Postnatal decrease in transforming growth factor alpha is associated with enlarged ventricles, deficient amygdaloid vasculature and performance deficits

Distinct actions of ancestral vinclozolin and juvenile stress on neural gene expression in the male rat

Exposure to the endocrine disrupting chemical vinclozolin during gestation of an F0 generation and/or chronic restraint stress during adolescence of the F3 descendants affects behavior, physiology, and gene expression in the brain. Genes related to the networks of growth factors, signaling peptides, and receptors, steroid hormone receptors and enzymes, and epigenetic related factors were measured using quantitative polymerase chain reaction via Taqman low density arrays targeting 48 genes in the central amygdaloid nucleus, medial amygdaloid nucleus, medial preoptic area (mPOA), lateral hypothalamus (LH), and the ventromedial nucleus of the hypothalamus. We found that growth factors are particularly vulnerable to ancestral exposure in the central and medial amygdala; restraint stress during adolescence affected neural growth factors in the medial amygdala. Signaling peptides were affected by both ancestral exposure and stress during adolescence primarily in hypothalamic nuclei. Steroid hormone receptors and enzymes were strongly affected by restraint stress in the mPOA. Epigenetic related genes were affected by stress in the ventromedial nucleus and by both ancestral exposure and stress during adolescence independently in the central amygdala. It is noteworthy that the LH showed no effects of either manipulation. Gene expression is discussed in the context of behavioral and physiological measures previously published.

Loss of Thr286 phosphorylation disrupts synaptic CaMKIIα targeting, NMDAR activity and behavior in pre-adolescent mice

In order to provide insight into in vivo roles of CaMKIIα autophosphorylation at Thr286 during postnatal development, behavioral, biochemical, and electrophysiological phenotypes of pre-adolescent Thr286 to Ala CaMKIIα knock-in (T286A-KI) and WT mice were examined. T286A-KI mice displayed cognitive deficits in a novel object recognition test and an anxiolytic phenotype in the elevated plus maze, suggesting disruption of normal developmental processes. At the molecular level, the ratio of total CaMKIIα to CaMKIIβ in hippocampal lysates was significantly decreased≈2-fold in T286A-KI mice, and levels of both isoforms in synaptic subcellular fractions were decreased by≈80%. Total levels of GluA1 AMPA-glutamate receptor subunits and phosphorylation of GluA1 at the CaMKII site (Ser831) in synaptic fractions were unaltered, as were the frequency and amplitude of AMPAR-mediated spontaneous excitatory postsynaptic currents at hippocampal CA3-CA1 synapses. Synaptic levels of NMDA-glutamate receptor GluN1, GluN2A and GluN2B subunits also were unaltered. However, the reduced ratio of CaMKII to NMDAR subunits in synaptic fractions was linked to increased synaptic NMDAR-mediated currents in T286A-KI mice, apparently due to increased functional contributions by GluN2B NMDARs (assessed by Ro 25-6981 sensitivity). Thus, disruption of CaMKII synaptic targeting caused by elimination of Thr286 autophosphorylation leads to synaptic and behavioral deficits during pre-adolescence.

Enlarged lateral ventricles and aberrant behavior in mice overexpressing PDGF-B in embryonic neural stem cells

Platelet-derived growth factor (PDGF) is important in central nervous system (CNS) development, and aberrant expression of PDGF and its receptors has been linked to developmental defects and brain tumorigenesis. We previously found that neural stem and progenitor cells in culture produce PDGF and respond to it by autocrine and/or paracrine signaling. We therefore aimed to examine CNS development after PDGF overexpression in neural stem cells in vivo. Transgenic mice were generated with PDGF-B under control of a minimal nestin enhancer element, which is specific for embryonic expression and will not drive adult expression in mice. The resulting mouse showed increased apoptosis in the developing striatum, which suggests a disturbed regulation of progenitor cells. Later in neurodevelopment, in early postnatal life, mice displayed enlarged lateral ventricles. This enlargement remained into adulthood and it was more pronounced in male mice than in transgenic female mice. Nevertheless, there was an overall normal composition of cell types and numbers in the brain and the transgenic mice were viable and fertile. Adult transgenic males, however, showed behavioral aberrations and locomotor dysfunction. Thus, a tightly regulated expression of PDGF during embryogenesis is required for normal brain development and function in mice.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Longitudinal brain changes in early-onset psychosis

