Identification and functional characterisation of a novel dopamine beta hydroxylase gene variant associated with attention deficit hyperactivity disorder

Genomic profile of Parkinson's disease in Asians

Parkinson's Disease (PD) has witnessed an alarming rise in prevalence, highlighting the suboptimal nature of early diagnostic and therapeutic strategies. To address this issue, genetic testing has emerged as a potential avenue. In this comprehensive review, we have meticulously summarized the variants associated with PD in Asian populations. Our review reveals that these variants exert their influence on diverse biological pathways, encompassing the autophagy-lysosome pathway, cholesterol metabolism, circadian rhythm regulation, immune system response, and synaptic function. Conventionally, PD has been linked to other diseases; however, our findings shed light on a shared genetic susceptibility among these conditions, implying an underlying pathophysiological mechanism that unifies them. Moreover, it is noteworthy that these PD-associated variants can significantly impact drug responses during therapeutic interventions. This review not only provides a consolidated overview of the genetic variants associated with PD in Asian populations but also contributes novel insights into the intricate relationships between PD and other diseases by elucidating shared genetic components. These findings underscore the importance of personalized approaches in diagnosing and treating PD based on individual genetic profiles to optimize patient outcomes.

Multifactor Dimensionality Reduction Analysis to Evaluate the Association of Dopamine Beta-Hydroxylase (DΒH) Polymorphisms with Susceptibility to Dementia (SADEM Study)

Dementia is a multifactorial disease in which environmental, lifestyle, and genetic factors intervene. Population studies have been used in looking for the susceptibility genes for this disease. Since the activity of dopamine b hydroxylase (DβH) is reduced in the hippocampus and neocortex in the brain, changes in the physiological status of dopamine have been reported in Alzheimer's disease (AD) induced by this enzyme. Therefore, DBH polymorphisms have been associated with susceptibility to some neurological diseases such as AD, but few studies have investigated the relationship between these polymorphisms with other types of dementia, especially in Mexican populations. The aim of this study was to evaluate the association between single-nucleotide polymorphism (SNP) in the dopamine b-hydroxylase (DBH gene (rs1611115) and their interactions with environmental factors and the dementia risk. We examined the genotype of the gene DBH (rs1611115) polymorphism in patients with dementia and healthy. The interaction and the impact of DBH (rs1611115) polymorphism on dementia were examined through multifactor dimensionality reduction (MDR) analysis, and the results were verified by the Chi-square test. Hardy-Weinberg equilibrium (HWE) was also checked by the Chi-square test. The relative risk was expressed by odds ratio (OR) and 95%. A total of 221 dementia patients and 534 controls met the inclusion criteria of MDR analyses. The results of the MDR analysis showed that the development of dementia was positively correlated with interaction between the TT genotype of the DBH1 locus rs1611115 TT and diabetes, hypertension, and alcohol consumption (OR = 6.5: 95% CI = 4.5-9.5), originating further cognitive damage. These findings provide insight into the positive correlation between the metabolism and cardiovascular disorders and the presence of the T allele by means of a recessive model of DBH rs1611115 polymorphism with the suspensibility of dementia.

Catecholaminergic and cholinergic neuromodulation in autism spectrum disorder: A comparison to attention-deficit hyperactivity disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by social impairments and restricted, repetitive behaviors. Treatment of ASD is notoriously difficult and might benefit from identification of underlying mechanisms that overlap with those disturbed in other developmental disorders, for which treatment options are more obvious. One example of the latter is attention-deficit hyperactivity disorder (ADHD), given the efficacy of especially stimulants in treatment of ADHD. Deficiencies in catecholaminergic systems [dopamine (DA), norepinephrine (NE)] in ADHD are obvious targets for stimulant treatment. Recent findings suggest that dysfunction in catecholaminergic systems may also be a factor in at least a subgroup of ASD. In this review we scrutinize the evidence for catecholaminergic mechanisms underlying ASD symptoms, and also include in this analysis a third classic ascending arousing system, the acetylcholinergic (ACh) network. We complement this with a comprehensive review of DA-, NE-, and ACh-targeted interventions in ASD, and an exploratory search for potential treatment-response predictors (biomarkers) in ASD, genetically or otherwise. Based on this review and analysis we propose that (1) stimulant treatment may be a viable option for an ASD subcategory, possibly defined by genetic subtyping; (2) cerebellar dysfunction is pronounced for a relatively small ADHD subgroup but much more common in ASD and in both cases may point toward NE- or ACh-directed intervention; (3) deficiency of the cortical salience network is sizable in subgroups of both disorders, and biomarkers such as eye blink rate and pupillometric data may predict the efficacy of targeting this underlying deficiency via DA, NE, or ACh in both ASD and ADHD.

