Linkage analysis identifies a novel locus for restless legs syndrome on chromosome 2q in a South Tyrolean population isolate

Prevalence of restless legs syndrome in pregnant women in Oman and its effect on pregnancy and neonatal outcomes

BACKGROUND:

Restless legs syndrome (RLS) is a common sensorimotor disorder during pregnancy. The purpose of this study was to assess the prevalence of RLS and explore the associated risk factors and outcomes in Omani women in the first and third trimester and at 2-week postpartum.

MATERIALS AND METHODS:

This cross-sectional study included 305 pregnant women visiting four health centers in Muscat between May 2018 and October 2020. A structured questionnaire was used and data were collected through review of electronic records and face-to-face interviews. The International RLS Study Group criteria were used to diagnose RLS. Participants were interviewed during their first trimester, their third trimester, and at their 2-week postpartum visit. Results were presented as means and standard deviations or percentages, as appropriate. To assess the association between RLS and various variables, unpaired t-test or McNemar's test were used, as appropriate.

RESULTS:

The mean age at baseline was 29.8 ± 5.28 years. The prevalence of RLS was significantly higher in the third trimester (41.0%) than in the first trimester (15.7%) and postpartum period (15.1%) (P < 0.001), although there was no significant difference in severity. Family history and personal history of RLS were the only independent correlates of RLS (P < 0.001 and 0.002, respectively). No associations were noted with pregnancy and neonatal outcomes or other comorbidities, including anemia. However, there was a significant relationship between the development of RLS and weight gain during pregnancy (P = 0.023).

CONCLUSION:

One in six pregnant Omani women may be at risk of RLS during the first trimester, while one in 2–3 may be at risk in the third trimester, particularly those with a personal or family history of RLS and those who gain >12 kg during pregnancy.

Association Between CLOCK Gene Variants and Restless Legs Syndrome in Koreans

OBJECTIVE

Previous studies have suggested various causes of restless legs syndrome (RLS), including iron and dopamine concentrations in the brain. Genetic influences have also been reported in many studies. There is also a possibility that circadian clock genes may be involved because symptoms of RLS worsen at night. We investigated whether CLOCK and NPAS2 gene polymorphisms were associated with RLS.

METHODS

A total of 227 patients with RLS and 229 non-RLS matched controls were assessed according to the International Restless Legs Syndrome Study Group diagnostic criteria. Genotyping was performed using reverse transcription polymerase chain reaction and high-resolution melting curve analyses.

RESULTS

Although the genotype distributions of the CLOCK variants (rs1801260 and rs2412646) were not significantly different between patients with RLS and non-RLS controls, the allele frequencies of CLOCK rs1801260 showed marginally significant differences between the two groups (X2 =2.98, p=0.085). Furthermore, there was a significant difference in the distribution of CLOCK haplotypes (rs1801260-rs2412646) between patients with RLS and non-RLS controls (p=0.013). The distributions of allelic, genotypic, and haplotypic variants of NPAS2 (rs2305160 and rs6725296) were not significantly different between the two groups.

CONCLUSION

Our results suggest that CLOCK variants may be associated with decreased susceptibility to RLS.

Mineral absorption is an enriched pathway in a brain region of restless legs syndrome patients with reduced MEIS1 expression

Restless legs syndrome is a common complex disorder with different genetic and environmental risk factors. Here we used human cell lines to conduct an RNA-Seq study and observed how the gene showing the most significant association with RLS, MEIS1, acts as a regulator of the expression of many other genes. Some of the genes affected by its expression level are linked to pathways previously reported to be associated with RLS. We found that in cells where MEIS1 expression was either increased or prevented, mineral absorption is the principal dysregulated pathway. The mineral absorption pathway genes, HMOX1 and VDR are involved in iron metabolism and response to vitamin D, respectively. This shows a strong functional link to the known RLS pathways. We observed the same enrichment of the mineral absorption pathway in postmortem brain tissues of RLS patients showing a reduced expression of MEIS1. The expression of genes encoding metallothioneins (MTs) was observed to be dysregulated across the RNA-Seq datasets generated from both human cells and tissues. MTs are highly relevant to RLS as they bind intracellular metals, protect against oxidative stress and interact with ferritins which manage iron level in the central nervous system. Overall, our study suggests that in a subset of RLS patients, the contribution of MEIS1 appears to be associated to its downstream regulation of genes that are more directly involved in pathways that are relevant to RLS. While MTs have been implicated in the pathogenesis of neurodegenerative diseases such as Parkinson’s diseases, this is a first report to propose that they have a role in RLS.

MEIS1 and Restless Legs Syndrome: A Comprehensive Review

Restless legs syndrome (RLS) is a common sleep-related disorder for which the underlying biological pathways and genetic determinants are not well understood. The genetic factors so far identified explain less than 10% of the disease heritability. The first successful genome-wide association study (GWAS) of RLS was reported in 2007. This study identified multiple RLS associated risk variants including some within the non-coding regions of MEIS1. The MEIS1 GWAS signals are some of the strongest genetic associations reported for any common disease. MEIS1 belongs to the homeobox containing transcriptional regulatory network (HOX). Work in C. elegans showed a link between the MEIS1 ortholog and iron homeostasis, which is in line with the fact that central nervous system (CNS) iron insufficiency is thought to be a cause of RLS. Zebrafish and mice have been used to study the MEIS1 gene identifying an RLS-associated-SNP dependent enhancer activity from the highly conserved non-coding regions (HCNR) of MEIS1. Furthermore, this gene shows a lower expression of mRNA and protein in blood and thalamus of individuals with the MEIS1 RLS risk haplotype. Simulating this reduced MEIS1 expression in mouse models resulted in circadian hyperactivity, a phenotype compatible with RLS. While MEIS1 shows a strong association with RLS, the protein's function that is directly linked to an RLS biological pathway remains to be discovered. The links to iron and the enhancer activity of the HCNRs of MEIS1 suggest promising links to RLS pathways, however more in-depth studies on this gene's function are required. One important aspect of MEIS1's role in RLS is the fact that it encodes a homeobox containing transcription factor, which is essential during development. Future studies with more focus on the transcriptional regulatory role of MEIS1 may open novel venues for RLS research.

