Oxytocin, GABA, and dopamine interplay in autism.

Oxytocin plays an important role in brain development and is associated with various neurotransmitter systems in the brain. Abnormalities in the production, secretion, and distribution of oxytocin in the brain, at least during some stages of the development, are critical for the pathogenesis of neuropsychiatric diseases, particularly in the autism spectrum disorder. The etiology of autism includes changes in local sensory and dopaminergic areas of the brain, which are also supplied by the hypothalamic sources of oxytocin. It is very important to understand their mutual relationship. In this review, the relationship of oxytocin with several components of the dopaminergic system, gamma-aminobutyric acid (GABA) inhibitory neurotransmission and their alterations in the autism spectrum disorder is discussed. Special attention has been paid to the results describing a reduced expression of inhibitory GABAergic markers in the brain in the context of dopaminergic areas in various models of autism. It is presumed that the altered GABAergic neurotransmission, due to the absence or dysfunction of oxytocin at certain developmental stages, disinhibits the dopaminergic signaling and contributes to the autism symptoms.

Shank3 Deficiency Results in a Reduction in GABAergic Postsynaptic Puncta in the Olfactory Brain Areas.

Dysfunctional sensory systems, including altered olfactory function, have recently been reported in patients with autism spectrum disorder (ASD). Disturbances in olfactory processing can potentially result from gamma-aminobutyric acid (GABA)ergic synaptic abnormalities. The specific molecular mechanism by which GABAergic transmission affects the olfactory system in ASD remains unclear. Therefore, the present study aimed to evaluate selected components of the GABAergic system in olfactory brain regions and primary olfactory neurons isolated from Shank3-deficient (-/-) mice, which are known for their autism-like behavioral phenotype. Shank3 deficiency led to a significant reduction in GEPHYRIN/GABAAR colocalization in the piriform cortex and in primary neurons isolated from the olfactory bulb, while no change of cell morphology was observed. Gene expression analysis revealed a significant reduction in the mRNA levels of GABA transporter 1 in the olfactory bulb and Collybistin in the frontal cortex of the Shank3-/- mice compared to WT mice. A similar trend of reduction was observed in the expression of Somatostatin in the frontal cortex of Shank3-/- mice. The analysis of the expression of other GABAergic neurotransmission markers did not yield statistically significant results. Overall, it appears that Shank3 deficiency leads to changes in GABAergic synapses in the brain regions that are important for olfactory information processing, which may represent basis for understanding functional impairments in autism.

Mini review of molecules involved in altered postnatal neurogenesis in autism.

The neurobiology of autism is complex, but emerging research points to potential abnormalities and alterations in neurogenesis. The aim of the present review is to describe the advances in the understanding of the role of selected neurotrophins, neuropeptides, and other compounds secreted by neuronal cells in the processes of postnatal neurogenesis in conjunction with autism. We characterize the fundamental mechanisms of neuronal cell proliferation, generation of major neuronal cell types with special emphasis on neurogenic niches - the subventricular zone and hippocampal areas. We also discuss changes in intracellular calcium levels and calcium-dependent transcription factors in the context of the regulation of neurogenesis and cell fate determination. To sum up, this review provides specific insight into the known association between alterations in the function of the entire spectrum of molecules involved in neurogenesis and the etiology of autism pathogenesis.

Neonatal oxytocin treatment alters levels of precursor and mature BDNF forms and modifies the expression of neuronal markers in the male rat hippocampus.

