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Tuberous sclerosis complex (TSC) is a genetic disorder characterized by frequent noncancerous neoplasia in the brain, which can induce a range of severe neuropsychiatric symptoms in humans, resulting from out of control tissue growth. The causative spontaneous loss-of-function mutations have been also identified in rats. Herein, we studied histopathological and molecular changes in brain lesions of the Eker rat model carrying germline mutation of the tsc2 gene, predisposed to multiple neoplasias. Predominant subcortical tumors were analyzed, along with a rare form occurring within the pyriform lobe. The uniform composition of lesions supports the histochemical parity of malformations, with immunofluorescence data supporting their neuro-glial origin. Massive depletion of mature neurons and axonal loss were evident within lesions, with occasional necrotic foci implying advanced stage of pathology. Enrichment of mesenchymal-derived cell markers with hallmarks of neurogenesis and active microglia imply enhanced cell proliferation, with local immune response. The depletion of capillaries within the core was complemented by the formation of dense mesh of nascent vessels at the interface of neoplasia with healthy tissue, implying large-scale vascular remodeling. Taken as a whole, these findings present several novel features of brain tumors in Eker rat model, rendering it suitable for studies of the pathobiology and progression of primary brain tumors, with therapeutic interventions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13311-019-00812-6) contains supplementary material, which is available to authorized users.

Mutations in the SRGAP3 gene residing on chromosome 3p25 have previously been associated with intellectual disability. Genome-wide association studies have also revealed SRGAP3, together with genes from the same cellular network, as risk genes for schizophrenia. SRGAP3 regulates cytoskeletal dynamics through the RHO protein RAC1. RHO proteins are known to be involved in cytoskeletal reorganization during brain development to control processes such as synaptic plasticity. To elucidate the importance of SRGAP3 in brain development, we generated Srgap3-knockout mice. Ten percent of these mice developed a hydrocephalus and died before adulthood. Surviving mice showed various neuroanatomical changes, including enlarged lateral ventricles, white matter tracts, and dendritic spines together with molecular changes, including an increased basal activity of RAC1. Srgap3(-/-) mice additionally exhibited a complex behavioral phenotype. Behavioral studies revealed an impaired spontaneous alternation and social behavior, while long-term memory was unchanged. The animals also had tics. Lower locomotor activity was observed in male Srgap3(-/-) only. Srgap3(-/-) mice showed increased methylphenidate stimulation in males and an impaired prepulse inhibition in females. Together, the results show neurodevelopmental aberration in Srgap3(-/-) mice, with many of the observed phenotypes matching several schizophrenia-related intermediate phenotypes. Mutations of SRGAP3 may thus contribute to various neurodevelopmental disorders.

Mental retardation (MR) affects up to two percent of the population and is usually accompanied by impaired learning and memory. MR is frequently associated with mutations of genes involved in Rho signal transduction cascades. Rho signal transduction pathways regulate axonal and dendritic growth during embryonic development and morphological adaptations of dendritic spines during synaptic plasticity in adult neurons. The MEGAP/SRGAP3 protein is part of the Rho signal transduction cascades. Mutation of MEGAP (Mental disorder associated GTPase-activating protein) gene is present in some patients who have MR, ataxia and monosomy for the distal portion of the short arm of chromosome 3. Here, we investigated the pattern of mouse MEGAP mRNA expression during embryonic development. Mouse embryos and brain sections from stage E10 to adults were analysed by in-situ hybridisation for MEGAP transcript in whole-mount and in brain sections. We demonstrate here robust expression of MEGAP mRNA in the whole central nervous system of E10 embryos. At E12, we also detected MEGAP in dorsal root ganglia. This pattern narrows in adult animals into an expression mainly in hippocampus and cortex. Our findings support the presumed role of MEGAP in Rho-associated MR.