Haplotype Association of the MAP2K5 Gene with Antipsychotics-Induced Symptoms of Restless Legs Syndrome among Patients with Schizophrenia

OBJECTIVE

Restless legs syndrome (RLS) is considered a genetic disease and, following a genome-wide association study conducted in 2007, the mitogen-activated protein kinase 5 (MAP2K5) gene has been regarded as the promising candidate gene for RLS. The present study investigated whether polymorphisms of MAP2K5 are associated with antipsychotics-induced RLS in schizophrenia.

METHODS

We assessed antipsychotics-induced RLS symptoms in 190 Korean schizophrenic patients using the diagnostic criteria of the International Restless Legs Syndrome Study Group. Five single-nucleotide polymorphisms (SNPs) of MAP2K5 were genotyped. We investigated genetic and haplotypic associations of these five SNPs with the risk of antipsychotics-induced RLS symptoms.

RESULTS

We divided the 190 subjects into 2 groups: 1) those with RLS symptoms (n=96) and 2) those without RLS symptoms (n=94). There were no significant intergroup differences in the distributions of the genotypes and alleles of the rs1026732, rs11635424, rs12593813, rs4489954, and rs3784709 SNPs. However, the haplotype analysis showed that the G-G-G-G-T (rs1026732-rs11635424-rs12593813-rs4489954-rs3784709) haplotype was associated with RLS symptoms (permutation p=0.033).

CONCLUSION

These data suggest that a haplotype of MAP2K5 polymorphisms confers increased susceptibility to antipsychotics-induced RLS symptoms in schizophrenic patients.

Association of BTBD9 and MAP2K5/SKOR1 With Restless Legs Syndrome in Chinese Population

Study Objectives

The aim of the study was to investigate the relationship between genetic factors and primary restless legs syndrome (RLS) in Chinese population.

Methods

A total of 116 RLS patients and 200 controls were recruited and the diagnosis of RLS was based on the criteria of International RLS Study Group. Polymer chain reaction (PCR) and sequencing were used to detect 19 single nucleotide polymorphisms (SNPs) in six genetic loci (MEIS1, BTBD9, PTPRD, MAP2K5/SKOR1, TOX3, and Intergenic region of 2p14).

Results

Our study found that one SNP increased the risk of RLS in Chinese population: rs6494696 of MAP2K5/SKOR1 (odds ratio [OR] = 0.09, p < .0001, recessive model). A further meta-analysis of RLS in Asian population found that two SNPs of BTBD9 increased the risk of RLS: rs9296249 of BTBD9 (OR = 1.44, p = .000, T allele), rs9357271 of BTBD9 (OR = 1.38, p = .021, dominant model).

Conclusion

Our results confirmed the association of BTBD9 and MAP2K5/SKOR1 with primary RLS in Chinese population.

MEIS1, a Promising Candidate Gene, Is Not Associated with the Core Symptoms of Antipsychotic-Induced Restless Legs Syndrome in Korean Schizophrenia Patients

OBJECTIVE

Restless legs syndrome (RLS) is a distressing sleep disorder to which individuals appear to be genetically predisposed. In the present study, we assumed that antipsychotic-induced RLS symptoms were attributable to differences in individual genetic susceptibility, and investigated whether MEIS1, a promising candidate gene, was associated with antipsychotic-induced RLS symptoms in schizophrenia patients.

METHODS

All subjects were diagnosed with schizophrenia by board-certified psychiatrists using the Korean version of the Structured Clinical Interview for DSM-IV. We assessed antipsychotic-induced RLS symptoms in 190 Korean schizophrenic patients using the diagnostic criteria of the International Restless Legs Syndrome Study Group. Genotyping was performed for the rs2300478 and rs6710341 polymorphisms of the MEIS1 gene.

RESULTS

We divided subjects into RLS symptom (n=96) and non-symptom (n=94) groups. There was no significant between-group difference in the genotype or allele frequencies of the two polymorphisms investigated, nor in the frequency of the rs2300478-rs6710341 haplotype.

CONCLUSION

Our data do not suggest that the rs2300478 and rs6710341 polymorphisms of the MEIS1 gene are associated with the core symptoms of antipsychotic-induced RLS in schizophrenia; different genetic mechanisms may underlie antipsychotic-induced vs. primary RLS.

