Olaf Ninnemann - Academia.edu (original) (raw)

Papers by Olaf Ninnemann

European Journal of Neuroscience, Mar 1, 2000

Lesion-induced neuronal plasticity in the adult central nervous system of higher vertebrates appe... more Lesion-induced neuronal plasticity in the adult central nervous system of higher vertebrates appears to be controlled by region-and layer-speci®c molecules. In this study we demonstrate that membrane-bound hippocampal outgrowth-promoting molecules, as present during the development of the entorhino-hippocampal system and absent or masked in the adult hippocampus, appear 10 days after transection of the perforant pathway. We used an outgrowth preference assay to analyse the outgrowth preference of axons from postnatal entorhinal explants on alternating membrane lanes obtained from hippocampus deafferented from its entorhinal input taken 4, 10, 20, 30 and 80 days post-lesion and from adult control hippocampus. Neurites from the entorhinal cortex preferred to extend axons on hippocampal membranes disconnected from their entorhinal input for 10 days in comparison with membranes obtained from unlesioned adult animals. Membranes obtained from hippocampi disconnected from their entorhinal input for 10 days were equally as attractive for growing entorhinal cortex (EC) axons as membranes from early postnatal hippocampi. Further analysis of membrane properties in an outgrowth length assay showed that entorhinal axons extended signi®cantly longer on stripes of lesioned hippocampal membranes in comparison with unlesioned hippocampal membranes. This effect was most prominent 10 days after lesion, a time point at which axonal sprouting and reactive synaptogenesis are at their peak. Phospholipase treatment of membranes obtained from unlesioned hippocampi of adult animals strongly promoted the outgrowth length of entorhinal axons on these membranes but did not affect their outgrowth preference for deafferented hippocampal membranes. Our results indicate that membrane-bound outgrowth-promoting molecules are reactivated in the adult hippocampus following transection of the perforant pathway, and that neonatal entorhinal axons are able to respond to these molecules. These ®ndings support the hypothesis of a temporal accessibility of membrane-bound factors governing the layer-speci®c sprouting of remaining axons following perforant path lesion in vivo.

Developmental Biology, Jul 1, 1999

In this study the role of membrane-associated molecules involved in entorhinohippocampal pathfind... more In this study the role of membrane-associated molecules involved in entorhinohippocampal pathfinding was examined. First outgrowth preferences of entorhinal neurites were analyzed on membrane carpets obtained from their proper target area, the hippocampus, and compared to preferences on control membranes from brain regions which do not receive afferent connections from the entorhinal cortex. On a substrate consisting of alternating lanes of hippocampal and control membranes, entorhinal neurites exhibited a strong tendency to grow on lanes of hippocampal membrane. These tissue-specific outgrowth preferences were maintained even on membrane preparations from adult brain tissue devoid of myelin. To determine the possible maturation dependence of these membranes, we examined guidance preferences of entorhinal neurites on hippocampal membranes of different developmental stages ranging from embryonic to postnatal and adult. Given a choice between alternating lanes of embryonic (E15-E16) and neonatal (P0-P1) hippocampal membranes, entorhinal neurites preferred to extend on neonatal membranes. No outgrowth preferences were observed on membranes obtained between E19 and P10. From P10 onward there was a reoccurrence of a preference for postnatal membrane lanes when neurites were presented with a choice between P15, P30, and adult membranes (>P60). This choice behavior of entorhinal neurites temporally correlates with the ingrowth of the perforant path into the hippocampus and with the stabilization of this brain area in vivo. Experiments in which postnatal and adult hippocampal membranes were heat inactivated or treated to remove molecules sensitive to phosphatidylinositol-specific phospholipase C demonstrated that entorhinal fiber preferences were controlled in this assay by attractive guidance cues and were independent of phosphatidylinositol-sensitive linked molecules. Moreover, entorhinal neurites displayed a positive discrimination for membrane-associated guidance cues of their target field, thus preferring to grow on membranes from the molecular layer of the dentate gyrus compared with CA3 or hilus membranes. Heat-inactivation experiments indicated that preferential growth of entorhinal axons is due to a specific attractivity of the molecular layer substrate. The data presented demonstrate that outgrowth of entorhinal fibers on hippocampal membranes is target and maturation dependent.