Noradrenergic genes polymorphisms and response to methylphenidate in children with ADHD: A systematic review and meta-analysis

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder, and methylphenidate (MPH) is considered one of the first-line medicine for ADHD. Unfortunately, this medication is only effective for some children with ADHD. This meta-analysis was conducted to evaluate whether noradrenergic gene polymorphisms impact the efficacy of MPH in children with ADHD.

METHODS

Candidate gene studies published in English until March 1, 2020, were identified through literature searches on PubMed, Web of Science, and Embase. Data were pooled from individual clinical trials considering MPH pharmacogenomics. According to the heterogeneity, the odds ratio and mean differences were calculated by applying fixed-effects or random-effects models.

RESULTS

This meta-analysis includes 15 studies and 1382 patients. Four polymorphisms of the NET gene (rs5569, rs28386840, rs2242446, rs3785143) and 2 polymorphisms of the α2A-adrenergic receptor gene (ADRA2A) gene (MspI and DraI) were selected for the analysis. In the pooled data from all studies, T allele carriers of the rs28386840 polymorphism were significantly more likely to respond to MPH (P < .001, ORTcarriers = 2.051, 95% confidence interval [CI]:1.316, 3.197) and showed a relationship with significantly greater hyperactive-impulsive symptoms improvement (P < .001, mean difference:1.70, 95% CI:0.24, 3.16). None of the ADRA2A polymorphisms correlated significantly with MPH response as a whole. However, G allele carriers of the MspI polymorphism showed a relationship with significantly inattention symptoms improvement (P < .001, mean difference:0.31, 95% CI: 0.15, 0.47).

CONCLUSION

Our meta-analysis results indicate that the noradrenergic gene polymorphisms may impact MPH response. The NET rs28386840 is linked to improved MPH response in ADHD children. And the ADRA2A MspI is associated with inattention symptom improvements. Further investigations with larger samples will be needed to confirm these results.Registration: PROSPERO (no. CRD42021265830).

Panel-based targeted exome sequencing reveals novel candidate susceptibility loci for age-related cataracts in Chinese Cohort

BACKGROUND

Age-related cataracts (ARC) is the most common blinding eye disease worldwide, and its incidence tend to become younger. However, the relationship between genetic factors and mechanisms is not fully understood. The aim of the study was to further clarify the relationship between ARC and genetic mechanisms in East Asian populations and to elucidate the pathogenesis.

METHODS

The study collected 191 sporadic cataracts and 208 healthy people from the eastern provinces of China, with an average age of about 60 years. All participants were subjected to a comprehensive ophthalmic clinical examination and peripheral blood samples were collected and their genomic DNA was extracted. Mutations were screened among 792 candidate genes to enhance understanding of the disease through targeted capture and high-throughput sequencing.

RESULTS

We identified novel candidate susceptibility gene, which may serve as a potential susceptibility factor leading to an increase in the incidence of age-related cataracts. Three novel loci are associated with age-related cataracts significant significance: rs129882 in DBH (p = 5.27E-07, odds ratio = 3.9), rs1800280 in DMD (p = 2.85E-06, odds ratio = 1.4) and rs2871776 in ATP13A2 (p = 4.18E-05, odds ratio = 0.04). Gene-gene interaction analysis revealed that the most significant interactions between genes include the interaction between DBH and TUB (rs17847537 in TUB, rs129882 in DBH, p-value = 2.12E-14), and the interaction between DBH and DMD (rs1800280 in DMD, rs129882 in DBH, p-value = 2.12E-14). Pathway analysis shows that the most significant processes are concentrated in response to light stimulation (adjusted p-Value = 5.56E-03), response to radiation (adjusted P-Value = 5.56E-03), abiotic stimulus (adjusted p-Value = 5.56E-03). eQTL analysis shows that DBH rs129882 could regulate the expression of DBH mRNA in various tissues including retina.

