Reelin restricts dendritic growth of interneurons in the neocortex.

Reelin is a large secreted glycoprotein that regulates neuronal migration, lamination and establishment of dendritic architecture in the embryonic brain. Reelin expression switches postnatally from Cajal-Retzius cells to interneurons. However, reelin function in interneuron development is still poorly understood. Here, we have investigated the role of reelin in interneuron development in the postnatal neocortex. To preclude early cortical migration defects caused by reelin deficiency, we employed a conditional reelin knockout (RelncKO) mouse to induce postnatal reelin deficiency. Induced reelin deficiency caused dendritic hypertrophy in distal dendritic segments of neuropeptide Y-positive (NPY+) and calretinin-positive (Calr+) interneurons, and in proximal dendritic segments of parvalbumin-positive (Parv+) interneurons. Chronic recombinant Reelin treatment rescued dendritic hypertrophy in Relncko interneurons. Moreover, we provide evidence that RelncKO interneuron hypertrophy is due to presynaptic GABABR dysfunction. Thus, GABABRs in RelncKO interneurons were unable to block N-type (Cav2.2) Ca2+ channels that control neurotransmitter release. Consequently, the excessive Ca2+ influx through AMPA receptors, but not NMDA receptors, caused interneuron dendritic hypertrophy. These findings suggest that reelin acts as a 'stop-growth-signal' for postnatal interneuron maturation.

Developmental HCN channelopathy results in decreased neural progenitor proliferation and microcephaly in mice.

The development of the cerebral cortex relies on the controlled division of neural stem and progenitor cells. The requirement for precise spatiotemporal control of proliferation and cell fate places a high demand on the cell division machinery, and defective cell division can cause microcephaly and other brain malformations. Cell-extrinsic and -intrinsic factors govern the capacity of cortical progenitors to produce large numbers of neurons and glia within a short developmental time window. In particular, ion channels shape the intrinsic biophysical properties of precursor cells and neurons and control their membrane potential throughout the cell cycle. We found that hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel subunits are expressed in mouse, rat, and human neural progenitors. Loss of HCN channel function in rat neural stem cells impaired their proliferation by affecting the cell-cycle progression, causing G1 accumulation and dysregulation of genes associated with human microcephaly. Transgene-mediated, dominant-negative loss of HCN channel function in the embryonic mouse telencephalon resulted in pronounced microcephaly. Together, our findings suggest a role for HCN channel subunits as a part of a general mechanism influencing cortical development in mammals.

Perforin affects regeneration in a mouse spinal cord injury model.

MATERIALS AND METHODS: Locomotor outcomes in perforin-deficient (Pfp-/-) mice and wild-type littermate controls were measured after severe compression injury of the lower thoracic spinal cord up to six weeks after injury. RESULTS: According to both the Basso mouse scale score and single frame motion analysis, motor recovery of Pfp-/- mice was similar to wild-type controls. Interestingly, immunohistochemical analysis of cell types at six weeks after injury showed enhanced cholinergic reinnervation of spinal motor neurons caudal to the lesion site and neurofilament-positive structures at the injury site in Pfp-/- mice, whereas numbers of microglia/macrophages and astrocytes were decreased compared with controls. CONCLUSIONS: We conclude that, although, loss of perforin does not change the locomotor outcome after injury, it beneficially affects diverse cellular features, such as number of axons, cholinergic synapses, astrocytes and microglia/macrophages at or caudal to the lesion site. Perforin's ability to contribute to Rag2's influence on locomotion was observed in mice doubly deficient in perforin and Rag2 which recovered better than Rag2-/- or Pfp-/- mice, suggesting that natural killer cells can cooperate with T- and B-cells in spinal cord injury.

Pharmacology of repair after peripheral nerve injury.

