Fibroblast growth factor 20 polymorphisms and haplotypes strongly influence risk of Parkinson disease

FGF20

Fibroblast growth factor 20 (FGF20) is a neurotrophic factor and a member of the FGF9 subfamily. It was first identified in Xenopus embryos and was isolated shortly thereafter from the adult rat brain. Its receptors include FGFR4, FGFR3b, FGFR2b and the FGFRc splice forms. In adults it is highly expressed in the brain, while it is expressed in a variety of regions during embryonic development, including the inner ear, heart, hair placodes, mammary buds, dental epithelium and limbs. As a result of its wide-spread expression, FGF20 mouse mutants exhibit a variety of phenotypes including congenital deafness, lack of hair, small kidneys and delayed mammary ductal outgrowth. FGF20 is also associated with human diseases including Parkinson's Disease, cancer and hereditary deafness.

Research progress of fibroblast growth factor in nervous system diseases

Fibroblast growth factors (FGF) are a group of structurally related polypeptides which constitute an elaborate signaling system with their receptors. Evidence accumulated in the years suggests that the FGF family plays a key role in the repair of central nervous system injury. The main protective mechanisms include activating the expression of PI3K-Akt, peroxisome proliferator-activated receptor (PPARγ) and other signals; inhibiting NF-κB-mediated inflammatory response, oxidative stress and apoptosis; regulating neuronal differentiation and neuronal excitability as well as participating in protection of neurovascular units and nerve function repair. This paper comprehensively summarizes the latest research progress in FGF signaling related to diseases of the central nervous system such as cerebral infarction, cerebral hemorrhage, traumatic brain injury, Alzheimer's disease, Parkinson's disease, epilepsy and depression, aiming to provide scientific basis and reference for the development of innovative FGF drugs for the prevention and treatment of neurological diseases.

Developmental pathways linked to the vulnerability of adult midbrain dopaminergic neurons to neurodegeneration

The degeneration of dopaminergic and other neurons in the aging brain is considered a process starting well beyond the infantile and juvenile period. In contrast to other dopamine-associated neuropsychiatric disorders, such as schizophrenia and drug addiction, typically diagnosed during adolescence or young adulthood and, thus, thought to be rooted in the developing brain, Parkinson's Disease (PD) is rarely viewed as such. However, evidences have accumulated suggesting that several factors might contribute to an increased vulnerability to death of the dopaminergic neurons at an already very early (developmental) phase in life. Despite the remarkable ability of the brain to compensate such dopamine deficits, the early loss or dysfunction of these neurons might predispose an individual to suffer from PD because the critical threshold of dopamine function will be reached much earlier in life, even if the time-course and strength of naturally occurring and age-dependent dopaminergic cell death is not markedly altered in this individual. Several signaling and transcriptional pathways required for the proper embryonic development of the midbrain dopaminergic neurons, which are the most affected in PD, either continue to be active in the adult mammalian midbrain or are reactivated at the transition to adulthood and under neurotoxic conditions. The persistent activity of these pathways often has neuroprotective functions in adult midbrain dopaminergic neurons, whereas the reactivation of silenced pathways under pathological conditions can promote the survival and even regeneration of these neurons in the lesioned or aging brain. This article summarizes our current knowledge about signaling and transcription factors involved in midbrain dopaminergic neuron development, whose reduced gene dosage or signaling activity are implicated in a lower survival rate of these neurons in the postnatal or aging brain. It also discusses the evidences supporting the neuroprotection of the midbrain dopaminergic system after the external supply or ectopic expression of some of these secreted and nuclear factors in the adult and aging brain. Altogether, the timely monitoring and/or correction of these signaling and transcriptional pathways might be a promising approach to a much earlier diagnosis and/or prevention of PD.

Fibroblast growth factor 20 attenuates pathological cardiac hypertrophy by activating the SIRT1 signaling pathway

Cardiac hypertrophy occurs initially in response to an increased cardiac load as a compensatory mechanism to maintain cardiac output. However, sustained pathological hypertrophy can develop into heart failure and cause sudden death. Fibroblast growth factor 20 (FGF20) is a member of the fibroblast growth factor family, which involved in apoptosis, aging, inflammation, and autophagy. The precise function of FGF20 in pathological cardiac hypertrophy is unclear. In this study, we demonstrated that FGF20 was significantly decreased in response to hypertrophic stimulation. In contrast, overexpression of FGF20 protected against pressure overload-induced cardiac hypertrophy. Mechanistically, we found that FGF20 upregulates SIRT1 expression, causing deacetylation of FOXO1; this effect promotes the transcription of downstream antioxidant genes, thus inhibits oxidative stress. In content, the anti-hypertrophic effect of FGF20 was largely counteracted in SIRT1-knockout mice, accompanied by an increase in oxidative stress. In summary, our findings reveal a previously unknown protective effect of FGF20 on pathological cardiac hypertrophy by reducing oxidative stress through activation of the SIRT1 signaling pathway. FGF20 is a potential novel molecular target for preventing and treating pressure overload-induced myocardial injury.

Quantitative assessment of the effect of FGF20 rs1721100 and rs12720208 variant on the risk of sporadic Parkinson's disease: a meta-analysis

OBJECTIVES

While many studies have investigated the associations between fibroblast growth factor 20 (FGF20) rs1721100 (C/G) and rs12720208 (C/T) polymorphisms and susceptibility to Parkinson's disease (PD), their results are controversial. Our present meta-analysis estimated the overall association between FGF20 rs1721100 and rs12720208 polymorphisms and the risk of sporadic PD.