European Journal of Neuroscience, 1999

Myelin is crucial for the stabilization of the entorhinohippocampal projection during late develo... more Myelin is crucial for the stabilization of the entorhinohippocampal projection during late development and is a non‐permissive substrate for regrowing axons after lesion in the adult brain. We used two in vitro assays to analyse the impact of myelin on rat entorhinohippocampal projection neurons. A stripe assay was used to study the impact of myelin on the choice behaviour of axons from the entorhinal cortex (EC). Given a choice between alternating hippocampal membrane lanes from developmental stages ranging from early postnatal to adult, EC axons preferred to extend on early postnatal hippocampal membranes. Neither the neutralization of myelin‐associated factors by a specific antibody (IN‐1) nor the separation of myelin from membranes interfered with the axons' choice behaviour. The entorhinal axons showed no preference in the membrane combination of adult and myelin‐free adult hippocampal membranes. These stripe assay experiments demonstrate that support for EC axon choice in the developing hippocampus is maturation‐dependent and is not influenced by myelin. The application of IN‐1 in the outgrowth assay and the separation of myelin from membranes, enhanced elongation of outgrowing entorhinal axons on adult hippocampal membranes, whereas a control antibody did not. This shows that myelin‐associated factors have a strong inhibitory effect on the outgrowth length of entorhinal axons. In conclusion, we suggest that axonal elongation in the entorhinohippocampal system during development is strongly influenced by myelin‐associated growth inhibition factors and that specific target finding of entorhinal axons is regulated by a different mechanism.

The FASEB Journal, Nov 1, 2002

Excitotoxic brain lesions, such as stroke and epilepsy, lead to increasing destruction of neurons... more Excitotoxic brain lesions, such as stroke and epilepsy, lead to increasing destruction of neurons hours after the insult. The deadly cascade of events involves detrimental actions by free radicals and the activation of proapoptotic transcription factors, which finally result in neuronal destruction. Here, we provide direct evidence that the nutritionally essential trace element selenium has a pivotal role in neuronal susceptibility to excitotoxic lesions. First, we observed in neuronal cell cultures that addition of selenium in the form of selenite within the physiological range protects against excitotoxic insults and even attenuates primary damage. The neuroprotective effect of selenium is not directly mediated via antioxidative effects of selenite but requires de novo protein synthesis. Gel shift analysis demonstrates that this effect is connected to the inhibition of glutamate-induced NF-κB and AP-1 activation. Furthermore, we provide evidence that selenium deficiency in vivo results in a massive increase in susceptibility to kainate-induced seizures and cell loss. These findings indicate the importance of selenium for prevention and therapy of excitotoxic brain damage. Key words: seizure • oxidative glutamate toxicity • neuronal cell death • hippocampus • NF-κB S elenium has been shown to be a nutritionally essential trace element to mammals, including humans (1, 2). Selenium is an integral part of glutathione peroxidase (GPx), an antioxidant enzyme, as well as several other selenoproteins (3, 4). It has been identified as the component in bovine serum that is necessary for maintaining neurons in serum-free media (2). Health conditions such as immune function (5), viral infection (6), reproduction problems (7), mood disorders (8), skeletal myopathy and macrocytosis (9), seizures (10), cancer (11), and cardiovascular diseases (12) have been linked to selenium deficiency. These also include an increased severity of infectious diseases such as Keshan disease, an endemic cardiomyopathy,

Neuroscience, Sep 1, 2003

The cortical information flow via the perforant path represents a major excitatory projection to ... more The cortical information flow via the perforant path represents a major excitatory projection to the hippocampus. Lesioning this projection leads to massive degeneration and subsequently to reorganization in its termination zones as well as in primary non-affected subfields of the hippocampus. The molecular mechanisms and factors which are involved in the postlesional events are poorly defined. Using a differential display reverse transcription-polymerase chain reaction (DDRT-PCR) strategy, we located one band which occurred only in control hippocampus lanes and almost disappeared in the lanes of lesioned hippocampi. By sequencing, we identified the corresponding gene as cholecystokinin (CCK). Northern blot analysis confirmed a decreased transcription of CCK after lesion. In situ hybridization analysis was performed for localization and quantification of altered CCK transcription. We noted a significant downregulation of CCK transcription in the hippocampus (20%) and in the contralateral cortex (12%) 1-day after lesion (dal) and an increased signal in the ipsilateral cortex (10.5%). This pattern was altered, showing upregulation of CCK mRNA expression, reaching its highest level of 70% above control levels at 5 dal. In the hippocampus, the control level was reached again at 21 dal, whereas the cortex reached the control level at 10 dal. In comparison, the mRNA transcripts of the receptors CCK A and CCK B remained unchanged. Since CCK-containing neurons are involved in the modulation of pyramidal and granule cell excitability, our data indicate a time course correlation between CCK mRNA expression and postlesional axonal sprouting response in the hippocampus.

