Developmental regulation of the neuronal‐specific isoform of K‐CL cotransporter KCC2 in postnatal rat brains

We examined the expression of the KCC2 isoform of the K‐Cl cotransporter in the developing and adult brain, using an affinity‐purified antibody directed against a unique region of the KCC2 protein. Expression was shown to be limited to neurons at the cell bodies and cell processes in the hippocampus and cerebellum. Expression seemed to be the highest at the end of processes that originated from the CA1 pyramidal cells. Developmental up‐regulation of KCC2 expression was demonstrated in the entire rat brain by Northern and Western blot analyses, and in the hippocampus by immunofluorescence. Level of KCC2 expression was minimal at birth and increased significantly during postnatal development. This pattern of expression was opposite to the one of the Na‐K‐2Cl cotransporter that is highly expressed in immature brain and decreases during development. The up‐regulation of the K‐Cl cotransporter expression is consistent with the developmental down‐regulation of the intracellular Cl⁻ concentration in neurons. The level of intracellular Cl⁻, in turn, determines the excitatory versus inhibitory response of the neurotransmitter γ‐aminobutyric acid in the immature versus mature brain. Finally, KCC2 expression was shown in dorsal root ganglion neurons, demonstrating that expression of the cotransporter is not strictly confined to central nervous system neurons. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 558–568, 1999     

Cdk5 activity is required for Purkinje cell dendritic growth in cell‐autonomous and non‐cell‐autonomous manners

Cyclin‐dependent kinase 5 (Cdk5) is recognized as a unique member among other Cdks due to its versatile roles in many biochemical processes in the nervous system. The proper development of neuronal dendrites is required for the formation of complex neural networks providing the physiological basis of various neuronal functions. We previously reported that sparse dendrites were observed on cultured Cdk5‐null Purkinje cells and Purkinje cells in Wnt1^cre‐mediated Cdk5 conditional knockout (KO) mice. In the present study, we generated L7^cre‐mediated p35; p39 double KO (L7^cre‐p35^f/f; p39^–/–) mice whose Cdk5 activity was eliminated specifically in Purkinje cells of the developing cerebellum. Consequently, these mice exhibited defective Purkinje cell migration, motor coordination deficiency and a Purkinje dendritic abnormality similar to what we have observed before, suggesting that dendritic growth of Purkinje cells was cell‐autonomous in vivo . We found that mixed and overlay cultures of WT cerebellar cells rescued the dendritic deficits in Cdk5‐null Purkinje cells, however, indicating that Purkinje cell dendritic development was also supported by non‐cell‐autonomous factors. We then again rescued these abnormalities in vitro by applying exogenous brain‐derived neurotrophic factor (BDNF). Based on the results from culture experiments, we attempted to rescue the developmental defects of Purkinje cells in L7^cre‐p35^f/f; p39^–/– mice by using a TrkB agonist. We observed partial rescue of morphological defects of dendritic structures of Purkinje cells. These results suggest that Cdk5 activity is required for Purkinje cell dendritic growth in cell‐autonomous and non‐cell‐autonomous manners. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1175–1187, 2017     

Mice lacking Asic3 show reduced anxiety‐like behavior on the elevated plus maze and reduced aggression

Sensing external stimulation is crucial for central processing in the brain and subsequent behavioral expression. Although sensory alteration or deprivation may result in behavioral changes, most studies related to the control of behavior have focused on central mechanisms. Here we created a sensory deficit model of mice lacking acid‐sensing ion channel 3 (Asic3^?/?) to probe behavioral alterations. ASIC3 is predominately distributed in the peripheral nervous system. RT‐PCR and immunohistochemistry used to examine the expression of Asic3 in the mouse brain showed near‐background mRNA and protein levels of ASIC3 throughout the whole brain, except for the sensory mesencephalic trigeminal nucleus. Consistent with the expression results, Asic3 knockout had no effect on synaptic plasticity of the hippocampus and the behavioral tasks of motor function, learning and memory. In anxiety behavior tasks, Asic3^?/? mice spent more time in the open arms of an elevated plus maze than did their wild‐type littermates. Asic3^?/? mice also displayed less aggressiveness toward intruders but more stereotypic repetitive behaviors during resident–intruder testing than did wild‐type littermates. Therefore, loss of ASIC3 produced behavioral changes in anxiety and aggression in mice, which suggests that ASIC3‐dependent sensory activities might relate to the central process of emotion modulation.     

