3' UTR (AGG)n repeat of glial cell line-derived neurotrophic factor (GDNF) gene polymorphism in schizophrenia

MicroRNA-Mediated Suppression of Glial Cell Line-Derived Neurotrophic Factor Expression Is Modulated by a Schizophrenia-Associated Non-Coding Polymorphism

Plasma levels of glial cell line-derived neurotrophic factor (GDNF), a pivotal regulator of differentiation and survival of dopaminergic neurons, are reportedly decreased in schizophrenia. To explore the involvement of GDNF in the pathogenesis of the disease, a case-control association analysis was performed between five non-coding single nucleotide polymorphisms (SNP) across the GDNF gene and schizophrenia. Of them, the 'G' allele of the rs11111 SNP located in the 3' untranslated region (3'-UTR) of the gene was found to associate with schizophrenia. In silico analysis revealed that the rs11111 'G' allele might create binding sites for three microRNA (miRNA) species. To explore the significance of this polymorphism, transient co-transfection assays were performed in human embryonic kidney 293T (HEK293T) cells with a luciferase reporter construct harboring either the 'A' or 'G' allele of the 3'-UTR of GDNF in combination with the hsa-miR-1185-1-3p pre-miRNA. It was demonstrated that in the presence of the rs11111 'G' (but not the 'A') allele, hsa-miR-1185-2-3p repressed luciferase activity in a dose-dependent manner. Deletion of the miRNA binding site or its substitution with the complementary sequence abrogated the modulatory effect. Our results imply that the rs11111 'G' allele occurring more frequently in patients with schizophrenia might downregulate GDNF expression in a miRNA-dependent fashion.

Novel missense variants in brain morphogenic genes associated with depression and schizophrenia

Introduction

Impaired function of brain morphogenic genes is considered one of the predisposing factors for the manifestation of psychiatric and cognitive disorders, such as paranoid schizophrenia (SCZ) and major depressive disorder (MDD). Identification of such genes (genes of neurotrophic factors and guidance molecules among them) and their deleterious genetic variants serves as a key to diagnosis, prevention, and possibly treatment of such disorders. In this study, we have examined the prevalence of genomic variants in brain morphogenic genes in individuals with SCZ and MDD within a Russian population.

Methods

We have performed whole-exome sequencing of 21 DNA samples: 11 from individuals with SCZ and 10 with MDD, followed by ARMS (Amplification-Refractory Mutation System) based screening of detected single nucleotide variants (SNVs) in larger groups: 102 for individuals with SCZ, 79 for those with MDD and 103 for healthy donors.

Results

Whole-exome sequencing has revealed 226 missense mutations in 79 genes (out of 140 studied), some of which occur in patients with psychiatric disorders significantly more frequently than in healthy donors. We have identified previously undescribed genomic variants in brain morphogenic genes: CDH2 (rs1944294-T and rs17445840-T), DCHS2 (rs11935573-G and rs12500437-G/T) and CDH23 (rs1227051-G/A), significantly associated with the incidence of SCZ and MDD in the Russian population. For some SNVs (rs6265-T, rs1944294-T, rs11935573-G, rs4760-G) sex-biased differences in their prevalence between SCZ/MDD patients and healthy donors was detected.

Discussion

However, the functional significance of the SNVs identified has still to be confirmed in cellular and animal models. Once it is fulfilled, these SNVs have the potential to complement the diagnostic toolbox for assessing susceptibility to mental disorders. The data obtained indirectly confirm the importance of adequate brain structure formation for its correct functioning and preservation of mental health.

Morphogenetic theory of mental and cognitive disorders: the role of neurotrophic and guidance molecules

Mental illness and cognitive disorders represent a serious problem for the modern society. Many studies indicate that mental disorders are polygenic and that impaired brain development may lay the ground for their manifestation. Neural tissue development is a complex and multistage process that involves a large number of distant and contact molecules. In this review, we have considered the key steps of brain morphogenesis, and the major molecule families involved in these process. The review provides many indications of the important contribution of the brain development process and correct functioning of certain genes to human mental health. To our knowledge, this comprehensive review is one of the first in this field. We suppose that this review may be useful to novice researchers and clinicians wishing to navigate the field.

