PTPRD (protein tyrosine phosphatase receptor type delta) is associated with restless legs syndrome

Genome-wide meta-analyses of restless legs syndrome yield insights into genetic architecture, disease biology and risk prediction

Restless legs syndrome (RLS) affects up to 10% of older adults. Their healthcare is impeded by delayed diagnosis and insufficient treatment. To advance disease prediction and find new entry points for therapy, we performed meta-analyses of genome-wide association studies in 116,647 individuals with RLS (cases) and 1,546,466 controls of European ancestry. The pooled analysis increased the number of risk loci eightfold to 164, including three on chromosome X. Sex-specific meta-analyses revealed largely overlapping genetic predispositions of the sexes (rg = 0.96). Locus annotation prioritized druggable genes such as glutamate receptors 1 and 4, and Mendelian randomization indicated RLS as a causal risk factor for diabetes. Machine learning approaches combining genetic and nongenetic information performed best in risk prediction (area under the curve (AUC) = 0.82-0.91). In summary, we identified targets for drug development and repurposing, prioritized potential causal relationships between RLS and relevant comorbidities and risk factors for follow-up and provided evidence that nonlinear interactions are likely relevant to RLS risk prediction.

Drosophila noktochor regulates night sleep via a local mushroom body circuit

We show that a sleep-regulating, Ig-domain protein (NKT) is secreted from Drosophila mushroom body (MB) α'/β' neurons to act locally on other MB cell types. Pan-neuronal or broad MB expression of membrane-tethered NKT (tNkt) protein reduced sleep, like that of an NKT null mutant, suggesting blockade of a receptor mediating endogenous NKT action. In contrast, expression in neurons requiring NKT (the MB α'/β' cells), or non-MB sleep-regulating centers, did not reduce night sleep, indicating the presence of a local MB sleep-regulating circuit consisting of communicating neural subtypes. We suggest that the leucocyte-antigen-related like (Lar) transmembrane receptor may mediate NKT action. Knockdown or overexpression of Lar in the MB increased or decreased sleep, respectively, indicating the receptor promotes wakefulness. Surprisingly, selective expression of tNkt or knockdown of Lar in MB wake-promoting cells increased rather than decreased sleep, suggesting that NKT acts on wake- as well as sleep-promoting cell types to regulate sleep.

Neural conditional ablation of the protein tyrosine phosphatase receptor Delta PTPRD impairs gliogenesis in the developing mouse brain cortex

Neurodevelopmental disorders are characterized by alterations in the development of the cerebral cortex, including aberrant changes in the number and function of neural cells. Although neurogenesis is one of the most studied cellular processes in these pathologies, little evidence is known about glial development. Genetic association studies have identified several genes associated with neurodevelopmental disorders. Indeed, variations in the PTPRD gene have been associated with numerous brain disorders, including autism spectrum disorder, restless leg syndrome, and schizophrenia. We previously demonstrated that constitutive loss of PTPRD expression induces significant alterations in cortical neurogenesis, promoting an increase in intermediate progenitors and neurons in mice. However, its role in gliogenesis has not been evaluated. To assess this, we developed a conditional knockout mouse model lacking PTPRD expression in telencephalon cells. Here, we found that the lack of PTPRD in the mouse cortex reduces glial precursors, astrocytes, and oligodendrocytes. According to our results, this decrease in gliogenesis resulted from a reduced number of radial glia cells at gliogenesis onset and a lower gliogenic potential in cortical neural precursors due to less activation of the JAK/STAT pathway and reduced expression of gliogenic genes. Our study shows PTPRD as a regulator of the glial/neuronal balance during cortical neurodevelopment and highlights the importance of studying glial development to understand the etiology of neurodevelopmental diseases.

Behavioral and genetic architecture of fear conditioning and related phenotypes

Contextual fear conditioning is a form of Pavlovian learning during which an organism learns to fear previously neutral stimuli following their close temporal presentation with an aversive stimulus. In mouse models, freezing behavior is typically used to quantify learned fear. This dependent variable is the sum of multiple processes, including associative/configural learning, fear and anxiety, and general activity. To explore phenotypic constructs underlying contextual fear conditioning and correlated behaviors, as well as factors that may contribute to individual differences in learning and mental health, we tested BXD recombinant inbred strains previously found to show extreme contextual fear conditioning phenotypes and BXD parental strains, C57BL/6J and DBA/2J, in a series of tests including locomotor, anxiety, contextual/cued fear conditioning and non-associative hippocampus-dependent learning behaviors. Hippocampal expression of two previously identified candidate genes for contextual fear conditioning was also quantified. Behavioral and gene expression data were analyzed using exploratory factor analysis (EFA), which suggested five unique constructs representing activity/anxiety/exploration, associative fear learning, anxiety, post-shock freezing, and open field activity phenotypes. Associative fear learning and expression of one candidate gene, Hacd4, clusteredas a construct withinthefactor analysis. Post-shock freezingduring fear conditioning and expression of candidate gene Ptprd emerged as another unique construct, highlighting theindependenceof freezing after footshock from other fear conditioning variables in the current dataset.EFA results additionally suggest shared phenotypic variance in adaptive murine behaviors related to anxiety, general activity, and exploration. These findings inform understanding of fear learning and underlying biological mechanisms that may interact to produce individual differences in fear- and learning-related behaviors in mice.

Mice lacking Ptprd exhibit deficits in goal-directed behavior and female-specific impairments in sensorimotor gating

Protein Tyrosine Phosphatase receptor type D (PTPRD) is a member of the protein tyrosine phosphatase family that mediates cell adhesion and synaptic specification. Genetic studies have linked Ptprd to several neuropsychiatric phenotypes, including Restless Leg Syndrome (RLS), opioid abuse disorder, and antipsychotic-induced weight gain. Genome-wide association studies (GWAS) of either pediatric obsessive-compulsive traits, or Obsessive-Compulsive Disorder (OCD), have identified loci near PTPRD as genome-wide significant, or strongly suggestive for this trait. We assessed Ptprd wild-type (WT), heterozygous (HT), and knockout (KO) mice for behavioral dimensions that are altered in OCD, including anxiety and exploration (open field test, dig test), perseverative behavior (splash-induced grooming, spatial d), sensorimotor gating (prepulse inhibition), and home cage goal-directed behavior (nest building). No effect of genotype was observed in any measure of the open field test, dig test, or splash test. However, Ptprd KO mice of both sexes showed impairments in nest building behavior. Finally, female, but not male, Ptprd KO mice showed deficits in prepulse inhibition, an operational measure of sensorimotor gating that is reduced in female, but not male, OCD patients. Our results indicate that constitutive lack of Ptprd may contribute to the development of certain domains that are altered OCD, including goal-directed behavior, and reduced sensorimotor gating specifically in females.