Conditional KIAA1549:BRAF mice reveal brain region‐ and cell type‐specific effects

Low‐grade brain tumors (pilocytic astrocytomas) that result from a genomic rearrangement in which the BRAF kinase domain is fused to the amino terminal of the KIAA1549 gene (KIAA1549:BRAF fusion; f‐BRAF) commonly arise in the cerebellum of young children. To model this temporal and spatial specificity in mice, we generated conditional KIAA1549:BRAF strains that coexpresses green fluorescent protein (GFP). Although both primary astrocytes and neural stem cells (NSCs) from these mice express f‐BRAF and GFP as well as exhibit increased MEK activity, only f‐BRAF‐expressing NSCs exhibit increased proliferation in vitro. Using Cre driver lines in which KIAA1549:BRAF expression was directed to NSCs (f‐BRAF; BLBP‐Cre mice), astrocytes (f‐BRAF; GFAP‐Cre mice), and NG2 progenitor cells (f‐BRAF; NG2‐Cre mice), increased glial cell numbers were observed only in the cerebellum of f‐BRAF; BLBP‐Cre mice in vivo. The availability of this unique KIAA1549:BRAF conditional transgenic mouse strain will enable future mechanistic studies aimed at defining the developmentally–regulated temporal and spatial determinants that underlie low‐grade astrocytoma formation in children. genesis 51:708–716. © 2013 Wiley Periodicals, Inc.     

Comparison of Amino-acid Sequences of Hypothalamic Peptide,Brain-specific Histone and Myelin Basic Protein

SEVERAL studies have described the basic proteins of porcine central nervous tissue. Shome and Saffran¹ have isolated and purified a large peptide (or small protein) of molecular weight about 14,000 from acetone-dried hog hypothalamic powder. Sixteen of the approximately twenty-six tryptic digest fragments of this protein have been sequenced. The protein has no pressor or ACTH-releasing activity. Tomasi-and Kornguth² purified and partially characterized a basic protein from pig brain and, on the basis of fluorescent antibody studies, they concluded that this protein is a brain-specific histone, found in neurone nuclei (or nucleoli) of several animals^3–5.     

Analysis of Messenger RNA Coding for S100 Protein in the Mammalian Brain

S100 protein is a brain-specific protein which is absent at birth and first appears in rabbit brain 2–3 days after birth. To determine how the synthesis of this brain-specific protein is regulated, mRNA was isolated from brain polysomes and assayed for S100 protein mRNA activity by in vitro translation in a heterologous cell-free system and immunoprecipitation of released polypeptides with rabbit anti-S I00 protein antiserum. 5100 protein mRNA was detected primarily in small polysomes containing five to eight ribosomes, and virtually no S 100 protein mRNA was present in polysomes containing more than eight ribosomes. S100 protein mRNA was not detected in brain polysomes at stages prior to the induction of synthesis of S100 protein, i.e., in fetal brain or in 1-day neonates. The amount of S100 protein mRNA in polysomes of the cerebral cortex and cerebellum was measured to see if it correlated with the level of S100 protein in the two regions of adult brain. The cerebellum, which contained three to four times the level of S100 protein in the cerebral cortex, contained four times more S100 protein mRNA.     