Impaired Latent Inhibition in GDNF-Deficient Mice Exposed to Chronic Stress

Increased reactivity to stress is maladaptive and linked to abnormal behaviors and psychopathology. Chronic unpredictable stress (CUS) alters catecholaminergic neurotransmission and remodels neuronal circuits involved in learning, attention and decision making. Glial-derived neurotrophic factor (GDNF) is essential for the physiology and survival of dopaminergic neurons in substantia nigra and of noradrenergic neurons in the locus coeruleus. Up-regulation of GDNF expression during stress is linked to resilience; on the other hand, the inability to up-regulate GDNF in response to stress, as a result of either genetic or epigenetic modifications, induces behavioral alterations. For example, GDNF-deficient mice exposed to chronic stress exhibit alterations of executive function, such as increased temporal discounting. Here we investigated the effects of CUS on latent inhibition (LI), a measure of selective attention and learning, in GDNF-heterozygous (HET) mice and their wild-type (WT) littermate controls. No differences in LI were found between GDNF HET and WT mice under baseline experimental conditions. However, following CUS, GDNF-deficient mice failed to express LI. Moreover, stressed GDNF-HET mice, but not their WT controls, showed decreased neuronal activation (number of c-Fos positive neurons) in the nucleus accumbens shell and increased activation in the nucleus accumbens core, both key regions in the expression of LI. Our results add LI to the list of behaviors affected by chronic stress and support a role for GDNF deficits in stress-induced pathological behaviors relevant to schizophrenia and other psychiatric disorders.

Glial Cell Line-Derived Neurotrophic Factor (GDNF) serum level in women with schizophrenia and depression, correlation with clinical and metabolic parameters

AIM

Neurotrophic factors have been implicated in neuropsychiatric disorders, including schizophrenia and depression. Glial Cell Line-Derived Neurotrophic Factor (GDNF) promotes development, differentiation, and protection of dopaminergic, serotonergic, GABAergic and noradrenergic neurons as well as glial cells in different brain regions. This study examined serum levels of GDNF in schizophrenia and depression and its correlation with metabolic parameters during 8 weeks of treatment.

METHODS

Serum GDNF level, fasting serum glucose and lipid profile were measured at baseline and week 8 in 133 women: 55 with schizophrenia, 30 with a first episode depression and 48 healthy controls. The severity of the symptoms was evaluated using Positive and Negative Syndrome Scale (PANSS), 17-item Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI).

RESULTS

There was statistically significant higher GDNF level in schizophrenia at baseline when compared with week 8. Correlations of GDNF with PANSS in schizophrenia and cholesterol level in depression have also been detected.

CONCLUSIONS

To our knowledge, this is the first study which correlates GDNF levels with metabolic parameters. Our results show no differences in GDNF serum level between schizophrenia, a first depressive episode, and healthy controls. GDNF serum level did not correlate with metabolic parameters except for total cholesterol in depression.

Association between smoking behaviour and genetic variants of glial cell line-derived neurotrophic factor

Glial cell line-derived neurotrophic factor (GDNF) promotes development and differentiation of dopaminergic neurons, thus it has an important role in dopamine-related neuropsychiatric disorders. Since the role of dopamine system in smoking is well established, we hypothesized that GDNF gene variants may affect smoking behaviour. Self-reported data on smoking behaviour (never smoked, quit, occasional, or regular smokers) and level of nicotine addiction (Hooked on Nicotine Checklist and Fagerstrom Nicotine Addiction Scale), anxiety, as well as buccal samples were obtained from 930 Hungarian young adults (18-35 years). Genetic analysis involved eight GDNF single-nucleotide polymorphisms (SNP) (rs1981844, rs3812047, rs3096140, rs2973041, rs2910702, rs1549250, rs2973050 and rs11111). Allele-wise association analyses of the eight GDNF SNPs provided a significant association between smoking behaviour and rs3096140 (P=0.0039). The minor allele (C) was more frequent in those groups who smoked in some form (quit, occasional or regular smokers) as compared to those who never smoked (P = 0.0046). This result remained significant after Bonferroni correction for multiple testing. In the ever smoking group, no significant differences were found in the level of nicotine addiction by the alleles of these polymorphisms. Also, no significant interaction of rs3096140 and smoking categories were observed on anxiety mean scores. Although previous data demonstrated an association between GDNF rs2910704 and severity of methamphetamine use to the best of our knowledge, this is the first study on the role of GDNF genetic variations in smoking behaviour. Our results suggest that GDNF rs3096140 might be involved in the genetic background of smoking, independent of anxiety characteristics.

Diverse glial cell line-derived neurotrophic factor (GDNF) support between mania and schizophrenia: a comparative study in four major psychiatric disorders

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) have essential roles in synaptic plasticity which is involved in pathogenesis and treatment of psychiatric disorders. However, it is not clear whether they act simultaneously during illness states in major psychiatric disorders.