Protein tyrosine phosphatase receptor type delta (PTPRD) gene in an animal model of restless legs syndrome

The pathophysiology of the restless legs syndrome (RLS) is related to dopaminergic dysfunction, reduced iron and variations in gene expression, such as the protein tyrosine phosphatase receptor type delta gene (PTPRD). Animal models could be key to achieving a mechanistic understanding of RLS and to facilitate efficient platforms for evaluating new therapeutics. Thus, the aim of this study was to evaluate the expression of PTPRD, of genes and proteins associated with RLS, the sleep patterns and the cardiovascular parameters in an animal model of RLS (spontaneously hypertensive rat [SHR]). Rats were divided into two groups: (i) Wistar-Kyoto and (ii) SHR. Cardiovascular parameters were assessed by tail plethysmography. Polysomnography was used to analyse the sleep pattern (24 h). For the PTPRD analyses, quantitative polymerase chain reaction (qPCR) and indirect enzyme-linked immunosorbent assay (ELISA) techniques were used. To evaluate the tyrosine hydroxylase enzyme, dopamine transporter (DAT) and type 2 dopaminergic receptor, qPCR and Western Blotting techniques were used. For the quantification of iron, ferritin and transferrin, the ELISA method was used. SHRs had higher blood pressure, alterations in sleep pattern, lower expression of protein content of PTPRD, lower expression of DAT, and lower serum concentrations of ferritin. These data suggest that the behavioural, physiological, and molecular changes observed in SHRs provide a useful animal model of RLS, reinforcing the importance of this strain as an animal model of this sleep disorder.

A retrospective analysis of phosphatase catalytic subunit gene variants in patients with rare disorders identifies novel candidate neurodevelopmental disease genes

Rare genetic disorders represent some of the most severe and life-limiting conditions that constitute a considerable burden on global healthcare systems and societies. Most individuals affected by rare disorders remain undiagnosed, highlighting the unmet need for improved disease gene discovery and novel variant interpretation. Aberrant (de) phosphorylation can have profound pathological consequences underpinning many disease processes. Numerous phosphatases and associated proteins have been identified as disease genes, with many more likely to have gone undiscovered thus far. To begin to address these issues, we have performed a systematic survey of de novo variants amongst 189 genes encoding phosphatase catalytic subunits found in rare disease patients recruited to the 100,000 Genomes Project (100 kGP), the largest national sequencing project of its kind in the United Kingdom. We found that 49% of phosphatases were found to carry de novo mutation(s) in this cohort. Only 25% of these phosphatases have been previously linked to genetic disorders. A gene-to-patient approach matching variants to phenotypic data identified 9 novel candidate rare-disease genes: PTPRD, PTPRG, PTPRT, PTPRU, PTPRZ1, MTMR3, GAK, TPTE2, PTPN18. As the number of patients undergoing whole genome sequencing increases and information sharing improves, we anticipate that reiterative analysis of genomic and phenotypic data will continue to identify candidate phosphatase disease genes for functional validation. This is the first step towards delineating the aetiology of rare genetic disorders associated with altered phosphatase function, leading to new biological insights and improved clinical outcomes for the affected individuals and their families.

Restless Legs Syndrome and Periodic Limb Movements of Sleep: From Neurophysiology to Clinical Practice

SUMMARY

This article summarizes restless legs syndrome (RLS), periodic limb movements of sleep, and periodic limb movement disorder. RLS is a common sleep disorder with a prevalence of 5% to 15% in the general population. RLS can present in childhood, and incidence increases with age. RLS can be idiopathic or secondary to iron deficiency, chronic renal failure, peripheral neuropathy, and medications such as antidepressants (with higher rates for mirtazapine and venlafaxine, while bupropion may reduce symptoms at least in the short term), dopamine antagonists (neuroleptic antipsychotic agents and antinausea medications), and possibly antihistamines. Management includes pharmacologic agents (dopaminergic agents, alpha-2 delta calcium channel ligands, opioids, benzodiazepines) and nonpharmacologic therapies (iron supplementation, behavioral management). Periodic limb movements of sleep are an electrophysiologic finding commonly accompanying RLS. On the other hand, most individuals with periodic limb movements of sleep do not have RLS. The clinical significance of the movements has been argued. Periodic limb movement disorder is a distinct sleep disorder that arises in individuals without RLS and is a diagnosis of exclusion.

Inherited deletion of 9p22.3-p24.3 and duplication of 18p11.31-p11.32 associated with neurodevelopmental delay: Phenotypic matching of involved genes

We describe a 3.5-year-old Iranian female child and her affected 10-month-old brother with a maternally inherited derivative chromosome 9 [der(9)]. The postnatally detected rearrangement was finely characterized by aCGH analysis, which revealed a 15.056 Mb deletion of 9p22.3-p24.3p22.3 encompassing 14 OMIM morbid genes such as DOCK8, KANK1, DMRT1 and SMARCA2, and a gain of 3.309 Mb on 18p11.31-p11.32 encompassing USP14, THOC1, COLEC12, SMCHD1 and LPIN2. We aligned the genes affected by detected CNVs to clinical and functional phenotypic features using PhenogramViz. In this regard, the patient's phenotype and CNVs data were entered into PhenogramViz. For the 9p deletion CNV, 53 affected genes were identified and 17 of them were matched to 24 HPO terms describing the patient's phenotypes. Also, for CNV of 18p duplication, 22 affected genes were identified and six of them were matched to 13 phenotypes. Moreover, we used DECIPHER for in-depth characterization of involved genes in detected CNVs and also comparison of patient phenotypes with 9p and 18p genomic imbalances. Based on our filtration strategy, in the 9p22.3-p24.3 region, approximately 80 pathogenic/likely pathogenic/uncertain overlapping CNVs were in DECIPHER. The size of these CNVs ranged from 12.01 kb to 18.45 Mb and 52 CNVs were smaller than 1 Mb in size affecting 10 OMIM morbid genes. The 18p11.31-p11.32 region overlapped 19 CNVs in the DECIPHER database with the size ranging from 23.42 kb to 1.82 Mb. These CNVs affect eight haploinsufficient genes.

Putative Animal Models of Restless Legs Syndrome: A Systematic Review and Evaluation of Their Face and Construct Validity

Restless legs syndrome (RLS) is a sensorimotor disorder that severely affects sleep. It is characterized by an urge to move the legs, which is often accompanied by periodic limb movements during sleep. RLS has a high prevalence in the population and is usually a life-long condition. While its origins remain unclear, RLS is initially highly responsive to treatment with dopaminergic agonists that target D2-like receptors, in particular D2 and D3, but the long-term response is often unsatisfactory. Over the years, several putative animal models for RLS have been developed, mainly based on the epidemiological and neurochemical link with iron deficiency, treatment efficacy of D2-like dopaminergic agonists, or genome-wide association studies that identified risk factors in the patient population. Here, we present the first systematic review of putative animal models of RLS, provide information about their face and construct validity, and report their role in deciphering the underlying pathophysiological mechanisms that may cause or contribute to RLS. We propose that identifying the causal links between genetic risk factors, altered organ functions, and changes to molecular pathways in neural circuitry will eventually lead to more effective new treatment options that bypass the side effects of the currently used therapeutics in RLS, especially for long-term therapy.

Genome-wide analysis identified novel susceptible genes of restless legs syndrome in migraineurs

Background

Restless legs syndrome is a highly prevalent comorbidity of migraine; however, its genetic contributions remain unclear.

Objectives

To identify the genetic variants of restless legs syndrome in migraineurs and to investigate their potential pathogenic roles.

Methods

We conducted a two-stage genome-wide association study (GWAS) to identify susceptible genes for restless legs syndrome in 1,647 patients with migraine, including 264 with and 1,383 without restless legs syndrome, and also validated the association of lead variants in normal controls unaffected with restless legs syndrome (n = 1,053). We used morpholino translational knockdown (morphants), CRISPR/dCas9 transcriptional knockdown, transient CRISPR/Cas9 knockout (crispants) and gene rescue in one-cell stage embryos of zebrafish to study the function of the identified genes.