Peripheral nerve injuries are common and present with a broad spectrum of symptoms, some of which may be the cause of life-long disabilities. The peripheral nerves show a far greater capacity for regeneration than those in the central nervous system, and the process of nerve regeneration resembles developmental processes to a certain degree. The regeneration of peripheral nerves does not always lead to a full functional recovery. That is why surgical methods are still the most reliable therapeutic options after injuries of peripheral nerves. However, there is an array of potential pharmacological options that could enhance the repair processes after surgery. This review gives a summary of the recent literature relevant to different classes of pharmacologically active substances that are used either as supplements or off-label as potential enhancers of peripheral nerve repair. Antioxidants, vitamins, calcium channel blockers, immunosuppressive drugs, growth factors, and neuroactive glycans are among the most researched in this field. More research is necessary to understand their mechanisms of action at the cellular and molecular level, and randomized clinical trials in order to establish their efficacy and safety, as well as possible synergistic or adverse interactions among them.

The impact of hyperpolarization-activated cyclic nucleotide-gated (HCN) and voltage-gated potassium KCNQ/Kv7 channels on primary microglia function.

BACKGROUND: Microglia are essential to maintain cell homeostasis in the healthy brain and are activated after brain injury. Upon activation, microglia polarize towards different phenotypes. The course of microglia activation is complex and depends on signals in the surrounding milieu. Recently, it has been suggested that microglia respond to ion currents, as a way of regulating their activity and function. METHODS AND RESULTS: Under the hypothesis that HCN and KCNQ/Kv7 channels impact on microglia, we studied primary rat microglia in the presence or absence of specific pharmacological blockade or RNA silencing. Primary microglia expressed the subunits HCN1-4, Kv7.2, Kv7.3, and Kv7.5. The expression of HCN2, as well as Kv7.2 and Kv7.3, varied among different microglia phenotypes. The pharmacological blockade of HCN channels by ZD7288 resulted in cell depolarization with slowly rising intracellular calcium levels, leading to enhanced survival and reduced proliferation rates of resting microglia. Furthermore, ZD7288 treatment, as well as knockdown of HCN2 RNA by small interfering RNA, resulted in an attenuation of later microglia activation-both towards the anti- and pro-inflammatory phenotype. However, HCN channel inhibition enhanced the phagocytic capacity of IL4-stimulated microglia. Blockade of Kv7/KCNQ channel by XE-991 exclusively inhibited the migratory capacity of resting microglia. CONCLUSION: These observations suggest that the HCN current contributes to various microglia functions and impacts on the course of microglia activation, while the Kv7/KCNQ channels affect microglia migration. Characterizing the role of HCN channels in microglial functioning may offer new therapeutic approaches for targeted modulation of neuroinflammation as a hallmark of various neurological disorders.

The Na+/H+ Exchanger Nhe1 Modulates Network Excitability via GABA Release.

Brain functions are extremely sensitive to pH changes because of the pH-dependence of proteins involved in neuronal excitability and synaptic transmission. Here, we show that the Na+/H+ exchanger Nhe1, which uses the Na+ gradient to extrude H+, is expressed at both inhibitory and excitatory presynapses. We disrupted Nhe1 specifically in mice either in Emx1-positive glutamatergic neurons or in parvalbumin-positive cells, mainly GABAergic interneurons. While Nhe1 disruption in excitatory neurons had no effect on overall network excitability, mice with disruption of Nhe1 in parvalbumin-positive neurons displayed epileptic activity. From our electrophysiological analyses in the CA1 of the hippocampus, we conclude that the disruption in parvalbumin-positive neurons impairs the release of GABA-loaded vesicles, but increases the size of GABA quanta. The latter is most likely an indirect pH-dependent effect, as Nhe1 was not expressed in purified synaptic vesicles itself. Conclusively, our data provide first evidence that Nhe1 affects network excitability via modulation of inhibitory interneurons.

Impact of neural cell adhesion molecule deletion on regeneration after mouse spinal cord injury.