Neuropeptide oxytocin appears to be involved in the formation of hippocampal circuitry, underlying social memory and behaviour. Recent studies point to the role of oxytocin in regulating the levels of nerve growth factors that could influence neurogenesis and neuritogenesis during the early stages of brain development. Therefore, the aim of the present study was to evaluate the early developmental effect of oxytocin administration (P2 and P3 days, two doses, 5 µg/pup, s.c.) on the expression of 1) brain-derived neurotrophic factor (BDNF) isoforms and 2) GABAergic and glutamatergic markers in the male rat hippocampus. Furthermore, we evaluated the branching of dendrites of primary hippocampal GABAergic and glutamatergic neurons in response to incubation with oxytocin (1 µM). We found that after oxytocin administration, levels of proBDNF increased on P5 and mBDNF on P7 in the CA1 hippocampal region. We also observed a reduction in the expression of glutamatergic marker (VGluT2) on P7 compared to P5 in control and oxytocin treated rats. During the early developmental stages (P5, P7, P9) the expression of GABAergic markers (Gad65 and Gad67) decreased regardless of oxytocin treatment. Incubation in a presence of oxytocin reduced branching of glutamatergic hippocampal neurons and the opposite stimulatory effect of oxytocin was observed in GABAergic neurons. These findings suggest that oxytocin affects neurotrophin isoforms in the male rat hippocampus in the early stages of development, which could explain changes in glutamatergic neurons and their morphology.

Effects of antipsychotics, haloperidol and olanzapine, on the expression of apoptosis-related genes in mouse mHippoE-2 cells and rat hippocampus.

Objective. Modified levels of pro- (caspase3, Bax) and anti-apoptotic (Bcl-2) regulatory proteins have been detected in certain brain areas of schizophrenic patients indicating a possible dysregulation of apoptosis. In the present study, effects of antipsychotics, haloperidol (HAL) and olanzapine (OLA), on the gene expression of caspase3 (casp3), Bax and Bcl-2 were studied in vitro in mouse hippocampal mHippoE-2 cell line and in vivo in the hippocampus of MK-801 animal schizophrenia model with the aim to provide evidence that antipsychotics may affect the activity of apoptosis-related markers. Methods. mHippoE-2 cells were incubated with MK-801 (20 µM), HAL (10 µM), and OLA (10 µM) alone or combined, MK-801+HAL/OLA, for 24, 48, and 72 h. Male Sprague Dawley rats were injected with saline or MK-801 (0.5 mg/kg) for 6 days and since the 7th day, they were treated with vehicle (VEH), HAL (1 mg/kg) or OLA (2 mg/kg) for the next 7 days. The casp3, Bax and Bcl-2 gene expression in mHippoE-2 cells and rat hippocampus was measured by RT-PCR. Results. In mHippoE-2 cells, casp3 gene expression was increased by MK-801 and OLA treatments alone for 48 h, HAL treatment alone for 24 and 72 h, and co-treatment with MK-801+OLA for 24 and 72 h compared to controls. HAL and OLA suppressed the stimulatory effect of MK-801 on casp3 mRNA levels in cells after 48 h of incubation. Bax mRNA levels in mHippoE-2 cells were decreased after HAL treatment for 24 and 48 h, and also after co-treatment with MK-801+HAL for 72 h. In vivo, MK-801 decreased mRNA levels of both pro-apoptotic markers, casp3 and Bax, in hippocampus of VEH-treated rats and Bax mRNA levels in hippocampus of HAL-treated animals. OLA reversed the inhibitory effect of MK-801 on casp3 expression in the VEH-treated animals. Neither MK-801 nor antipsychotics induced changes in the gene expression of anti-apoptotic marker Bcl-2 in mHippoE-2 cells as well as hippocampus of rats. Conclusions. The results of the present study demonstrate that antipsychotics, HAL and OLA, may affect mRNA levels of pro-apoptotic markers in hippocampal cells in vitro, but not in vivo. The obtained data do not clearly support the assumed potentiating role of MK-801 in inducing apoptosis in specific brain areas and a possible protective role of antipsychotics against induction of apoptosis. The obtained data may contribute to a deeper insight into the neurodevelopmental changes connected with schizophrenia.

Effect of Haloperidol and Olanzapine on Hippocampal Cells' Proliferation in Animal Model of Schizophrenia.