Results

We identified two novel susceptibility loci rs6021854 (in VSTM2L) and rs79823654 (in CCDC141) to be associated with restless legs syndrome in migraineurs, which remained significant when compared to normal controls. Two different morpholinos targeting vstm2l and ccdc141 in zebrafish demonstrated behavioural and cytochemical phenotypes relevant to restless legs syndrome, including hyperkinetic movements of pectoral fins and decreased number in dopaminergic amacrine cells. These phenotypes could be partially reversed with gene rescue, suggesting the specificity of translational knockdown. Transcriptional CRISPR/dCas9 knockdown and transient CRISPR/Cas9 knockout of vstm2l and ccdc141 replicated the findings observed in translationally knocked-down morphants.

Conclusions

Our GWAS and functional analysis suggest VSTM2L and CCDC141 are highly relevant to the pathogenesis of restless legs syndrome in migraineurs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01409-9.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

LAR Receptor Tyrosine Phosphatase Family in Healthy and Diseased Brain

Protein phosphatases are major regulators of signal transduction and they are involved in key cellular mechanisms such as proliferation, differentiation, and cell survival. Here we focus on one class of protein phosphatases, the type IIA Receptor-type Protein Tyrosine Phosphatases (RPTPs), or LAR-RPTP subfamily. In the last decade, LAR-RPTPs have been demonstrated to have great importance in neurobiology, from neurodevelopment to brain disorders. In vertebrates, the LAR-RPTP subfamily is composed of three members: PTPRF (LAR), PTPRD (PTPδ) and PTPRS (PTPσ), and all participate in several brain functions. In this review we describe the structure and proteolytic processing of the LAR-RPTP subfamily, their alternative splicing and enzymatic regulation. Also, we review the role of the LAR-RPTP subfamily in neural function such as dendrite and axon growth and guidance, synapse formation and differentiation, their participation in synaptic activity, and in brain development, discussing controversial findings and commenting on the most recent studies in the field. Finally, we discuss the clinical outcomes of LAR-RPTP mutations, which are associated with several brain disorders.

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.

Neurodevelopmental Disorders in Patients With Complex Phenotypes and Potential Complex Genetic Basis Involving Non-Coding Genes, and Double CNVs

Neurodevelopmental disorders (NDDs) are a heterogeneous class of brain diseases, with a complex genetic basis estimated to account for up to 50% of cases. Nevertheless, genetic diagnostic yield is about 20%. Array-comparative genomic hybridization (array-CGH) is an established first-level diagnostic test able to detect pathogenic copy number variants (CNVs), however, most identified variants remain of uncertain significance (VUS). Failure of interpretation of VUSs may depend on various factors, including complexity of clinical phenotypes and inconsistency of genotype-phenotype correlations. Indeed, although most NDD-associated CNVs are de novo, transmission from unaffected parents to affected children of CNVs with high risk for NDDs has been observed. Moreover, variability of genetic components overlapped by CNVs, such as long non-coding genes, genomic regions with long-range effects, and additive effects of multiple CNVs can make CNV interpretation challenging. We report on 12 patients with complex phenotypes possibly explained by complex genetic mechanisms, including involvement of antisense genes and boundaries of topologically associating domains. Eight among the 12 patients carried two CNVs, either de novo or inherited, respectively, by each of their healthy parents, that could additively contribute to the patients’ phenotype. CNVs overlapped either known NDD-associated or novel candidate genes (PTPRD, BUD13, GLRA3, MIR4465, ABHD4, and WSCD2). Bioinformatic enrichment analyses showed that genes overlapped by the co-occurring CNVs have synergistic roles in biological processes fundamental in neurodevelopment. Double CNVs could concur in producing deleterious effects, according to a two-hit model, thus explaining the patients’ phenotypes and the incomplete penetrance, and variable expressivity, associated with the single variants. Overall, our findings could contribute to the knowledge on clinical and genetic diagnosis of complex forms of NDD.

Protein tyrosine phosphatases in cell adhesion

Adhesive structures between cells and with the surrounding matrix are essential for the development of multicellular organisms. In addition to providing mechanical integrity, they are key signalling centres providing feedback on the extracellular environment to the cell interior, and vice versa. During development, mitosis and repair, cell adhesions must undergo extensive remodelling. Post-translational modifications of proteins within these complexes serve as switches for activity. Tyrosine phosphorylation is an important modification in cell adhesion that is dynamically regulated by the protein tyrosine phosphatases (PTPs) and protein tyrosine kinases. Several PTPs are implicated in the assembly and maintenance of cell adhesions, however, their signalling functions remain poorly defined. The PTPs can act by directly dephosphorylating adhesive complex components or function as scaffolds. In this review, we will focus on human PTPs and discuss their individual roles in major adhesion complexes, as well as Hippo signalling. We have collated PTP interactome and cell adhesome datasets, which reveal extensive connections between PTPs and cell adhesions that are relatively unexplored. Finally, we reflect on the dysregulation of PTPs and cell adhesions in disease.

The Protein Tyrosine Phosphatase Receptor Delta Regulates Developmental Neurogenesis

PTPRD is a receptor protein tyrosine phosphatase that is genetically associated with neurodevelopmental disorders. Here, we asked whether Ptprd mutations cause aberrant neural development by perturbing neurogenesis in the murine cortex. We show that loss of Ptprd causes increases in neurogenic transit-amplifying intermediate progenitor cells and cortical neurons and perturbations in neuronal localization. These effects are intrinsic to neural precursor cells since acute Ptprd knockdown causes similar perturbations. PTPRD mediates these effects by dephosphorylating receptor tyrosine kinases, including TrkB and PDGFRβ, and loss of Ptprd causes the hyperactivation of TrkB and PDGFRβ and their downstream MEK-ERK signaling pathway in neural precursor cells. Moreover, inhibition of aberrant TrkB or MEK activation rescues the increased neurogenesis caused by knockdown or homozygous loss of Ptprd. These results suggest that PTPRD regulates receptor tyrosine kinases to ensure appropriate numbers of intermediate progenitor cells and neurons, suggesting a mechanism for its genetic association with neurodevelopmental disorders.

Large genome-wide association study identifies three novel risk variants for restless legs syndrome

Restless legs syndrome (RLS) is a common neurological sensorimotor disorder often described as an unpleasant sensation associated with an urge to move the legs. Here we report findings from a meta-analysis of genome-wide association studies of RLS including 480,982 Caucasians (cases = 10,257) and a follow up sample of 24,977 (cases = 6,651). We confirm 19 of the 20 previously reported RLS sequence variants at 19 loci and report three novel RLS associations; rs112716420-G (OR = 1.25, P = 1.5 × 10-18), rs10068599-T (OR = 1.09, P = 6.9 × 10-10) and rs10769894-A (OR = 0.90, P = 9.4 × 10-14). At four of the 22 RLS loci, cis-eQTL analysis indicates a causal impact on gene expression. Through polygenic risk score for RLS we extended prior epidemiological findings implicating obesity, smoking and high alcohol intake as risk factors for RLS. To improve our understanding, with the purpose of seeking better treatments, more genetics studies yielding deeper insights into the disease biology are needed.

Association of genetic variants in migraineurs with and without restless legs syndrome

Objective

Several single‐nucleotide polymorphisms (SNPs) are associated with restless legs syndrome (RLS). This study investigated whether or not additional SNP variants increase the risk of RLS in migraineurs and in migraine with aura (MA) and migraine without aura (MoA) subgroups.