METHODS

We performed a comprehensive literature search of the PubMed, Web of Science, Embase, Chinese National Knowledge Infrastructure, and Wanfang Medicine electronic databases, which was updated in April 2021. Based on strict inclusion and exclusion criteria, the analysis included a total of 10 papers involving 14 studies with 5262 cases of PD and 6075 controls. Review Manager 5.4 software was used to assess the available data from each study. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the association between the FGF20 rs1721100 and rs12720208 polymorphisms and sporadic PD risk.

RESULTS

Our results showed that the FGF20 rs1721100 G allele frequency and genotype distribution did not differ between PD patients and controls. Similarly, the FGF20 rs12720208 T allele frequency and genotype distribution did not differ significantly between the two groups. A subgroup analysis of Asian and Caucasian populations also showed the same results.

CONCLUSIONS

The results of this meta-analysis indicated that neither the rs1721100 C/G nor the rs12720208 C/T variants were associated with sporadic PD susceptibility.

Uncovering the impact of noncoding variants in neurodegenerative brain diseases

Neurodegenerative brain diseases (NBDs) are characterized by cognitive decline and movement impairments caused by neuronal loss in different brain regions. A large fraction of the genetic heritability of NBDs is not explained by the current known mutations. Genome-wide association studies identified novel disease-risk loci, adding to the genetic basis of NBDs. Many of the associated variants reside in noncoding regions with distinct molecular functions. Genetic variation in these regions can alter functions and contribute to disease pathogenesis. Here, we discuss noncoding variants associated with NBDs. Methods for better functional interpretation of noncoding variation will expand our knowledge of the genetic architecture of NBDs and broaden the routes for therapeutic strategies.

Circulating proteins protect against renal decline and progression to end-stage renal disease in patients with diabetes

Diabetic kidney disease (DKD) and its major clinical manifestation, progressive renal decline that leads to end-stage renal disease (ESRD), are a major health burden for individuals with diabetes. The disease process that underlies progressive renal decline comprises factors that increase risk as well as factors that protect against this outcome. Using untargeted proteomic profiling of circulating proteins from individuals in two independent cohorts with type 1 and type 2 diabetes and varying stages of DKD followed for 7 to 15 years, we identified three elevated plasma proteins-fibroblast growth factor 20 (OR, 0.69; 95% CI, 0.54 to 0.88), angiopoietin-1 (OR, 0.72; 95% CI, 0.57 to 0.91), and tumor necrosis factor ligand superfamily member 12 (OR, 0.75; 95% CI, 0.59 to 0.95)-that were associated with protection against progressive renal decline and progression to ESRD. The combined effect of these three protective proteins was demonstrated by very low cumulative risk of ESRD in those who had baseline concentrations above median for all three proteins, whereas the cumulative risk of ESRD was high in those with concentrations below median for these proteins at the beginning of follow-up. This protective effect was shown to be independent from circulating inflammatory proteins and clinical covariates and was confirmed in a third cohort of diabetic individuals with normal renal function. These three protective proteins may serve as biomarkers to stratify diabetic individuals according to risk of progression to ESRD and might also be investigated as potential therapeutics to delay or prevent the onset of ESRD.

Fibroblast Growth Factor 20 Gene Polymorphism in Parkinson's Disease in Asian Population: A Meta-Analysis

Parkinson's disease (PD) is a neurodegenerative disease with the pathological hallmark of Lewy bodies and Lewy neurites composed of α-synuclein. The SNP rs591323 is one of the risk loci located near the FGF20 gene that has been implicated in PD. The variation of FGF20 in the 3' untranslated region was shown to increase α-synuclein expression. We examined the association of rs591323 with the risk of PD in a Taiwanese population and conducted a meta-analysis, including our study and two other studies from China, to further confirm the role of this SNP in Taiwanese/Chinese populations. A total of 586 patients with PD and 586 health controls (HCs) were included in our study. We found that the minor allele (A) and the AA + GA genotype under the dominant model are significantly less frequent in PD than in controls. The meta-analysis consisted of 1950 patients with PD and 2073 healthy controls from three studies. There was significant association between rs591323 and the risk of PD in the additive (Z = -3.96; p < 0.0001) and the dominant models (Z = -4.01; p < 0.0001). Our study results and the meta-analysis support the possible protective role of the rs591323 A allele in PD in Taiwanese/Chinese populations.

Parkinson's disease and pesticides: Are microRNAs the missing link?

Parkinson's disease (PD) is a common neurodegenerative disorder that leads to significant morbidity and decline in the quality of life. It develops due to loss of dopaminergic neurons in the substantia nigra pars compacta, and among its pathogenic factors oxidative stress plays a critical role in disease progression. Pesticides are a broad class of chemicals widely used in agriculture and households for the protection of crops from insects and fungi. Several of them have been incriminated as risk factors for PD, but the underlying mechanisms have yet to be fully understood. MicroRNAs (miRNAs) are small, non-coding RNA molecules that play an important role in regulating mRNA translation and protein synthesis. miRNA levels have been shown to be affected in several diseases as well. Since the studies on the association between pesticides and PD have yet to reach definitive conclusions, here we review recent evidence on deregulated microRNAs upon pesticide exposure, and attempt to find an overlap between miRNAs deregulated in PD and pesticides, as a missing link between the two, and enhance future research in this direction.

