Association of EGF polymorphism with schizophrenia in Finnish men

Schizophrenia Animal Modeling with Epidermal Growth Factor and Its Homologs: Their Connections to the Inflammatory Pathway and the Dopamine System

Epidermal growth factor (EGF) and its homologs, such as neuregulins, bind to ErbB (Her) receptor kinases and regulate glial differentiation and dopaminergic/GABAergic maturation in the brain and are therefore implicated in schizophrenia neuropathology involving these cell abnormalities. In this review, we summarize the biological activities of the EGF family and its neuropathologic association with schizophrenia, mainly overviewing our previous model studies and the related articles. Transgenic mice as well as the rat/monkey models established by perinatal challenges of EGF or its homologs consistently exhibit various behavioral endophenotypes relevant to schizophrenia. In particular, post-pubertal elevation in baseline dopaminergic activity may illustrate the abnormal behaviors relevant to positive and negative symptoms as well as to the timing of this behavioral onset. With the given molecular interaction and transactivation of ErbB receptor kinases with Toll-like receptors (TLRs), EGF/ErbB signals are recruited by viral infection and inflammatory diseases such as COVID-19-mediated pneumonia and poxvirus-mediated fibroma and implicated in the immune-inflammatory hypothesis of schizophrenia. Finally, we also discuss the interaction of clozapine with ErbB receptor kinases as well as new antipsychotic development targeting these receptors.

Exploring the journey of emodin as a potential neuroprotective agent: Novel therapeutic insights with molecular mechanism of action

Emodin is an anthraquinone derivative found in the roots and bark of a variety of plants, molds, and lichens. Emodin has been used as a traditional medication for more than 2000 years and is still common in numerous herbal drugs. Emodin is plentiful in the three plant families, including Polygonaceae (Rheum, Rumex, and Polygonum spp.), Fabaceae (Cassia spp.), and Rhamnaceae (Rhamnus, Frangula, and Ventilago spp.). Emerging experimental evidences indicate that emodin confers a wide range of pharmacological activities; special focus was implemented toward neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, cerebral ischemia, anxiety and depression, schizophrenia, chronic hyperglycemic peripheral neuropathy, etc. Numerous preclinical evidences were established in support of the neuroprotection of emodin. However, this review highlighted the role of emodin as a potent neurotherapeutic agent; therefore, its evidence-based functionality on neurological disorders (NDs).

Elevation of EGR1/zif268, a Neural Activity Marker, in the Auditory Cortex of Patients with Schizophrenia and its Animal Model

The family of epidermal growth factor (EGF) including neuregulin-1 are implicated in the neuropathology of schizophrenia. We established a rat model of schizophrenia by exposing perinatal rats to EGF and reported that the auditory pathophysiological traits of this model such as prepulse inhibition, auditory steady-state response, and mismatch negativity are relevant to those of schizophrenia. We assessed the activation status of the auditory cortex in this model, as well as that in patients with schizophrenia, by monitoring the three neural activity-induced proteins: EGR1 (zif268), c-fos, and Arc. Among the activity markers, protein levels of EGR1 were significantly higher at the adult stage in EGF model rats than those in control rats. The group difference was observed despite an EGF model rat and a control rat being housed together, ruling out the contribution of rat vocalization effects. These changes in EGR1 levels were seen to be specific to the auditory cortex of this model. The increase in EGR1 levels were detectable at the juvenile stage and continued until old ages but displayed a peak immediately after puberty, whereas c-fos and Arc levels were nearly indistinguishable between groups at all ages with an exception of Arc decrease at the juvenile stage. A similar increase in EGR1 levels was observed in the postmortem superior temporal cortex of patients with schizophrenia. The commonality of the EGR1 increase indicates that the EGR1 elevation in the auditory cortex might be one of the molecular signatures of this animal model and schizophrenia associating with hallucination.

Decreased Serum EGF in First-episode and Chronic Schizophrenia Patients: Negative Correlation with Psychopathology

Previous studies have demonstrated that neurotrophic factors may play a critical role in the severity of clinical symptoms in schizophrenia. However, it remains unknown whether serum levels of epidermal growth factor (EGF) in schizophrenia are similar to those observed in the case of other neurotrophic factors. Therefore, we compared serum EGF concentrations in first-episode drug-naive (FEP) patients and medicated chronic schizophrenic patients with healthy controls in order to explore whether EGF levels are related to psychopathological symptoms. We measured the serum levels of EGF in 78 first-episode medication-naive schizophrenia patients, 76 medicated chronic schizophrenic patients, and 75 healthy controls using the sandwich ELISA method. Disease severity were measured using the positive and negative syndrome scale (PANSS). Serum EGF levels showed a significant decrease in schizophrenia patients in comparison to healthy subjects. Serum EGF levels in FEP patients are indistinguishable from chronic cases. EGF levels were related to PANSS general symptom subscales in both FEP never-medicated and medicated patients. It is interesting that serum EGF levels were negatively correlated with the PANSS cognitive subscales, with the exception of the patients with chronic schizophrenia. Our preliminary results indicated that EGF may play a role in this illness and that it could be used as a potential biomarker of disease severity. Moreover, EGF may be associated with cognitive subscales of PANSS in FEP patients. Future studies should investigate the relationship between EGF and cognitive function as measured using standardized neuropsychological assessments to identify potential biomarkers related with cognition.