Progressive losses of cortical gray matter volumes and increases in ventricular volumes have been reported in patients with childhood-onset schizophrenia (COS) during adolescence. Longitudinal studies suggest that the rate of cortical loss seen in COS during adolescence plateaus during early adulthood. Patients with first-episode adolescent-onset schizophrenia show less marked progressive changes, although the number of studies in this population is small. Some studies show that, although less exaggerated, progressive changes are also present in nonschizophrenia early-onset psychosis. The greater loss of brain tissue seen in COS, even some years after the first episode, as compared to adolescent- or adult-onset schizophrenia may be due to variables such as sample bias (more severe, treatment refractory sample of childhood-onset patients studied), a process uniquely related to adolescent development in COS, differential brain effects of drug treatment in this population, clinical outcome, or interactions among these variables. Findings from both cross-sectional studies of first-episode patients and longitudinal studies in COS and adolescent onset support the concept of early-onset schizophrenia as a progressive neurodevelopmental disorder with both early and late developmental abnormalities. Future studies should look for correlates at a cellular level and for pathophysiological explanations of volume changes in these populations. The association of risk genes involved in circuitries associated with schizophrenia and their relationship to developmental trajectories is another promising area of future research.

Gene x environment effects: stress and memory dysfunctions caused by stress and gonadal factor irregularities during puberty in control and TGF-alpha hypomorphic mice

The maturation of many neural functions occurs during puberty. An abnormal development of these processes, in the context of genetic vulnerability, may result in sex- and age-dependent penetrance of neuropsychiatric disorders. Reduced transforming growth factors-alpha (TGF-alpha) expression in Waved-1 (Wa-1) mice impairs the stress response and fear memory in adult males, but are absent or far less prominent in adult females and in pubertal males. Gonadectomy around the onset of puberty, when the mutant anatomical and behavioral phenotypes are undetectable, results in significant gene x environment effects. Adult control males show reduced physiological stress response as a result of gonadectomy, but not adult Wa-1 males. In females, pubertal gonadectomy elevates specific anxiety parameters only in adult control mice. There also are general sex-specific effects of pubertal gonadectomy on adult stress and fear memory. Surgical stress alone also induces sex- and genotype-dependent effects, albeit in different behavioral parameters than those affected by gonadectomy. We conclude that normal development of stress and memory processes is reliant on the levels of stress and gonadal factors during puberty, the effects of which are modulated by genetic factors and sex.

Waved-1 mutant mice are hypersensitive to the locomotor actions of cocaine

Transforming growth factor-alpha (TGFalpha) is a well-known regulator of many developmental processes, and is expressed heavily in basal forebrain and striatal regions. When TGFalpha is reduced in Waved-1 (Wa-1) mutant mice, brain anatomy, biogenic amines, stress response, and behavior are normal prior to, but altered following puberty. As an initial screen for possible alterations in nigrostriatal and mesolimbic dopamine (DA) systems, we tested adult Wa-1 mutant mice in an open field, following acute injection with cocaine (15 mg/kg). Wa-1 mice exhibited significantly greater ambulatory distance, number of ambulatory episodes, and cocaine-induced motor stereotypies than do controls. These data indicate that adult Wa-1 mice are hypersensitive to the locomotor effects of cocaine and provide a new potential link between neurodevelopmental processes and adult psychostimulant responsiveness.

Expression of Tgfα in the suprachiasmatic nuclei of nocturnal and diurnal rodents

Transforming growth factor alpha (TGFalpha) in the suprachiasmatic nuclei (SCN) has been proposed as an inhibitory signal involved in the control of daily locomotor activity. This assumption is based mainly on studies performed in nocturnal hamsters. To test whether the transcriptional regulation of Tgfalpha can be correlated with the timing of overt activity in other species, we compared Tgfalpha expression in the SCN of nocturnal Swiss mice and of diurnal Arvicanthis housed under a light/dark cycle (LD) or transferred to constant darkness (DD). In agreement with data on hamsters, Tgfalpha mRNA levels in the mouse SCN showed peak and trough levels around (subjective) dawn and dusk, respectively, roughly corresponding to the period of rest and activity in this species. In contrast, in Arvicanthis housed in DD, the circadian rhythm of SCN Tgfalpha was similar to that of the mice in spite of opposite phasing of locomotor activity. Furthermore, in Arvicanthis exposed to LD, Tgfalpha mRNA levels were constitutively high throughout the day. A tonic role of light in the regulation of Tgfalpha in Arvicanthis was confirmed by an increased expression of Tgfalpha in response to a 6-h exposure to light during daytime in animals otherwise kept in DD. In conclusion, this study shows that, contrary to what is observed in mice, Tgfalpha mRNA levels in the SCN of Arvicanthis do not match timing of locomotor activity and are modulated by light.