CONCLUSION

Our study indicates rs129882 and rs1800280 loci are associated with age-related cataracts, which enlarge the gene map of age-related cataracts.

Dopamine β hydroxylase (DBH) polymorphisms do not contribute towards the clinical course of Wilson's disease in Indian patients

BACKGROUND

Wilson's disease (WD) is a rare copper metabolism disorder with hepatic and neurological symptoms. Dopamine β hydroxylase (DBH) encodes a copper-dependent mono-oxygenase that converts dopamine to norepinephrine, thereby regulating the endogenous dopamine content in the neurons. Polymorphisms of DBH have been reported to be associated with several neurological diseases, such as Parkinson's disease, Alzheimer's disease, schizophrenia and attention-deficit hyperactivity disorder, which have overlapping neurological symptoms with WD. The present study aimed to assess the role of DBH polymorphisms on the clinical course of WD.

METHODS

In total, 141 WD patients from India were included in the present study. Three polymorphisms of DBH (rs1611115 in the promoter, rs1108580 in exon 2 and rs129882 in 3'-UTR) were screened for their association with the clinical attributes (hepatic and neurological features) and age of onset of WD using a polymerase chain reaction-restriction fragment length polymorphsm method and sequencing approach. The distribution of genotype or allele frequencies was tested using 2 × 2 contingency chi-squared and logistic regression analysis (additive, dominant and recessive model).

RESULTS

The genotypic and allelic frequencies of these single nucleotide polymophisms did not vary significantly along with the clinical symptoms (hepatic and neurological) or the age of onset of WD. No significant association was observed when we analyzed our samples with respect to harboring different kinds of ATP7B mutations (nonsense/in-del and missense).

CONCLUSIONS

The data obtained in the present study suggest that the selected DBH variants are unlikely to have any significant contribution towards modifying the clinical symptoms of Indian WD patients.

Dopamine β Hydroxylase (DBH) is a potential modifier gene associated with Parkinson's disease in Eastern India

BACKGROUND

Parkinson's disease (PD) is the debilitating movement disorder, distinguished by dopaminergic and norepinephrinergic neurodegeneration. Apart from candidate gene mutations, several modifier loci have been reported to be associated with the disease manifestation. The Dopamine β-Hydroxylase (DBH) maintains cellular dopamine content and regulates dopamine turn over in neurons. Genetic polymorphisms of DBH are associated with PD and are found to alter plasma DBH activity in patients compared to healthy controls. Therefore, DBH activity in plasma could be a potential and easily detectable biomarkers for alteration of dopaminergic neuronal function in PD.

METHODS

Plasma DBH activity has been assessed among PD cases and age-matched controls to identify correlation with PD. To elucidate the role of DBH polymorphisms in Eastern Indian PD patients, three SNPs (rs1611115, rs1108580 and rs129882) were selected and screened by PCR-RFLP and DNA sequencing analysis.

RESULTS

The T-allele of rs129882 was more prevalent among patients than controls posing risk (p-value = 0.02, OR = 1.404, 95% CI = 1.047-1.883) towards PD. The dual-Luciferase assay in SHSY5Y cell line revealed that the T-allele of rs129882 increases Luciferase signal (p =  0.0269). However, the rs1611115 and rs1108580 did not show association with PD; plasma DBH activity was not significantly different between patients and controls (p-value > 0.05). Haplotypes constructed with three SNPs showed that the CAT haplotype to pose risk, TAC haplotype to provide protection against early disease onset and CGT being protective against non-motor symptoms.

CONCLUSION

These data suggest that DBH might influence the susceptibility of PD.