Neonatal exposure to an inflammatory cytokine, epidermal growth factor, results in the deficits of mismatch negativity in rats

Perinatal exposure to epidermal growth factor (EGF) induces various cognitive and behavioral abnormalities after maturation in non-human animals, and is used for animal models of schizophrenia. Patients with schizophrenia often display a reduction of mismatch negativity (MMN), which is a stimulus-change specific event-related brain potential. Do the EGF model animals also exhibit the MMN reduction as schizophrenic patients do? This study addressed this question to verify the pathophysiological validity of this model. Neonatal rats received repeated administration of EGF or saline and were grown until adulthood. Employing the odd-ball paradigm of distinct tone pitches, tone-evoked electroencephalogram (EEG) components were recorded from electrodes on the auditory and frontal cortices of awake rats, referencing an electrode on the frontal sinus. The amplitude of the MMN-like potential was significantly reduced in EGF-treated rats compared with saline-injected control rats. The wavelet analysis of the EEG during a near period of tone stimulation revealed that synchronization of EEG activity, especially with beta and gamma bands, was reduced in EGF-treated rats. Results suggest that animals exposed to EGF during a perinatal period serve as a promising neurodevelopmental model of schizophrenia.

Molecular mechanisms involved in epidermal growth factor receptor-mediated inhibition of dopamine D3 receptor signaling

The phenomenon wherein the signaling by a given receptor is regulated by a different class of receptors is termed transactivation or crosstalk. Crosstalk between receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs) is highly diverse and has unique functional implications because of the distinct structural features of the receptors and the signaling pathways involved. The present study used the epidermal growth factor receptor (EGFR) and dopamine D₃ receptor (D₃R), which are both associated with schizophrenia, as the model system to study crosstalk between RTKs and GPCRs. Loss-of-function approaches were used to identify the cellular components involved in the tyrosine phosphorylation of G protein-coupled receptor kinase 2 (GRK2), which is responsible for EGFR-induced regulation of the functions of D₃R. SRC proto-oncogene (Src, non-receptor tyrosine kinase), heterotrimeric G protein Gβγ subunit, and endocytosis of EGFR were involved in the tyrosine phosphorylation of GRK2. In response to EGF treatment, Src interacted with EGFR in a Gβγ-dependent manner, resulting in the endocytosis of EGFR. Internalized EGFR in the cytosol mediated Src/Gβγ-dependent tyrosine phosphorylation of GRK2. The binding of tyrosine-phosphorylated GRK2 to the T142 residue of D₃R resulted in uncoupling from G proteins, endocytosis, and lysosomal downregulation. This study identified the molecular mechanisms involved in the EGFR-mediated regulation of the functions of D₃R, which can be extended to the crosstalk between other RTKs and GPCRs.

Association of EGF, IGFBP-3 and TP53 Gene Polymorphisms with Major Depressive Disorder in Slovak Population

BACKGROUND

Major depressive disorder (MDD) is a main public health concern worldwide. Despite extensive investigations, the exact mechanisms responsible for MDD have not been identified. Epidermal growth factor (EGF) and insulin growth factor binding protein-3 (IGFBP-3) are involved in brain function. Tumour suppressor protein p53 is widely involved in neuronal death in response to different forms of acute insults and neurological disorders. The present study focuses on the possible associations of the single-nucleotide polymorphisms (SNP) of EGF A61G (rs4444903), IGFBP-3 C32G (rs2854746) and TP53 G72C (rs1042522) genes with MDD risk in the Slovak population.

METHODS

The present case-control association study was carried out in 111 confirmed MDD patients and 207 healthy subjects. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

Logistic regression analysis showed no association between SNPs of selected genes and MDD risk in the Slovak population. However, the stratification of individuals by gender revealed that males carrying IGFBP-3 G alleles (G32G or GG) had marginally increased risk for developing MDD as compared to CC homozygous males (p=0.09). In women, inverse association was observed between SNP rs1042522 and MDD risk (p=0.04 for recessive model).

CONCLUSION

Our results suggest the protective effect of minor allele 72C of TP53 gene towards MDD. The disruption of mechanisms involved in cell survival and death regulation may be involved in pathophysiology of MDD.

Dopamine-prolactin pathway potentially contributes to the schizophrenia and type 2 diabetes comorbidity

Schizophrenia (SCZ) and type 2 diabetes (T2D) are clinically associated, and common knowledge attributes this association to side effects of antipsychotic treatment. However, even drug-naive patients with SCZ are at increased risk for T2D. Dopamine dysfunction has a central role in SCZ. It is well-known that dopamine constitutively inhibits prolactin (PRL) secretion via the dopamine receptor 2 (DR2D). If dopamine is increased or if dopamine receptors hyperfunction, PRL may be reduced. During the first SCZ episode, low PRL levels are associated with worse symptoms. PRL is essential in human and social bonding, as well as it is implicated in glucose homeostasis. Dopamine dysfunction, beyond contributing to SCZ symptoms, may lead to altered appetite and T2D. To our knowledge, there are no studies of the genetics of the SCZ-T2D comorbidity focusing jointly on the dopamine and PRL pathway in the attempt to capture molecular heterogeneity correlated to possible disease manifestation heterogeneity. In this dopamine-PRL pathway-focused-hypothesis-driven review on the association of SCZ with T2D, we report a specific revision of what it is known about PRL and dopamine in relation to what we theorize is one of the missing links between the two disorders. We suggest that new studies are necessary to establish the genetic role of PRL and dopamine pathway in SCZ-T2D comorbidity.