The neural cell adhesion molecule (NCAM) plays important functional roles in development of the nervous system. We investigated the influence of a constitutive ablation of NCAM on the outcome of spinal cord injury. Transgenic mice lacking NCAM (NCAM-/-) were subjected to severe compression injury of the lower thoracic spinal cord using wild-type (NCAM+/+) littermates as controls. According to the single-frame motion analysis, the NCAM-/- mice showed reduced locomotor recovery in comparison to control mice at 3 and 6 weeks after injury, indicating an overall positive impact of NCAM on recovery after injury. Also the Basso Mouse Scale score was lower in NCAM-/- mice at 3 weeks after injury, whereas at 6 weeks after injury the difference between genotypes was not statistically significant. Worse locomotor function was associated with decreased monoaminergic and cholinergic innervation of the spinal cord caudal to the injury site and decreased axonal regrowth/sprouting at the site of injury. Astrocytic scar formation at the injury site, as assessed by immunohistology for glial fibrillary acidic protein at and around the lesion site was increased in NCAM-/- compared with NCAM+/+ mice. Migration of cultured monolayer astrocytes from NCAM-/- mice was reduced as assayed by scratch wounding. Numbers of Iba-1 immunopositive microglia were not different between genotypes. We conclude that constitutive NCAM deletion in young adult mice reduces recovery after spinal cord injury, validating the hypothesized beneficial role of this molecule in recovery after injury.

The extracellular matrix glycoprotein tenascin-R regulates neurogenesis during development and in the adult dentate gyrus of mice.

Abnormal generation of inhibitory neurons that synthesize γ-aminobutyric acid (GABAergic) is characteristic of neuropsychological disorders. We provide evidence that the extracellular matrix molecule tenascin-R (TNR) - which is predominantly expressed by a subpopulation of interneurons - plays a role in the generation of GABAergic and granule neurons in the murine dentate gyrus by regulating fate determination of neural stem or progenitor cells (NSCs). During development, absence of TNR in constitutively TNR-deficient (TNR(-/-)) mice results in increased numbers of dentate gyrus GABAergic neurons, decreased expression of its receptor ß1 integrin, increased activation of p38 MAPK and increased expression of the GABAergic specification gene Ascl1. Postnatally, increased GABAergic input to adult hippocampal NSCs in TNR(-/-) mice is associated not only with increased numbers of GABAergic and, particularly, parvalbumin-immunoreactive neurons, as seen during development, but also with increased numbers of granule neurons, thus contributing to the increased differentiation of NSCs into granule cells. These findings indicate the importance of TNR in the regulation of hippocampal neurogenesis and suggest that TNR acts through distinct direct and indirect mechanisms during development and in the adult.

Intraspinal Delivery of Polyethylene Glycol-coated Gold Nanoparticles Promotes Functional Recovery After Spinal Cord Injury.

Failure of the mammalian central nervous system (CNS) to regenerate effectively after injury leads to mostly irreversible functional impairment. Gold nanoparticles (AuNPs) are promising candidates for drug delivery in combination with tissue-compatible reagents, such as polyethylene glycol (PEG). PEG administration in CNS injury models has received interest for potential therapy, but toxicity and low bioavailability prevents clinical application. Here we show that intraspinal delivery of PEG-functionalized 40-nm-AuNPs at early stages after mouse spinal cord injury is beneficial for recovery. Positive outcome of hind limb motor function was accompanied by attenuated inflammatory response, enhanced motor neuron survival, and increased myelination of spared or regrown/sprouted axons. No adverse effects, such as body weight loss, ill health, or increased mortality were observed. We propose that PEG-AuNPs represent a favorable drug-delivery platform with therapeutic potential that could be further enhanced if PEG-AuNPs are used as carriers of regeneration-promoting molecules.

Interaction of the cell adhesion molecule CHL1 with vitronectin, integrins, and the plasminogen activator inhibitor-2 promotes CHL1-induced neurite outgrowth and neuronal migration.