Association between restless legs syndrome and CLOCK and NPAS2 gene polymorphisms in schizophrenia

Previous studies have suggested that there is a genetic basis to restless legs syndrome (RLS) development. Occurrence of antipsychotic-induced RLS could also be due to differences in genetic susceptibility. We investigated whether CLOCK and NPAS2 gene polymorphisms are associated with RLS in schizophrenic patients on antipsychotics because RLS symptoms usually manifest during the evening and night. We assessed symptoms of RLS in 190 Korean schizophrenic patients on antipsychotics and divided the subjects into two groups according to the International Restless Legs Syndrome Study Group diagnostic criteria: (i) subjects who met all the criteria and (ii) the remaining subjects who did not meet all the criteria. We found a significant difference in the number of subjects with different genotype and allele carrier frequencies for the CLOCK gene (rs2412646) between the two groups (p = 0.031 and 0.010, respectively). Distribution of CLOCK haplotypes (rs2412646-rs1801260) was significantly different between schizophrenic patients with and without RLS (p = 0.021). However, the distributions of allelic, genotypic, and haplotypic variants of NPAS2 (rs2305160 and rs6725296) were not significantly different between the two groups. Our results suggest that CLOCK polymorphisms are associated with increased susceptibility of schizophrenic patients to RLS. We hypothesize that RLS in schizophrenia patients treated with antipsychotics may be a very mild akathisia that manifests during the night and is under control of circadian oscillation.

Association of restless legs syndrome variants in Korean patients with restless legs syndrome

STUDY OBJECTIVES

Recent genome-wide association studies (GWAS) for Caucasians identified several allelic variants associated with increased risk of developing restless legs syndrome (RLS), also known as Willis-Ekbom disease. Although the pathogenic mechanisms of RLS are not entirely understood, it is becoming increasingly evident that many diseases such as RLS can be attributed to an epistasis. The study objectives were to evaluate whether the associations of RLS with all loci determined in previous GWAS for Caucasians can be replicated significantly for the Korean population and to elucidate whether an epistasis plays a role in the pathogenesis of RLS.

DESIGN SETTING AND PARTICIPANTS

DNA from 320 patients with RLS and 320 age- and sex-matched controls were genotyped for variants in the RLS loci.

MEASUREMENTS AND RESULTS

A significant association was found for rs3923809 and rs9296249 in BTBD9 (P < 0.0001 and P = 0.001, respectively); the odds ratio (OR) for rs3923809 was 1.61 (P < 0.0001) to 1.88 (P < 0.0001) and the OR for rs9296249 was 1.44 (P = 0.001) to 1.73 (P = 0.002), according to the model of inheritance. The OR for the interaction between rs3923809 in BTBD9 and rs4626664 in PTPRD was 2.05 (P < 0.0001) in the additive model, 1.80 (P = 0.002) in the dominant model and 2.47 (P = 0.004) in the recessive model. There was no significant association between genotypes of all tested single nucleotide polymorphisms and the mean value of serum iron parameters.

CONCLUSIONS

Our results suggest that the role of BTBD9 in the pathogenesis of restless legs syndrome is more universal across populations than previously reported and more efforts should be focused on the role of epistasis in the genetic architecture of restless legs syndrome.

Exome sequencing in a family with restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) has a high familial aggregation. To date, several loci and genetic risk factors have been identified, but no causative gene mutation has been found.

METHODS

We evaluated a German family with autosomal dominantly inherited RLS in 7 definitely and 2 possibly affected members by genome-wide linkage analysis and exome sequencing.

RESULTS

We identified three novel missense and one splice site variant in the PCDHA3, WWC2, ATRN, and FAT2 genes that segregated with RLS in the family. All four exons of the PCDHA3 gene, the most plausible candidate, were sequenced in 64 unrelated RLS cases and 250 controls. This revealed three additional rare missense variants (frequency <1%) of unknown pathogenicity in 2 patients and 1 control.

CONCLUSIONS

We present the first next-generation sequencing study on RLS and suggest PCDHA3 as a candidate gene for RLS.

The BTBD9 gene may be associated with antipsychotic-induced restless legs syndrome in schizophrenia

OBJECTIVE

A genome-wide association study and several replication studies have shown significant association between BTBD9 gene single nucleotide polymorphisms and restless legs syndrome (RLS). The aim of this study is to investigate the association between the BTBD9 gene polymorphisms and antipsychotic-induced RLS in schizophrenic patients.

METHODS

Restless legs syndrome symptoms were evaluated using the diagnostic criteria of the International Restless Legs Syndrome Study Group in 190 Korean schizophrenic patients. We genotyped the rs9357271 and rs3923809 polymorphisms of the BTBD9 gene in schizophrenic patients with (n = 96) and without (n = 94) RLS symptoms.

RESULTS

There was a significant difference in the allele frequency (χ(2) = 8.14, p = 0.004) of the rs9357271 polymorphism between schizophrenic patients with and without RLS symptoms. Significant genotypic association of this single nucleotide polymorphisms with RLS symptoms was also observed for the dominant model (χ(2) = 10.32, p = 0.001) and heterozygous model (χ(2) = 10.9, p = 0.001). When we compared the frequencies of the rs3923809-rs9357271 haplotypes between the two groups, the overall haplotype frequencies were significantly different (permuted p = 0.037), and the A-T haplotype was significantly more frequent in the RLS symptom group than in the no RLS symptom group (0.112 vs. 0.041, permuted p = 0.007).

CONCLUSIONS

These data suggest that the BTBD9 gene is associated with antipsychotic-induced RLS symptoms in schizophrenic patients.