Pathological Implications of Oxidative Stress in Patients and Animal Models with Schizophrenia: The Role of Epidermal Growth Factor Receptor Signaling

Proinflammatory cytokines perturb brain development and neurotransmission and are implicated in various psychiatric diseases, such as schizophrenia and depression. These cytokines often induce the production of reactive oxygen species (ROS) and regulate not only cell survival and proliferation but also inflammatory process and neurotransmission. Under physiological conditions, ROS are moderately produced in mitochondria but are rapidly scavenged by reducing agents in cells. However, brain injury, ischemia, infection, or seizure-like neural activities induce inflammatory cytokines and trigger the production of excessive amounts of ROS, leading to abnormal brain functions and psychiatric symptoms. Protein phosphatases, which are involved in the basal silencing of cytokine receptor activation, are the major targets of ROS. Consistent with this, several ROS scavengers, such as polyphenols and unsaturated fatty acids, attenuate both cytokine signaling and psychiatric abnormalities. In this review, we list the inducers, producers, targets, and scavengers of ROS in the brain and discuss the interaction between ROS and cytokine signaling implicated in schizophrenia and its animal models. In particular, we present an animal model of schizophrenia established by perinatal exposure to epidermal growth factor and illustrate the pathological role of ROS and antipsychotic actions of ROS scavengers, such as emodin and edaravone.

Disruption of the ErbB signaling in adolescence increases striatal dopamine levels and affects learning and hedonic-like behavior in the adult mouse

The ErbB signaling pathway has been genetically and functionally implicated in schizophrenia. Numerous findings support the dysregulation of Neuregulin (NRG) and epidermal growth factor (EGF) signaling in schizophrenia. However, it is unclear whether alterations of these pathways in the adult brain or during development are involved in the pathophysiology of schizophrenia. Herein we characterized the behavioral profile and molecular changes resulting from pharmacologically blocking the ErbB signaling pathway during a critical period in the development of decision making, planning, judgments, emotions, social cognition and cognitive skills, namely adolescence. We demonstrate that chronic administration of the pan-ErbB kinase inhibitor JNJ-28871063 (JNJ) to adolescent mice elevated striatal dopamine levels and reduced preference for sucrose without affecting locomotor activity and exploratory behavior. In adulthood, adolescent JNJ-treated mice continue to consume less sucrose and needed significantly more correct-response trials to reach the learning criterion during the discrimination phase of the T-maze reversal learning task than their saline-injected controls. In addition, JNJ mice exhibited deficit in reference memory but not in working memory as measured in the radial arm maze. Inhibition of the pathway during adolescence did not affect exploratory behavior and locomotor activity in the open field, social interaction, social memory, and reversal learning in adult mice. Our data suggest that alteration of ErbB signaling during adolescence resulted in changes in the dopaminergic systems that emerge in pathological learning and hedonic behavior in adulthood, and pinpoints the possible role of the pathway in the development of cognitive skills and motivated behavior.

Neuropathologic implication of peripheral neuregulin-1 and EGF signals in dopaminergic dysfunction and behavioral deficits relevant to schizophrenia: their target cells and time window

Neuregulin-1 and epidermal growth factor (EGF) are implicated in the pathogenesis of schizophrenia. To test the developmental hypothesis for schizophrenia, we administered these factors to rodent pups, juveniles, and adults and characterized neurobiological and behavioral consequences. These factors were also provided from their transgenes or infused into the adult brain. Here we summarize previous results from these experiments and discuss those from neuropathological aspects. In the neonatal stage but not the juvenile and adult stages, subcutaneously injected factors penetrated the blood-brain barrier and acted on brain neurons, which later resulted in persistent behavioral and dopaminergic impairments associated with schizophrenia. Neonatally EGF-treated animals exhibited persistent hyperdopaminergic abnormalities in the nigro-pallido-striatal system while neuregulin-1 treatment resulted in dopaminergic deficits in the corticolimbic dopamine system. Effects on GABAergic and glutamatergic systems were transient or limited. Even in the adult stage, intracerebral administration and transgenic expression of these factors produced similar but not identical behavioral impairments, although the effects of intracerebral administration were reversible. These findings suggest that dopaminergic development is highly vulnerable to circulating ErbB ligands in the pre- and perinatal stages. Once maldevelopment of the dopaminergic system is established during early development, dopamine-associating behavioral deficits become irreversible and manifest at postpubertal stages.