Proceedings of the National Academy of Sciences of the United States of America, Dec 19, 1995

In most plants amino acids represent the major transport form for organic nitrogen. A sensitive s... more In most plants amino acids represent the major transport form for organic nitrogen. A sensitive selection system in yeast mutants has allowed identification of a previously unidentified amino acid transporter inArabidopsis.

The EMBO Journal, Mar 1, 1992

The DNA binding protein FIS is involved in processes like site specific DNA inversion, X excision... more The DNA binding protein FIS is involved in processes like site specific DNA inversion, X excision and stinulation of stable RNA synthesis in Escherichia coli. The amount of FIS protein is subject to dramatic changes during growth. We demonstrate thatfis is part of an operon with one ORF of unknown function preceding the fis gene. Regulation of fis synthesis occurs at the transcriptional level. Within 15 min after nutritional upshift a large burst offis mRNA is produced which levels off when cells begin to grow. By mutational analysis using promoter-lacZ fusions we demonstrate that the fis promoter is autoregulated by FIS. Growth phase regulation of the fis promoter depends on the presence of a GC motif downstream of the-10 region. We show that the fis promoter is subject to stringent control and discuss this unusual feature with respect to the known and putative functions FIS serves in E.coli.

The FASEB Journal, Dec 13, 2006

The let-7 miRNA regulates developmental timing in C. elegans and is an important paradigm for inv... more The let-7 miRNA regulates developmental timing in C. elegans and is an important paradigm for investigations of miRNA functions in mammalian development. We have examined the role of miRNA precursor processing in the temporal control and lineage specificity of the let-7 miRNA. In situ hybridization (ISH) in E9.5 mouse embryos revealed early induction of let-7 in the developing central nervous system. The expression pattern of three let-7 family members closely resembled that of the brain-enriched miRNAs mir-124, mir-125 and mir-128. Comparison of primary, precursor, and mature let-7 RNA levels during both embryonic brain development and neural differentiation of embryonic stem cells and embryocarcinoma (EC) cells suggest post-transcriptional regulation of let-7 accumulation. Reflecting these results, let-7 sensor constructs were strongly down-regulated during neural differentiation of EC cells and displayed lineage specificity in primary cells. Neural differentiation of EC cells was accompanied by an increase in let-7 precursor processing activity in vitro. Furthermore, undifferentiated and differentiated cells contained distinct precursor RNA binding complexes. A neuron-enhanced binding complex was shown by antibody challenge to contain the miRNA pathway proteins Argonaute1 and FMRP. Developmental regulation of the processing pathway correlates with differential localization of the proteins Argonaute, FMRP, MOV10, and TNRC6B in self-renewing stem cells and neurons.

The EMBO Journal, Aug 1, 1994

Despite the important role of the ammonium ion in metabolism, i.e. as a form of nitrogen that is ... more Despite the important role of the ammonium ion in metabolism, i.e. as a form of nitrogen that is taken up from the soil by microorganisms and plants, little is known at the molecular level about its transport across biomembranes. Biphasic uptake kinetics have been observed in roots of several plant species. To study such transport processes, a mutant yeast strain that is deficient in two NH4+ uptake systems was used to identify a plant NH4+ transporter. Expression of an Arabidopsis cDNA in the yeast mutant complemented the uptake deficiency. The cDNA AMTI contains an open reading frame of 501 amino acids and encodes a highly hydrophobic protein with 9-12 putative membrane spanning regions. Direct uptake measurements show that mutant yeast cells expressing the protein are able to take up [14C]methylamine. Methylamine uptake can be efficiently competed by NH4+ but not by K+. The methylamine uptake is optimal at pH 7 with a Km of 65 ,uM and a K; for NH4+ of '10 gM, is energydependent and can be inhibited by protonophores. The plant protein is highly related to an NH4+ transporter from yeast (Marini et al., accompanying manuscript). Sequence homologies to genes of bacterial and animal origin indicate that this type of transporter is conserved over a broad range of organisms. Taken together, the data provide strong evidence that a gene for the plant high affinity NH4' uptake has been identified.