Aberrant neurogenesis in the subventricular zone (SVZ) and hippocampus (HIP) contributes to schizophrenia pathogenesis. Haloperidol (HAL) and olanzapine (OLA), commonly prescribed antipsychotics for schizophrenia treatment, affect neurogenesis too. The effect of HAL and OLA on an mHippoE-2 cell line was studied in vitro where we measured the cell number and projection length. In vivo, we studied the gene expression of DCX, Sox2, BDNF, and NeuN in the SVZ and HIP in an MK-801-induced animal schizophrenia model. Cells were incubated with HAL, OLA, and MK-801 for 24, 48, and 72 h. Animals were injected for 6 days with saline or MK801 (0.5 mg/kg), and from the 7th day with either vehicle HAL (1 mg/kg) or OLA (2 mg/kg), for the next 7 days. In vitro, HAL and OLA dose/time-dependently suppressed cells' proliferation and shortened their projection length. HAL/OLA co-treatment with MK-801 for 24 h reversed HAL's/OLA's inhibitory effect. In vivo, HAL and OLA suppressed DCX and NeuN genes' expression in the HIP and SVZ. MK-801 decreased DCX and NeuN genes' expression in the HIP and OLA prevented this effect. The data suggest that subchronic HAL/OLA treatment can inhibit DCX and NeuN expression. In an MK-801 schizophrenia model, OLA reversed the MK-801 inhibitory effect on DCX and NeuN and HAL reversed the effect on DCX expression; however, only in the HIP.

Gene expression levels of DNA methyltransferase enzymes in Shank3-deficient mouse model of autism during early development.

Objectives. The balance between DNA methylation and demethylation is crucial for the brain development. Therefore, alterations in the expression of enzymes controlling DNA methylation patterns may contribute to the etiology of neurodevelopmental disorders, including autism. SH3 and multiple ankyrin repeat domains 3 (Shank3)-deficient mice are commonly used as a well-characterized transgenic model to investigate the molecular mechanisms of autistic symptoms. DNA methyltransferases (DNMTs), which modulate several cellular processes in neurodevelopment, are implicated in the pathophysiology of autism. In this study, we aimed to describe the gene expression changes of major Dnmts in the brain of Shank3-deficient mice during early development. Methods and Results. The Dnmts gene expression was analyzed by qPCR in 5-day-old homo-zygous Shank3-deficient mice. We found significantly lower Dnmt1 and Dnmt3b gene expression levels in the frontal cortex. However, no such changes were observed in the hippocampus. However, significant increase was observed in the expression of Dnmt3a and Dnmt3b genes in the hypothalamus of Shank3-deficient mice. Conclusions. The present data indicate that abnormalities in the Shank3 gene are accompanied by an altered expression of DNA methylation enzymes in the early brain development stages, therefore, specific epigenetic control mechanisms in autism-relevant models should be more extensively investigated.

Photodynamic therapy of multidrug resistant leukemic murine cells by 3,6-bis(alkylthiourea)acridine hydrochlorides.

Efforts to overcome multidrug resistance in cancer have led to the development of several novel strategies including photodynamic therapy (PDT). PDT is based on the use of photosensitizers (PSs) photoactivation, which causes the formation of reactive oxygen species that can induce cell death. In the last decade, the development of new PSs has been significantly accelerated. Recently, acridine-3,6-dialkyldithiourea hydrochlorides (AcrDTUs) have been investigated as a new group of PSs and we have shown that PDT/AcrDTUs caused cell death of mouse leukemic cells L1210. In this study, we investigated the efficacy of PDT/AcrDTUs for the treatment of L1210/VCR cells as a model of chemoresistant cells (overexpressing P-glycoprotein, P-gp). The photoactivation (365 nm, 1.05 J/cm2) increased the cytotoxicity of AcrDTUs 10-15 times. Inhibition of P-gp (verapamil) has been shown to have no significant effect on the accumulation of propyl-AcrDTU (the most potent derivative) in L1210/VCR cells. The intracellular distribution of this acridine derivative has been studied. Prior to irradiation of the resistant cells, propyl-AcrDTU was sequestered mainly in the cytosol, partly in the mitochondria, and, unlike in the sensitive cells, the AcrDTU was not found in the lysosomes. PDT with 1 µM propyl-AcrDTU induced cell shrinkage and "ladder DNA" formation, and although a drastic decrease of the intracellular ATP level was observed at the same time, there was no increase in extracellular LDH activity. AIF in the nucleus can induce DNA fragmentation and we have actually observed a mitochondrio-nuclear translocation of AIF. We concluded that AcrDTUs are photocytotoxic against L1210/VCR cells and that mitochondria play an important role in cell death induced by PDT.

