vitro. In this work, we show that during early stages of development in chick embryos there is another source of FGF2, besides that of the neuroepithelium, which affects the brain primordium, since the cerebrospinal fluid (E-CSF) contains several isoforms of this factor. We also demonstrate, both in vitro and in vivo, that the FGF2 from the E-CSF has an effect on the regulation of neuroepithelial cell behavior, including cell proliferation and neurogenesis. In order to clarify putative sources of FGF2 in embryonic tissues, we detected by in situ hybridization high levels of mRNA expression in notochord, mesonephros and hepatic primordia, and low levels in brain neuroectoderm, corroborated by semiquantitative PCR analysis. Furthermore, we show that the notochord segregates several FGF2 isoforms which modify the behavior of the neuroepithelial cells in vitro. In addition, we show that the FGF2 ligand is present in the embryonic serum; and, by means of labeled FGF2, we prove that this factor passes via the neuroepithelium from the embryonic serum to the E-CSF in vivo. Considering all these results, we propose that, in chick embryos, the behavior of brain neuroepithelial stem cells at the earliest stages of development is influenced by the action of the FGF2 contained within the E-CSF which could have an extraneural origin, thus suggesting a new and complementary way of regulating brain development. © 2006 Elsevier Inc. All rights reserved

Retinoic acid, under cerebrospinal fluid control, induces neurogenesis during early brain development

Producción CientíficaOne of the more intriguing subjects in neuroscience is how a precursor or stem cell is induced to differentiate into a neuron. Neurogenesis begins early in brain development and suddenly becomes a very intense process, which is related with the influence of Retinoic Acid. Here, using a biological test (F9-1.8 cells) in chick embryos, we show that ―in vivo‖ embryonic cerebrospinal fluid regulates mesencephalic-rombencephalic Isthmic Retinoic Acid synthesis and this effect has a direct influence on mesencephalic neuroepithelial precursors, inducing a significant increase in neurogenesis. This effect is mediated by the Retinol Binding Protein present in the embryonic cerebrospinal fluid. The knowledge of embryonic neurogenetic stimulus could be useful in the control of adult brain neurogenesis.Ministerio de Educación y Ciencia (BFU207/6516)Junta de Castilla y León (Consejería de Educación, GR195

Chondroitin sulphate mediated fusion of brain: neural folds in rat embryons

Producción CientíficaPrevious studies have demonstrated that during neural fold fusion in different species, an apical extracellular material rich in glycoconjugates is involved. However, the composi- tion and the biological role of this material remain undeter- mined. In this paper, we show that this extracellular matrix in rat increases notably prior to contact between the neural folds, suggesting the dynamic behaviour of the secretory process. Immunostaining has allowed us to demonstrate that this extracellular matrix contains chondroitin sulphate proteoglycan (CSPG), with a spatio-temporal distribution pattern, suggesting a direct relationship with the process of adhesion. The degree of CSPG involvement in cephalic neu- ral fold fusion in rat embryos was determined by treatment with specific glycosidases. In vitro rat embryo culture and microinjection techniques were employed to carry out se- lective digestion, with chondroitinase AC, of the CSPG on the apical surface of the neural folds; this was done immediately prior to the bonding of the cephalic neural folds. In all the treated embryos, cephalic defects of neural fold fusion could tant role in the fusion of the cephalic neural folds in rat em- bryos, which implies that this proteoglycan could be in- volved in cellular recognition and adhesion. Abbreviations used in this paper CSPG chondroitin sulphate proteoglycan HSPG heparan sulphate proteoglycan PBS phosphate-buffered saline SEM scanning electron microscopy be detected. These results show that CSPG plays an impor

Embryonic Cerebrospinal Fluid Activates Neurogenesis of Neural Precursors within the Subventricular Zone of the Adult Mouse Brain

Producción CientíficaIntroduction: There is a nondeveloped neurogenic potential in the adult mammalian brain, which could be the basis for neuroregenerative strategies. Many research efforts have been made to understand the control mechanisms which regulate the transition from a neural precursor to a neuron in the adult brain. Embryonic cerebrospinal fluid (CSF) is a complex fluid which has been shown to play a key role in neural precursor behavior during development, working as a powerful neurogenic inductor. We tested if the neurogenic properties of embryonic CSF are able to increase the neurogenic activity of neuronal precursors from the subventricular zone (SVZ) in the brains of adult mice. Results: Our results show that mouse embryonic CSF significantly increases the neurogenic activity in precursor cells from adult brain SVZ. This intense neurogenic effect was specific for embryonic CSF and was not induced by adult CSF. Conclusions: Embryonic CSF is a powerful neurogenesis inductor in homologous neuronal precursors in the adult brain. This property of embryonic CSF could be a useful tool in neuroregeneration strategies

Polarización y control génico en el desarrollo

Se explican los fundamentos de la polaricación y control génico durante el desarrolloDepartamento de Anatomía y Radiologí