The cell adhesion molecule close homolog of L1 (CHL1) plays important functional roles in the developing and adult nervous system. In search of the binding partners that mediate the diverse and sometimes opposing functions of CHL1, the extracellular matrix-associated proteins vitronectin and plasminogen activator inhibitor-2 (PAI-2) were identified as novel CHL1 interaction partners and tested for involvement in CHL1-dependent functions during mouse cerebellar development. CHL1-induced cerebellar neurite outgrowth and cell migration at postnatal days 6-8 were inhibited by a CHL1-derived peptide comprising the integrin binding RGD motif, and by antibodies against vitronectin or several integrins, indicating a vitronectin-dependent integrin-mediated pathway. A PAI-2-derived peptide, or antibodies against PAI-2, urokinase type plasminogen activator (uPA), uPA receptor, and several integrins reduced cell migration. CHL1 colocalized with vitronectin, PAI-2, and several integrins in cerebellar granule cells, suggesting an association among these proteins. Interestingly, at the slightly earlier age of 4-5 d, cerebellar neurons did not depend on CHL1 for neuritogenesis and cell migration. However, differentiation of progenitor cells into neurons at this stage was dependent on homophilic CHL1-CHL1 interactions. These observations indicate that homophilic CHL1 trans-interactions regulate differentiation of neuronal progenitor cells at early postnatal stages, while heterophilic trans-interactions of CHL1 with vitronectin, integrins, and the plasminogen activator system regulate neuritogenesis and neuronal cell migration at a later postnatal stage of cerebellar morphogenesis. Thus, within very narrow time windows in postnatal cerebellar development, distinct types of molecular interactions mediated by CHL1 underlie the diverse functions of this protein.

Age-dependent loss of parvalbumin-expressing hippocampal interneurons in mice deficient in CHL1, a mental retardation and schizophrenia susceptibility gene.

In humans, deletions/mutations in the CHL1/CALL gene are associated with mental retardation and schizophrenia. Juvenile CHL1-deficient (CHL1(-/-) ) mice have been shown to display abnormally high numbers of parvalbumin-expressing (PV(+) ) hippocampal interneurons and, as adults, display behavioral traits observed in neuropsychiatric disorders. Here, we addressed the question whether inhibitory interneurons and synaptic plasticity in the CHL1(-/-) mouse are affected during brain maturation and in adulthood. We found that hippocampal, but not neocortical, PV(+) interneurons were reduced with age in CHL1(-/-) mice, from a surplus of +27% at 1 month to a deficit of -20% in adulthood compared with wild-type littermates. This loss occurred during brain maturation, correlating with microgliosis and enhanced interleukin-6 expression. In parallel with the loss of PV(+) interneurons, the inhibitory input to adult CA1 pyramidal cells was reduced and a deficit in short- and long-term potentiation developed at CA3-CA1 excitatory synapses between 2 and 9 months of age in CHL1(-/-) mice. This deficit could be abrogated by a GABAA receptor agonist. We propose that region-specific aberrant GABAergic synaptic connectivity resulting from the mutation and a subsequently enhanced synaptic elimination during brain maturation lead to microgliosis, increase in pro-inflammatory cytokine levels, loss of interneurons, and impaired synaptic plasticity. Close homolog of L1-deficient (CHL1(-/-) ) mice have abnormally high numbers of parvalbumin (PV)-expressing hippocampal interneurons in juvenile animals, but in adult animals a loss of these cells is observed. This loss correlates with an increased density of microglia (M), enhanced interleukin-6 (IL6) production and a deficit in short- and long-term potentiation at CA3-CA1 excitatory synapses. Furthermore, adult CHL1(-/-) mice display behavioral traits similar to those observed in neuropsychiatric disorders of humans.

The Neuroprotective Effect of Neural Cell Adhesion Molecule L1 in the Hippocampus of Aged Alzheimer's Disease Model Mice.