Tuberous sclerosis complex (TSC) is a common hereditary disorder caused by mutations in either the TSC1 or TSC2 genes, and characterized by severe epilepsy, cerebral hamartomas and mental retardation. We have used rats that are heterozygous for an autosomal-dominant germline mutation in the TSC2 gene (TSC2+/- rats) to examine the consequences of TSC2 mutations for hippocampal synaptic plasticity. While basal synaptic transmission in the Schaffer collateral-CA1 synapse was not altered, paired-pulse plasticity was significantly enhanced in TSC2+/- rats (interpulse intervals 20-200 ms). Moreover, TSC2+/- rats exhibited a marked reduction of different forms of synaptic plasticity. Long-term potentiation (LTP) elicited following high-frequency tetanization of Schaffer collaterals was significantly decreased from 1.45 +/- 0.05-fold potentiation to 1.15 +/- 0.04 (measured after 60 min). This difference in LTP levels between TSC2+/- and wild-type rats also persisted in the presence of the gamma-aminobutyric acid (GABA)(A) receptor antagonist bicuculline. In addition to changed LTP, the level of long-term depression (LTD) elicited by different forms of low-frequency stimulation was significantly less in TSC2+/- rats. These results suggest that TSC2 mutations may cause hippocampal synapses to lose much of their potential for activity-dependent synaptic modification. An understanding of the underlying molecular pathways may suggest new therapeutic approaches aimed at inhibiting the development of the profound mental retardation in TSC.

Death ligand-mediated apoptosis is a promising strategy of gene therapy for human malignant glioma. We here report that the infection of human malignant glioma cell lines with an adenoviral vector encoding full length human Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand (Ad-Apo2L/TRAIL) results in strong Apo2L/TRAIL transgene expression and the release of full-length Apo2L/TRAIL into the cell culture medium. However, Ad-Apo2L/TRAIL is a poor inducer of cell death, even in the presence of inhibitors of protein synthesis, in human glioma cell lines which are sensitive to soluble recombinant human His-tagged Apo2L/TRAIL (amino acids 114-281). Moreover, Ad-Apo2L/TRAIL gene transfer inhibits soluble His-tagged Apo2L/TRAIL-induced apoptosis, strongly suggesting that the adenovirally encoded full-length Apo2L/TRAIL is not a suitable molecule for glioma cancer gene therapy. This study has important implications for the future development of therapeutic strategies aiming at death receptor activation in refractory cancers such as malignant glioma.

Caspases are essential components of the mammalian cell death machinery. Caspase 9 is positioned at the apex of the pro-apoptotic signaling cascade induced by cytochrome c release from mitochondria. The splicing variant caspase 9-short (caspase 9S) lacks the catalytic domain and may therefore act as an endogenous inhibitor of caspase 9. Here, we report that human astrocytoma and neuroblastoma cell lines strongly express caspase 9 and 9S mRNA, whereas non-neoplastic human astrocytes show little caspase 9 and 9S mRNA expression. Transient overexpression of caspase 9S protects LN-229 astrocytoma cells from CD95 ligand (CD95L)-mediated apoptosis. However, stable overexpression of either caspase 9 or caspase 9S does not alter the sensitivity of LN-18 and LN-229 astrocytoma lines to CD95L or cytotoxic drugs. We conclude that the expression levels of caspase 9 or caspase 9S do not play a major role in determining vulnerability to apoptosis in human astrocytoma cells.

Long-term potentiation (LTP) is a cellular model for persistent synaptic plasticity in the mammalian brain. Like several forms of memory, long-lasting LTP requires cAMP-mediated activation of protein kinase A (PKA) and is dependent on gene transcription. Consequently, activity-dependent genes such as c- fos that contain cAMP response elements (CREs) in their 5′ regulatory region have been studied intensely. More recently, arg3.1/arc became of interest, because after synaptic stimulation, arg3.1/arc mRNA is rapidly induced and distributed to dendritic processes and may be locally translated there to facilitate synapse-specific modifications. However, to date nothing is known about the signaling mechanisms involved in the induction of this gene. Here we report that arg3.1/arc is robustly induced with LTP stimulation even at intensities that are not sufficient to activate c- fos expression. Unlike c- fos , the 5′ regulatory region of arg3.1/arc does not contain a CRE consensus sequence and arg3.1/arc is unresponsive to cAMP in NIH3T3 and Neuro2a cells. However, in PC12 cells and primary cultures of hippocampal neurons, arg3.1/arc can be induced by cAMP and calcium. This induction requires the activity of PKA and mitogen-activated protein kinase, suggesting a neuron-specific pathway for the activation of arg3.1/arc expression.