Shank3 Deficiency is Associated With Altered Profile of Neurotransmission Markers in Pups and Adult Mice.

Alterations in the balance between excitation and inhibition, especially in the brain's critical developmental periods, are considered an integral part of the pathophysiology of autism. However, the precise mechanisms have not yet been established. SH3 and multiple Ankyrin repeat domains 3 (Shank3) deficient mice represent a well-established transgenic model of a neurodevelopmental disorder with autistic symptomatology. In this study, we characterize the consequences of Shank3 deficiency according to (1) expression of specific markers of different neuronal populations in pups and adult mice and (2) social behaviour and anxiety in adult mice. Our research found enhanced expression of serotonin transporter and choline acetyltransferase in the hippocampus and hypothalamus in Shank3-deficient pups. We demonstrated marked brain region differences in expression of excitatory glutamatergic markers in pups and adult Shank3 deficient mice. We also observed reduced expression of inhibitory GABAergic markers and GABA receptor subunits in several brain areas in both pups and adult Shank3 deficient mice. Further analysis of dopaminergic brain areas (nucleus accumbens, ventral tegmental area) revealed lower expression levels of GABAergic markers in adult Shank3 deficient mice. Adult Shank3- deficient mice exhibited excessive repetitive behaviour, a higher level of anxiety, and lower locomotor activity. Our data support the theory of an imbalance between excitatory and inhibitory neurotransmission in conditions of abnormal SHANK3 protein. We therefore suggest that autism-like conditions are accompanied by reduced expression of GABAergic markers in the brain during early development as well as in the adult age, which could be associated with long-lasting behavioural abnormalities.

The effects of testosterone on gene expression of cell-adhesion molecules and scaffolding proteins: The role of sex in early development.

Sex-specific differences in brain plasticity appear to be organised by testosterone, which is particularly important during the early stages of development. The main purpose of the present study was to examine the sex differences in mRNA and protein levels of selected cell-adhesion molecules and scaffolding proteins on postnatal days 5 (P5) and 9 (P9) in the rat hippocampus, as well as evaluate the effects of testosterone treatment (100 nM, 48 hr) on synaptic proteins in SH-SY5Y (neuron-like) and U-87MG (astrocyte-like) cells. The gene expression levels of Neuroligin 3 and 'SH3 and multiple ankyrin repeat domains protein' 1 and 3 (SHANK1 and SHANK3) were significantly lower in males compared to females at P5. At P9, a similar significant trend towards a decrease in mRNA expression and protein levels of SHANK3 was found in males. Testosterone treatment induced a significant decrease of Neuroligin 1-3 mRNA expression in both SH-SY5Y and U-87MG cells. SHANK1 and SHANK3 mRNA levels significantly decreased in U-87MG cells response to testosterone presence. The presented results demonstrate that the association of selected postsynaptic cell-adhesion molecules and scaffolding proteins is sex-related. Testosterone appears to be particularly involved in the developmental mechanisms related to neuroplasticity.

The epigenetic regulation of synaptic genes contributes to the etiology of autism.