Developmental expression of P<Subscript>5</Subscript> ATPase mRNA in the mouse

P₅ ATPases (ATP13A1 through ATP13A5) are found in all eukaryotes. They are currently poorly characterized and have unknown substrate specificity. Recent evidence has linked two P₅ ATPases to diseases of the nervous system, suggesting possible importance of these proteins within the nervous system. In this study we determined the relative expression of mouse P5 ATPases in development using quantitative real time PCR. We have shown that ATP13A1 and ATP13A2 were both expressed similarly during development, with the highest expression levels at the peak of neurogenesis. ATP13A3 was expressed highly during organogenesis with one of its isoforms playing a more predominant role during the period of neuronal development. ATP13A5 was expressed most highly in the adult mouse brain. We also assessed the expression of these genes in various regions of the adult mouse brain. ATP13A1 to ATP13A4 were expressed differentially in the cerebral cortex, hippocampus, brainstem and cerebellum while levels of ATP13A5 were fairly constant between these brain regions. Moreover, we demonstrated expression of the ATP13A4 protein in the corresponding brain regions using immunohistochemistry. In summary, this study furthers our knowledge of P₅-type ATPases and their potentially important role in the nervous system.     

Enhanced transport of plant‐produced rabies single‐chain antibody‐RVG peptide fusion protein across an in cellulo blood–brain barrier device

The biomedical applications of antibody engineering are developing rapidly and have been expanded to plant expression platforms. In this study, we have generated a novel antibody molecule in planta for targeted delivery across the blood–brain barrier (BBB). Rabies virus (RABV) is a neurotropic virus for which there is no effective treatment after entry into the central nervous system. This study investigated the use of a RABV glycoprotein peptide sequence to assist delivery of a rabies neutralizing single‐chain antibody (ScFv) across an in cellulo model of human BBB. The 29 amino acid rabies virus peptide (RVG) recognizes the nicotinic acetylcholine receptor (nAchR) at neuromuscular junctions and the BBB. ScFv and ScFv‐RVG fusion proteins were produced in Nicotiana benthamiana by transient expression. Both molecules were successfully expressed and purified, but the ScFv expression level was significantly higher than that of ScFv‐RVG fusion. Both ScFv and ScFv‐RVG fusion molecules had potent neutralization activity against RABVin cellulo. The ScFv‐RVG fusion demonstrated increased binding to nAchR and entry into neuronal cells, compared to ScFv alone. Additionally, a human brain endothelial cell line BBB model was used to demonstrate that plant‐produced ScFv‐RVG^P fusion could translocate across the cells. This study indicates that the plant‐produced ScFv‐RVG^P fusion protein was able to cross the in celluloBBB and neutralize RABV.     

A Novel cdc2-Related Protein Kinase Expressed in the Nervous System

Abstract: We report the cloning and characterization of a cDNA encoding a cdc2-related protein kinase, named PFTAIRE, that is expressed primarily in the postnatal and adult nervous system. We have demonstrated by in situ hybridization and indirect immunofluorescence that several populations of terminally differentiated neurons and some neuroglia expressed PFTAIRE mRNA and protein. In neurons, PFTAIRE protein was localized in the nucleus and cytoplasm of cell bodies. The anatomical, cellular, and ontogenic patterns of PFTAIRE expression in the nervous system differed from those of p34^cdc2 and cdk5, which are expressed in brain and several other mitotic tissues. Proteins of ～58–60 kDa coprecipitated specifically with PFTAIRE from cytosolic protein preparations of adult mouse brain and transfected cells. These proteins appeared to be the major endogenous substrates associated with this kinase activity. The temporal and spatial expression patterns of PFTAIRE in the postnatal and adult nervous system suggest that PFTAIRE kinase activity may be associated with the postmitotic and differentiated state of cells in the nervous system and that its function may be distinct from those of p34^cdc2 and cdk5.     

Complex Cell Response depends on Interslit Spacing

PSYCHOPHYSICAL studies have established that the human central visual system contains a large number of independent channels each of which responds maximally to a selectively oriented sine wave grating of a given spatial frequency and hardly at all to gratings of spatial frequencies differing by a factor of two^1–4. Electrophysiological studies with moving sinusoidally modulated grating patterns have demonstrated that there exists a class of neurones in the striate cortex of cats⁵ and monkeys⁶ each member of which is maximally selective to a given spatial frequency and orientation.     