Pallidal hyperdopaminergic innervation underlying D2 receptor-dependent behavioral deficits in the schizophrenia animal model established by EGF

Epidermal growth factor (EGF) is one of the ErbB receptor ligands implicated in schizophrenia neuropathology as well as in dopaminergic development. Based on the immune inflammatory hypothesis for schizophrenia, neonatal rats are exposed to this cytokine and later develop neurobehavioral abnormality such as prepulse inhibition (PPI) deficit. Here we found that the EGF-treated rats exhibited persistent increases in tyrosine hydroxylase levels and dopamine content in the globus pallidus. Furthermore, pallidal dopamine release was elevated in EGF-treated rats, but normalized by subchronic treatment with risperidone concomitant with amelioration of their PPI deficits. To evaluate pathophysiologic roles of the dopamine abnormality, we administered reserpine bilaterally to the globus pallidus to reduce the local dopamine pool. Reserpine infusion ameliorated PPI deficits of EGF-treated rats without apparent aversive effects on locomotor activity in these rats. We also administered dopamine D1-like and D2-like receptor antagonists (SCH23390 and raclopride) and a D2-like receptor agonist (quinpirole) to the globus pallidus and measured PPI and bar-hang latencies. Raclopride (0.5 and 2.0 µg/site) significantly elevated PPI levels of EGF-treated rats, but SCH23390 (0.5 and 2.0 µg/site) had no effect. The higher dose of raclopride induced catalepsy-like changes in control animals but not in EGF-treated rats. Conversely, local quinpirole administration to EGF-untreated control rats induced PPI deficits and anti-cataleptic behaviors, confirming the pathophysiologic role of the pallidal hyperdopaminergic state. These findings suggest that the pallidal dopaminergic innervation is vulnerable to circulating EGF at perinatal and/or neonatal stages and has strong impact on the D2-like receptor-dependent behavioral deficits relevant to schizophrenia.

Antipsychotic potential of quinazoline ErbB1 inhibitors in a schizophrenia model established with neonatal hippocampal lesioning

Hyper-signaling of the epidermal growth factor receptor family (ErbB) is implicated in the pathophysiology of schizophrenia. Various quinazoline inhibitors targeting ErbB1 or ErbB2 - 4 have been developed as anti-cancer agents and might be useful for antipsychotic treatment. In the present study, we used an animal model of schizophrenia established by neonatal hippocampal lesioning and evaluated the neurobehavioral consequences of ErbB1-inhibitor treatment. Subchronic administration of the ErbB1 inhibitor ZD1839 to the cerebroventricle of rats receiving neonatal hippocampal lesioning ameliorated deficits in prepulse inhibition as well as those in the latent inhibition of tone-dependent fear learning. There were no apparent adverse effects on basal learning scores or locomotor activity, however. The administration of other ErbB1 inhibitors, PD153035 and OSI-774, similarly attenuated the prepulse inhibition impairment of this animal model. In parallel, there were decreases in ErbB1 phosphorylation in animals treated with ErbB1 inhibitors. These results indicate an antipsychotic potential of quinazoline ErbB1 inhibitors. ErbB receptor tyrosine kinases may be novel therapeutic targets for schizophrenia or its related psychotic symptoms.

No association of EGF 5'UTR variant A61G and hepatocellular carcinoma in Chinese patients with chronic hepatitis B virus infection

OBJECTIVE

Epidermal growth factor (EGF) has many biological functions, including mitogenesis, tumorigenesis, and proliferation of epidermal tissues. Previous studies have reported that the EGF +61 (A/G) single nucleotide polymorphism in the 5'-untranslated region of the EGF gene is functional, and is associated with development of hepatocellular carcinoma (HCC) in liver cirrhosis and various malignancy. Our aim was to investigate whether EGF gene A61G polymorphism could be implicated in susceptibility to and/or clinicopathological characteristics of HCC in Chinese patients with chronic hepatitis B virus (HBV) infection.

METHODS

This polymorphism was studied in 387 patients with chronic HBV infection and in 208 healthy volunteers using restriction fragment-length polymorphism. The patients were divided into two groups: those without (n = 172) and those with HCC (n = 215). These 215 HCC patients with chronic HBV infection were designated as cases, and the remaining 172 patients without HCC served as controls.

RESULTS

There were no significant differences in EGF genotype or allelic frequencies between cases and controls nor was EGF genotype or allelic frequencies associated with tumour number, size, growth phase, stage, and invasiveness. We also found ethnic heterogeneity in the functional EGF polymorphism.

CONCLUSIONS

The present results show that although EGF gene A61G polymorphism is associated with development of HCC in liver cirrhosis, it is not sufficient for HCC in Chinese patients with chronic HBV infection.

Association between epidermal growth factor polymorphism and esophageal squamous cell carcinoma susceptibility

Genetic factors are known to be important in the development of esophageal squamous cell carcinoma (ESCC). Epidermal growth factor (EGF) can activate several signaling pathways leading to proliferation, differentiation, and tumorigenesis of epithelial tissues by binding with its receptor. Interindividual variations in EGF production were genetically contributed to EGF +61 G/A polymorphism. The purpose of this study is to investigate the potential association between EGF gene polymorphism and ESCC in a Chinese population. In this study, we analyzed single nucleotide polymorphism of EGF +61 G/A in 158 patients with ESCC and 212 age- and sex-matched controls in a Chinese population using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) strategy and DNA sequencing. The variant genotypes of GA/AA were associated with a significantly decreased risk of ESCC compared with the wild-type homozygote GG (OR = 0.657, 95% CI: 0.434-0.996). However, no significant difference was observed between the EGF +61 G/A polymorphism and the risk of ESCC when the analyses were stratified in terms of age, gender, smoking status, different clinical stage, and lymph node status. The EGF +61 G/A polymorphism is associated with ESCC in a Chinese population. Our data suggests that the EGF gene may play a role in the development of ESCC.