Nature Neuroscience, Aug 1, 2004

... Reply to 'Is PRG-1 a new lipid phosphatase?'. Anja U Bräuer 1 , Nicolai E Savaskan ... more ... Reply to 'Is PRG-1 a new lipid phosphatase?'. Anja U Bräuer 1 , Nicolai E Savaskan 1 , Hartmut Kühn 2 , Siegfried Prehn 2 , Olaf Ninnemann 1 & Robert Nitsch 1 ... 07 May 2012 09 May 2012;Hussein Bin Ali St., Jabal Amman, Amman, 00962, Jordan. More science events. ...

Hippocampus, 2000

Cell recognition molecules of the immunoglobulin superfamily are involved in the formation, estab... more Cell recognition molecules of the immunoglobulin superfamily are involved in the formation, establishment, and plasticity of neural circuits in the central nervous system (CNS). We used a polymerase chain reaction-based approach to specifically amplify molecules with conserved sequence elements of immunoglobulin-like domains. This approach enabled us to isolate Kilon, a novel immunoglobulin that has been described by Funatsu et al. (J Biol Chem 1999;274: 8224-8230) from the hippocampus. The sequence of Kilon shows a high degree of homology to that of the chicken protein neurotractin, a molecule involved in neurite outgrowth and capable of interacting with LAMP. In situ hybridization analysis was performed to analyze the Kilon mRNA distribution in the developing and adult rat brain and to compare it to that of LAMP mRNA. Kilon mRNA was found to be specifically expressed in the dentate gyrus (DG) of the adult rat, whereas LAMP transcripts were present in all regions of the hippocampal formation. These results were corroborated by RT-PCR semiquantification of gene expression in microdissected tissue prepared from the DG and the CA1 region of the hippocampus. We also performed mRNA expression analysis of both genes following hippocampal deafferentation and seizure, but neither Kilon nor LAMP gene expression showed significant alterations after lesioning on the in situ hybridization level. Our results show that the expression patterns of Kilon and LAMP during development and in the mature hippocampus are clearly distinguishable from one another, which suggests different roles for these related molecules in the hippocampus.

Nucleic Acids Research, 1991

FIS protein is involved in several different cellular processes stimulating site-specific recombi... more FIS protein is involved in several different cellular processes stimulating site-specific recombination in phages Mu and X as well as transcription of stable RNA operons in E.coli. We have performed a mutational analysis of fis and provide genetic and biochemical evidence that a truncated version of FIS lacking the Nterminal region is sufficient for specific DNA binding and for stimulating X excision. These mutants also retain their ability to autoregulate fis gene expression. Such mutant proteins, however, cannot stimulate the enhancer dependent DNA inversion reaction.

The Cerebellum, Oct 11, 2022

Homozygous variants in the peptidyl-tRNA hydrolase 2 gene (PTRH2) cause infantile-onset multisyst... more Homozygous variants in the peptidyl-tRNA hydrolase 2 gene (PTRH2) cause infantile-onset multisystem neurologic, endocrine, and pancreatic disease. The objective is to delineate the mechanisms underlying the core cerebellar phenotype in this disease. For this, we generated constitutive (Ptrh2LoxPxhCMVCre, Ptrh2 −/− mice) and Purkinje cell (PC) specific (Ptrh2LoxPxPcp2Cre, Ptrh2 ΔPC mice) Ptrh2 mutant mouse models and investigated the effect of the loss of Ptrh2 on cerebellar development. We show that Ptrh2 −/− knockout mice had severe postnatal runting and lethality by postnatal day 14. Ptrh2 ΔPC PC specific knockout mice survived until adult age; however, they showed progressive cerebellar atrophy and functional cerebellar deficits with abnormal gait and ataxia. PCs of Ptrh2 ΔPC mice had reduced cell size and density, stunted dendrites, and lower levels of ribosomal protein S6, a readout of the mammalian target of rapamycin pathway. By adulthood, there was a marked loss of PCs. Thus, we identify a cell autonomous requirement for PTRH2 in PC maturation and survival. Loss of PTRH2 in PCs leads to downregulation of the mTOR pathway and PC atrophy. This suggests a molecular mechanism underlying the ataxia and cerebellar atrophy seen in patients with PTRH2 mutations leading to infantile-onset multisystem neurologic, endocrine, and pancreatic disease.