Identification of biomarkers associated with Parkinson's disease by gene expression profiling studies and bioinformatics analysis

Parkinson's disease (PD) is associated with a selective loss of the neurons in the midbrain area called the substantia nigra pars compacta and the loss of projecting nerve fibers in the striatum. Predominant pathological hallmarks of PD are the degeneration of discrete neuronal populations and progressive accumulation of α-synuclein-containing intracytoplasmic inclusions called Lewy bodies and dystrophic Lewy neuritis. There is currently no therapy to terminate or delay the neurodegenerative process as the exact mechanisms underlying the pathogenesis of PD require further investigation. The identification and validation of novel biomarkers for the diagnosis of PD is a great challenge using contemporary approaches and optimizing sampling handling as well as interpretation using bioinformatics analysis. In this review, recent evidences associated with multi-omic data-sets and molecular mechanisms underlying PD are examined. A combined mapping of several transcriptional evidences could establish a patient-specific signature for early diagnose of PD though eligible systems biology tools, which can also help develop effective drug-based therapeutic approaches.

Mechanisms by which fibroblast growth factor 20 improves motor performance in a mouse model of Parkinson's disease

Genome-wide studies have reported that Parkinson’s disease is associated with abnormal expression of various growth factors. In this study, male C57BL/6 mice aged 10 weeks were used to establish Parkinson’s disease models using an intraperitoneal injection of 60 mg/kg 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. 28 days later, 10 or 100 ng fibroblast growth factor 20 was injected intracerebroventricularly. The electrophysiological changes in the mouse hippocampus were recorded using a full-cell patch clamp. Expression of Kv4.2 in the substantia nigra was analyzed using a western blot assay. Serum malondialdehyde levels were analyzed by enzyme-linked immunosorbent assay. The motor coordination of mice was evaluated using the rotarod test. The results showed that fibroblast growth factor 20 decreased A-type potassium current in neurons of the substantia nigra, increased long-term potentiation amplitude in the hippocampus, and downregulated Kv4.2 expression. A high dose of fibroblast growth factor 20 reduced serum malondialdehyde levels and enhanced the motor coordination of mice. These findings confirm that fibroblast growth factor 20 has a therapeutic effect on the toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and its mechanism of action is associated with the inhibition of A-type K⁺ currents and Kv4.2 expression. All animal procedures were approved by the Animal Care and Use Committee of Qilu Hospital of Shandong University, China in 2017 (approval No. KYLL-2017-0012).

Effects of rs591323 on serotonin transporter availability in healthy male subjects

OBJECTIVES

We aimed to investigate the association between genetic factors of SNPs dopamine transporter (DAT) and serotonin transporter (SERT) availabilities in healthy controls.

METHODS

The study population consisted of healthy controls with screening ¹²³I-FP-CIT single-photon emission computed tomography. Specific binding of ¹²³I-FP-CIT regarding DAT and SERT was calculated using a region of interest analysis. VOI template was applied to measure specific binding ratios (SBRs) of caudate nucleus, putamen, striatum, midbrain, and pons.

RESULTS

One hundred sixty healthy controls (male 106, female 54, 61.0 ± 11.5 years) were included in this study. Sex difference did not exist in DAT availabilities of caudate nucleus (p = 0.5344), putamen (p = 0.5006), and striatum (p = 0.5056). However, male subjects had higher SERT availabilities of both midbrain (p = 0.0436), and pons (p = 0.0061). Therefore, we analyzed the effect of SNP on DAT availabilities of subjects in all, and that on SERT availabilities of males and females separately. None of 19 SNPs included in this study showed the effect on DAT availabilities. However, rs591323 in Fibroblast Growth Factor 20 on chromosome 8 had a significant impact on SERT availability of both midbrain (p = 0.0056) and pons (p = 0.0007).

CONCLUSION

SNP rs591323 of risk loci for Parkinson's disease is associated with SERT availability of healthy male subjects.

Pharmacokinetics, tissue distribution, and excretion of FGF-21 following subcutaneous administration in rats

As one of the fibroblast growth factor (FGF) superfamily, FGF-21 has been extensively investigated for its functions and roles since its discovery. It has been demonstrated to be one of the key regulators for glucose and lipid metabolism, and exhibits beneficial effects on cardiovascular disease. However, studies focusing on its pharmacokinetic behavior in vivo as a novel therapeutic agent have not been reported. In the present study, rapid and sensitive analytical approaches including radioactivity assay and assay after precipitation/separation by high performance liquid chromatography (HPLC) were established to determine the content of FGF-21 tagged with 125 I in plasma, tissue, and excrement. The results indicated that FGF-21 were quickly absorbed into systematic circulation and slowly eliminated; Cmax and exposure increased in a dose-dependent manner, exhibiting a typical linear pharmacokinetic pattern. Tissue distribution also confirmed that the kidney is the primary organ for FGF-21 to be distributed, even though radioactivity of FGF-21 was recovered in all tissues examined. In addition, the results also supported that urinary excretion was the critical route for FGF-21 to be eliminated. The study fully clarifies the pharmacokinetic behavior of FGF-21 and can provide valuable information and support further safety and toxicology development.

The potential role of neuroinflammation and transcription factors in Parkinson disease

Parkinson disease (PD) is a neurodegenerative disorder characterized by dopaminergic neurons affected by inflammatory processes. Post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines, confirming an ongoing neuroinflammation in the affected brain regions. These inflammatory mediators may activate transcription factors—notably nuclear factor κB, Ying-Yang 1 (YY1), fibroblast growth factor 20 (FGF20), and mammalian target of rapamycin (mTOR)—which then regulate downstream signaling pathways that in turn promote death of dopaminergic neurons through death domain-containing receptors. Dopaminergic neurons are vulnerable to oxidative stress and inflammatory attack. An increased level of inducible nitric oxide synthase observed in the substantia nigra and striatum of PD patients suggests that both cytokine—and chemokine-induced toxicity and inflammation lead to oxidative stress that contributes to degeneration of dopaminergic neurons and to disease progression. Lipopolysaccharide activation of microglia in the proximity of dopaminergic neurons in the substantia nigra causes their degeneration, and this appears to be a selective vulnerability of dopaminergic neurons to inflammation. In this review, we will look at the role of various transcription factors and signaling pathways in the development of PD.