Methods

Migraineurs with and without RLS were genotyped using an Affymetrix array. We performed association analyses for the entire cohort and the MA and MoA subgroups, which were divided further into episodic migraine (EM) and chronic migraine (CM). Potential correlations between SNPs and clinical indices in migraineurs with RLS were examined by multivariate regression analysis.

Results

The rs77234324 and rs79004933 SNPs were found in migraineurs with (P = 2.57E‐07) and without (P = 3.03E‐07) RLS. The A allele frequency for rs77234324 (on LGR6) was 0.1321 in migraineurs with RLS and 0.0166 in those without RLS (odds ratio, 8.978). The T allele frequency for rs79004933 (in the intergenic region) was 0.1981 in migraineurs with RLS and 0.0446 in those without (odds ratio, 5.281). rs2858654, rs76770509, rs4243475 in UTRN, rs150762626, and rs2668375 were identified in migraine with and without RLS in the MoA subgroup (P = 7.56E‐09, P = 2.30E‐08, P = 1.19E‐07, P = 6.86E‐07, and P = 8.05E‐07, respectively). There was a suggestion of an association between rs10510331 (P = 1.50E‐06) and CM and EM in patients with MoA and RLS. Multivariate regression showed a significant relationship between rs79004933 and the Beck Depression Inventory score.

Interpretation

rs77234324 in LGR6 and rs79004933 in the intergenic region were associated with RLS in migraineurs. Five SNPs increased the risk of RLS in patients with MoA.

Splice-dependent trans-synaptic PTPδ-IL1RAPL1 interaction regulates synapse formation and non-REM sleep

Alternative splicing regulates trans‐synaptic adhesions and synapse development, but supporting in vivo evidence is limited. PTPδ, a receptor tyrosine phosphatase adhering to multiple synaptic adhesion molecules, is associated with various neuropsychiatric disorders; however, its in vivo functions remain unclear. Here, we show that PTPδ is mainly present at excitatory presynaptic sites by endogenous PTPδ tagging. Global PTPδ deletion in mice leads to input‐specific decreases in excitatory synapse development and strength. This involves tyrosine dephosphorylation and synaptic loss of IL1RAPL1, a postsynaptic partner of PTPδ requiring the PTPδ‐meA splice insert for binding. Importantly, PTPδ‐mutant mice lacking the PTPδ‐meA insert, and thus lacking the PTPδ interaction with IL1RAPL1 but not other postsynaptic partners, recapitulate biochemical and synaptic phenotypes of global PTPδ‐mutant mice. Behaviorally, both global and meA‐specific PTPδ‐mutant mice display abnormal sleep behavior and non‐REM rhythms. Therefore, alternative splicing in PTPδ regulates excitatory synapse development and sleep by modulating a specific trans‐synaptic adhesion.

Emerging Concepts of the Pathophysiology and Adverse Outcomes of Restless Legs Syndrome

Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is a common neurological disorder affecting up to 5% to 10% of the population, but it remains an underdiagnosed condition. RLS/WED is characterized by uncomfortable sensations, mainly in the legs, which appear during inactivity and worsen in the evening or at night. The prevalence of RLS/WED and periodic leg movements (PLMs) is increased in patients with sleep-disordered breathing, particularly in those with OSA, the most common sleep disorder encountered in sleep centers. New advances in the pathophysiology of RLS/WED have shown important implications for various genetic markers, neurotransmitter dysfunction, and iron deficiency. A practical approach to RLS/WED management includes an accurate diagnosis, the identification of reversible contributing factors, and the use of nonpharmacological therapies, including iron substitution (oral or IV) therapy. Many pharmacological agents are effective for the treatment of RLS/WED. Until recently, the first-line treatment of RLS/WED consisted of low-dose dopamine agonists (DA). However, given the fact that DAs cause high rates of augmentation of symptoms, international guidelines recommend that whenever possible the initial treatment of choice should be an α2δ ligand, and avoidance of dopaminergic agents unless absolutely necessary. If necessary, the lowest effective dose should be used for only the shortest possible time. The symptoms of RLS/WED can disrupt the quality of sleep as well as the quality of life. IV iron therapy may be considered in patients with refractory RLS. A better understanding of RLS/WED pathophysiology will allow patients to receive tailored therapy, resulting in an improved quality of life.

Restless Legs Syndrome in Patients with Behçet's Disease and Multiple Sclerosis: Prevalence, Associated Conditions and Clinical Features

INTRODUCTION

To investigate the prevalence and characteristics of Restless Legs Syndrome (RLS) in patients with Behçet's Disease (BD) and Multiple Sclerosis (MS).

METHODS

Consecutive patients with BD and MS seen in the outpatient clinic were included in the study. As a control group, volunteer subjects without a known peripheral or central nervous system disorder were included. The BD group was divided into two sub-groups as BD with neurological involvement [Neuro-Behçet's Disease (NBD)] and BD without any neurological involvement (other BD) for further evaluation. Data on demographic characteristics, medical history and family history were collected, and all patients underwent neurological examination. The patients were evaluated for the presence of diagnostic criteria for RLS. The features and severity of RLS were evaluated in patients with RLS using Restless Legs Syndrome Identification Form, and the International Restless Legs Syndrome Study Group (IRLSSG) Rating Scale. The clinical and radiological findings of patients with BD and MS were retrieved from their medical files.

RESULTS

The study included a total of 96 patients with BD (mean age 39.9±11.8; 51 males; 41 patients with NBD) and 97 patients with MS (mean age 34.97±4.1 years; 24 males). There were 100 healthy control subjects (mean age 36.18±11.10 years; 46 males). RLS was more prevalent in MS (22.8%) and NBD (22%) groups compared to the control group (10%; p=0.004 and 0.029, respectively) with a statistically significant difference. The prevalence of RLS was higher in MS patients with less disability. Most severe RLS symptoms were observed in the MS group. The rate of sleep disorders was also higher in MS group. Although stress appeared to be a factor worsening RLS in all groups, its prevalence was higher in the MS group (p=0.011). There was no correlation between the distribution of magnetic resonance imaging lesions and RLS in both MS and NBD groups.

CONCLUSIONS

It is well established that RLS can accompany disorders involving the peripheral and central nervous systems such as all types of peripheral neuropathy, myelopathy, and Parkinson's disease. The present study showed that MS and NBD also seem to be a risk factor for RLS, being associated with more severe symptoms.

Structural basis of liprin-α-promoted LAR-RPTP clustering for modulation of phosphatase activity

Leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs) are cell adhesion molecules involved in mediating neuronal development. The binding of LAR-RPTPs to extracellular ligands induces local clustering of LAR-RPTPs to regulate axon growth and synaptogenesis. LAR-RPTPs interact with synaptic liprin-α proteins via the two cytoplasmic phosphatase domains, D1 and D2. Here we solve the crystal structure of LAR_D1D2 in complex with the SAM repeats of liprin-α3, uncovering a conserved two-site binding mode. Cellular analysis shows that liprin-αs robustly promote clustering of LAR in cells by both the liprin-α/LAR interaction and the oligomerization of liprin-α. Structural analysis reveals a unique homophilic interaction of LAR via the catalytically active D1 domains. Disruption of the D1/D1 interaction diminishes the liprin-α-promoted LAR clustering and increases tyrosine dephosphorylation, demonstrating that the phosphatase activity of LAR is negatively regulated by forming clusters. Additionally, we find that the binding of LAR to liprin-α allosterically regulates the liprin-α/liprin-β interaction.

Leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs) mediate guided axon growth and synapse formation and liprin-α proteins are their intracellular binding partners. Here the authors present the crystal structure of the phosphatase domains from the LAR-RPTP family member LAR bound to the SAM repeats of liprin-α3 and show that liprin-α binding enhances LAR cluster formation and reduces LAR phosphatase activity in cells.

Rotigotine suppresses sleep-related muscle activity augmented by injection of dialysis patients' sera in a mouse model of restless legs syndrome

Idiopathic restless legs syndrome (RLS) has a genetic basis wherein BTBD9 is associated with a higher risk of RLS. Hemodialysis patients also exhibit higher rates of RLS compared with the healthy population. However, little is known about the relationship of BTBD9 and end-stage renal disease to RLS pathophysiology. Here we evaluated sleep and leg muscle activity of Btbd9 mutant (MT) mice after administration of serum from patients with either idiopathic or RLS due to end-stage renal disease (renal RLS) and investigated the efficacy of treatment with the dopamine agonist rotigotine. At baseline, the amount of rapid eye movement (REM) sleep was decreased and leg muscle activity during non-REM (NREM) sleep was increased in MT mice compared to wild-type (WT) mice. Wake-promoting effects of rotigotine were attenuated by injection of serum from RLS patients in both WT and MT mice. Leg muscle activity during NREM sleep was increased only in MT mice injected with serum from RLS patients of ideiopatic and renal RLS. Subsequent treatment with rotigotine ameliorated this altered leg muscle activity. Together these results support previous reports showing a relationship between the Btbd9/dopamine system and RLS, and elucidate in part the pathophysiology of RLS.

Genetic and epidemiological characterization of restless legs syndrome in Québec

Currently, a total of 19 genetic loci are associated with the risk for developing RLS. This study aimed to assess these RLS predisposing genetic variants, as well as investigate the epidemiological profile and diagnostic features of individuals with RLS in the Québec population, using an interviewer–administered questionnaire. A total of 18 RLS-associated variants were genotyped in the Québec population-based CARTaGENE cohort. A case–control series consisting of 1,362 RLS cases and 1,379 age-matched unaffected controls was used to conduct a genetic and epidemiological association study that integrated the first four RLS diagnostic features of affected individuals, as well as additional RLS-related questions (e.g. frequency of the symptoms and number of total pregnancies in female). Five RLS-predisposing variants were significantly associated after Bonferroni correction and an additional five variants were nominally associated with RLS (p < 0.05). BTBD9 was the strongest genetic risk factor in our cohort (rs9296249, OR = 1.71, p = 9.57 × 10−10). The patient group that met all four essential diagnostic criteria of RLS provided the most significant genetic findings. These results suggest that employing the questionnaire which included standard diagnostic criteria of RLS could improve the accuracy of the survey-based studies.

NGL-3 in the regulation of brain development, Akt/GSK3b signaling, long-term depression, and locomotive and cognitive behaviors

Netrin-G ligand-3 (NGL-3) is a postsynaptic adhesion molecule known to directly interact with the excitatory postsynaptic scaffolding protein postsynaptic density-95 (PSD-95) and trans-synaptically with leukocyte common antigen-related (LAR) family receptor tyrosine phosphatases to regulate presynaptic differentiation. Although NGL-3 has been implicated in the regulation of excitatory synapse development by in vitro studies, whether it regulates synapse development or function, or any other features of brain development and function, is not known. Here, we report that mice lacking NGL-3 (Ngl3^−/− mice) show markedly suppressed normal brain development and postnatal survival and growth. A change of the genetic background of mice from pure to hybrid minimized these developmental effects but modestly suppressed N-methyl-D-aspartate (NMDA) receptor (NMDAR)-mediated synaptic transmission in the hippocampus without affecting synapse development, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR)-mediated basal transmission, and presynaptic release. Intriguingly, long-term depression (LTD) was near-completely abolished in Ngl3^−/− mice, and the Akt/glycogen synthase kinase 3β (GSK3β) signaling pathway, known to suppress LTD, was abnormally enhanced. In addition, pharmacological inhibition of Akt, but not activation of NMDARs, normalized the suppressed LTD in Ngl3^−/− mice, suggesting that Akt hyperactivity suppresses LTD. Ngl3^−/− mice displayed several behavioral abnormalities, including hyperactivity, anxiolytic-like behavior, impaired spatial memory, and enhanced seizure susceptibility. Among them, the hyperactivity was rapidly improved by pharmacological NMDAR activation. These results suggest that NGL-3 regulates brain development, Akt/GSK3β signaling, LTD, and locomotive and cognitive behaviors.

IL1B polymorphism is associated with essential tremor in Chinese population

BACKGROUND

The aim of the study was to investigate the genetic risk factors of essential tremor (ET) in Chinese Population.

METHODS

A total of 225 ET patients (25 ET patients also had restless legs syndrome (RLS) and were excluded from final analysis) and 229 controls were recruited. The diagnosis of ET was based on the Consensus Statement of the Movement Disorders Society on tremor. Polymerase chain reaction (PCR) and sequencing were used to detect 12 single nucleotide polymorphisms (SNPs) in seven candidate genes for RLS (HMOX1, HMOX2, VDR, IL17A, IL1B, NOS1 and ADH1B).

RESULTS

We found that one SNP was associated with the risk of ET in Chinese population after adjusting for age and gender: rs1143633 of IL1B (odds ratio [OR] =2.57, p = 0.003, recessive model), and the statistical result remained significant after Bonferroni correction. Then, we performed a query in Genotype-tissue Expression (GTEx), Brain eQTL Almanac (Braineac) databases and Blood expression quantitative trait loci (eQTL) browser. The significant association was only found between genotype at rs1143633 and IL1B expression level of putamen and white matter in Braineac database, which was more prominent with homozygous (GG) carriers.

CONCLUSIONS

Our study firstly reported the association of IL1B polymorphism with the risk of ET in Chinese population. However, the association might only suggest a marker of IL1B SNP associated with ET instead of the casual variant. Further studies are needed to confirm our finding.

Caenorhabditis elegans and its applicability to studies on restless legs syndrome

Restless legs syndrome (RLS) is a common neurological disorder in the United States. This disorder is characterized by an irresistible urge to move the legs, although the symptoms vary in a wide range. The pathobiology of RLS has been linked to iron (Fe) deficiency and dopaminergic (DAergic) dysfunction. Several genetic factors have been reported to increase the risk of RLS. Caenorhabditis elegans (C. elegans) is a well-established animal model with a fully sequenced genome, which is highly conserved with mammals. Given the detailed knowledge of its genomic architecture, ease of genetic manipulation and conserved biosynthetic and metabolic pathways, as well as its small size, ease of maintenance, speedy generation time and large brood size, C. elegans provides numerous advantages in studying RLS-associated gene-environment interactions. Here we will review current knowledge about RLS symptoms, pathology and treatments, and discuss the application of C. elegans in RLS study, including the worm homologous genes and methods that could be performed to advance the pathophysiology RLS.

Synaptic organizers: synaptic adhesion-like molecules (SALMs)

Synaptic adhesion-like molecules (SALMs), also known as leucine-rich repeat and fibronectin III domain-containing proteins (LRFNs), are a family of synaptic adhesion molecules that consist of five members. SALMs exhibit functions in regulating neurite outgrowth and branching, synapse formation, and synapse maturation. Recent clinical studies have shown an association of SALMs with diverse neurological disorders. In this review article, we summarize structural mechanisms of the interaction of SALMs with leukocyte common antigen (LAR) family receptor tyrosine phosphatases (LAR-RPTPs) for synaptic activity, based on recent advances in the structural biology of SALMs.