TGF-β is a putative mediator of immunosuppression associated with malignant glioma and other types of cancer. Subtilisin-like proprotein convertases such as furin are thought to mediate TGF-β processing. Here we report that human malignant glioma cell lines express furin mRNA and protein, exhibit furin-like protease (FLP) activity, and release active furin into the cell culture supernatant. FLP activity is not modulated by exogenous TGF-β or neutralizing TGF-β Abs. Exposure of LN-18 and T98G glioma cell lines to the furin inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethylketone, inhibits processing of the TGF-β1 and TGF-β2 precursor molecules and, consequently, the release of mature bioactive TGF-β molecules. Ectopic expression of PDX, a synthetic antitrypsin analog with antifurin activity, in the glioma cells inhibits FLP activity, TGF-β processing, and TGF-β release. Thus, subtilisin-like proprotein convertases may represent a novel target for the immunotherapy of malignant glioma and other cancers or pathological conditions characterized by enhanced TGF-β bioactivity.

Infection of the central nervous system by streptococci is known to result in severe bacterial meningitis, however some strains have low pathogenic potential and affect the brain only in immunocompromised patients. Here we report the first case of an otherwise healthy non immunocompromised young adult woman who developed meningitis caused by Streptococcus dysgalactiae subspecies equisimilis. The patient was in the 17th week of her 3rd pregnancy. The course of the disease was quickly remittent under antibiotic treatment.

Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3) in commissural axon guidance using a knockout (KO) mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptors Robo1 and Robo2 and immunohistochemistry studies showed that srGAP3 co-localises with Robo1 in the ventral and lateral funiculus and with Robo2 in the lateral funiculus. Stalling axons have been reported in the floor-plate of Slit and Robo mutant spinal cords but our axon tracing experiments revealed no dorsal commissural axon stalling in the floor plate of the srGAP3 KO mouse. Interestingly we observed a significant thickening of the ventral funiculus and a thinning of the lateral funiculus in the srGAP3 KO spinal cord, which has also recently been reported in the Robo2 KO. However, axons in the enlarged ventral funiculus of the srGAP3 KO are Robo1 positive but do not express Robo2, indicating that the thickening of the ventral funiculus in the srGAP3 KO is not a Robo2 mediated effect. We suggest a role for srGAP3 in the lateral positioning of post crossing axons within the ventrolateral funiculus.

Arc/Arg3.1 is robustly induced by plasticity-producing stimulation and specifically targeted to stimulated synaptic areas. To investigate the role of Arc/Arg3.1 in synaptic plasticity and learning and memory, we generated Arc/Arg3.1 knockout mice. These animals fail to form long-lasting memories for implicit and explicit learning tasks, despite intact short-term memory. Moreover, they exhibit a biphasic alteration of hippocampal long-term potentiation in the dentate gyrus and area CA1 with an enhanced early and absent late phase. In addition, long-term depression is significantly impaired. Together, these results demonstrate a critical role for Arc/Arg3.1 in the consolidation of enduring synaptic plasticity and memory storage. © 2006 Elsevier Inc. All rights reserved.

The facilitation of hippocampus-based, long-lasting synaptic plasticity, which is frequently investigated in model systems such as long-term potentiation (LTP) and in learning paradigms such as the Morris water maze, is associated with several cellular key events: Ca(2+) influx through the N-methyl-D-aspartate (NMDA) receptor, generation of cyclic AMP (cAMP) and activation of protein kinase A (PKA), phosphorylation of mitogen-associated protein kinase (MAPK) and cAMP-response element-binding protein (CREB), and subsequent transcription of plasticity-associated genes. Recently, a signal-transduction cascade from cAMP/PKA to MAPK was discovered, which seems to be neuron-specific and comprises the critical events of hippocampus-based long-term plasticity described here into one single cascade. A major alternative to cAMP/PKA-MAPK signaling are the cascades from Ca(2+) to MAPK via Ras. However, Ras is inhibited by PKA. This article reviews the studies that argue for the existence of two competing pathways, and discusses their implication for the molecular mechanisms underlying synaptic plasticity.

In animals and several cellular models of synaptic plasticity, long-lasting changes in synaptic strength are dependent on gene transcription and translation. Here we demonstrate that Pim-1, a serine/threonine kinase closely related to Pim-2 and Pim-3, is induced in hippocampus in response to stimuli that evoke long-term potentiation (LTP). Mice deficient for Pim-1 show normal synaptic transmission and short-term plasticity. However, they fail to consolidate enduring LTP even though Pim-2 and Pim-3 are constitutively expressed in the hippocampus and Pim-3 expression is similarly induced by synaptic activity. Thus, expression of Pim-1 is required for LTP. Its level of expression and, consequently, its capacity to phosphorylate target proteins in dendritic and nuclear compartments of stimulated neurons might be a determining factor for the establishment of long-lasting changes in synaptic strength.