Clozapine-induced ERK1 and ERK2 signaling in prefrontal cortex is mediated by the EGF receptor

The atypical antipsychotic drug clozapine is effective in treatment-refractory schizophrenia. The intracellular signaling pathways that mediate clozapine action remain unknown. A potential candidate is the mitogen-activated protein kinase extracellular signal-regulated kinase (MAPK-ERK) cascade that links G-protein-coupled receptor and ErbB growth factor signaling systems, thereby regulating synaptic plasticity and connectivity, processes impaired in schizophrenia. Here, we examined how clozapine differentially modulated phosphorylation of the MAPK isoforms, ERK1/ERK2 in primary murine prefrontal cortical neurons compared to the typical antipsychotic drug haloperidol. While clozapine and haloperidol acutely decreased cortical pERK1 activation, only clozapine but not haloperidol stimulated pERK1 and pERK2 with continued drug exposure. This delayed ERK increase however, did not occur via the canonical dopamine D(2)-Gi/o-PKA or serotonin 5HT(2A)-Gq-phospholipase-C-linked signaling pathways. Rather, epidermal growth factor (EGF) receptor signaling mediated clozapine-induced ERK activation, given dose-dependent reduction of pERK1 and pERK2 stimulation with the EGF receptor inhibitor, AG1478. Immunocytochemical studies indicated that clozapine treatment increased EGF receptor (Tyr1068) phosphorylation. In vivo mouse treatment studies supported the in vitro findings with initial blockade, subsequent activation, and normalization of the cortical ERK response over 24 h. Furthermore, in vivo clozapine-induced ERK activation was significantly reduced by AG1478. This is the first report that clozapine action on prefrontal cortical neurons involves the EGF signaling system. Since EGF receptor signaling has not been previously linked to antipsychotic drug action, our findings may implicate the EGF system as a molecular substrate in treatment-resistant schizophrenia.

Sex-specific association of epidermal growth factor gene polymorphisms with acute respiratory distress syndrome

Epidermal growth factor (EGF) is involved in alveolar epithelial repair, lung fluid clearance and inflammation, and is regulated by sex hormones. An unmatched, nested case-control study was conducted to evaluate the associations of EGF variants with acute respiratory distress syndrome (ARDS) and the role of sex on the associations between EGF variants and ARDS. Patients with ARDS risk factors upon intensive care unit admission were enrolled. Cases were 416 Caucasians who developed ARDS and controls were 1,052 Caucasians who did not develop ARDS. Cases were followed for clinical outcomes and 60-day mortality. One functional single nucleotide polymorphism (SNP), rs4444903, and six haplotype-tagging SNPs spanning the entire EGF gene were genotyped. No individual SNP or haplotype was associated with ARDS risk or outcomes in all subjects. Sex-stratified analyses showed opposite effects of EGF variants on ARDS in males versus in females. SNPs rs4444903, rs2298991, rs7692976 and rs4698803, and haplotypes GGCGTC and ATCAAG were associated with ARDS risk in males. No associations were observed in females. Interaction analysis showed that rs4444903, rs2298991, rs7692976 and rs6533485 significantly interacted with sex for ARDS risk. The present study suggests that associations of epidermal growth factor gene variants with acute respiratory distress syndrome risk are modified by sex. The current findings should be replicated in other populations.

No association between epidermal growth factor and epidermal growth factor receptor polymorphisms and nasopharyngeal carcinoma

Numerous candidate genes have been proposed as susceptibility factors for the development of nasopharyngeal carcinoma (NPC). Epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) interaction plays a pivotal role in cell proliferation, differentiation, and tumourigenesis of epithelial tissues. To our knowledge, however, no study has examined the relationship between the EGF/EGFR and NPC. The aim of this study is to investigate the potential association between single-nucleotide polymorphisms of EGF +61 G/A and EGFR +2073 A/T and NPC. A total of 173 patients with NPC and 206 age- and sex-matched controls were the participants. Genotypes were determined using a polymerase chain reaction-restriction fragment length polymorphism strategy and DNA sequencing. There were no significant differences in the genotype and allele frequencies of EGF +61 G/A and EGFR +2073 A/T polymorphisms between the group of patients with NPC and the control group in a Chinese population (for EGF +61 G/A: OR=1.29, 95% CI: 0.95-1.74; for EGFR +2073 A/T: OR=0.91, 95% CI: 0.67-1.23). Further studies are still needed to explore the complicated interaction between environmental factors and EGF +61 G/A and EGFR +2073 A/T polymorphisms in the risk of NPC, particularly in ethnically different populations.