Making the case for a candidate vulnerability gene in schizophrenia: Convergent evidence for regulator of G-protein signaling 4 (RGS4)

Both genetic and environmental factors have been associated with an increased risk for schizophrenia. These factors are not mutually exclusive; a single gene can be a genetic factor (due to a mutation in the gene sequence) and a target of a physiological response to an environmental stimulus, both with the common endpoint of altered expression of the gene. Regulator of G-protein signaling 4 (RGS4) has been implicated as such a gene from three lines of evidence. First, a subset of genetic studies revealed an association between schizophrenia and non-functional polymorphisms in the RGS4 gene. Second, across the cortical mantle the expression of RGS4 mRNA is decreased in a diagnosis-specific manner in subjects with schizophrenia. Third, neurobiological studies demonstrate that RGS4 is highly responsive to environmental stimuli and capable of modulating the function of G-protein coupled neurotransmitter receptors implicated in schizophrenia. RGS4 is an example of a molecule that may underlie increased vulnerability through either genetic or non-genetic mechanisms, which we suggest may be typical of other genes in a complex, polygenic disorder such as schizophrenia.

Transforming growth factor-α induces sex-specific neurochemical imbalance in the stress- and memory-associated brain structures

Transforming growth factor-alpha (TGFalpha) is a well-known regulator of many developmental processes. However, its role in adult nervous system is yet unclear. Studies have shown that TGFalpha can regulate stress and memory behavior in adult mice. When TGFalpha is reduced in Waved-1 (Wa-1) mutant mice, the stress response and memory are impaired predominantly in males and only after puberty. To determine the neurochemical changes resulting from the reduced TGFalpha levels that could explain the reported behavioral outcomes, biogenic amine and amino acid levels were determined in the brain regions associated with stress and memory. Interestingly, sex-specific alterations in neurochemical levels were detected, including elevated noradrenaline and reduced glutamate levels in striatum of Wa-1 males, increased noradrenaline and reduced serotonin metabolite levels in hippocampus of Wa-1 females, reduced serotonin metabolite levels in cortex and amygdala of Wa-1 females, and reduced noradrenaline, dopamine, serotonin, glutamate and glycine levels in hypothalamus of Wa-1 females compared to their respective controls. Increased dopamine turnover in cortex and reduced dopamine and serotonin turnover in amygdala were observed in both male and female Wa-1 mice. The data indicate sex-specific alterations of specific neurochemicals as a result of reduced TGFalpha expression, which may underlie sex-dependent stress response and memory impairment in Wa-1 mice.

Postpubertal sex differentiation of forebrain structures and functions depend on transforming growth factor-alpha

Sex- and age-associated deficits in brain structure and behavior are reported in a number of neuropsychiatric disorders. Although genetic and environmental factors are thought to contribute to the pathogenesis, there are only few examples in clinical or experimental systems that have identified specific causes. Here, we report that transforming growth factor-alpha (TGFalpha) may regulate sex- and age-dependent development of forebrain structures and associated neural functions after puberty. Waved-1 (Wa-1) mice inherit an autosomal recessive, spontaneous mutation that results in a postnatal reduction in TGFalpha gene expression. The assessment of forebrain structures using a three-dimensional magnetic resonance microscopy indicated ventricular enlargement and striatal reduction in both male and female Wa-1 adult mice, with Wa-1 males exhibiting a more severe phenotype. In contrast, the hippocampal volume was reduced only in adult Wa-1 males. Similarly, behavioral analyses showed impaired auditory and contextual fear learning in adult Wa-1 males only, whereas abnormal stress response was expressed by both male and female adult Wa-1 mice. Interestingly, all behavioral deficits were absent before full sexual maturation, despite some slight forebrain structural abnormalities. These results suggest that TGFalpha may regulate postpubertal, sex differentiation in ventricular and periventricular anatomy and associated behavior, affecting predominantly males. In particular, the adult male-specific reduction in hippocampal volume may reflect an age- and sex-specific regulation of stress homeostasis and fear learning. Furthermore, a lack of a behavioral phenotype, despite anatomical alterations in peripubertal Wa-1 mice, suggests that analysis of certain neuroanatomical features at puberty may predict neurobehavioral deficits in adulthood.