The yin and yang of α-synuclein-associated epigenetics in Parkinson's disease

Parkinson's disease is the second most prevalent neurodegenerative disorder. The main neuropathological hallmarks of the disease are the degeneration of dopaminergic neurons in the substantia nigra pars compacta and the accumulation of protein inclusions known as Lewy bodies. Recently, great attention has been given to the study of genes associated with both familial and sporadic forms of Parkinson's disease. Among them, the α-synuclein gene is believed to play a central role in the disease and is, therefore, one of the most studied genes. Parkinson's disease is a complex disorder and, as such, derives from the interaction between genetic and environmental factors. Here, we offer an update on the landscape of epigenetic-mediated regulation of gene expression that has been linked with α-synuclein and associated with Parkinson's disease. We also provide an overview of how epigenetic modifications can influence the transcription and/or translation of the α-synuclein gene and, on the other hand, how α-synuclein function/dysfunction can, per se, affect the epigenetic landscape. Finally, we discuss how a deeper understanding of the epigenetic profile of α-synuclein may enable the development of novel therapeutic approaches for Parkinson's disease and other synucleinopathies.

Metabolic role of fibroblast growth factor 21 in liver, adipose and nervous system tissues

The hepatokine fibroblast growth factor 21 (FGF21) is a novel polypeptide ligand, which is involved in glucose and lipid metabolism, and contributes significantly to lowering body weight and enhancing insulin sensitivity. A large number of pre-clinical and clinical results demonstrate that FGF21 is a potential drug target for treating obesity and type 2 diabetes mellitus. In the present review, the tissue specific actions and molecular mechanisms of FGF21 are discussed with a focus on the liver, adipose tissue and nervous system, as well as investigating the outcomes of clinical trials of FGF21, with the aim of interpreting and delineating the complexity physiology of FGF21.

Role of microRNAs in the Regulation of α-Synuclein Expression: A Systematic Review

Growing evidence suggests that increased levels of α-synuclein might contribute to the pathogenesis of Parkinson’s disease (PD) and therefore, it is crucial to understand the mechanisms underlying α-synuclein expression. Recently, microRNAs (miRNAs) have emerged as key regulators of gene expression involved in several diseases such as PD and other neurodegenerative disorders. A systematic literature search was performed here to identify microRNAs that directly or indirectly impact in α-synuclein expression/accumulation and describe its mechanism of action. A total of 27 studies were incorporated in the review article showing evidences that six microRNAs directly bind and regulate α-synuclein expression while several miRNAs impact on α-synuclein expression indirectly by targeting other genes. In turn, α-synuclein overexpression also impacts miRNAs expression, indicating the complex network between miRNAs and α-synuclein. From the current knowledge on the central role of α-synuclein in PD pathogenesis/progression, miRNAs are likely to play a crucial role at different stages of PD and might potentially be considered as new PD therapeutic approaches.

Dysregulated fibroblast growth factor (FGF) signaling in neurological and psychiatric disorders

The role of the fibroblast growth factor (FGF) system in brain-related disorders has received considerable attention in recent years. To understand the role of this system in neurological and psychiatric disorders, it is important to identify the specific members of the FGF family that are implicated, their location and the various mechanisms they can be modulated. Each disorder appears to impact specific molecular players in unique anatomical locations, and all of these could conceivably become targets for treatment. In the last several years, the issue of how to target this system directly has become an area of increasing interest. To date, the most promising therapeutics are small molecule inhibitors and antibodies that modulate FGF receptor (FGFR) function. Beyond attempting to modify the primary players affected by a given brain disorder, it may prove useful to target molecules, such as membrane-bound or extracellular proteins that interact with FGF ligands or FGFRs to modulate signaling.

Current disease modifying approaches to treat Parkinson's disease

Parkinson's disease (PD is a progressive neurological disorder characterized by the degeneration and death of midbrain dopamine and non-dopamine neurons in the brain leading to motor dysfunctions and other symptoms, which seriously influence the quality of life of PD patients. The drug L-dopa can alleviate the motor symptoms in PD, but so far there are no rational therapies targeting the underlying neurodegenerative processes. Despite intensive research, the molecular mechanisms causing neuronal loss are not fully understood which has hampered the development of new drugs and disease-modifying therapies. Neurotrophic factors are by virtue of their survival promoting activities attract candidates to counteract and possibly halt cell degeneration in PD. In particular, studies employing glial cell line-derived neurotrophic factor (GDNF) and its family member neurturin (NRTN), as well as the recently described cerebral dopamine neurotrophic factor (CDNF) and the mesencephalic astrocyte-derived neurotrophic factor (MANF) have shown positive results in protecting and repairing dopaminergic neurons in various models of PD. Other substances with trophic actions in dopaminergic neurons include neuropeptides and small compounds that target different pathways impaired in PD, such as increased cell stress, protein handling defects, dysfunctional mitochondria and neuroinflammation. In this review, we will highlight the recent developments in this field with a focus on trophic factors and substances having the potential to beneficially influence the viability and functions of dopaminergic neurons as shown in preclinical or in animal models of PD.