A cyclooxygenase-2 inhibitor ameliorates behavioral impairments induced by striatal administration of epidermal growth factor

Consistent with the hypothesis that neuroinflammatory processes contribute to the neuropathology of schizophrenia, the protein levels of epidermal growth factor (EGF) and its receptor ErbB1 are abnormal in patients with schizophrenia. To evaluate neuropathological significance of this abnormality, we established an animal model for behavioral deficits by administering EGF into the striatum and evaluated the effects of cyclooxygenase-2 (Cox-2) inhibitor celecoxib. Intracranial infusion of EGF into the striatum of adult male rats activated ErbB1 and induced neurobehavioral impairments observed in several schizophrenia models. Unilateral EGF infusion to the striatum lowered prepulse inhibition (PPI) in a dose-dependent manner and impaired latent learning of active shock avoidance without affecting basal learning ability. Bilateral EGF infusion similarly affected PPI. In contrast, EGF infusion to the nucleus accumbens did not induce a behavioral deficit. Intrastriatal EGF infusion also increased Cox-2 expression, elevated tyrosine hydroxylase activity, and upregulated the levels of dopamine and its metabolites. Subchronic administration of celecoxib (10 mg/kg, p.o.) ameliorated the abnormalities in PPI and latent learning as well as normalized dopamine metabolism. We conclude that this EGF-triggered neuroinflammatory process is mediated in part by Cox-2 activity and perturbs dopamine metabolism to generate neurobehavioral abnormalities.

Impaired basolateral sorting of pro-EGF causes isolated recessive renal hypomagnesemia

Primary hypomagnesemia constitutes a rare heterogeneous group of disorders characterized by renal or intestinal magnesium (Mg(2+)) wasting resulting in generally shared symptoms of Mg(2+) depletion, such as tetany and generalized convulsions, and often including associated disturbances in calcium excretion. However, most of the genes involved in the physiology of Mg(2+) handling are unknown. Through the discovery of a mutation in the EGF gene in isolated autosomal recessive renal hypomagnesemia, we have, for what we believe is the first time, identified a magnesiotropic hormone crucial for total body Mg(2+) balance. The mutation leads to impaired basolateral sorting of pro-EGF. As a consequence, the renal EGFR is inadequately stimulated, resulting in insufficient activation of the epithelial Mg(2+) channel TRPM6 (transient receptor potential cation channel, subfamily M, member 6) and thereby Mg(2+) loss. Furthermore, we show that colorectal cancer patients treated with cetuximab, an antagonist of the EGFR, develop hypomagnesemia, emphasizing the significance of EGF in maintaining Mg(2+) balance.

Interactions among genes in the ErbB-Neuregulin signalling network are associated with increased susceptibility to schizophrenia

BACKGROUND

Evidence of genetic association between the NRG1 (Neuregulin-1) gene and schizophrenia is now well-documented. Furthermore, several recent reports suggest association between schizophrenia and single-nucleotide polymorphisms (SNPs) in ERBB4, one of the receptors for Neuregulin-1. In this study, we have extended the previously published associations by investigating the involvement of all eight genes from the ERBB and NRG families for association with schizophrenia.

METHODS

Eight genes from the ERBB and NRG families were tested for association to schizophrenia using a collection of 396 cases and 1,342 blood bank controls ascertained from Aberdeen, UK. A total of 365 SNPs were tested. Association testing of both alleles and genotypes was carried out using the fast Fisher's Exact Test (FET). To understand better the nature of the associations, all pairs of SNPs separated by >or= 0.5 cM with at least nominal evidence of association (P < 0.10) were tested for evidence of pairwise interaction by logistic regression analysis.

RESULTS

42 out of 365 tested SNPs in the eight genes from the ERBB and NRG gene families were significantly associated with schizophrenia (P < 0.05). Associated SNPs were located in ERBB4 and NRG1, confirming earlier reports. However, novel associations were also seen in NRG2, NRG3 and EGFR. In pairwise interaction tests, clear evidence of gene-gene interaction was detected for NRG1-NRG2, NRG1-NRG3 and EGFR-NRG2, and suggestive evidence was also seen for ERBB4-NRG1, ERBB4-NRG2, ERBB4-NRG3 and ERBB4-ERBB2. Evidence of intragenic interaction was seen for SNPs in ERBB4.

CONCLUSION

These new findings suggest that observed associations between NRG1 and schizophrenia may be mediated through functional interaction not just with ERBB4, but with other members of the NRG and ERBB families. There is evidence that genetic interaction among these loci may increase susceptibility to schizophrenia.

Epidermal growth factor 61 A/G polymorphism and uterine cervical cancer

Cervical cancer, the second most common malignancy in women worldwide, is almost invariably associated with infection by human papillomavirus (HPV). However, although many women are infected with high-risk types of HPV, only a subset of infected women will ever develop cervical cancer. Therefore, host genetic factor may play a role in cervical carcinogenesis. Alterations in epidermal growth factor receptor (EGFR) are common events in cervical cancer. Therefore, we hypothesized that a functional polymorphism in the 5′ untranslated region of the epidermal growth factor (EGF) gene, a natural ligand of the EGFR, may play a role in the cervical carcinogenesis and tumor invasiveness. We assessed the possible association between EGF +61 A/G polymorphism and cervical cancer risk in a hospital-based case–control study among 337 Korean women (168 cases, 169 age-matched controls). The frequencies of EGF +61 allele and genotype were not different between cases and controls. We observed increasing trend of lymph node metastasis from A/A homozygous genotype toward G/G homozygous genotype. We did not find any evidence that EGF +61 A/G polymorphism was associated with individual susceptibility of cervical cancer. However, although it was not statistically significant, the increasing trend of lymph node metastasis according to EGF genotype suggests the possibility that individual variance of EGF expression may be associated with cervical cancer invasiveness. We also confirmed that there exists striking ethnic heterogeneity of EGF genotype between Caucasian and East Asian population

Association study between epidermal growth factor receptor and epidermal growth factor polymorphisms and endometriosis in a Japanese population

OBJECTIVE

We investigated a possible association between endometriosis and polymorphisms in the genes encoding epidermal growth factor (EGF) receptor (EGFR) and EGF in a Japanese population.