Pharmacological Characterization of Somatostatin Receptors in the Rat Cerebellum During Development

Abstract: Somatostatin (SRIF) receptors (SRIF-Rs) are transiently expressed in a germinative lamina of the rat cerebellum, the external granule cell layer. The appearance of SRIF-Rs coincides with the expression of SRIF-like immunoreactivity in the cerebellum. However, the cellular location of SRIF-Rs does not overlap with the distribution of SRIF-like immunoreactivity, with the latter being restricted to ascending fibers arising from the brainstem, to perikarya within the white matter, and to some Purkinje cells. The characterization of SRIF-Rs in the immature (13–day-old) rat cerebellum was conducted by means of binding experiments in membraneenriched preparations and autoradiography, using two radioligands, [¹²⁵I-Tyr⁰,D-Trp⁸]SRIF-14 ([¹²⁵I-Tyr⁰,d -Trp⁸]S14) and ^I25I-SMS 204–090. The pharmacological profile of cerebellar SRIF-Rs was compared with that of adult cortical SRIF-Rs. Saturation studies performed in 13–day-old rat cerebellum showed that the A'_D values for [¹²⁵I-Tyr⁰,D-Trp⁸]S14 and ¹²⁵I-SMS 204–090 binding were 0.35 ± 0.04 and 0.39 ± 0.01 nM, respectively. The corresponding B_max values were 52.7 ± 4.8 and 49.9 ± 5.3 fmol/mg of protein, a result indicating that radioligands with high specific radioactivity (2,000 Ci/mmol) bind to a single class of high-affinity sites (SSI). Competition studies showed that different D-Trp-sub-stituted analogs displaced [¹²⁵I-Tyr⁰,d -Trp⁸]S14 binding with Hill coefficients >1, a finding indicating the existence of different subtypes of binding sites. When [Tyr⁰,d -Trp⁸]S14 was used as a competitor, two sites were resolved by Scatchard analysis in both 13–day-old cerebellum and adult cerebral cortex. The higher-affinity sites correspond to the SSI subtype identified in saturation experiments, whereas the lower-affinity sites most likely correspond to the SS2 subtype. Ionic supplementation studies showed that divalent cations were required to obtain maximal specific binding on the SSI sites. In particular, Mn²⁺ was the most efficient cation for promoting binding of [¹²⁵I-Tyr⁰,d -Trp⁸]S14. Addition of GTP to the incubation buffer induced a marked reduction of specific binding. The results obtained by membrane binding assays were similar to those obtained by quantitative autoradiography, a result indicating that the microenvironment of SRIF-Rs was preserved in both types of tissue preparations. Receptors expressed in the developing rat cerebellum exhibited the same K_D and similar pharmacological profile as those observed in the adult rat cortex. These results show that SRIF-binding sites transiently expressed in the external granule cell layer of the cerebellum of young rats are indistinguishable from adult rat brain SRIF-Rs. The extremely high density of SRIF-Rs found in the external granule cell layer in 13–day-old rats suggests that SRIF may play a pivotal role in the proliferation and/or differentiation of these germinative cells.     