METHODS

BDNF and GDNF serum levels were measured concomitantly by enzyme-linked immunosorbent assay (ELISA) method in 171 patients diagnosed with schizophrenia (n=33), bipolar disorder-manic episode (n=39), bipolar/unipolar depression (n=64, 24/40) and obsessive-compulsive disorder (n=35) according to DSM-IV, and 78 healthy volunteers. SCID-I and SCID non-patient version were used for clinical evaluation of the patients and healthy volunteers, respectively. Correlations between the two trophic factor levels, and illness severity scores, duration of illness and medication dosages were studied across different illnesses.

RESULTS

While patients had equally lower BDNF levels in all diagnoses, GDNF levels were significantly higher in mania and lower in schizophrenia compared to healthy controls. BDNF levels were negatively correlated to illness severity scores in affective episodes (mania and depression). Longer duration of illness (>5 years) had an impact on lower GDNF levels in schizophrenia. BDNF levels and antipsychotic drug dosages in schizophrenia, and GDNF levels and antidepressant drug dosages in obsessive-compulsive disorder were positively correlated.

CONCLUSION

Our data confirmed the evidence of equally deficient neuronal support by BDNF in all major psychiatric illnesses, but suggested a diverse glial functioning between schizophrenia and mania.

Association of the GDNF gene with depression and heroin dependence, but not schizophrenia, in a Chinese population

The association of seven GDNF tag SNPs with depression, heroin dependence (HD) and schizophrenia was evaluated in Chinese. An increased risk of HD and depression was associated with rs2910709 T/T genotype and rs884344 C allele, respectively, suggesting GDNF is a novel susceptibility gene for depression and HD.

Glial cell line-derived neurotrophic factor (GDNF) as a novel candidate gene of anxiety

Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophic factor for dopaminergic neurons with promising therapeutic potential in Parkinson's disease. A few association analyses between GDNF gene polymorphisms and psychiatric disorders such as schizophrenia, attention deficit hyperactivity disorder and drug abuse have also been published but little is known about any effects of these polymorphisms on mood characteristics such as anxiety and depression. Here we present an association study between eight (rs1981844, rs3812047, rs3096140, rs2973041, rs2910702, rs1549250, rs2973050 and rs11111) GDNF single nucleotide polymorphisms (SNPs) and anxiety and depression scores measured by the Hospital Anxiety and Depression Scale (HADS) on 708 Caucasian young adults with no psychiatric history. Results of the allele-wise single marker association analyses provided significant effects of two single nucleotide polymorphisms on anxiety scores following the Bonferroni correction for multiple testing (p = 0.00070 and p = 0.00138 for rs3812047 and rs3096140, respectively), while no such result was obtained on depression scores. Haplotype analysis confirmed the role of these SNPs; mean anxiety scores raised according to the number of risk alleles present in the haplotypes (p = 0.00029). A significant sex-gene interaction was also observed since the effect of the rs3812047 A allele as a risk factor of anxiety was more pronounced in males. In conclusion, this is the first demonstration of a significant association between the GDNF gene and mood characteristics demonstrated by the association of two SNPs of the GDNF gene (rs3812047 and rs3096140) and individual variability of anxiety using self-report data from a non-clinical sample.

A genome-wide linkage and association scan reveals novel loci for hypertension and blood pressure traits

Hypertension is caused by the interaction of environmental and genetic factors. The condition which is very common, with about 18% of the adult Hong Kong Chinese population and over 50% of older individuals affected, is responsible for considerable morbidity and mortality. To identify genes influencing hypertension and blood pressure, we conducted a combined linkage and association study using over 500,000 single nucleotide polymorphisms (SNPs) genotyped in 328 individuals comprising 111 hypertensive probands and their siblings. Using a family-based association test, we found an association with SNPs on chromosome 5q31.1 (rs6596140; P<9×10⁻⁸) for hypertension. One candidate gene, PDC, was replicated, with rs3817586 on 1q31.1 attaining P = 2.5×10⁻⁴ and 2.9×10⁻⁵ in the within-family tests for DBP and MAP, respectively. We also identified regions of significant linkage for systolic and diastolic blood pressure on chromosomes 2q22 and 5p13, respectively. Further family-based association analysis of the linkage peak on chromosome 5 yielded a significant association (rs1605685, P<7×10⁻⁵) for DBP. This is the first combined linkage and association study of hypertension and its related quantitative traits with Chinese ancestry. The associations reported here account for the action of common variants whereas the discovery of linkage regions may point to novel targets for rare variant screening.