Alzheimer's disease (AD) is a severe neurodegenerative disorder and the most common form of dementia, causing the loss of cognitive function. Our previous study has shown, using a doubly mutated mouse model of AD (APP/PS1), that the neural adhesion molecule L1 directly binds amyloid peptides and decreases plaque load and gliosis when injected as an adeno-associated virus construct (AAV-L1) into APP/PS1 mice. In this study, we microinjected AAV-L1, using a Hamilton syringe, directly into the 3-month-old APP/PS1 mouse hippocampus and waited for a year until significant neurodegeneration developed. We stereologically counted the principal neurons and parvalbumin-positive interneurons in the hippocampus, estimated the density of inhibitory synapses around principal cells, and compared the AAV-L1 injection models with control injections of green fluorescent protein (AAV-GFP) and the wild-type hippocampus. Our results show that there is a significant loss of granule cells in the dentate gyrus of the APP/PS1 mice, which was improved by AAV-L1 injection, compared with the AAV-GFP controls (p < 0.05). There is also a generalized loss of parvalbumin-positive interneurons in the hippocampus of APP/PS1 mice, which is ameliorated by AAV-L1 injection, compared with the AAV-GFP controls (p < 0.05). Additionally, AAV-L1 injection promotes the survival of inhibitory synapses around the principal cells compared with AAV-GFP controls in all three hippocampal subfields (p < 0.01). Our results indicate that L1 promotes neuronal survival and protects the synapses in an AD mouse model, which could have therapeutic implications.

The Role of Tenascin-C on the Structural Plasticity of Perineuronal Nets and Synaptic Expression in the Hippocampus of Male Mice.

Neuronal plasticity is a crucial mechanism for an adapting nervous system to change. It is shown to be regulated by perineuronal nets (PNNs), the condensed forms of the extracellular matrix (ECM) around neuronal bodies. By assessing the changes in the number, intensity, and structure of PNNs, the ultrastructure of the PNN mesh, and the expression of inhibitory and excitatory synaptic inputs on these neurons, we aimed to clarify the role of an ECM glycoprotein, tenascin-C (TnC), in the dorsal hippocampus. To enhance neuronal plasticity, TnC-deficient (TnC-/-) and wild-type (TnC+/+) young adult male mice were reared in an enriched environment (EE) for 8 weeks. Deletion of TnC in TnC-/- mice showed an ultrastructural reduction of the PNN mesh and an increased inhibitory input in the dentate gyrus (DG), and an increase in the number of PNNs with a rise in the inhibitory input in the CA2 region. EE induced an increased inhibitory input in the CA2, CA3, and DG regions; in DG, the change was also followed by an increased intensity of PNNs. No changes in PNNs or synaptic expression were found in the CA1 region. We conclude that the DG and CA2 regions emerged as focal points of alterations in PNNs and synaptogenesis with EE as mediated by TnC.

Mice Mutated in the First Fibronectin Domain of Adhesion Molecule L1 Show Brain Malformations and Behavioral Abnormalities.

The X-chromosome-linked cell adhesion molecule L1 (L1CAM), a glycoprotein mainly expressed by neurons in the central and peripheral nervous systems, has been implicated in many neural processes, including neuronal migration and survival, neuritogenesis, synapse formation, synaptic plasticity and regeneration. L1 consists of extracellular, transmembrane and cytoplasmic domains. Proteolytic cleavage of L1's extracellular and transmembrane domains by different proteases generates several L1 fragments with different functions. We found that myelin basic protein (MBP) cleaves L1's extracellular domain, leading to enhanced neuritogenesis and neuronal survival in vitro. To investigate in vivo the importance of the MBP-generated 70 kDa fragment (L1-70), we generated mice with an arginine to alanine substitution at position 687 (L1/687), thereby disrupting L1's MBP cleavage site and obliterating L1-70. Young adult L1/687 males showed normal anxiety and circadian rhythm activities but enhanced locomotion, while females showed altered social interactions. Older L1/687 males were impaired in motor coordination. Furthermore, L1/687 male and female mice had a larger hippocampus, with more neurons in the dentate gyrus and more proliferating cells in the subgranular layer, while the thickness of the corpus callosum and the size of lateral ventricles were normal. In summary, subtle mutant morphological changes result in subtle behavioral changes.

Generation and nuclear translocation of sumoylated transmembrane fragment of cell adhesion molecule L1.