Genetic analysis of FGF20 variants in Chinese Han patients with essential tremor

Essential tremor (ET) is one of the most frequent neurological disorders with elusive etiology, typically characterized by postural and kinetic tremors. Evidence reveals that genetic components are implicated in the development of ET and there are some overlaps between ET and Parkinson's disease in clinical features and etiology. Variants in the fibroblast growth factor 20 gene (FGF20) have been reported to be associated with the risk of Parkinson's disease. To evaluate the association between the FGF20 gene variants and ET susceptibility, we conducted genetic analysis of five FGF20 variants (rs1721100, rs1989754, rs10089600, rs12720208, and rs17550360) in 200 patients with ET and 426 ethnically-matched Chinese Han normal controls. Statistical analysis did not identify significant differences in genotypic or allelic frequencies of variants between ET patients and normal controls (all P>0.05). No related haplotype was found to be related to the risk of ET. The findings indicate the FGF20 gene might not play a dominating role in the genetic predisposition to ET in Chinese Han population.

High production in E. coli of biologically active recombinant human fibroblast growth factor 20 and its neuroprotective effects

Fibroblast growth factor 20 (FGF20) has a wide range of biological activities; its expression is most pronounced in neural tissues where it has functions in development and neuroprotection. Given these activities, interest in the clinical applications of FGF20 is rising, which will lead to increasing demand for active recombinant human FGF20 (rhFGF20). To improve the production of rhFGF20, an artificial gene encoding fgf20 was cloned into pET3a and expressed in E. coli BL21(DE3)pLysS. By optimizing induction conditions, we successfully induced large amounts of insoluble rhFGF20. Following solubilization and refolding of the rhFGF20 from inclusion bodies, it was purified by HiTrap heparin affinity chromatography to a purity of over 96% with a yield of 218 mg rhFGF20/100 g wet cells. The purified rhFGF20 could stimulate proliferation of both NIH 3T3 cells and PC-12 cells, measured by the MTT assay. In a model of Aβ25-35-induced apoptosis on PC-12 cells, rhFGF20 had a clear protective effect. RT-PCR and Western blot analysis of apoptosis-related genes and proteins revealed that the FGF20-derived protective mechanism was likely due to the relief of endoplasmic reticulum stress (ER stress). In conclusion, the approach described here may be a better means to produce active rhFGF20 in good quantity, thereby allowing for its future pharmacological and clinical use.

New suggestive genetic loci and biological pathways for attention function in adult attention-deficit/hyperactivity disorder

Attention deficit is one of the core symptoms of the attention-deficit/hyperactivity disorder (ADHD). However, the specific genetic variants that may be associated with attention function in adult ADHD remain largely unknown. The present study aimed to identifying SNPs associated with attention function in adult ADHD and tested whether these associations were enriched for specific biological pathways. Commissions, hit-reaction time (HRT), the standard error of HRT (HRTSE), and intraindividual coefficient variability (ICV) of the Conners Continuous Performance Test (CPT-II) were assessed in 479 unmedicated adult ADHD individuals. A Genome-Wide Association Study (GWAS) was conducted for each outcome and, subsequently, gene set enrichment analyses were performed. Although no SNPs reached genome-wide significance (P < 5E-08), 27 loci showed suggestive evidence of association with the CPT outcomes (P < E-05). The most relevant associated SNP was located in the SORCS2 gene (P = 3.65E-07), previously associated with bipolar disorder (BP), Alzheimer disease (AD), and brain structure in elderly individuals. We detected other genes suggested to be involved in synaptic plasticity, cognitive function, neurological and neuropsychiatric disorders, and smoking behavior such as NUAK1, FGF20, NETO1, BTBD9, DLG2, TOP3B, and CHRNB4. Also, several of the pathways nominally associated with the CPT outcomes are relevant for ADHD such as the ubiquitin proteasome, neurodegenerative disorders, axon guidance, and AD amyloid secretase pathways. To our knowledge, this is the first GWAS and pathway analysis of attention function in patients with persistent ADHD. Overall, our findings reinforce the conceptualization of attention function as a potential endophenotype for studying the molecular basis of adult ADHD. © 2015 Wiley Periodicals, Inc.

The Fibroblast Growth Factor signaling pathway

The signaling component of the mammalian Fibroblast Growth Factor (FGF) family is comprised of eighteen secreted proteins that interact with four signaling tyrosine kinase FGF receptors (FGFRs). Interaction of FGF ligands with their signaling receptors is regulated by protein or proteoglycan cofactors and by extracellular binding proteins. Activated FGFRs phosphorylate specific tyrosine residues that mediate interaction with cytosolic adaptor proteins and the RAS-MAPK, PI3K-AKT, PLCγ, and STAT intracellular signaling pathways. Four structurally related intracellular non-signaling FGFs interact with and regulate the family of voltage gated sodium channels. Members of the FGF family function in the earliest stages of embryonic development and during organogenesis to maintain progenitor cells and mediate their growth, differentiation, survival, and patterning. FGFs also have roles in adult tissues where they mediate metabolic functions, tissue repair, and regeneration, often by reactivating developmental signaling pathways. Consistent with the presence of FGFs in almost all tissues and organs, aberrant activity of the pathway is associated with developmental defects that disrupt organogenesis, impair the response to injury, and result in metabolic disorders, and cancer. For further resources related to this article, please visit the WIREs website.