Association analysis of the GDNF gene with methamphetamine use disorder in a Japanese population

Methamphetamine (MAP) dependence is a highly heritable and aberrant dopaminergic signaling that has been implicated in the disease. Glial cell line-derived neurotrophic factor (GDNF), which plays an important role in the survival of dopaminergic neurons, may be involved in this disorder. In this study, we examined the association between GDNF and MAP dependence using a Japanese population-based sample. We selected eight single nucleotide polymorphisms (SNPs) in the GDNF locus for the association analysis. When patients with MAP dependence were divided into two subgroups consisting of multi-substance and MAP-only users, we detected a significant association between these two groups and the tagging SNP, rs2910704 (after Bonferroni's correction; allele P=0.034). Thus, GDNF is likely to be related to the severity of MAP use in the Japanese population.

Linking oligodendrocyte and myelin dysfunction to neurocircuitry abnormalities in schizophrenia

Multiple lines of evidence in schizophrenia, from brain imaging, studies in postmortem brains, and genetic association studies, have implicated oligodendrocyte and myelin dysfunction in this disease. Recent studies suggest that oligodendrocyte and myelin dysfunction leads to changes in synaptic formation and function, which could lead to cognitive dysfunction, a core symptom of schizophrenia. Furthermore, there is accumulating data linking oligodendrocyte and myelin dysfunction with dopamine and glutamate abnormalities, both of which are found in schizophrenia. These findings implicate oligodendrocyte and myelin dysfunction as a primary change in schizophrenia, not only as secondary consequences of the illness or treatment. Strategies targeting oligodendrocyte and myelin abnormalities could therefore provide therapeutic opportunities for patients suffering from schizophrenia.

Genetic association of the GDNF alpha-receptor genes with schizophrenia and clozapine response

GDNF (glial-cell-line derived neurotrophic factor) is a potent neurotrophic factor for dopaminergic neurons. Neuropsychiatric diseases and their treatments are associated with alterations in the levels of both GDNF and its receptor family (GDNF family receptor alpha or GFRA). GFRA1, GFRA2 and GFRA3 are located in chromosomal regions with suggestive linkage to schizophrenia. In this study we analyzed polymorphisms located in all four known GFRA genes and examined association with schizophrenia and clozapine response. We examined SNPs across the genes GFRA1-4 in 219 matched case-control subjects, 85 small nuclear families and 140 schizophrenia patients taking clozapine for 6months. We observed that GFRA3 rs11242417 and GFRA1 rs11197557 variants were significantly associated with schizophrenia after combining results from both schizophrenia samples. Furthermore, we found an overtransmission of the G-C GFRA1 rs7920934-rs730357 haplotype to subjects with schizophrenia and association of A-T-G-G GFRA3 rs10036665-rs10952-rs11242417-rs7726580 with schizophrenia in the case-control sample. On the other hand, GFRA2 variants were not associated with schizophrenia diagnosis but subjects carrying T-G-G rs1128397-rs13250096-rs4567028 haplotype were more likely to respond to clozapine treatment. The statistical significance of results survived permutation testing but not Bonferroni correction. We also found nominally-significant evidence for interactions between GFRA1, 2 and 3 associated with schizophrenia and clozapine response, consistent with the locations of these three genes within linkage regions for schizophrenia.

Association of the NPAS3 gene and five other loci with response to the antipsychotic iloperidone identified in a whole genome association study

A whole genome association study was performed in a phase 3 clinical trial conducted to evaluate a novel antipsychotic, iloperidone, administered to treat patients with schizophrenia. Genotypes of 407 patients were analyzed for 334,563 single nucleotide polymorphisms (SNPs). SNPs associated with iloperidone efficacy were identified within the neuronal PAS domain protein 3 gene (NPAS3), close to a translocation breakpoint site previously observed in a family with schizophrenia. Five other loci were identified that include the XK, Kell blood group complex subunit-related family, member 4 gene (XKR4), the tenascin-R gene (TNR), the glutamate receptor, inotropic, AMPA 4 gene (GRIA4), the glial cell line-derived neurotrophic factor receptor-alpha2 gene (GFRA2), and the NUDT9P1 pseudogene located in the chromosomal region of the serotonin receptor 7 gene (HTR7). The study of these polymorphisms and genes may lead to a better understanding of the etiology of schizophrenia and of its treatment. These results provide new insight into response to iloperidone, developed with the ultimate goal of directing therapy to patients with the highest benefit-to-risk ratio.