Transport of a hyaluronan-binding protein in brain tissue

Hyaluronan is an unsulfated linear glycosaminoglycan with the ability to nucleate extracellular matrices by the formation of aggregates with lecticans. These matrices are essential during development of the central nervous system. In the prospective white matter of the developing brain hyaluronan is organized into fiber-like structures according to confocal microscopy of fixed slices which may guide the migration of neural precursor cells [Baier, C., S.L. Baader, J. Jankowski, V. Gieselmann, K. Schilling, U. Rauch, and J. Kappler. 2007. Hyaluronan is organized into fiber-like structures along migratory pathways in the developing mouse cerebellum. Matrix Biol. 26: 348–58]. By using plasmon surface resonance, microinjection into brain slices and fluorescence correlation spectroscopy, we show that the brain-specific lecticans bind to, but also dissociate rather rapidly from hyaluronan. After microinjection into native cerebellar slices a GFP-tagged hyaluronan-binding neurocan fragment was enriched at binding sites in the prospective white matter, which had a directional orientation and formed local stationary concentration gradients in areas where binding sites are abundant. Fluorescence correlation spectroscopy measurements at fixed brain slices revealed that fiber-bound neurocan-GFP was mobile with D_{fiber(neurocan-GFP)} = 4 × 10^? 10 cm²/s. Therefore, we propose that hyaluronan-rich fibers in the prospective white matter of the developing mouse cerebellum can guide the diffusion of lecticans. Since lecticans bind a variety of growth and mobility factors, their guided diffusion may contribute to the transport of these polypeptides and to the formation of concentration gradients. This mechanism could serve to encode positional information during development.     

Large extracellular space leads to neuronal susceptibility to ischemic injury in a Na<Superscript>+</Superscript>/<Emphasis Type="Bold">K</Emphasis><Superscript>+</Superscript> pumps–dependent manner

The extent of anoxic depolarization (AD), the initial electrophysiological event during ischemia, determines the degree of brain region–specific neuronal damage. Neurons in higher brain regions exhibiting nonreversible, strong AD are more susceptible to ischemic injury as compared to cells in lower brain regions that exhibit reversible, weak AD. While the contrasting ADs in different brain regions in response to oxygen–glucose deprivation (OGD) is well established, the mechanism leading to such differences is not clear. Here we use computational modeling to elucidate the mechanism behind the brain region–specific recovery from AD. Our extended Hodgkin–Huxley (HH) framework consisting of neural spiking dynamics, processes of ion accumulation, and ion homeostatic mechanisms unveils that glial–vascular K⁺ clearance and Na⁺/K⁺–exchange pumps are key to the cell’s recovery from AD. Our phase space analysis reveals that the large extracellular space in the upper brain regions leads to impaired Na⁺/K⁺–exchange pumps so that they function at lower than normal capacity and are unable to bring the cell out of AD after oxygen and glucose is restored.     

Regional distribution of binding sites for the nitric oxide synthase inhibitorl-[3H]Nitroarginine in rat brain

The regional distribution of N^G-nitro-l-[³H]arginine (L-[³H]NOARG) binding to different regions of rat brain was studied by quantitative autoradiography. These studies revealed highest density of binding sites in cerebellum, anterior olfactory nucleus, islands of Calleja and substantia nigra with appreciable binding site densities in inferior colliculus, superior colliculus, olfactory tubercle and dorsal tegmental nucleus. The regional distribution of L-[³H]NOARG binding, is in good agreement with the distribution of nitric oxide synthase studied previously by NADPH-diaphorase staining and immunohistochemistry using antibodies against neuronal nitric oxide synthase. The kinetics of L-[³H]NOARG binding to the cytosolic preparations of cerebral cortex, cerebellum, hippocampus and striatum was studied using an in vitro binding technique. Specific L-[³H]NOARG binding was of nanomolar affinity, saturable, and best fit to a single-site model in all four brain regions. These studies support the potential use of L-[³H]NOARG binding as a tool for further elucidation of the regional distribution and functional properties of NOS in the central nervous system.     

Taurine in the developing cat: Uptake and release in different brain areas

Taurine is an important modulator of neuronal activity in the immature brain. In kittens, taurine deficiency causes serious dysfunction in the cerebellar and cerebral visual cortex. The processes of taurine transport in vitro were now studied for the first time in different brain areas in developing and adult cats. The uptake of taurine consisted initially of two saturable components, high- and low-affinity, in synaptosomal preparations from the developing cerebral cortex and cerebellum, but the high-affinity uptake component completely disappeared during maturation. The release of both endogenous and preloaded labeled taurine from brain slices measured in a superfusion system was severalfold stimulated with a slow onset by depolarizing K⁺ (50 mM) concentrations. K⁺ stimulation released markedly more taurine from the cerebral cortex, cerebellum and brain stem in kittens than in adult cats. The responses were largest in the cerebellum. Both uptake and release of taurine are thus highly efficient in the brain of kittens and may be of significance in view of the vulnerability of cats to taurine deficiency.     