An evidence-based approach to identify aging-related genes in Caenorhabditis elegans

Background

Extensive studies have been carried out on Caenorhabditis elegans as a model organism to elucidate mechanisms of aging and the effects of perturbing known aging-related genes on lifespan and behavior. This research has generated large amounts of experimental data that is increasingly difficult to integrate and analyze with existing databases and domain knowledge. To address this challenge, we demonstrate a scalable and effective approach for automatic evidence gathering and evaluation that leverages existing experimental data and literature-curated facts to identify genes involved in aging and lifespan regulation in C. elegans.

Results

We developed a semantic knowledge base for aging by integrating data about C. elegans genes from WormBase with data about 2005 human and model organism genes from GenAge and 149 genes from GenDR, and with the Bio2RDF network of linked data for the life sciences. Using HyQue (a Semantic Web tool for hypothesis-based querying and evaluation) to interrogate this knowledge base, we examined 48,231 C. elegans genes for their role in modulating lifespan and aging. HyQue identified 24 novel but well-supported candidate aging-related genes for further experimental validation.

Conclusions

We use semantic technologies to discover candidate aging genes whose effects on lifespan are not yet well understood. Our customized HyQue system, the aging research knowledge base it operates over, and HyQue evaluations of all C. elegans genes are freely available at http://hyque.semanticscience.org.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0469-4) contains supplementary material, which is available to authorized users.

Genetic analysis implicates APOE, SNCA and suggests lysosomal dysfunction in the etiology of dementia with Lewy bodies

Clinical and neuropathological similarities between dementia with Lewy bodies (DLB), Parkinson's and Alzheimer's diseases (PD and AD, respectively) suggest that these disorders may share etiology. To test this hypothesis, we have performed an association study of 54 genomic regions, previously implicated in PD or AD, in a large cohort of DLB cases and controls. The cohort comprised 788 DLB cases and 2624 controls. To minimize the issue of potential misdiagnosis, we have also performed the analysis including only neuropathologically proven DLB cases (667 cases). The results show that the APOE is a strong genetic risk factor for DLB, confirming previous findings, and that the SNCA and SCARB2 loci are also associated after a study-wise Bonferroni correction, although these have a different association profile than the associations reported for the same loci in PD. We have previously shown that the p.N370S variant in GBA is associated with DLB, which, together with the findings at the SCARB2 locus, suggests a role for lysosomal dysfunction in this disease. These results indicate that DLB has a unique genetic risk profile when compared with the two most common neurodegenerative diseases and that the lysosome may play an important role in the etiology of this disorder. We make all these data available.

Large-scale meta-analysis of genome-wide association data identifies six new risk loci for Parkinson's disease

We conducted a meta-analysis of Parkinson's disease genome-wide association studies using a common set of 7,893,274 variants across 13,708 cases and 95,282 controls. Twenty-six loci were identified as having genome-wide significant association; these and 6 additional previously reported loci were then tested in an independent set of 5,353 cases and 5,551 controls. Of the 32 tested SNPs, 24 replicated, including 6 newly identified loci. Conditional analyses within loci showed that four loci, including GBA, GAK-DGKQ, SNCA and the HLA region, contain a secondary independent risk variant. In total, we identified and replicated 28 independent risk variants for Parkinson's disease across 24 loci. Although the effect of each individual locus was small, risk profile analysis showed substantial cumulative risk in a comparison of the highest and lowest quintiles of genetic risk (odds ratio (OR) = 3.31, 95% confidence interval (CI) = 2.55-4.30; P = 2 × 10(-16)). We also show six risk loci associated with proximal gene expression or DNA methylation.

Quantitative assessment of the association between fibroblast growth factor 20 rs1721100 C/G polymorphism and the risk of sporadic Parkinson's diseases: a meta-analysis

Fibroblast growth factor 20 (FGF20) is a neurotrophic factor which enhances the survival of rat midbrain dopamine neurons. Genetic variation in FGF20 may influence the risk of occurrence and development in Parkinson's diseases (PD). Many studies have evaluated the association between FGF20 rs1721100 C/G polymorphism and the risk of sporadic PD; however, published data are still controversial. The aim of the present meta-analysis was to evaluate the association of FGF20 rs1721100 C/G polymorphism with susceptibility of PD. The summary odds ratio (OR) with its 95 % confidence interval (CI) was calculated to estimate the association. Five case-control studies with a total of 3,463 sporadic PD cases and 4,606 controls were finally included into this meta-analysis. Neither the basic allele frequencies nor the genotypic distributions of rs1721100 C/G within FGF20 were different between two groups when all studies were pooled into the meta-analysis. Subgroup analysis by ethnicity showed FGF20 rs1721100 C/G polymorphism was significantly associated with increased risk in the heterozygote comparison model (CG versus GG: OR = 0.83, 95 % CI, 0.72-0.95, P = 0.009) in Asians but not in Caucasians. Overall, this meta-analysis suggests that FGF20 rs1721100 C/G polymorphism is associated with sporadic PD in Asians.

Association studies of sporadic Parkinson's disease in the genomic era

Parkinson's disease is a common age-related progressive neurodegenerative disorder. Over the last 10 years, advances have been made in our understanding of the etiology of the disease with the greatest insights perhaps coming from genetic studies, including genome-wide association approaches. These large scale studies allow the identification of genomic regions harboring common variants associated to disease risk. Since the first genome-wide association study on sporadic Parkinson's disease performed in 2005, improvements in study design, including the advent of meta-analyses, have allowed the identification of ~21 susceptibility loci. The first loci to be nominated were previously associated to familial PD (SNCA, MAPT, LRRK2) and these have been extensively replicated. For other more recently identified loci (SREBF1, SCARB2, RIT2) independent replication is still warranted. Cumulative risk estimates of associated variants suggest that more loci are still to be discovered. Additional association studies combined with deep re-sequencing of known genome-wide association study loci are necessary to identify the functional variants that drive disease risk. As each of these associated genes and variants are identified they will give insight into the biological pathways involved the etiology of Parkinson's disease. This will ultimately lead to the identification of molecules that can be used as biomarkers for diagnosis and as targets for the development of better, personalized treatment.