Fine-mapping of restless legs locus 4 (RLS4) identifies a haplotype over the SPATS2L and KCTD18 genes

Restless legs syndrome (RLS) is a sleep-related movement disorder that affects up to 15 % of the population. Linkage studies have identified several genomic loci in single families (12q, 14q, 9p, 2q, 20p and 16p, respectively). However, confirmation of these loci has not always been achieved, and causative mutations have not yet been identified. The locus on chromosome 2q33 (RLS4) was identified in two South Tyrolean families who shared a haplotype of microsatellite marker alleles across an 8.2-cM region. To pinpoint the gene localisation within RLS4, additional families from the same geographic region were evaluated, and linkage was replicated in one family. Within the candidate region, we initially found a haplotype of 23 single nucleotide polymorphism markers spanning 131.6 Kb shared by all affected members of the three linked families. Using a next generation sequencing approach, we further restricted the shared candidate region to 46.9 Kb over the potassium channel-related gene KCTD18 and exons 10-13 of SPATS2L.

A novel locus for restless legs syndrome on chromosome 13q

BACKGROUND

Restless legs syndrome (RLS) is a sensorimotor disorder in which affected individuals suffer from uncomfortable sensations and an urge to move their lower limbs; it occurs mainly in resting situations during the evening or at night. Multiple chromosomal loci have been mapped for RLS through family-based linkage analysis, and genome-wide association studies but causative mutations have not been identified yet.

METHOD

We identified an RLS family from the eastern part of central Turkey which has 10 patients suffering from this syndrome. Whole genome linkage analysis was performed in family members who consented for study (9 affected and 2 unaffected).

RESULTS

A theoretical maximum logarithm of the odds score of 3.29 was identified at chromosome 13q32.3-33.2. This result shows strong genetic linkage to this locus.

CONCLUSIONS

We demonstrated a genetic linkage at chromosome 13 in a RLS family. Further investigation in this linkage area may reveal a causative gene leading to RLS phenotype and may illuminate the pathogenesis of this disease. This study supports the genetic heterogeneity in the pathogenesis of this syndrome.

Phenocopies in families with essential tremor and restless legs syndrome challenge Mendelian laws. Epigenetics might provide answers

Essential Tremor (ET) and Restless Legs Syndrome (RLS) are both highly heritable neurological disorders. The frequent occurrence of multi-incident families suggests the existence of highly penetrant alleles. However, linkage analyses and positional cloning approaches performed within the last 10 years essentially failed to identify responsible mutations. Several loci were found, but their relevance was questioned given the occurrence of suspected phenocopies in many of those families. Remarkably, in some ET and RLS families with an apparent autosomal dominant mode of transmission, the proportion of affected individuals was higher than the expected 50% and therefore suggests a non-mendelian inheritance in some cases. In fact, there is increasing evidence that epigenetic modifications, which refer to changes in gene expression without changes in DNA sequence, can be transmitted to the next generation. Moreover, epigenetic information can be transferred from one allele of a gene to the other allele of the same gene; if then inherited to the next generation, the offspring consequently presents phenotypic properties related to the untransmitted allele. This phenomenon known as paramutation is well documented in plants and has recently been shown to occur also in mammals. Here, I explore the possibility that it is the epigenetic and not only the genetic state which confers disease risk in families. Inheritance of epigenetic mutations along with paramutational events have the potential to explain the non-mendelian features in the genetics of both diseases.

Association studies of variants in MEIS1, BTBD9, and MAP2K5/SKOR1 with restless legs syndrome in a US population

BACKGROUND

A genome-wide association study (GWAS) identified significant association between variants in MEIS1, BTBD9, and MAP2K5/SKOR1 and restless legs syndrome (RLS). However, many independent replication studies are needed to unequivocally establish a valid genotype-phenotype association across various populations. To further validate the GWAS findings, we investigated three variants, rs2300478 in MEIS1, rs9357271 in BTBD9, and rs1026732 in MAP2K5/SKOR1 in 38 RLS families and 189 RLS patients/560 controls from the US for their association with RLS.

METHOD

Both family-based and population-based case-control association studies were carried out.

RESULTS

The family-based study showed that SNP rs1026732 in MAP2K5/SKOR1 was significantly associated with RLS (P=0.01). Case-control association studies showed significant association between all three variants and RLS (P=0.0001/OR=1.65, P=0.0021/OR=1.59, and P=0.0011/OR=1.55 for rs2300478, rs9357271, and rs1026732, respectively).

CONCLUSION

Variants in MEIS1, BTBD9, and MAP2K5/SKOR1 confer a significant risk of RLS in a US population.

Epidemiology of restless legs syndrome: a synthesis of the literature

Restless legs syndrome (RLS) has gained considerable attention in the recent years: nearly 50 community-based studies have been published in the last decade around the world. The development of strict diagnostic criteria in 1995 and their revision in 2003 helped to stimulate research interest on this syndrome. In community-based surveys, RLS has been studied as: 1) a symptom only, 2) a set of symptoms meeting minimal diagnostic criteria of the international restless legs syndrome study group (IRLSSG), 3) meeting minimal criteria accompanied with a specific frequency and/or severity, and 4) a differential diagnosis. In the first case, prevalence estimates in the general adult population ranged from 9.4% to 15%. In the second case, prevalence ranged from 3.9% to 14.3%. When frequency/severity is added, prevalence ranged from 2.2% to 7.9% and when differential diagnosis is applied prevalence estimates are between 1.9% and 4.6%. In all instances, RLS prevalence is higher in women than in men. It also increases with age in European and North American countries but not in Asian countries. Symptoms of anxiety and depression have been consistently associated with RLS. Overall, individuals with RLS have a poorer health than non-RLS but evidence for specific disease associations is mixed. Future epidemiological studies should focus on systematically adding frequency and severity in the definition of the syndrome in order to minimize the inclusion of cases mimicking RLS.