The functions of the cell adhesion molecule L1 in the developing and adult nervous system are triggered by homophilic and heterophilic interactions that stimulate signal transductions that activate cellular responses. Here, we show that stimulation of signaling by function-triggering L1 antibodies or L1-Fc leads to serine protease-dependent cleavage of full-length L1 at the plasma membrane and generation of a sumoylated transmembrane 70-kDa fragment comprising the intracellular and transmembrane domains and part of the extracellular domain. The 70-kDa transmembrane fragment is transported from the plasma membrane to a late endosomal compartment, released from endosomal membranes into the cytoplasm, and transferred from there into the nucleus by a pathway that depends on importin and chromatin-modifying protein 1. Mutation of the sumoylation site at Lys(1172) or of the nuclear localization signal at Lys(1147) abolished L1-stimulated generation or nuclear import of the 70-kDa fragment, respectively. Nuclear import of the 70-kDa fragment may activate cellular responses in parallel or in association with phosphorylation-dependent signaling pathways. Alterations in the levels of the 70-kDa fragment during development and in the adult after spinal cord injury or in a mouse model of Alzheimer disease suggest that this fragment is functionally implicated in development, regeneration, neurodegeneration, tumorigenesis, and possibly synaptic plasticity in the mature nervous system.

Adhesion molecule L1 binds to amyloid beta and reduces Alzheimer's disease pathology in mice.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder and the most common cause of elderly dementia. In an effort to contribute to the potential of molecular approaches to reduce degenerative processes we have tested the possibility that the neural adhesion molecule L1 ameliorates some characteristic cellular and molecular parameters associated with the disease in a mouse model of AD. Three-month-old mice overexpressing mutated forms of amyloid precursor protein and presenilin-1 under the control of a neuron-specific promoter received an injection of adeno-associated virus encoding the neuronal isoform of full-length L1 (AAV-L1) or, as negative control, green fluorescent protein (AAV-GFP) into the hippocampus and occipital cortex. Four months after virus injection, the mice were analyzed for histological and biochemical parameters of AD. AAV-L1 injection decreased the Aß plaque load, levels of Aß42, Aß42/40 ratio and astrogliosis compared with AAV-GFP controls. AAV-L1 injected mice also had increased densities of inhibitory synaptic terminals on pyramidal cells in the hippocampus when compared with AAV-GFP controls. Numbers of microglial cells/macrophages were similar in both groups, but numbers of microglial cells/macrophages per plaque were increased in AAV-L1 injected mice. To probe for a molecular mechanism that may underlie these effects, we analyzed whether L1 would directly and specifically interact with Aß. In a label-free binding assay, concentration dependent binding of the extracellular domain of L1, but not of the close homolog of L1 to Aß40 and Aß42 was seen, with the fibronectin type III homologous repeats 1-3 of L1 mediating this effect. Aggregation of Aß42 in vitro was reduced in the presence of the extracellular domain of L1. The combined observations indicate that L1, when overexpressed in neurons and glia, reduces several histopathological hallmarks of AD in mice, possibly by reduction of Aß aggregation. L1 thus appears to be a candidate molecule to ameliorate the pathology of AD, when applied in therapeutically viable treatment schemes.

Dermatan sulfotransferase Chst14/D4st1, but not chondroitin sulfotransferase Chst11/C4st1, regulates proliferation and neurogenesis of neural progenitor cells.

Chondroitin sulfates (CSs) and dermatan sulfates (DSs) are enriched in the microenvironment of neural stem cells (NSCs) during development and in the adult neurogenic niche, and have been implicated in mechanisms governing neural precursor migration, proliferation and differentiation. In contrast to previous studies, in which a chondroitinaseABC-dependent unselective deglycosylation of both CSs and DSs was performed, we used chondroitin 4-O-sulfotransferase-1 (Chst11/C4st1)- and dermatan 4-O-sulfotransferase-1 (Chst14/D4st1)-deficient NSCs specific for CSs and DSs, respectively, to investigate the involvement of specific sulfation profiles of CS and DS chains, and thus the potentially distinct roles of CSs and DSs in NSC biology. In comparison to wild-type controls, deficiency for Chst14 resulted in decreased neurogenesis and diminished proliferation of NSCs accompanied by increased expression of GLAST and decreased expression of Mash-1, and an upregulation of the expression of the receptors for fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF). By contrast, deficiency in Chst11 did not influence NSC proliferation, migration or differentiation. These observations indicate for the first time that CSs and DSs play distinct roles in the self-renewal and differentiation of NSCs.