Epigenetic mechanisms greatly affect the developing brain, as well as the maturation of synapses with pervasive, long-lasting consequences on behavior in adults. Substantial evidence exists that implicates dysregulation of epigenetic mechanisms in the etiology of neurodevelopmental disorders. Therefore, this review explains the role of enzymes involved in DNA methylation and demethylation in neurodevelopment by emphasizing changes of synaptic genes and proteins. Epigenetic causes of sex-dependent differences in the brain are analyzed in conjunction with the pathophysiology of autism spectrum disorders. Special attention is devoted to the epigenetic regulation of the melanoma-associated antigen-like gene 2 (MAGEL2) found in Prader-Willi syndrome, which is known to be accompanied by autistic symptoms.

The impact of oxytocin on neurite outgrowth and synaptic proteins in Magel2-deficient mice.

Oxytocin contributes to the regulation of cytoskeletal and synaptic proteins and could, therefore, affect the mechanisms of neurodevelopmental disorders, including autism. Both the Prader-Willi syndrome and Schaaf-Yang syndrome exhibit autistic symptoms involving the MAGEL2 gene. Magel2-deficient mice show a deficit in social behavior that is rescued following the postnatal administration of oxytocin. Here, in Magel2-deficient mice, we showed that the neurite outgrowth of primary cultures of immature hippocampal neurons is reduced. Treatment with oxytocin reversed this abnormality. In the hippocampus of Magel2-deficient pups, we further demonstrated that several transcripts of neurite outgrowth-associated proteins, synaptic vesicle proteins, and cell-adhesion molecules are decreased. In the juvenile stage, when neurons are mature, normalization or even overexpression of most of these markers was observed, suggesting a delay in the neuronal maturation of Magel2-deficient pups. Moreover, we found reduced transcripts of the excitatory postsynaptic marker, Psd95 in the hippocampus and we observed a decrease of PSD95/VGLUT2 colocalization in the hippocampal CA1 and CA3 regions in Magel2-deficient mice, indicating a defect in glutamatergic synapses. Postnatal administration of oxytocin upregulated postsynaptic transcripts in pups; however, it did not restore the level of markers of glutamatergic synapses in Magel2-deficient mice. Overall, Magel2 deficiency leads to abnormal neurite outgrowth and reduced glutamatergic synapses during development, suggesting abnormal neuronal maturation. Oxytocin stimulates the expression of numerous genes involved in neurite outgrowth and synapse formation in early development stages. Postnatal oxytocin administration has a strong effect on development that should be considered for certain neuropsychiatric conditions in infancy.

The role of selected postsynaptic scaffolding proteins at glutamatergic synapses in autism-related animal models.

Pathological changes in synapse formation, plasticity, and development are caused by altered trafficking and assembly of postsynaptic scaffolding proteins at sites of glutamatergic and gamma-aminobutyric acid (GABA)ergic synapses, suggesting their involvement in the etiology of neurodevelopmental disorders, including autism. Several autism-related mouse models have been developed in recent years for studying molecular, cellular, and behavioural defects in order to understand the etiology of autism and test the potential treatment strategies. In this review, we explain the role of alterations in selected postsynaptic scaffolding proteins in relevant transgene autism-like mouse models. We also provide a summary of selected animal models by paying special attention to interactions between guanylate kinases or membrane-associated guanylate kinases (MAGUKs), as well as other synapse protein components which form functional synaptic networks. The study of early developmental stages of autism-relevant animal models can help us understand the origin and development of diverse autistic symptomatology.

Abnormal neuronal morphology and altered synaptic proteins are restored by oxytocin in autism-related SHANK3 deficient model.