Aging results in reduced epidermal growth factor receptor signaling, diminished olfactory neurogenesis, and deficits in fine olfactory discrimination

Previous studies demonstrating olfactory interneuron involvement in olfactory discrimination and decreased proliferation in the forebrain subventricular zone with age led us to ask whether olfactory neurogenesis and, consequently, olfactory discrimination were impaired in aged mice. Pulse labeling showed that aged mice (24 months of age) had fewer new interneurons in the olfactory bulb than did young adult (2 months of age) mice. However, the aged mice had more olfactory interneurons in total than their younger counterparts. Aged mice exhibited no differences from young adult mice in their ability to discriminate between two discrete odors but were significantly poorer at performing discriminations between similar odors (fine olfactory discrimination). Leukemia inhibitory factor receptor heterozygote mice, which have less neurogenesis and fewer olfactory interneurons than their wild-type counterparts, performed more poorly at fine olfactory discrimination than the wild types, suggesting that olfactory neurogenesis, rather than the total number of interneurons, was responsible for fine olfactory discrimination. Immunohistochemistry and Western blot analyses revealed a selective reduction in expression levels of epidermal growth factor (EGF) receptor (EGFR) signaling elements in the aged forebrain subventricular zone. Waved-1 mutant mice, which express reduced quantities of transforming growth factor-alpha, the predominant EGFR ligand in adulthood, phenocopy aged mice in olfactory neurogenesis and performance on fine olfactory discrimination tasks. These results suggest that the impairment in fine olfactory discrimination with age may result from a reduction in EGF-dependent olfactory neurogenesis.

Sex differences in expression of transforming growth factor-α and epidermal growth factor receptor mRNA in waved-1 and C57Bl6 mice

A reduction of transforming growth factor-alpha (TGFalpha) expression in the spontaneous Waved-1 (Wa-1) mutant mouse causes specific behavioral and anatomical changes, including reduced fear learning and stress response and enlarged lateral ventricles. These alterations are observed predominantly in male Wa-1 mice after puberty. We hypothesized that regional differences in the expression of TGFalpha and its receptor, epidermal growth factor receptor (EGFR), may regulate the sexual dimorphism of the brain structures and functions during postnatal development. In general, fear learning-associated structures, including hippocampus and amygdala, showed maximum expression before puberty, regardless of genotype. In contrast, an overall temporal delay in the rise of both transcript levels, which peaked around or after puberty onset, was observed for the major stress regulatory hypothalamo-pituitary-adrenal axis. This pattern of expression was reversed for amygdala EGFR and hypothalamus TGFalpha and EGFR transcripts in males. When regional TGFalpha expression was compared between control and Wa-1 mice, far more complex patterns than expected were observed that revealed sex- and structure-dependent differences. In fact, the amygdala, hypothalamus, and pituitary TGFalpha expression pattern in Wa-1 exhibited a clear sex dependency across various age groups. Surprisingly, there was no compensatory up-regulation of the EGFR transcript in Wa-1 mice. The observed expression patterns of the TGFalpha signaling system during normal development and in the Wa-1 mutant mouse suggest complex sex- and age-dependent transcription regulatory mechanisms.