Restless legs syndrome, periodic leg movements, and periodic limb movement disorder in children

The characteristic symptoms of restless legs syndrome (RLS) have been known for hundreds of years and were first reported in medicine in the 1600s. Clinicians must consider potential mimics, comorbid, and associated conditions when evaluating children with RLS symptoms. The traditional differentiation of RLS from periodic limb movement disorder (PLMD) is noted in children as well as adults. Because current pediatric RLS research is sparse, this article provides the most up-to-date evidence-based as well as consensus opinion-based information on the subject of childhood RLS and PLMD. Prevalence, pathophysiology, diagnosis, treatment, and clinical associations are discussed.

Genome-wide association studies of sleep disorders

Sleep disorders tend to be complex diseases, with multiple genes and environmental factors interacting to contribute to phenotypes. Our understanding of the genetic underpinnings of sleep disorders has benefited from recent genome-wide association studies (GWAS). We review principles underlying GWAS and discuss recent GWAS for restless legs syndrome and narcolepsy. These studies have identified four gene variants associated with restless legs syndrome (BTBD9, MEIS1, MAP2K5/LBXCOR1, and PTPRD) and two variants associated with narcolepsy (one in the T-cell receptor α locus and another between CPT1B and CHKB). These discoveries have opened new lines of research to understand the pathophysiology of these disorders. In addition to GWAS, we expect that new technologies, such as next-generation sequencing, and continued use of animal models will provide important contributions to our understanding of the genetic basis of sleep disorders.

Family-based and population-based association studies validate PTPRD as a risk factor for restless legs syndrome

OBJECTIVE

We previously mapped a genetic locus for restless legs syndrome (RLS) to chromosome 9p22-24 (RLS3) and a later genome-wide association study (GWAS) implicated the PTPRD gene at the RLS3 locus as a susceptibility gene for RLS. However, from the standpoint of genetics, the GWAS association needs to be validated by independent studies. In this study, we used both family-based and population-based association studies to assess the association between PTPRD and RLS in an American Caucasian population.

METHODS

We genotyped two intronic SNPs rs1975197 and rs4626664 in PTPRD in 144 family members from 15 families and a case control cohort of 189 patients and 560 controls. Direct DNA sequence analysis was used to screen coding exons and exon-intron boundaries of PTPRD for rare mutations.

RESULTS

A family-based sibling transmission disequilibrium test showed association of RLS with SNP rs1975197 (P = 0.015), but not with rs4626664 (P = 0.622). The association with rs1975197 was significantly replicated by a population-based case control association study (allelic P = 0.0004, odds ratio = 1.68; genotypic P = 0.0013 and 0.0003 for an additive and dominant model, respectively). One rare p.E1639D variant was identified in exon 39 in kindred RLS40005. The rare D1639 allele did not co-segregate with RLS in the family, suggesting that p.E1639D variant is not a causative mutation.

CONCLUSIONS

This represents the first independent study to validate the association between PTPRD variants and RLS. Both family-based and population-based association studies suggest that PTPRD variant rs1975197 confers risk of RLS.

Association study between antipsychotic-induced restless legs syndrome and polymorphisms of monoamine oxidase genes in schizophrenia

OBJECTIVE

This study aimed to investigate whether the monoamine oxidase (MAO) A and B genes are associated with antipsychotic-induced restless legs syndrome (RLS) in schizophrenia.

METHODS

We assessed antipsychotic-induced RLS symptoms in 190 Korean schizophrenic patients and divided the subjects into two groups: those with RLS symptoms (n = 96) and those without RLS symptoms (n = 94). Genotyping was performed for the variable number of tandem repeat (VNTR) polymorphism of the MAOA gene and A644G polymorphism of the MAOB gene.

RESULTS

There was no significant difference in the genotype and allele frequencies of all polymorphisms investigated between these two groups. However, the result of global haplotype analysis showed a significant difference in haplotype frequencies between male subjects with and without RLS symptoms (p = 0.013). The interaction between two polymorphisms had a significant effect on the RLS scores of both male (p = 0.047) and female (p = 0.028) patients.

CONCLUSIONS

These data do not suggest that the MAOA gene VNTR and MAOB gene A644G polymorphisms are associated with antipsychotic-induced RLS symptoms in schizophrenia. However, we found that the haplotype frequencies differed between the male schizophrenic patients with and without RLS symptom and the interaction between the two polymorphisms had a significant influence on the RLS scores of patients with schizophrenia.

Advances in the science of genomics in restless legs syndrome

Restless legs syndrome (RLS) is a sleep and movement disorder that affects up to 15% of the population across the lifespan. Many health care providers have doubted its validity as an illness and are uncertain as to the implications of health care outcomes. The cause of RLS is unknown. Common treatment options include dopaminergics, benzodiazepines, and opioids; however, the pharmacogenetic mechanisms of treatment are unknown. One of the greatest genetic discoveries in 2007 was the identification of genetic variance associated with RLS. There is, however, a lack of knowledge related to RLS and its genetic basis. Therefore, the purposes of this article are to (a) provide information about the science of clinical care related to RLS; (b) present a systematic review of the literature on the status of genetics/genomics of RLS, including the discovery of associated genetic variance; and (c) identify implications of the current state of the science for health care providers and biobehavioral researchers. With the continuing genetic discoveries in RLS, health care providers, specifically nurses who play a major role in research, genetic counseling, and education, need to understand the implications of this sleep and movement disorder for patients across the lifespan.