The best-laid plans go oft awry: synaptogenic growth factor signaling in neuropsychiatric disease

Growth factors play important roles in synapse formation. Mouse models of neuropsychiatric diseases suggest that defects in synaptogenic growth factors, their receptors, and signaling pathways can lead to disordered neural development and various behavioral phenotypes, including anxiety, memory problems, and social deficits. Genetic association studies in humans have found evidence for similar relationships between growth factor signaling pathways and neuropsychiatric phenotypes. Accumulating data suggest that dysfunction in neuronal circuitry, caused by defects in growth factor-mediated synapse formation, contributes to the susceptibility to multiple neuropsychiatric diseases, including epilepsy, autism, and disorders of thought and mood (e.g., schizophrenia and bipolar disorder, respectively). In this review, we will focus on how specific synaptogenic growth factors and their downstream signaling pathways might be involved in the development of neuropsychiatric diseases.

Inventing new medicines: The FGF21 story

Since the discovery of insulin in 1921, protein therapeutics have become vital tools in the treatment of diabetes mellitus. This heritage has been extended with the comparatively recent introduction of recombinant and re-engineered insulins, in addition to the advent of GLP1 agonists. FGF21 represents an example of a novel experimental protein therapy which is able to induce favorable metabolic effects in various species ranging from rodents to man.

The aim of this review is to communicate the story of the FGF21 drug discovery path from identification in a functional in vitro screen, to the eventual evaluation of its utility in patients. Given that the development of FGF21 advanced hand-in-hand with rapidly evolving scientific research around this target, we have also attempted to describe our view of recent developments regarding the mechanistic understanding of FGF21 biology.

Deficiency of zebrafish fgf20a results in aberrant skull remodeling that mimics both human cranial disease and evolutionarily important fish skull morphologies

The processes that direct skull remodeling are of interest to both human-oriented studies of cranial dysplasia and evolutionary studies of skull divergence. There is increasing awareness that these two fields can be mutually informative when natural variation mimics pathology. Here we describe a zebrafish mutant line, devoid of blastema (dob), which does not have a functional fgf20a protein, and which also presents cranial defects similar to both adaptive and clinical variation. We used geometric morphometric methods to provide quantitative descriptions of the effects of the dob mutation on skull morphogenesis. In combination with "whole-mount in situ hybridization" labeling of normal fgf20a expression and assays for osteoblast and osteoclast activity, the results of these analyses indicate that cranial dysmorphologies in dob zebrafish are generated by aberrations in post-embryonic skull remodeling via decreased osteoblasotgenesis and increased osteoclastogenesis. Mutational effects include altered skull vault geometries and midfacial hypoplasia that are consistent with key diagnostic signs for multiple human craniofacial syndromes. These phenotypic shifts also mimic changes in the functional morphology of fish skulls that have arisen repeatedly in several highly successful radiations (e.g., damselfishes and East-African rift-lake cichlids). Our results offer the dob/fgf20a mutant as an experimentally tractable model with which to examine post-embryonic skull development as it relates to human disease and vertebrate evolution.

Advances with microRNAs in Parkinson's disease research

Parkinson's disease (PD) is the second-most common age-dependent neurodegenerative disorder and is caused by severe degeneration of dopaminergic neurons in the substantia nigra pars compacta. Unfortunately, current treatment only targets symptoms and involves dopamine replacement therapy, which does not counteract progressive degeneration. MicroRNAs (miRNAs) are a class of small RNA molecules implicated in post-transcriptional regulation of gene expression during development. Recent studies show that miRNAs are playing an important role in the pathophysiology of PD. miRNA-based therapy is a powerful tool with which to study gene function, investigate the mechanism of the disease, and validate drug targets. In this review, we focus on the recent advances of the use of miRNAs in the pathogenesis of PD.

Polymorphisms affecting miRNA regulation: a new level of genetic variation affecting disorders and diseases of the human CNS

The recognition of people and/or populations at a high risk for the development of various types of neurological disorders and diseases is not only key to improved screening programs and earlier detection, but it also provides hope for appropriate treatment and care. Genetic alterations that change gene-expression levels have long been investigated for association with the development of pathological neurological conditions. Gene regulation by miRNAs is a relatively new area of study, and published evidence suggests that alterations in this process may be associated with increased disease risk. Here, the authors review the current data for association between single nucleotide polymorphisms (SNPs) and miRNA-mediated gene regulation (miR-SNPs) in human neuropsychiatric and neurodegenerative diseases. Additionally, we present an approach to detect and identify functional miR-SNPs for the purpose of carrying out large-scale genetic association studies. The growing body of literature suggests that miR-SNPs are emerging as a powerful tool, both to study the pathobiology of diseases, as well as aiding in its diagnosis and prognosis.