Effects of bisphenol-A and other endocrine disruptors compared with abnormalities of schizophrenia: an endocrine-disruption theory of schizophrenia

In recent years, numerous substances have been identified as so-called "endocrine disruptors" because exposure to them results in disruption of normal endocrine function with possible adverse health outcomes. The pathologic and behavioral abnormalities attributed to exposure to endocrine disruptors like bisphenol-A (BPA) have been studied in animals. Mental conditions ranging from cognitive impairment to autism have been linked to BPA exposure by more than one investigation. Concurrent with these developments in BPA research, schizophrenia research has continued to find evidence of possible endocrine or neuroendocrine involvement in the disease. Sufficient information now exists for a comparison of the neurotoxicological and behavioral pathology associated with exposure to BPA and other endocrine disruptors to the abnormalities observed in schizophrenia. This review summarizes these findings and proposes a theory of endocrine disruption, like that observed from BPA exposure, as a pathway of schizophrenia pathogenesis. The review shows similarities exist between the effects of exposure to BPA and other related chemicals with schizophrenia. These similarities can be observed in 11 broad categories of abnormality: physical development, brain anatomy, cellular anatomy, hormone function, neurotransmitters and receptors, proteins and factors, processes and substances, immunology, sexual development, social behaviors or physiological responses, and other behaviors. Some of these similarities are sexually dimorphic and support theories that sexual dimorphisms may be important to schizophrenia pathogenesis. Research recommendations for further elaboration of the theory are proposed.

Association analysis of the glial cell line-derived neurotrophic factor (GDNF) gene in schizophrenia

The glial cell line-derived neurotrophic factor (GDNF) gene is located within a region of chromosome 5 (5p14.1-q13.3) that has been highlighted as a potential schizophrenia susceptibility locus by a number of genome scans. GDNF is neurotrophic and is also thought to be involved in differentiation of dopaminergic neurones. The GDNF gene is, therefore, a positional and functional candidate gene for schizophrenia. It is of additional interest because altered GDNF mRNA and protein expression has been reported in response to antipsychotics and the psychotomimetic phencyclidine, and two previous studies, focussed on a single variant, have reported weak support for genetic association between GDNF and schizophrenia in small samples. To test the hypothesis that GDNF is a susceptibility gene for schizophrenia, we performed a detailed association study. We chose 9 SNPs that spanned a genomic region of 40 kb and fully encompassed GDNF. SNPs were genotyped in a sample of 673 schizophrenic patients and 716 matched controls, all of Caucasian origin and all collected from the UK or Ireland. Of the 9 SNPs genotyped 2 showed nominally significant genotypic association at the P< or =0.05 level (rs2973050; OR=1.11; P-value=0.007 and rs2910702; OR=1.14; P-value=0.039). Permutation testing to allow for multiple comparisons of non-independent markers gave a corrected genotypic P-value of 0.052 for rs2973050. We also genotyped an (AGG)(n) repeat located in the 3' UTR of the GDNF but this showed no evidence for association. We conclude that our sample does not provide independent statistically significant evidence for association between GDNF and schizophrenia, nor does it replicate previous specific reports of association.

An investigation of the neurotrophic factor genes GDNF, NGF, and NT3 in susceptibility to ADHD

Attention deficit hyperactivity disorder (ADHD) is a common, highly heritable, neurodevelopmental disorder with onset in early childhood. Genes involved in neuronal development and growth are, thus, important etiological candidates and neurotrophic factors have been hypothesized to play a role in the pathogenesis of ADHD. Glial derived neurotrophic factor (GDNF), nerve growth factor (NGF (beta subunit)), and neurotrophic factor 3 (NT3) are members of the neurotrophin family and are involved in the survival, differentiation, and maintenance of neuronal cells. We have examined 10 coding and intronic single nucleotide polymorphisms (SNPs) across GDNF, NGF, and NT3 in a family-based association sample of 120 DSM-IV ADHD probands and their biological parents, as well as a case-control analysis with 120 sex-matched controls. Borderline significant overtransmission of the C allele of a non-synonymous C/T SNP (rs6330) in NGF which codes an alanine/valine change was found in the family-based sample (Chi-square = 3.69, odds ratio (OR) = 1.65, P = 0.05). Although this SNP is located in the 5' pro-NGF sequence and not the mature NGF protein, it may affect intracellular processing and secretion of NGF.