METHODS

We compared the distribution of the Egfr+2073 A/T and Egf+61 G/A polymorphisms by polymerase chain reaction-restriction fragment length polymorphism analysis in 146 affected women and 181 controls.

RESULTS

No significant differences in the frequency and genotype distribution of the Egfr+2073 A/T and Egf+61 G/A polymorphisms were found between endometriosis patients with all disease stages and controls. Stratification by disease stage had no effect on the results.

CONCLUSION

The Egfr+2073 A/T and Egf+61 G/A polymorphisms are not associated with an increased risk of endometriosis in a Japanese population.

Partial evidence of an association between epidermal growth factor A61G polymorphism and age at onset in male schizophrenia

Epidermal growth factor (EGF) is a well-known neurotrophic factor regulating the development of various neuronal cells, including dopaminergic neurons, and dysfunction of EGF signals has been demonstrated as a risk factor for schizophrenia. Recently, several researchers have investigated associations including age at onset (AAO) with EGF A61G functional polymorphism, but the results of these studies have been controversial. Thus, we investigated whether A61G plays a role in predisposition to schizophrenia and its effects on AAO. Our subjects included 190 patients with schizophrenia and 347 controls. We assessed three different points of AAO: age at first occurrence of positive psychotic symptoms, medication, and hospitalization as a patient with schizophrenia. We found no differences in allele and genotype frequencies between patients and controls or associations between A61G and AAOs across stratified points in the entire sample and in each gender. However, we found significant gender differences in patients with the AA genotype in all stratified points of AAOs. Subset analyses of G allele distribution between clinical subsets with an AAO cutoff of 20 years revealed that male patients with early onset schizophrenia were more likely to exhibit the common AA homozygote than male patients with adulthood onset schizophrenia. In conclusion, although we were unable to support an association between EGF A61G and schizophrenia, the AA genotype might play a disease-modifying role differentially according to gender.

Recent progress in animal modeling of immune inflammatory processes in schizophrenia: implication of specific cytokines

Epidemiologic studies demonstrate significant environmental impact of maternal viral infection and obstetric complications on the risk of schizophrenia and indicate their detrimental influences on brain development in this disorder. Based on these findings, animal models for schizophrenia have been established using double stranded RNA, bacterial lipopolysaccharides, hippocampal lesion, or prenatal/perinatal ischemia. Key molecules regulating such immune/inflammatory reactions are cytokines, which are also involved in brain development, regulating dopaminergic and GABAergic differentiation, and synaptic maturation. Specific members of the cytokine family, such as interleukin-1, epidermal growth factor, and neuregulin-1, are induced after infection and brain injury; therefore, certain cytokines are postulated to have a central role in the neurodevelopmental defects of schizophrenia. Recently, to test this hypothesis, a variety of cytokines were administered to rodent pups. Cytokines administered in the periphery penetrated the immature blood-brain barrier and perturbed phenotypic neural development. Among the many cytokines examined, epidermal growth factor (or potentially other ErbB1 ligands) and interleukin-1 specifically induced the most severe and persistent behavioral and cognitive abnormalities, most of which were ameliorated by antipsychotics. These animal experiments illustrate that, during early development, these cytokine activities in the periphery perturbs normal brain development and impairs later psychobehavioral and/or cognitive traits. The neurodevelopmental and behavioral consequences of prenatal/perinatal cytokine activity are compared with those of other schizophrenia models and cytokine interactions with genes are also discussed in this review.

Distinct Influences of Neonatal Epidermal Growth Factor Challenge on Adult Neurobehavioral Traits in Four Mouse Strains

Epidermal growth factor (EGF) receptor (ErbB1) signals regulate dopaminergic development and function and are implicated in schizophrenia. We evaluated genetic effects on neurobehavioral changes induced by neonatal EGF administration, using four mouse strains. Subcutaneous EGF administration increased phosphorylation of brain ErbB1 in all strains, although DBA/2 and C57BL/6 mice had lower basal phosphorylation. Neonatal EGF treatment differentially influenced physical and behavioral/cognitive development, depending on mouse strain. Prepulse inhibition was decreased in DBA/2 and C57BL/6 mice but not C3H/He and ddY mice. Locomotor activity was accelerated in DBA/2 mice, but reduced in ddY mice. EGF treatment enhanced fear-learning performance with a tone cue in DBA/2 mice, but decreased performance with tone and context cues in C3H/He and ddY mice, respectively. The strain-dependent behavioral sensitivity was correlated with basal ErbB1 phosphorylation. Genetic components regulating brain ErbB1 signaling strongly influence the direction and strength of behavioral responses stemming from the neonatal neurotrophic perturbation.