Ropinirole in restless legs syndrome and periodic limb movement disorder

Restless legs syndrome and periodic limb movement disorder of sleep are now recognized as prevalent, distinct, yet overlapping disorders affecting all age groups. Although delineation of the mechanisms underlying these disorders continues to be the focus of very intense research efforts, it has become apparent that there is a prominent role for dopaminergic agents in the clinical management of these patients. Among the various dopaminergic drugs, ropinirole has undergone relatively intense and critical scrutiny, and appears to provide a safe and efficacious treatment option for patients with these two conditions. The more recent development of a controlled formulation for this drug is likely to yield additional benefits such as improved adherence and reduced fluctuations in daytime and nighttime symptoms. However, there is not enough evidence at this time to support such assumption.

No significance of the COMT val158met polymorphism in restless legs syndrome

The catechol-O-methyltransferase (COMT) val(158)met polymorphism, which codes for the substitution of valine (val) by methionine (met) leading to a reduced COMT activity in homo- or heterozygous individuals, is associated with individual pain sensitivity and dopaminergic responses in Parkinson's disease as well as with various chronic painful diseases. Recent investigations support the notion of an alteration of the medial pain pathway as well as of the descending inhibitory control system in restless legs syndrome (RLS), that both involve dopaminergic transmission as well. Thus, the distribution of the COMT val(158)met polymorphism was assessed in 298 RLS patients and compared with 135 healthy controls in relation to sex, age of onset and family history. The data revealed no significant differences in the distribution of the COMT val(158)met polymorphism in RLS patients compared with the control group, also when the heterozygous and the homozygous group containing the (158)met allele were combined. In addition, sex, age of onset and family history were not associated with the COMT val(158)met polymorphism in this German population of RLS patients. The present study adds to previous mostly negative investigations on the genetic determination of dopaminergic transmission in RLS, which have - so far - only detected an association of the MAO-A activity and RLS in females in a French-Canadian population. Further investigations assessing the different COMT haplotypes and experimental and clinical parameters are nevertheless warranted.

Parkin gene modifies the effect of RLS4 on the age at onset of restless legs syndrome (RLS)

A co-occurrence of restless legs syndrome (RLS) and Parkin mutations has been described. In South Tyrolean RLS patients, a novel RLS locus has been found (RLS4) and recurrent Parkin mutations have been reported. By a systematic screen we investigated the presence of founder Parkin mutations in South Tyrolean RLS patients with known carrier status at the RLS4 locus and assessed whether these mutations alone or in combination influence the RLS phenotype measured by three quantitative RLS traits (age at onset (AAO) and two severity measurements). The Parkin mutation alone showed no effect, whereas RLS4 had a significant effect on the AAO (P = 0.0096, decrease of AAO of 9.1 years), but did not influence severity. Carriers of both, a Parkin mutation and the RLS4 haplotype, showed an association with AAO (P = 0.0016), corresponding to an anticipation of RLS onset age of 16.9 years. However, there was no effect on the disease severity. Our results suggest that the occurrence of a heterozygous Parkin mutation works in tandem with the gene at the RLS4 locus to lower the AAO in RLS.

Update on the management of restless legs syndrome: existing and emerging treatment options

Restless legs syndrome (RLS) is a sensorimotor disorder, characterized by a circadian variation of symptoms involving an urge to move the limbs (usually the legs) as well as paresthesias. There is a primary (familial) and a secondary (acquired) form, which affects a wide variety of individuals, such as pregnant women, patients with end-stage renal disease, iron deficiency, rheumatic disease, and persons taking medications. The symptoms reflect a circadian fluctuation of dopamine in the substantia nigra. RLS patients have lower dopamine and iron levels in the substantia nigra and respond to both dopaminergic therapy and iron administration. Iron, as a cofactor of dopamine production and a regulator of the expression of dopamine type 2-receptor, has an important role in the RLS etiology. In the management of the disease, the first step is to investigate possible secondary causes and their treatment. Dopaminergic agents are considered as the first-line therapy for moderate to severe RLS. If dopaminergic drugs are contraindicated or not efficacious, or if symptoms are resistant and unremitting, gabapentin or other antiepileptic agents, benzodiazepines, or opioids can be used for RLS therapy. Undiagnosed, wrongly diagnosed, and untreated RLS is associated with a significant impairment of the quality of life.

The genetics of sleep disorders in humans: narcolepsy, restless legs syndrome, and obstructive sleep apnea syndrome

Sleep disorders are a group of neurological disorders known to cause public health problems associated with interference with daily activities including cognitive problems, poor job performance and reduced productivity. There is strong evidence emerging for the presence of genes influencing sleep disorders, such as narcolepsy (NRCLP), restless legs syndrome (RLS), and obstructive sleep apnea syndrome (OSAS). NRCLP is typically characterized by excessive daytime sleepiness, cataplexy, sleep paralysis and hallucinations. RLS is manifested by compelling need to move the legs and usually experienced when trying to sleep. OSAS is major sleep problem characterized by recurrent episodes of upper airway collapse and obstruction during sleep. In the recent years, many research groups have attempted to identify the susceptibility and candidate genes for NRCLP, RLS, and OSAS through the sequential analyses of genetic linkage and association. The purpose of this review is to summarize some of remarkable molecular advances in sleep and sleep disorders, thereby providing a greater understanding of the complex sleep processes, and a platform for future therapeutic interventions.