A single nucleotide polymorphism in dopamine beta hydroxylase (rs6271(C>T)) is over-represented in inflammatory bowel disease patients and reduces circulating enzyme

Inflammatory bowel diseases (IBD) are associated with altered neuronal regulation of the gastrointestinal (GI) tract and release of norepinephrine (NE). As sympathetic innervation of the GI tract modulates motility, blood flow, and immune function, changes in NE signaling may alter the risk of developing IBD. Dopamine beta-hydroxylase (DβH), the enzyme responsible for NE production, has been suggested to play a critical role in IBD, however the exact mechanism is unknown. We hypothesized that genetic variants of DβH could increase the risk of IBD. We performed genetic analysis on 45 IBD patients and 74 controls. IBD patients were screened by targeted exome sequencing and compared with NeuroX DβH single nucleotide polymorphism (SNP) genotyping data of the controls. Serum DβH protein levels for 15 IBD patients and 13 controls were evaluated using immunoblots and competitive ELISA. Seven SNPs were observed from DβH targeted exome sequencing in the 45 IBD patients. A single non-synonymous SNP, rs6271 (Arg549Cys), had a significant association with IBD patients; the odds ratio was a 5.6 times higher SNP frequency in IBD patients compared to controls (p = 0.002). We also examined the function and availability of the protein in both the IBD and control patients' sera bearing DβH Arg549Cys. Both control and IBD subjects bearing the heterozygote allele had statistically lower DβH protein levels while the intrinsic enzyme activity was higher. This is the first report of a noradrenergic genetic polymorphism (rs6271; Arg549Cys) associated with IBD. This polymorphism is associated with significantly lower levels of circulating DβH.

Genetic association study of dyslexia and ADHD candidate genes in a Spanish cohort: Implications of comorbid samples

Dyslexia and attention deficit hyperactivity disorder (ADHD) are two complex neuro-behaviorally disorders that co-occur more often than expected, so that reading disability has been linked to inattention symptoms. We examined 4 SNPs located on genes previously associated to dyslexia (KIAA0319, DCDC2, DYX1C1 and FOXP2) and 3 SNPs within genes related to ADHD (COMT, MAOA and DBH) in a cohort of Spanish children (N = 2078) that met the criteria of having one, both or none of these disorders (dyslexia and ADHD). We used a case-control approach comparing different groups of samples based on each individual diagnosis. In addition, we also performed a quantitative trait analysis with psychometric measures on the general population (N = 3357). The results indicated that the significance values for some markers change depending on the phenotypic groups compared and/or when considering pair-wise marker interactions. Furthermore, our quantitative trait study showed significant genetic associations with specific cognitive processes. These outcomes advocate the importance of establishing rigorous and homogeneous criteria for the diagnosis of cognitive disorders, as well as the relevance of considering cognitive endophenotypes.

Understanding Neurodevelopmental Disorders: The Promise of Regulatory Variation in the 3'UTRome

Neurodevelopmental disorders have a strong genetic component, but despite widespread efforts, the specific genetic factors underlying these disorders remain undefined for a large proportion of affected individuals. Given the accessibility of exome sequencing, this problem has thus far been addressed from a protein-centric standpoint; however, protein-coding regions only make up ∼1% to 2% of the human genome. With the advent of whole genome sequencing we are in the midst of a paradigm shift as it is now possible to interrogate the entire sequence of the human genome (coding and noncoding) to fill in the missing heritability of complex disorders. These new technologies bring new challenges, as the number of noncoding variants identified per individual can be overwhelming, making it prudent to focus on noncoding regions of known function, for which the effects of variation can be predicted and directly tested to assess pathogenicity. The 3'UTRome is a region of the noncoding genome that perfectly fulfills these criteria and is of high interest when searching for pathogenic variation related to complex neurodevelopmental disorders. Herein, we review the regulatory roles of the 3'UTRome as binding sites for microRNAs or RNA binding proteins, or during alternative polyadenylation. We detail existing evidence that these regions contribute to neurodevelopmental disorders and outline strategies for identification and validation of novel putatively pathogenic variation in these regions. This evidence suggests that studying the 3'UTRome will lead to the identification of new risk factors, new candidate disease genes, and a better understanding of the molecular mechanisms contributing to neurodevelopmental disorders.