PTPRD: neurobiology, genetics, and initial pharmacology of a pleiotropic contributor to brain phenotypes

Receptor-type protein tyrosine phosphatase, receptor type D (PTPRD) has likely roles as a neuronal cell adhesion molecule and synaptic specifier. Interest in its neurobiology and genomics has been stimulated by results from human genetics and mouse models for phenotypes related to addiction, restless leg syndrome, neurofibrillary pathology in Alzheimer's disease, cognitive impairment/intellectual disability, mood lability, and obsessive-compulsive disorder. We review PTPRD's discovery, gene family, candidate homomeric and heteromeric binding partners, phosphatase activities, brain distribution, human genetic associations with nervous system phenotypes, and mouse model data relevant to these phenotypes. We discuss the recently reported discovery of the first small molecule inhibitor of PTPRD phosphatase, the identification of its addiction-related effects, and the implications of these findings for the PTPRD-associated brain phenotypes. In assembling PTPRD neurobiology, human genetics, and mouse genetic and pharmacological datasets, we provide a compelling picture of the roles played by PTPRD, its variation, and its potential as a target for novel therapeutics.

Iron for the treatment of restless legs syndrome

BACKGROUND

Restless legs syndrome (RLS) is a common neurologic disorder that is associated with peripheral iron deficiency in a subgroup of patients. It is unclear whether iron therapy is effective treatment for RLS.

OBJECTIVES

To evaluate the efficacy and safety of oral or parenteral iron for the treatment of restless legs syndrome (RLS) when compared with placebo or other therapies.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, PsycNFO, and CINAHL for the time period January 1995 to September 2017. We searched reference lists for additional published studies. We searched Clinicaltrials.gov and other clinical trial registries (September 2017) for ongoing or unpublished studies.

SELECTION CRITERIA

Controlled trials comparing any formulation of iron with placebo, other medications, or no treatment, in adults diagnosed with RLS according to expert clinical interview or explicit diagnostic criteria.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality, with discussion to reach consensus in the case of any disagreement. The primary outcome considered in this review was restlessness or unpleasant sensations, as experienced subjectively by the patient. We combined treatment/control differences in the outcomes across studies using random-effects meta-analyses. We analysed continuous data using mean differences (MDs) where possible and performed standardised mean difference (SMD) analyses when different measurements were used across studies. We calculated risk ratios (RRs) for dichotomous data using the Mantel-Haenszel method and 95% confidence intervals (CIs). We analysed study heterogeneity using the I² statistic. We used standard methodological procedures expected by Cochrane. We performed GRADE analysis using GRADEpro.

MAIN RESULTS

We identified and included 10 studies (428 total participants, followed for 2-16 weeks) in this review. Our primary outcome was restlessness or uncomfortable leg sensations, which was quantified using the International Restless Legs Scale (IRLS) (range, 0 to 40) in eight trials and a different RLS symptom scale in a ninth trial. Nine studies compared iron to placebo and one study compared iron to a dopamine agonist (pramipexole). The possibility for bias among the trials was variable. Three studies had a single element with high risk of bias, which was lack of blinding in two and incomplete outcome data in one. All studies had at least one feature resulting in unclear risk of bias.Combining data from the seven trials using the IRLS to compare iron and placebo, use of iron resulted in greater improvement in IRLS scores (MD -3.78, 95% CI -6.25 to -1.31; I²= 66%, 7 studies, 345 participants) measured 2 to 12 weeks after treatment. Including an eighth study, which measured restlessness using a different scale, use of iron remained beneficial compared to placebo (SMD -0.74, 95% CI -1.26 to -0.23; I² = 80%, 8 studies, 370 participants). The GRADE assessment of certainty for this outcome was moderate.The single study comparing iron to a dopamine agonist (pramipexole) found a similar reduction in RLS severity in the two groups (MD -0.40, 95% CI -5.93 to 5.13, 30 participants).Assessment of secondary outcomes was limited by small numbers of trials assessing each outcome. Iron did not improve quality of life as a dichotomous measure (RR 2.01, 95% CI 0.54 to 7.45; I²=54%, 2 studies, 39 participants), but did improve quality of life measured on continuous scales (SMD 0.51, 95% CI 0.15 to 0.87; I²= 0%, 3 studies, 128 participants), compared to placebo. Subjective sleep quality was no different between iron and placebo groups (SMD 0.19, 95% CI -0.18 to 0.56; I² = 9%, 3 studies, 128 participants), nor was objective sleep quality, as measured by change in sleep efficiency in a single study (-35.5 +/- 92.0 versus -41.4 +/- 98.2, 18 participants). Periodic limb movements of sleep were not significantly reduced with iron compared to placebo ( SMD -0.19, 95% CI -0.70 to 0.32; I² = 0%, 2 studies, 60 participants). Iron did not improve sleepiness compared to placebo, as measured on the Epworth Sleepiness Scale (data not provided, 1 study, 60 participants) but did improve the daytime tiredness item of the RLS-6 compared to placebo (least squares mean difference -1.5, 95% CI -2.5 to -0.6; 1 study, 110 participants). The GRADE rating for secondary outcomes ranged from low to very low.Prespecified subgroup analyses showed more improvement with iron in those trials studying participants on dialysis. The use of low serum ferritin levels as an inclusion criteria and the use or oral versus intravenous iron did not show significant subgroup differences.Iron did not result in significantly more adverse events than placebo (RR 1.48, 95% CI 0.97 to 2.25; I²=45%, 6 studies, 298 participants). A single study reported that people treated with iron therapy experienced fewer adverse events than the active comparator pramipexole.

AUTHORS' CONCLUSIONS

Iron therapy probably improves restlessness and RLS severity in comparison to placebo. Iron therapy may not increase the risk of side effects in comparison to placebo. We are uncertain whether iron therapy improves quality of life in comparison to placebo. Iron therapy may make little or no difference to pramipexole in restlessness and RLS severity, as well as in the risk of adverse events. The effect on secondary outcomes such as quality of life, daytime functioning, and sleep quality, the optimal timing and formulation of administration, and patient characteristics predicting response require additional study.

Immunoglobulin-Like Receptors and Their Impact on Wiring of Brain Synapses

Synapse formation is mediated by a surprisingly large number and wide variety of genes encoding many different protein classes. One of the families increasingly implicated in synapse wiring is the immunoglobulin superfamily (IgSF). IgSF molecules are by definition any protein containing at least one Ig-like domain, making this family one of the most common protein classes encoded by the genome. Here, we review the emerging roles for IgSF molecules in synapse formation specifically in the vertebrate brain, focusing on examples from three classes of IgSF members: ( a) cell adhesion molecules, ( b) signaling molecules, and ( c) immune molecules expressed in the brain. The critical roles for IgSF members in regulating synapse formation may explain their extensive involvement in neuropsychiatric and neurodevelopmental disorders. Solving the IgSF code for synapse formation may reveal multiple new targets for rescuing IgSF-mediated deficits in synapse formation and, eventually, new treatments for psychiatric disorders caused by altered IgSF-induced synapse wiring.