Replication of restless legs syndrome loci in three European populations

BACKGROUND

Restless legs syndrome (RLS) is associated with common variants in three intronic and intergenic regions in MEIS1, BTBD9, and MAP2K5/LBXCOR1 on chromosomes 2p, 6p and 15q.

METHODS

Our study investigated these variants in 649 RLS patients and 1230 controls from the Czech Republic (290 cases and 450 controls), Austria (269 cases and 611 controls) and Finland (90 cases and 169 controls). Ten single nucleotide polymorphisms (SNPs) within the three genomic regions were selected according to the results of previous genome-wide scans. Samples were genotyped using Sequenom platforms.

RESULTS

We replicated associations for all loci in the combined samples set (rs2300478 in MEIS1, p = 1.26 x 10(-5), odds ratio (OR) = 1.47, rs3923809 in BTBD9, p = 4.11 x 10(-5), OR = 1.58 and rs6494696 in MAP2K5/LBXCOR1, p = 0.04764, OR = 1.27). Analysing only familial cases against all controls, all three loci were significantly associated. Using sporadic cases only, we could confirm the association only with BTBD9.

CONCLUSION

Our study shows that variants in these three loci confer consistent disease risks in patients of European descent. Among the known loci, BTBD9 seems to be the most consistent in its effect on RLS across populations and is also most independent of familial clustering.

Clinical and genetic description of a family with a high prevalence of autosomal dominant restless legs syndrome

OBJECTIVE

To conduct clinical and molecular genetic analyses of the members of an extended family in Central Indiana with a high prevalence of restless legs syndrome (RLS).

PARTICIPANTS AND METHODS

From February 1, 2006, through August 31, 2008, we collected data from members of this family, which is of English descent. Genealogical methods were used to expand the family tree, and family members were screened with an RLS questionnaire. Telephone interviews and personal examinations were performed at Mayo Clinic and during a field trip to Central Indiana. Blood samples were collected for molecular genetic analysis. A follow-up telephone interview was conducted 1 year later.

RESULTS

The family tree spans 7 generations with 88 living members, 30 of whom meet the criteria for diagnosis of RLS established by the International Restless Legs Syndrome Study Group. Three affected family members also have Parkinson disease or essential tremor. The mode of RLS inheritance is compatible with an autosomal dominant pattern. The affected family members do not exhibit linkage to the 5 known RLS loci or mutations in the RLS susceptibility genes MEIS1 and BTBD9.

CONCLUSION

Of 88 members of this single extended family in Central Indiana, 30 were diagnosed as having RLS. Because our analysis shows that the disease is not linked to any of the known RLS loci or risk-associated genes, we postulate that members of this family may carry a gene mutation in a novel genetic locus.

Clinical and genetic description of a family with a high prevalence of autosomal dominant restless legs syndrome

OBJECTIVE

To conduct clinical and molecular genetic analyses of the members of an extended family in Central Indiana with a high prevalence of restless legs syndrome (RLS).

PARTICIPANTS AND METHODS

From February 1, 2006, through August 31, 2008, we collected data from members of this family, which is of English descent. Genealogical methods were used to expand the family tree, and family members were screened with an RLS questionnaire. Telephone interviews and personal examinations were performed at Mayo Clinic and during a field trip to Central Indiana. Blood samples were collected for molecular genetic analysis. A follow-up telephone interview was conducted 1 year later.

RESULTS

The family tree spans 7 generations with 88 living members, 30 of whom meet the criteria for diagnosis of RLS established by the International Restless Legs Syndrome Study Group. Three affected family members also have Parkinson disease or essential tremor. The mode of RLS inheritance is compatible with an autosomal dominant pattern. The affected family members do not exhibit linkage to the 5 known RLS loci or mutations in the RLS susceptibility genes MEIS1 and BTBD9.

CONCLUSION

Of 88 members of this single extended family in Central Indiana, 30 were diagnosed as having RLS. Because our analysis shows that the disease is not linked to any of the known RLS loci or risk-associated genes, we postulate that members of this family may carry a gene mutation in a novel genetic locus.

Restless legs syndrome: differential diagnosis and management with rotigotine

RLS is a common sleep disorder with distinctive clinical features. The prevalence of RLS in Caucasians and North Americans ranges from 5% to 10%. However, only some of these subjects (almost the 3% of the general population) report being affected by a frequent and severe form of the sleep disorder. RLS is diagnosed clinically by means of four internationally recognized criteria that summarize the main characteristics of the sleep disorder. Besides the essential criteria, supportive and associated features of RLS have been established by experts in order to help physicians treat patients with doubtful symptoms. Several clinical conditions may mimic this sleep disorder. In order to increase the sensibility and specificity of RLS diagnosis, doctors should perform a meticulous patient history and then an accurate physical and neurological examination. Dopamine agonists are recognized as the preferred first-line treatment for RLS. Rotigotine is a non-ergoline dopamine agonist with selectivity for D1, D2 and D3 receptors. The drug is administered via transdermal patches which release rotigotine for 24 hours. Four clinical trials demonstrated that this compound is able to improve RLS symptomatology with few and moderate adverse events. Head to head trials are required to compare the efficacy and tolerability of rotigotine with other dopamine agonists administered via oral intake. Rotigotine has been approved by the FDA and EMEA for Parkinson's disease. For the treatment of moderate to severe idiopathic RLS, rotigotine has been recommended for approval by the EMEA and is under review by the FDA.