INCORPORATION AND METABOLISM OF THE DIETARY TRANS-UNSATURATED FATTY ACID,ELAIDIC ACID,BY DEVELOPING RAT BRAIN1

Trans-unsaturated fatty acids, geometrical isomers of naturally occurring cis-acids, are dietary components and are incorporated into complex lipids of many tissues. There is little information about incorporation into brain and effects on CNS functions. In our experiments, mixtures of [l-¹⁴C]-elaidic acid and [9,10-³H]oleic were injected intragastrically into a total of 34 rats at 6, 12 and 16 days of age. Animals were killed 4, 8, 24, 48 and 96 h after administration and brain and liver lipids analyzed. With all ages examined, about 0.02–0.22% of the administered radioactivity from each fatty acid was found in brain lipids with incorporation increasing with time after administration. Phospholipids accounted for 60–85% of the total label from both fatty acids; of this phospholipid label, 40–50%, of the ¹⁴C was in unaltered irans-monoene. Up to 22% of the total ¹⁴C label recovered from brain was in cholesterol. By contrast to brain, labeling of liver lipid was much greater and was highest at 4 h after administration; there was proportionally less ¹⁴C or ³H label in palmitate and cholesterol compared to brain. Thus, intact trans-fatty acid, elaidic acid, was incorporated into developing brain, but at slower rates than into liver. These studies establish that the developing central nervous system does not exclude dietary trans-acids.     

The Expression Pattern of Classical MHC Class I Molecules in the Development of Mouse Central Nervous System

Classical major histocompatibility complex (MHC) class I, first identified in the immune system, is also expressed in the developing and adult central nervous system (CNS). Although the MHC class I molecules have been found to be expressed in the CNS of different species, a necessary step to elucidate the temporal and spatial expression patterns of MHC class I molecules in the brain development has never been taken. Frozen sections were made from the brains of embryonic and postnatal C57BL/6 J mice, and the expression of H-2D^b mRNA was examined by in situ hybridization. Immunofluorescence was also performed to define the cell types that express H2-D^b in P15 mice. At E10.5, the earliest stage we examined, H2-D^b was expressed in neuroepithelium of the brain vesicles. From E12.5 to P0, H2-D^b expression was mainly located at cerebral cortex, neuroepithelium of the lateral ventricle, neuroepithelium of aquaeductus and developing cerebellum. From P4 to adult, H2-D^b mRNA was detected at olfactory bulb, hippocampus, cerebellum and some nerve nuclei. The major cell types expressing H-2D^b in P15 hippocampus, cerebral cortex and olfactory bulb were neuron. H2-K^b signal paralleled that of H2-D^b and the expression levels of the two molecules were comparable throughout the brain. The investigation of the expression pattern of H-2D^b at both embryonic and postnatal stages is important for further understanding the physiological and pathological roles of H2-D^b in the developing CNS.     

The Similar Expression Pattern of MHC Class I Molecules in Human and Mouse Cerebellar Cortex

The major histocompatibility complex (MHC) class I molecules are considered to be important in the immune system. However, the results reported in the past decade indicate that they also play important roles in the central nervous system. Here we examined the expression of MHC I and β2-microglobulin (β2m) in human and mouse cerebellar cortex. The results show that MHC I molecules are expressed both in human and mouse cerebellar cortex during brain development. The expression of H-2K^b/D^b is gradually increased with the development of mouse cerebellar cortex, but finally decreased to a very low level. Similarly, the expression of HLA-B/C genes is increased in developing human cerebellar cortex, but decreased after birth. The spatial and temporal expression of β2m overlaps mostly with that of HLA-B/C molecules, and they are co-expressed in Purkinje cells. Our findings provide a fundamental basis to reveal the functions of neuronal MHC class I molecules in the development of human cerebellum.