Susceptibility to neurofibrillary tangles: role of the PTPRD locus and limited pleiotropy with other neuropathologies

Tauopathies, including Alzheimer's disease (AD) and other neurodegenerative conditions, are defined by a pathological hallmark: neurofibrillary tangles (NFTs). NFT accumulation is thought to be closely linked to cognitive decline in AD. Here, we perform a genome-wide association study for NFT pathologic burden and report the association of the PTPRD locus (rs560380, P=3.8 × 10^-8) in 909 prospective autopsies. The association is replicated in an independent data set of 369 autopsies. The association of PTPRD with NFT is not dependent on the accumulation of amyloid pathology. In contrast, we found that the ZCWPW1 AD susceptibility variant influences NFT accumulation and that this effect is mediated by an accumulation of amyloid β plaques. We also performed complementary analyses to identify common pathways that influence multiple neuropathologies that coexist with NFT and found suggestive evidence that certain loci may influence multiple different neuropathological traits, including tau, amyloid β plaques, vascular injury and Lewy bodies. Overall, these analyses offer an evaluation of genetic susceptibility to NFT, a common end point for multiple different pathologic processes.

Lack of Association Between Shape and Volume of Subcortical Brain Structures and Restless Legs Syndrome

Objective

Previous studies on patients with restless legs syndrome (RLS) yielded inconclusive results in the magnetic resonance imaging (MRI)-based analyses of alterations of subcortical structures in the brain. The aim of this study was to compare volumes as well as shapes of subcortical structures and the hippocampus between RLS cases and controls. Additionally, the associations between the genetic risks for RLS and subcortical volumes were investigated.

Methods

We compared volumetric as well as shape differences assessed by 3 T MRI in the caudate nucleus, hippocampus, globus pallidus, putamen, and thalamus in 39 RLS cases versus 117 controls, nested within a population-based sample. In a subsample, we explored associations between known genetic risk markers for RLS and the volumes of the subcortical structures and the hippocampus.

Results

No significant differences between RLS cases and controls in subcortical and hippocampal shapes and volumes were observed. Furthermore, the genetic risk for RLS was unrelated to any alterations of subcortical and hippocampal gray matter volume.

Interpretation

We conclude that neither RLS nor the genetic risk for the disease give rise to changes in hippocampal and subcortical shapes and gray matter volumes.

Genetic Insights Into Frailty: Association of 9p21-23 Locus With Frailty

Frailty is a complex aging phenotype associated with increased vulnerability to disability and death. Understanding the biological antecedents of frailty may provide clues to healthy aging. The genome-wide association study hotspot, 9p21-23 region, is a risk locus for a number of age-related complex disorders associated with frailty. Hence, we conducted an association study to examine whether variations in 9p21-23 locus plays a role in the pathogenesis of frailty in 637 community-dwelling Ashkenazi Jewish adults aged 65 and older enrolled in the LonGenity study. The strongest association with frailty (adjusted for age and gender) was found with the SNP rs518054 (odds ratio: 1.635, 95% CI = 1.241-2.154; p-value: 4.81 × 10^-04) intergenic and located between LOC105375977 and C9orf146. The prevalence of four SNPs (rs1324192, rs7019262, rs518054, and rs571221) risk alleles haplotype in this region was significantly higher (compared with other haplotypes) in frail older adults compared with non-frail older adults (29.7 vs. 20.8%, p = 0.0005, respectively). Functional analyses using in silico approaches placed rs518054 in the CTCF binding site as well as DNase hypersensitive region. Furthermore, rs518054 was found to be in an enhancer site of NFIB gene located downstream. NFIB is a transcription factor that promotes cell differentiation during development, has antiapoptotic effect, maintains stem cell populations in adult tissues, and also acts as epigenetic regulators. Our study found novel association of SNPs in the regulatory region in the 9p21-23 region with the frailty phenotype; signifying the importance of this locus in aging.

Exploring the pathogenesis of canine epilepsy using a systems genetics method and implications for anti-epilepsy drug discovery

Epilepsy is a common neurological disorder in domestic dogs. However, its complex mechanism involves multiple genetic and environmental factors that make it challenging to identify the real pathogenic factors contributing to epilepsy, particularly for idiopathic epilepsy. Conventional genome-wide association studies (GWASs) can detect various genes associated with epilepsy, although they primarily detect the effects of single-site mutations in epilepsy while ignoring their interactions. In this study, we used a systems genetics method combining both GWAS and gene interactions and obtained 26 significantly mutated subnetworks. Among these subnetworks, seven genes were reported to be involved in neurological disorders. Combined with gene ontology enrichment analysis, we focused on 4 subnetworks that included traditional GWAS-neglected genes. Moreover, we performed a drug enrichment analysis for each subnetwork and identified significantly enriched candidate anti-epilepsy drugs using a hypergeometric test. We discovered 22 potential drug combinations that induced possible synergistic effects for epilepsy treatment, and one of these drug combinations has been confirmed in the Drug Combination database (DCDB) to have beneficial anti-epileptic effects. The method proposed in this study provides deep insight into the pathogenesis of canine epilepsy and implications for anti-epilepsy drug discovery.

Structural basis of SALM5-induced PTPδ dimerization for synaptic differentiation

SALM5, a synaptic adhesion molecule implicated in autism, induces presynaptic differentiation through binding to the LAR family receptor protein tyrosine phosphatases (LAR-RPTPs) that have been highlighted as presynaptic hubs for synapse formation. The mechanisms underlying SALM5/LAR-RPTP interaction remain unsolved. Here we report crystal structures of human SALM5 LRR-Ig alone and in complex with human PTPδ Ig1–3 (MeA⁻). Distinct from other LAR-RPTP ligands, SALM5 mainly exists as a dimer with LRR domains from two protomers packed in an antiparallel fashion. In the 2:2 heterotetrameric SALM5/PTPδ complex, a SALM5 dimer bridges two separate PTPδ molecules. Structure-guided mutations and heterologous synapse formation assays demonstrate that dimerization of SALM5 is prerequisite for its functionality in inducing synaptic differentiation. This study presents a structural template for the SALM family and reveals a mechanism for how a synaptic adhesion molecule directly induces cis-dimerization of LAR-RPTPs into higher-order signaling assembly.

Synaptic adhesion molecules mediate synaptic differentiation and formation. Here the authors present the structures of the synaptic adhesion molecule SALM5 alone and in complex with the LAR family receptor protein tyrosine phosphatase (LAR-RPTP) PTPδ, which reveals how SALM5 dimerization facilitates higher-order signaling assembly of LAR-RPTPs.

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.

Identification of novel risk loci for restless legs syndrome in genome-wide association studies in individuals of European ancestry: a meta-analysis

BACKGROUND

Restless legs syndrome is a prevalent chronic neurological disorder with potentially severe mental and physical health consequences. Clearer understanding of the underlying pathophysiology is needed to improve treatment options. We did a meta-analysis of genome-wide association studies (GWASs) to identify potential molecular targets.

METHODS

In the discovery stage, we combined three GWAS datasets (EU-RLS GENE, INTERVAL, and 23andMe) with diagnosis data collected from 2003 to 2017, in face-to-face interviews or via questionnaires, and involving 15 126 cases and 95 725 controls of European ancestry. We identified common variants by fixed-effect inverse-variance meta-analysis. Significant genome-wide signals (p≤5 × 10-8) were tested for replication in an independent GWAS of 30 770 cases and 286 913 controls, followed by a joint analysis of the discovery and replication stages. We did gene annotation, pathway, and gene-set-enrichment analyses and studied the genetic correlations between restless legs syndrome and traits of interest.