Roles of FGF20 in dopaminergic neurons and Parkinson's disease

The fibroblast growth factor (FGF) family comprises 22 members with diverse functions in development and metabolism. Fgf20 was originally identified as a new Fgf preferentially expressed in the substantia nigra pars compacta (SNpc). Fgf20, which acts on proximal cells, significantly enhanced the survival of cultured dopaminergic neurons by activating the mitogen-activated protein kinase (MAPK) pathway through Fgf receptor 1c. In the rat model of Parkinson's disease, Fgf20 afforded significant protection against the loss of dopaminergic neurons. The significant correlation of Parkinson's disease with single-nucleotide polymorphisms in FGF20 indicates that the genetic variability of FGF20 can be a Parkinson's disease risk. Neural and embryonic stem (ES) cells have been considered as cell resources for restorative transplantation strategies in Parkinson's disease. Fgf20 promoted the differentiation of these stem cells into dopaminergic neurons, which attenuated neurological symptoms in animal models of Parkinson's disease. These findings indicate the importance of FGF20 for the differentiation and survival of dopaminergic neurons and the etiology and therapy of Parkinson's disease.

The genetics of Parkinson's disease: progress and therapeutic implications

The past 15 years has witnessed tremendous progress in our understanding of the genetic basis for Parkinson's disease (PD). Notably, whereas most mutations, such as those in SNCA, PINK1, PARK2, PARK7, PLA2G6, FBXO7, and ATP13A2, are a rare cause of disease, one particular mutation in LRRK2 has been found to be common in certain populations. There has been considerable progress in finding risk loci. To date, approximately 16 such loci exist; notably, some of these overlap with the genes known to contain disease-causing mutations. The identification of risk alleles has relied mostly on the application of revolutionary technologies; likewise, second-generation sequencing methods have facilitated the identification of new mutations in PD. These methods will continue to provide novel insights into PD. The utility of genetics in therapeutics relies primarily on leveraging findings to understand the pathogenesis of PD. Much of the investigation into the biology underlying PD has used these findings to define a pathway, or pathways, to pathogenesis by trying to fit disparate genetic defects onto the same network. This work has had some success, particularly in the context of monogenic disease, and is beginning to provide clues about potential therapeutic targets. Approaches toward therapies are also being provided more directly by genetics, notably by the reduction and clearance of alpha-synuclein and inhibition of Lrrk2 kinase activity. We believe this has been an exciting, productive time for PD genetics and, furthermore, that genetics will continue to drive the etiologic understanding and etiology-based therapeutic approaches in this disease.

Fibroblast growth factor-20 protects against dopamine neuron loss in vitro and provides functional protection in the 6-hydroxydopamine-lesioned rat model of Parkinson's disease

Fibroblast growth factor-20 (FGF-20) has been shown to protect dopaminergic neurons against a range of toxic insults in vitro, through activation of fibroblast growth factor receptor 1 (FGFR1). This study set out to examine whether FGF-20 also displayed protective efficacy in the unilateral, 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease. Initial studies demonstrated that, in embryonic ventral mesencephalic (VM) cultures, FGFR1 was expressed on tyrosine hydroxylase (TH)-positive neurons and that, in line with previous data, FGF-20 (100 and 500 ng/ml) almost completely protected these TH-positive neurons against 6-OHDA-induced toxicity. Co-localisation of FGFR1 and TH staining was also demonstrated in the substantia nigra pars compacta (SNpc) of naïve adult rat brain. In animals subject to 6-OHDA lesion of the nigrostriatal tract, supra-nigral infusion of FGF-20 (2.5 μg/day) for 6 days post-lesion gave significant protection (∼40%) against the loss of TH-positive cells in the SNpc and the loss of striatal TH immunoreactivity. This protection of the nigrostriatal tract was accompanied by a significant preservation of gross locomotion and fine motor movements and reversal of apomorphine-induced contraversive rotations, although forelimb akinesia, assessed using cylinder test reaching, was not improved. These results support a role for FGF-20 in preserving dopamine neuron integrity and some aspects of motor function in a rodent model of Parkinson's disease (PD) and imply a potential neuroprotective role for FGF-20 in this disease.

Genome-wide SNP scan of pooled DNA reveals nonsense mutation in FGF20 in the scaleless line of featherless chickens

Background

Scaleless (sc/sc) chickens carry a single recessive mutation that causes a lack of almost all body feathers, as well as foot scales and spurs, due to a failure of skin patterning during embryogenesis. This spontaneous mutant line, first described in the 1950s, has been used extensively to explore the tissue interactions involved in ectodermal appendage formation in embryonic skin. Moreover, the trait is potentially useful in tropical agriculture due to the ability of featherless chickens to tolerate heat, which is at present a major constraint to efficient poultry meat production in hot climates. In the interests of enhancing our understanding of feather placode development, and to provide the poultry industry with a strategy to breed heat-tolerant meat-type chickens (broilers), we mapped and identified the sc mutation.

Results

Through a cost-effective and labour-efficient SNP array mapping approach using DNA from sc/sc and sc/+ blood sample pools, we map the sc trait to chromosome 4 and show that a nonsense mutation in FGF20 is completely associated with the sc/sc phenotype. This mutation, common to all sc/sc individuals and absent from wild type, is predicted to lead to loss of a highly conserved region of the FGF20 protein important for FGF signalling. In situ hybridisation and quantitative RT-PCR studies reveal that FGF20 is epidermally expressed during the early stages of feather placode patterning. In addition, we describe a dCAPS genotyping assay based on the mutation, developed to facilitate discrimination between wild type and sc alleles.

Conclusions

This work represents the first loss of function genetic evidence supporting a role for FGF ligand signalling in feather development, and suggests FGF20 as a novel central player in the development of vertebrate skin appendages, including hair follicles and exocrine glands. In addition, this is to our knowledge the first report describing the use of the chicken SNP array to map genes based on genotyping of DNA samples from pooled whole blood. The identification of the sc mutation has important implications for the future breeding of this potentially useful trait for the poultry industry, and our genotyping assay can facilitate its rapid introgression into production lines.