Oxytocin has been suggested as a potential therapeutic agent in autism and other neuropsychiatric conditions. Although, the link between the deficit in "SH3 domain and ankyrin repeat containing protein 3" (SHANK3) and autism spectrum disorders is highly studied topic, developmental mechanisms are still poorly understood. In this study, we clearly confirm that SHANK3 deficiency is accompanied with abnormalities in neurite number and length, which are reversed by oxytocin treatment (1 µM, 48h) in primary hippocampal neurons. Transient silencing for the SHANK3 gene (siSHANK3) in neuron-like cell line (SH-SY5Y) revealed a significant decrease in the expression levels of Neurexins 1α, 1ß, 2α and 2ß. Oxytocin treatment compensated reduced levels of Synapsin I, PSD95 and Neuroligin 3 in siSHANK3 cells suggesting a marked potential of oxytocin to ameliorate defects present in conditions of SHANK3 deficiency. Further analysis of hippocampal tissue revealed that oxytocin application (0.1 µg/µl, s.c. at P2 and P3 day) affects levels of synaptic proteins and GTPases in both WT and SHANK3 deficient mice on day P5. Oxytocin stimulated the mRNA expression of RhoB and Rac1 in both WT and SHANK3 deficient mice. Our data suggest that autism relevant synaptic pathologies could be reversed by oxytocin treatment.

Neuronal morphology alterations in autism and possible role of oxytocin.

Current understanding of the neuroanatomical abnormalities in autism includes gross anatomical changes in several brain areas and microstructural alterations in neuronal cells as well. There are many controversies in the interpretation of the imaging data, evaluation of volume and size of particular brain areas, and their functional translation into a broad autism phenotype. Critical questions of neuronal pathology in autism include the concept of the reversible plasticity of morphological changes, volume alterations of brain areas, and both short- and long-term consequences of adverse events present during the brain development. At the cellular level, remodeling of the actin cytoskeleton is considered as one of the critical factors associated with the autism spectrum disorders. Alterations in the composition of the neuronal cytoskeleton, in particular abnormalities in the polymerization of actin filaments and their associated proteins underlie the functional consequences in behavior resulting in symptoms and clinical correlates of autism spectrum disorder. In the present review, a special attention is devoted to the role of oxytocin in experimental models of neurodevelopmental disorders manifesting alterations in neuronal morphology.

Molecular Mechanisms of Oxytocin Signaling at the Synaptic Connection.

Aberrant regulation of oxytocin signaling is associated with the etiology of neurodevelopmental disorders. Synaptic dysfunctions in neurodevelopmental disorders are becoming increasingly known, and their pathogenic mechanisms could be a target of potential therapeutic intervention. Therefore, it is important to pay attention to the role of oxytocin and its receptor in synapse structure, function, and neuron connectivity. An early alteration in oxytocin signaling may disturb neuronal maturation and may have short-term and long-term pathological consequences. At the molecular level, neurodevelopmental disorders include alterations in cytoskeletal rearrangement and neuritogenesis resulting in a diversity of synaptopathies. The presence of oxytocin receptors in the presynaptic and postsynaptic membranes and the direct effects of oxytocin on neuronal excitability by regulating the activity of ion channels in the cell membrane implicate that alterations in oxytocin signaling could be involved in synaptopathies. The ability of oxytocin to modulate neurogenesis, synaptic plasticity, and certain parameters of cytoskeletal arrangement is discussed in the present review.

Polysulfides and products of H2S/S-nitrosoglutathione in comparison to H2S, glutathione and antioxidant Trolox are potent scavengers of superoxide anion radical and produce hydroxyl radical by decomposition of H2O2.