FINDINGS

We identified and replicated 13 new risk loci for restless legs syndrome and confirmed the previously identified six risk loci. MEIS1 was confirmed as the strongest genetic risk factor for restless legs syndrome (odds ratio 1·92, 95% CI 1·85-1·99). Gene prioritisation, enrichment, and genetic correlation analyses showed that identified pathways were related to neurodevelopment and highlighted genes linked to axon guidance (associated with SEMA6D), synapse formation (NTNG1), and neuronal specification (HOXB cluster family and MYT1).

INTERPRETATION

Identification of new candidate genes and associated pathways will inform future functional research. Advances in understanding of the molecular mechanisms that underlie restless legs syndrome could lead to new treatment options. We focused on common variants; thus, additional studies are needed to dissect the roles of rare and structural variations.

FUNDING

Deutsche Forschungsgemeinschaft, Helmholtz Zentrum München-Deutsches Forschungszentrum für Gesundheit und Umwelt, National Research Institutions, NHS Blood and Transplant, National Institute for Health Research, British Heart Foundation, European Commission, European Research Council, National Institutes of Health, National Institute of Neurological Disorders and Stroke, NIH Research Cambridge Biomedical Research Centre, and UK Medical Research Council.

A Genome-Wide Association Study Identifies UTRN Gene Polymorphism for Restless Legs Syndrome in a Korean Population

OBJECTIVE

Restless legs syndrome (RLS) is a highly heritable and common neurological sensorimotor disease disturbing sleep. The objective of study was to investigate significant gene for RLS by performing GWA and replication study in a Korean population.

METHODS

We performed a GWA study for RLS symptom group (n=325) and non-RLS group (n=2,603) from the Korea Genome Epidemiology Study. We subsequently performed a replication study in RLS and normal controls (227 RLS and 229 controls) to confirm the present GWA study findings as well as previous GWA study results.

RESULTS

In the initial GWA study of RLS, we observed an association of rs11645604 (OR=1.531, p=1.18×10^-6) in MPHOSPH6 on chromosome 16q23.3, rs1918752 (OR=0.6582, p=1.93×10^-6) and rs9390170 (OR=0.6778, p=7.67×10^-6) in UTRN on chromosome 6q24. From the replication samples, we found rs9390170 in UTRN (p=0.036) and rs3923809 and rs9296249 in BTBD9 (p=0.045, p=0.046, respectively) were significantly associated with RLS. Moreover, we found the haplotype polymorphisms of rs9357271, rs3923809, and rs9296249 (overall p=5.69×10^-18) in BTBD9 was associated with RLS.

CONCLUSION

From our sequential GWA and replication study, we could hypothesize rs9390170 polymorphism in UTRN is a novel genetic marker for susceptibility to RLS. Regarding with utrophin, which is encoded by UTRN, is preferentially expressed in the neuromuscular synapse and myotendinous junctions, we speculate that utrophin is involved in RLS, particularly related to the neuromuscular aspects.

Individuals with Restless Legs Syndrome Tend to have Severe Depressive Symptoms: Findings from a Community-Based Cohort Study

Restless legs syndrome (RLS) is a sensorimotor neurological disturbance causing physical and psychological distress. Here, we investigated the severity and effect of depressive symptoms in RLS among a Korean cohort population. Depressive symptoms were more prevalent in the RLS group than in the non-RLS group [≥mild depression: odds ratio (OR)=1.95, p<0.001; ≥ moderate depression: OR=6.15, p<0.001; and ≥severe depression: OR=56.54, p<0.001], with a predominant proportion of severe depression (97%) in the RLS group. We found that difficulty falling asleep (OR=8.16, p<0.001), broken sleep (OR=11.66, p=0.001), early morning awakening (OR=8.5, p<0.001), and excessive daytime sleepiness (OR=3.04, p=0.031) were significantly frequent in individuals with severe depression in the RLS group. Red blood cell count was significantly low in individuals with severe depression in the RLS group (p=0.041). We found that severe depression was associated with RLS, suggesting the evaluation and management of mood symptoms and sleep-related and hematological features when treating RLS.

Restless Legs Syndrome: From Pathophysiology to Clinical Diagnosis and Management

Restless legs syndrome (RLS), a common neurological sensorimotor disorder in western countries, has gained more and more attention in Asian countries. The prevalence of RLS is higher in older people and females. RLS is most commonly related to iron deficiency, pregnancy and uremia. The RLS symptoms show a significant circadian rhythm and a close relationship to periodic limb movements (PLMs) in clinical observations, while the pathophysiological pathways are still unknown. The diagnostic criteria have been revised in 2012 to improve the validity of RLS diagnosis. Recent studies have suggested an important role of iron decrease of brain in RLS pathophysiology. Dopaminergic (DA) system dysfunction in A11 cell groups has been recognized long ago from clinical treatment and autopsy. Nowadays, it is believed that iron dysfunction can affect DA system from different pathways and opioids have a protective effect on DA system. Several susceptible single nucleotide polymorphisms such as BTBD9 and MEIS1, which are thought to be involved in embryonic neuronal development, have been reported to be associated with RLS. Several pharmacological and non-pharmacological treatment are discussed in this review. First-line treatments of RLS include DA agents and α2δ agonists. Augmentation is very common in long-term treatment of RLS which makes prevention and management of augmentation very important for RLS patients. A combination of different types of medication is effective in preventing and treating augmentation. The knowledge on RLS is still limited, the pathophysiology and better management of RLS remain to be discovered.

Pleiotropic genetic effects influencing sleep and neurological disorders

Research evidence increasingly points to the large impact of sleep disturbances on public health. Many aspects of sleep are heritable and genes influencing traits such as timing, EEG characteristics, sleep duration, and response to sleep loss have been identified. Notably, large-scale genome-wide analyses have implicated numerous genes with small effects on sleep timing. Additionally, there has been considerable progress in the identification of genes influencing risk for some neurological sleep disorders. For restless legs syndrome, implicated variants are typically in genes associated with neuronal development. By contrast, genes conferring risk for narcolepsy function in the immune system. Many genetic variants associated with sleep disorders are also implicated in neurological disorders in which sleep abnormalities are common; for example, variation in genes involved in synaptic homoeostasis are implicated in autism spectrum disorder and sleep-wake control. Further investigation into pleiotropic roles of genes influencing both sleep and neurological disorders could lead to new treatment strategies for a variety of sleep disturbances.

Iron, dopamine, genetics, and hormones in the pathophysiology of restless legs syndrome

Restless legs syndrome (RLS) is a common, chronic neurologic condition, which causes a persistent urge to move the legs in the evening that interferes with sleep. Human and animal studies have been used to study the pathophysiologic state of RLS and much has been learned about the iron and dopamine systems in relation to RLS. Human neuropathologic and imaging studies have consistently shown decreased iron in different brain regions including substantia nigra and thalamus. These same areas also demonstrate a state of relative dopamine excess. While it is not known how these changes in dopamine or iron produce the symptoms of RLS, genetic and hormone studies of RLS have identified other biologic systems or genes, such as the endogenous opioid and melanocortin systems and BTBD9 and MEIS1, that may explain some of the iron or dopamine changes in relation to RLS. This manuscript will review what is known about the pathophysiology of RLS, especially as it relates to changes in iron, dopamine, genetics, and hormonal systems.