Neonatal perturbation of neurotrophic signaling results in abnormal sensorimotor gating and social interaction in adults: implication for epidermal growth factor in cognitive development

Epidermal growth factor (EGF) and its structurally related proteins are implicated in the developmental regulation of various brain neurons, including midbrain dopaminergic neurons. There are EGF and EGF receptor abnormalities in both brain tissues and blood from schizophrenic patients. We administered EGF to neonatal rats to transiently perturb endogenous EGF receptor signaling and evaluated the neurobehavioral consequences. EGF-treatment-induced transient impairment in tyrosine hydroxylase expression. The animals grew normally, exhibited normal weight increase, glial growth, and gross brain structures, and later lost the tyrosine hydroxylase abnormality. During and after development, however, the rats began to display various behavioral abnormalities. Abnormal sensorimotor gating was apparent, as measured by deficits in prepulse inhibition of acoustic startle. Motor activity and social interaction scores of the EGF-treated animals were also impaired in adult rats, though not in earlier developmental stages. In parallel, there was a significant abnormality in dopamine metabolism in the brain stem of the adult animals. Gross learning ability appeared to be normal as measured by active avoidance. These behavioral alterations, which are often present in schizophrenic models, were ameliorated by subchronic treatment with clozapine. Although the molecular and/or physiologic background(s) of these behavioral abnormalities await further investigation, the results of the present experiment indicate that abnormal EGF receptor stimulation given during limited neonatal stages can result in severe and persistent cognitive/behavioral dysfunctions, which appear only in adulthood.

Schizophrenia as a disorder of neurodevelopment

A combination of genetic susceptibility and environmental perturbations appear to be necessary for the expression of schizophrenia. In addition, the pathogenesis of the disease is hypothesized to be neurodevelopmental in nature based on reports of an excess of adverse events during the pre- and perinatal periods, the presence of cognitive and behavioral signs during childhood and adolescence, and the lack of evidence of a neurodegenerative process in most individuals with schizophrenia. Recent studies of neurodevelopmental mechanisms strongly suggest that no single gene or factor is responsible for driving a highly complex biological process. Together, these findings suggest that combinatorial genetic and environmental factors, which disturb a normal developmental course early in life, result in molecular and histogenic responses that cumulatively lead to different developmental trajectories and the clinical phenotype recognized as schizophrenia.

Mapping adolescent brain change reveals dynamic wave of accelerated gray matter loss in very early-onset schizophrenia

Neurodevelopmental models for the pathology of schizophrenia propose both polygenetic and environmental risks, as well as early (pre/perinatal) and late (usually adolescent) developmental brain abnormalities. With the use of brain mapping algorithms, we detected striking anatomical profiles of accelerated gray matter loss in very early-onset schizophrenia; surprisingly, deficits moved in a dynamic pattern, enveloping increasing amounts of cortex throughout adolescence. Early-onset patients were rescanned prospectively with MRI, at 2-year intervals at three time points, to uncover the dynamics and timing of disease progression during adolescence. The earliest deficits were found in parietal brain regions, supporting visuospatial and associative thinking, where adult deficits are known to be mediated by environmental (nongenetic) factors. Over 5 years, these deficits progressed anteriorly into temporal lobes, engulfing sensorimotor and dorsolateral prefrontal cortices, and frontal eye fields. These emerging patterns correlated with psychotic symptom severity and mirrored the neuromotor, auditory, visual search, and frontal executive impairments in the disease. In temporal regions, gray matter loss was completely absent early in the disease but became pervasive later. Only the latest changes included dorsolateral prefrontal cortex and superior temporal gyri, deficit regions found consistently in adult studies. These emerging dynamic patterns were (i) controlled for medication and IQ effects, (ii) replicated in independent groups of males and females, and (iii) charted in individuals and groups. The resulting mapping strategy reveals a shifting pattern of tissue loss in schizophrenia. Aspects of the anatomy and dynamics of disease are uncovered, in a changing profile that implicates genetic and nongenetic patterns of deficits.

Molecular characterization of schizophrenia viewed by microarray analysis of gene expression in prefrontal cortex

Microarray expression profiling of prefrontal cortex from matched pairs of schizophrenic and control subjects and hierarchical data analysis revealed that transcripts encoding proteins involved in the regulation of presynaptic function (PSYN) were decreased in all subjects with schizophrenia. Genes of the PSYN group showed a different combination of decreased expression across subjects. Over 250 other gene groups did not show altered expression. Selected PSYN microarray observations were verified by in situ hybridization. Two of the most consistently changed transcripts in the PSYN functional gene group, N-ethylmaleimide sensitive factor and synapsin II, were decreased in ten of ten and nine of ten subjects with schizophrenia, respectively. The combined data suggest that subjects with schizophrenia share a common abnormality in presynaptic function. We set forth a predictive, testable model.