Cell, Sep 1, 2009

Plasticity related gene-1 (PRG-1) is a brain-specific membrane protein related to lipid phosphate... more Plasticity related gene-1 (PRG-1) is a brain-specific membrane protein related to lipid phosphate phosphatases, which acts in the hippocampus specifically at the excitatory synapse terminating on glutamatergic neurons. Deletion of prg-1 in mice leads to epileptic seizures and augmentation of EPSCs, but not IPSCs. In utero electroporation of PRG-1 into deficient animals revealed that PRG-1 modulates excitation at the synaptic junction. Mutation of the extracellular domain of PRG-1 crucial for its interaction with lysophosphatidic acid (LPA) abolished the ability to prevent hyperexcitability. As LPA application in vitro induced hyperexcitability in wild-type but not in LPA 2 receptor-deficient animals, and uptake of phospholipids is reduced in PRG-1-deficient neurons, we assessed PRG-1/LPA 2 receptordeficient animals, and found that the pathophysiology observed in the PRG-1-deficient mice was fully reverted. Thus, we propose PRG-1 as an important player in the modulatory control of hippocampal excitability dependent on presynaptic LPA 2 receptor signaling.

European Journal of Neuroscience, Feb 1, 1999

We analysed the effects of semaphorin D on axons from the developing rat entorhinal–hippocampal f... more We analysed the effects of semaphorin D on axons from the developing rat entorhinal–hippocampal formation. Explants from superficial layers of the entorhinal cortex and of the hippocampus anlage were obtained from various developmental stages and co‐cultured with cell aggregates expressing semaphorin D. Neurites extending from entorhinal explants that had been isolated from early embryonic stages (E16 and E17) were not affected by semaphorin D, but were repelled at later stages (E20 and E21). Axons from hippocampal neurons explanted at E21 were also repelled by semaphorin D. In situ hybridization studies revealed expression of the semaphorin D receptor neuropilin‐1 in the entorhinal cortex from stage E17 to stage P7, and in the dentate gyrus and CA1–3 regions between E17 and adulthood. These data suggest that semaphorin D is involved in the formation of the perforant pathway and acts, via the neuropilin‐1 receptor, as a repulsive signal that prevents entorhinal fibres from growing into the granular layer of the dentate gyrus. These data also suggest a role for semaphorin D in the development of intrahippocampal connections.

Neuroscience, 2003

Neuroscience, 2001

ÐIn this study, we performed in situ hybridization analysis of the expression pattern of two grow... more ÐIn this study, we performed in situ hybridization analysis of the expression pattern of two growth-associated proteins, stathmin and SCG10, in the hippocampus after unilateral lesion of the perforant pathway, the main excitatory input from the entorhinal cortex to the hippocampus. Stathmin is one of the major neural-enriched cytosolic phosphoproteins and a potential target of cyclic-AMP-dependent kinases [Jin L. W. et al. (1996) Neurobiol. Aging 17, 331±341; Leighton I. A. et al. (1993) Molec. Cell Biochem. 127/128, 151±156]. Three days after the lesion, stathmin messenger RNA was up-regulated ipsilaterally in the hilus, in the granule cell layer of the dentate gyrus and in the pyramidal cell layer of the CA1 region. Simultaneously, the hilar region of the contralateral dentate gyrus showed an increased stathmin messenger RNA expression. This altered expression pattern was observed until 15 days after lesion. Stathmin messenger RNA expression returned to a normal level until 21 days after lesion in all regions analysed. SCG10, a membrane-bound neuronal growth-associated protein belonging to the SCG10/stathmin gene family, did not show any alteration of messenger RNA expression after perforant path lesion. The temporal changes of stathmin messenger RNA expression in the ipsilateral hippocampus correspond well to the process of reactive synaptogenesis. The enhanced messenger RNA expression in the hilar region of the contralateral dentate gyrus might suggest a role in neurite elongation, since this region is the origin of commissural ®bres involved in the sprouting response in the deafferented hippocampus. The present study provides evidence that the induction of speci®c growth-associated proteins is differentially regulated in the hippocampus.