Ropinirole treatment for restless legs syndrome

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance. Ropinirole, a non-ergot dopamine agonist, has been widely studied for the treatment of moderate-to-severe primary RLS in a comprehensive clinical development program. In these studies, ropinirole was effective in significantly improving the symptoms of RLS, compared with placebo, in patients with moderate-to-severe primary RLS. These improvements are supported by data from individual studies, as well as by pooled analyses. Significant improvements in RLS symptoms were observed within 2 nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements; and on subjective measures of sleep, ropinirole was generally well tolerated. A newly developed extended-release formulation of ropinirole may benefit patients who warrant an extended duration of therapy.

Restless legs syndrome in women: a review

Restless legs syndrome (RLS) is a neurological disorder with significant negative impact on sleep and quality of life, yet data suggest that it is frequently underdiagnosed. The clinical features, diagnosis, epidemiology, pathophysiology, and treatment options for RLS are reviewed and discussed, with particular emphasis on RLS in women. RLS is characterized by unpleasant sensations causing an urge to move the legs. RLS symptoms are exacerbated by rest, relieved by movement, and worse at night than during the day. The motor and sensory symptoms of RLS can have a negative impact on patients' sleep, resulting in a reduction in daytime functioning and overall quality of life. The prevalence of RLS is reported to increase with age and to be up to almost twice as high in women as in men. The explanation for this is unknown, although there is evidence that parity may be a factor. Diagnosis of RLS is made using four essential criteria based on the patient's report of sensorimotor symptoms. Several large, double-blind, placebo-controlled studies have demonstrated that dopamine agonists, such as ropinirole and pramipexole, are an efficacious first-line therapy for the treatment of RLS symptoms. As RLS is more prevalent in women, professionals working in the field of women's health need to be aware of this condition, its differential diagnosis, and the treatment options available. Accurate diagnosis is essential to facilitate appropriate management and treatment. Dopamine agonists have been shown to be an effective therapy for patients with moderate to severe symptoms of RLS.

Genetics of restless legs syndrome

Restless legs syndrome (RLS) is a highly familial trait with heritability estimates of about 50%. It is a polygenetic disorder in which a number of variants contribute to the phenotype. Linkage studies in families with RLS revealed several loci but have not yet led to the identification of disease-causing sequence variants. Phenocopies, nonpenetrance, and possible intrafamilial heterogeneity make it difficult to define the exact candidate region. Genome-wide association studies identified variants within intronic or intergenic regions of MEIS1, BTBD9, and MAP2K5/LBOXCOR1. Carriers of one risk allele had a 50% increased risk of developing RLS. MEIS1 and LBXCOR1 are developmental factors and raise new pathophysiologic questions for RLS. These variants have weak and moderate effects and increase the risk of developing RLS. It is still possible that strong effects explain the occurrence of RLS in families. Therefore, linkage and association studies should be used congruently to dissect the complete genetic architecture of RLS.

[Restless-legs syndrome]

Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movements and is exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to 3% of the general population in Western countries. Supportive criteria include a family history, the presence of periodic-leg movements (PLM) when awake or asleep and a positive response to dopaminergic treatment. The RLS phenotypes include an early onset form, usually idiopathic with a familial history and a late onset form, usually secondary to peripheral neuropathy. Recently, an atypical RLS phenotype without PLM and l-DOPA resistant has been characterized. RLS can occur in childhood and should be distinguished from attention deficit/hyperactivity disorder, growing pains and sleep complaints in childhood. RLS should be included in the diagnosis of all patients consulting for sleep complaints or discomfort in the lower limbs. It should be differentiated from akathisia, that is, an urge to move the whole body without uncomfortable sensations. Polysomnographic studies and the suggested immobilization test can detect PLM. Furthermore, an l-DOPA challenge has recently been validated to support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor quality of life, depressive and anxious symptoms and may be a risk factor for cardiovascular disease. In most cases, RLS is idiopathic. It may also be secondary to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drugs, such as antipsychotics and antidepressants. The small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with many neurological and sleep disorders including Parkinson's disease, but does not predispose to these diseases. The pathophysiology of RLS includes an altered brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain control systems and a genetic susceptibility with nine loci and three polymorphisms in genes serving developmental functions. RLS treatment begins with the elimination of triggering factors and iron supplementation when deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA or codeine; the first-line treatment for moderate to severe RLS is dopaminergic agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid (oxycodone, tramadol) drugs can be used.

Ropinirole treatment for restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) is a chronic neurological disorder associated with sleep disturbance.

OBJECTIVE

Prepare a drug evaluation of the non-ergot dopamine agonist ropinirole in RLS.

METHODS

Review of scientific literature on RLS, particularly focusing on treatment with ropinirole.

CONCLUSION

Ropinirole has been studied for treatment of moderate to severe primary RLS in a comprehensive clinical development program. Ropinirole significantly improved symptoms of RLS, versus placebo, in patients with primary RLS. These improvements are supported by data from individual studies and pooled analyses. Significant improvements in RLS symptoms were observed within two nights of treatment. Ropinirole also produced significant benefits on objective measures of RLS motor symptoms, such as periodic leg movements, and subjective measures of sleep. Ropinirole was generally well tolerated.