Replicative homeostasis II: influence of polymerase fidelity on RNA virus quasispecies biology: implications for immune recognition, viral autoimmunity and other "virus receptor" diseases

Much of the worlds' population is in active or imminent danger from established infectious pathogens, while sporadic and pandemic infections by these and emerging agents threaten everyone. RNA polymerases (RNA_pol) generate enormous genetic and consequent antigenic heterogeneity permitting both viruses and cellular pathogens to evade host defences. Thus, RNA_pol causes more morbidity and premature mortality than any other molecule. The extraordinary genetic heterogeneity defining viral quasispecies results from RNA_pol infidelity causing rapid cumulative genomic RNA mutation a process that, if uncontrolled, would cause catastrophic loss of sequence integrity and inexorable quasispecies extinction. Selective replication and replicative homeostasis, an epicyclical regulatory mechanism dynamically linking RNApol fidelity and processivity with quasispecies phenotypic diversity, modulating polymerase fidelity and, hence, controlling quasispecies behaviour, prevents this happening and also mediates immune escape. Perhaps more importantly, ineluctable generation of broad phenotypic diversity after viral RNA is translated to protein quasispecies suggests a mechanism of disease that specifically targets, and functionally disrupts, the host cell surface molecules – including hormone, lipid, cell signalling or neurotransmitter receptors – that viruses co-opt for cell entry. This mechanism – "Viral Receptor Disease (VRD)" – may explain so-called "viral autoimmunity", some classical autoimmune disorders and other diseases, including type II diabetes mellitus, and some forms of obesity. Viral receptor disease is a unifying hypothesis that may also explain some diseases with well-established, but multi-factorial and apparently unrelated aetiologies – like coronary artery and other vascular diseases – in addition to diseases like schizophrenia that are poorly understood and lack plausible, coherent, pathogenic explanations.

Interaction of tumor necrosis alpha - G308A and epidermal growth factor gene polymorphisms in early-onset schizophrenia

The study population comprised 94 Finnish patients with DSM-IV diagnosis of schizophrenia. The patients were placed into two subgroups according to medication response to conventional neuroleptics. The aim of the study was to examine the frequency of tumor necrosis factor -308 (G > A) polymorphism in these patients and their 98 control subjects who were age- and gender-matched blood donors. Associations between TNFalpha -308 polymorphism alone and between the interaction of TNFalpha and epidermal growth factor gene polymorphisms, and medication response and age at onset of schizophrenia were also studied. The frequencies of TNFalpha A-allele were 11.7 % in patients and 12.8% in controls. The difference was not significant (p = 0.75). TNFalpha -308 polymorphism was not associated with medication response. However, patients with EGF AA and TNFalpha AG/AA genotype had a lower age at onset of schizophrenia compared with the rest of the patients not having this combination (20.0 years, 3.3 vs. 30.2 years, 10.1 mean + SD; p < 0.001). The results support earlier findings according to which TNFalpha polymorphism is not associated with the incidence of schizophrenia. On the other hand, the role of cytokines in schizophrenia may involve genetic interactions predisposing early onset of illness.

Cloninger's temperament dimensions and epidermal growth factor A61G polymorphism in Finnish adults

This study examines a link between human temperament and epidermal growth factor (EGF). There is evidence that dopaminergic neurotransmission in the central nervous system has a role in temperament, especially in novelty seeking. Functional polymorphism in EGF gene has an impact on EGF production, and EGF, in turn, appears to affect the development of midbrain dopaminergic neurons. Epidermal growth factor gene A61G polymorphisms were studied in a randomly selected sample of 292 Finnish adults. Their temperaments were assessed twice (with a 4-year test-retest interval) with Cloninger's Temperament and Character Inventory consisting of four dimensions, i.e. novelty seeking (NS), harm avoidance (HA), reward dependence (RD) and persistence (P). The findings on men showed a significant association between a presence of the G/G polymorphism and scoring in the highest tertile on NS in both test and retest. The same was true with men who scored high on RD, especially on sensitivity, in both tests. Among women, G/G polymorphism was associated with a stable high level of P. Importantly, temperament dimensions, as assessed with one test only, did not provide replicable associations with EGF polymorphism across the two measurements. Our results demonstrate the importance of reliable phenotype assessment and lend support to the hypothesis that dopaminergic activity is one factor underlying stable temperament.

No association of EGF polymorphism with schizophrenia in a Japanese population

Epidermal growth factor (EGF) signal regulates the development of dopaminergic neurons and monoamine metabolism. It is suggested that EGF protein levels are decreased in the brain and blood of patients with schizophrenia. A recent study has reported that a polymorphism in EGF gene (rs4444903) is associated with schizophrenia in Finnish men. To confirm this association for another population in larger samples, we conducted a case-control association study on a Japanese population (337 cases and 421 controls). No significant difference was observed in both the allelic and genotype distribution between cases and controls in women, men and total samples. Our results suggest that the polymorphism in EGF gene might not confer increased susceptibility for schizophrenia in a Japanese population.