Exogenous and endogenously produced sulfide derivatives, such as H2S/HS-/S2-, polysulfides and products of the H2S/S-nitrosoglutathione interaction (S/GSNO), affect numerous biological processes in which superoxide anion (O2-) and hydroxyl (OH) radicals play an important role. Their cytoprotective-antioxidant and contrasting pro-oxidant-toxic effects have been reported. Therefore, the aim of our work was to contribute to resolving this apparent inconsistency by studying sulfide derivatives/free radical interactions and their consequent biological effects compared to the antioxidants glutathione (GSH) and Trolox. Using the electron paramagnetic resonance (EPR) spin trapping technique and O2-, we found that a polysulfide (Na2S4) and S/GSNO were potent scavengers of O2- and cPTIO radicals compared to H2S (Na2S), GSH and Trolox, and S/GSNO scavenged the DEPMPO-OH radical. As detected by the EPR spectra of DEPMPO-OH, the formation of OH in physiological solution by S/GSNO was suggested. All the studied sulfide derivatives, but not Trolox or GSH, had a bell-shaped potency to decompose H2O2 and produced OH in the following order: S/GSNO > Na2S4 ≥ Na2S > GSH = Trolox = 0, but they scavenged OH at higher concentrations. In studies of the biological consequences of these sulfide derivatives/H2O2 properties, we found the following: (i) S/GSNO alone and all sulfide derivatives in the presence of H2O2 cleaved plasmid DNA; (ii) S/GSNO interfered with viral replication and consequently decreased the infectivity of viruses; (iii) the sulfide derivatives induced apoptosis in A2780 cells but inhibited apoptosis induced by H2O2; and (iv) Na2S4 modulated intracellular calcium in A87MG cells, which depended on the order of Na2S4/H2O2 application. We suggest that the apparent inconsistency of the cytoprotective-antioxidant and contrasting pro-oxidant-toxic biological effects of sulfide derivatives results from their time- and concentration-dependent radical production/scavenging properties and their interactions with O2-, OH and H2O2. The results imply a direct involvement of sulfide derivatives in O2- and H2O2/OH free radical pathways modulating antioxidant/toxic biological processes.

Abnormalities in interactions of Rho GTPases with scaffolding proteins contribute to neurodevelopmental disorders.

Accumulating evidence suggests that Rho GTPases, together with scaffolding SHANK proteins, and associated signaling pathways play a role in the development of autism symptoms in various conditions. Research data have brought information on multiple intracellular signaling pathways, including Rho-associated protein kinases and serine/threonine-protein kinases involved in cytoskeleton rearranging. Alterations in downstream effectors of GTPase signaling pathways are associated with neurodevelopmental disorders. Bioinformatics and experimental data show that complex genetic and molecular defects (GTPases, actin-binding proteins, kinases, neuropeptides) can result in neuronal remodeling, leading to the functional connectivity deficits that manifest as the heterogeneous autism spectrum phenotype. Finally, the known hormone and neuropeptide oxytocin appears to be a factor for consideration in therapeutic intervention.

The Role of Hypothalamic Neuropeptides in Neurogenesis and Neuritogenesis.

The hypothalamus is a source of neural progenitor cells which give rise to different populations of specialized and differentiated cells during brain development. Newly formed neurons in the hypothalamus can synthesize and release various neuropeptides. Although term neuropeptide recently undergoes redefinition, small-size hypothalamic neuropeptides remain major signaling molecules mediating short- and long-term effects on brain development. They represent important factors in neurite growth and formation of neural circuits. There is evidence suggesting that the newly generated hypothalamic neurons may be involved in regulation of metabolism, energy balance, body weight, and social behavior as well. Here we review recent data on the role of hypothalamic neuropeptides in adult neurogenesis and neuritogenesis with special emphasis on the development of food intake and social behavior related brain circuits.

Are Molecules Involved in Neuritogenesis and Axon Guidance Related to Autism Pathogenesis?

Autism spectrum disorder is a heterogeneous disease, and numerous alterations of gene expression come into play to attempt to explain potential molecular and pathophysiological causes. Abnormalities of brain development and connectivity associated with alterations in cytoskeletal rearrangement, neuritogenesis and elongation of axons and dendrites might represent or contribute to the structural basis of autism pathology. Slit/Robo signaling regulates cytoskeletal remodeling related to axonal and dendritic branching. Components of its signaling pathway (ABL and Cdc42) are suspected to be molecular bases of alterations of normal development. The present review describes the most important mechanisms underlying neuritogenesis, axon pathfinding and the role of GTPases in neurite outgrowth, with special emphasis on alterations associated with autism spectrum disorders. On the basis of analysis of publicly available microarray data, potential biomarkers of autism are discussed.