Tenascins and inflammation in disorders of the nervous system.

In vitro and in vivo studies on the role of tenascins have shown that the two paradigmatic glycoproteins of the tenascin family, tenascin-C (TnC) and tenascin-R (TnR) play important roles in cell proliferation and migration, fate determination, axonal pathfinding, myelination, and synaptic plasticity. As components of the extracellular matrix, both molecules show distinct, but also overlapping dual functions in inhibiting and promoting cell interactions depending on the cell type, developmental stage and molecular microenvironment. They are expressed by neurons and glia as well as, for TnC, by cells of the immune system. The functional relationship between neural and immune cells becomes relevant in acute and chronic nervous system disorders, in particular when the blood brain and blood peripheral nerve barriers are compromised. In this review, we will describe the functional parameters of the two molecules in cell interactions during development and, in the adult, in synaptic activity and plasticity, as well as regeneration after injury, with TnC being conducive for regeneration and TnR being inhibitory for functional recovery. Although not much is known about the role of tenascins in neuroinflammation, we will describe emerging knowledge on the interplay between neural and immune cells in autoimmune diseases, such as multiple sclerosis and polyneuropathies. We will attempt to point out the directions of experimental approaches that we envisage would help gaining insights into the complex interplay of TnC and TnR with the cells that express them in pathological conditions of nervous and immune systems.

COUP-TFII expressing interneurons in human fetal forebrain.

Transcription factor COUP-TFII in rodents is important for migration of cortical interneurons from caudal ganglionic eminence (CGE) to the neocortex. Since in human, unlike in rodents, cortical interneurons have both ganglionic eminence (GE) and dorsal cortical origin, we studied the distribution of COUP-TFII in the human developing neocortex from 9 to 22 gestational weeks. COUP-TFII is expressed at all stages studied in the GE and in various cortical zones, from the proliferative ventricular/subventricular zone (VZ/SVZ) to layer I. Gradients of COUP-TFII expression are present in the GE, with peak expression in the CGE, and in the neocortex, from high expression in the temporal and occipital cortex to moderate in the frontal and dorsal cortex. Double immunofluorescence with γ-aminobutyric acid (GABA), calretinin, or calbindin, established that subpopulations of interneurons express COUP-TFII. A small fraction of COUP-TFII(+) cells are progenitor cells that proliferate in the CGE (3.4 ± 0.3%) and in the cortical VZ/SVZ (1.7 ± 0.1%). In summary, COUP-TFII is expressed in the human fetal forebrain in GABAergic cells, according to its possible role in migration of cortical interneurons. The source of these cells seems to be the CGE and, to a smaller extent, the cortical VZ/SVZ.

The long-term effects of maternal deprivation on the number and size of inhibitory interneurons in the rat amygdala and nucleus accumbens.

Introduction: There is an increasing evidence supporting the hypothesis that traumatic experiences during early developmental periods might be associated with psychopathology later in life. Maternal deprivation (MD) in rodents has been proposed as an animal model for certain aspects of neuropsychiatric disorders. Methods: To determine whether early-life stress leads to changes in GABAergic, inhibitory interneurons in the limbic system structures, specifically the amygdala and nucleus accumbens, 9-day-old Wistar rats were exposed to a 24 h MD. On postnatal day 60 (P60), the rats were sacrificed for morphometric analysis and their brains were compared to the control group. Results: Results show that MD affect GABAergic interneurons, leading to the decrease in density and size of the calcium-binding proteins parvalbumin-, calbindin-, and calretinin-expressing interneurons in the amygdala and nucleus accumbens. Discussion: This study indicates that early stress in life leads to changes in the number and morphology of the GABAergic, inhibitory interneurons in the amygdala and nucleus accumbens, most probably due to the loss of neurons during postnatal development and it further contributes to understanding the effects of maternal deprivation on brain development.