A nationwide survey of Aicardi-Goutières syndrome patients identifies a strong association between dominant TREX1 mutations and chilblain lesions: Japanese cohort study.

OBJECTIVES: Aicardi-Goutières syndrome (AGS) is a rare, genetically determined, early onset progressive encephalopathy associated with autoimmune manifestations. AGS is usually inherited in an autosomal recessive manner. The disease is rare, therefore the clinical manifestations and genotype-phenotype correlations, particularly with regard to autoimmune diseases, are still unclear. Here we performed a nationwide survey of AGS patients in Japan and analysed the genetic and clinical data. METHODS: Patients were recruited via questionnaires sent to paediatric or adult neurologists in Japanese hospitals and institutions. Genetic analysis was performed and clinical data were collected. RESULTS: Fourteen AGS patients were identified from 13 families; 10 harboured genetic mutations. Three patients harboured dominant-type TREX1 mutations. These included two de novo cases: one caused by a novel heterozygous p.His195Tyr mutation and the other by a novel somatic mosaicism resulting in a p.Asp200Asn mutation. Chilblain lesions were observed in all patients harbouring dominant-type TREX1 mutations. All three patients harbouring SAMHD1 mutations were diagnosed with autoimmune diseases, two with SLE and one with SS. The latter is the first reported case. CONCLUSION: This study is the first to report a nationwide AGS survey, which identified more patients with sporadic AGS carrying de novo dominant-type TREX1 mutations than expected. There was a strong association between the dominant-type TREX1 mutations and chilblain lesions, and between SAMHD1 mutations and autoimmunity. These findings suggest that rheumatologists should pay attention to possible sporadic AGS cases presenting with neurological disorders and autoimmune manifestations.

Clinicopathological features of neuropathy associated with lymphoma.

Lymphoma causes various neurological manifestations that might affect any part of the nervous system and occur at any stage of the disease. The peripheral nervous system is one of the major constituents of the neurological involvement of lymphoma. In this study we characterized the clinical, electrophysiological and histopathological features of 32 patients with neuropathy associated with non-Hodgkin's lymphoma that were unrelated to complications resulting from treatment for lymphoma. Nine patients had pathologically-proven neurolymphomatosis with direct invasion of lymphoma cells into the peripheral nervous system. These patients showed lymphomatous cell invasion that was more prominent in the proximal portions of the nerve trunk and that induced demyelination without macrophage invasion and subsequent axonal degeneration in the portion distal from the demyelination site. Six other patients were also considered to have neurolymphomatosis because these patients showed positive signals along the peripheral nerve on fluorodeoxyglucose positron emission tomography imaging. Spontaneous pain can significantly disrupt daily activities, as frequently reported in patients diagnosed with neurolymphomatosis. In contrast, five patients were considered to have paraneoplastic neuropathy because primary peripheral nerve lesions were observed without the invasion of lymphomatous cells, with three patients showing features compatible with chronic inflammatory demyelinating polyneuropathy, one patient showing sensory ganglionopathy, and one patient showing vasculitic neuropathy. Of the other 12 patients, 10 presented with multiple mononeuropathies. These patients showed clinical and electrophysiological features similar to those of neurolymphomatosis rather than paraneoplastic neuropathy. Electrophysiological findings suggestive of demyelination were frequently observed, even in patients with neurolymphomatosis. Eleven of the 32 patients, including five patients with neurolymphomatosis, fulfilled the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic criteria of definite chronic inflammatory demyelinating polyneuropathy. Some of these patients, even those with neurolymphomatosis, responded initially to immunomodulatory treatments, including the administration of intravenous immunoglobulin and steroids. Patients with lymphoma exhibit various neuropathic patterns, but neurolymphomatosis is the major cause of neuropathy. Misdiagnoses of neurolymphomatosis as chronic inflammatory demyelinating polyneuropathy are frequent due to a presence of a demyelinating pattern and the initial response to immunomodulatory treatments. The possibility of the concomitance of lymphoma should be considered in various types of neuropathy, even if the diagnostic criteria of chronic inflammatory demyelinating polyneuropathy are met, particularly in patients complaining of pain.

Proteasome assembly defect due to a proteasome subunit beta type 8 (PSMB8) mutation causes the autoinflammatory disorder, Nakajo-Nishimura syndrome.

Nakajo-Nishimura syndrome (NNS) is a disorder that segregates in an autosomal recessive fashion. Symptoms include periodic fever, skin rash, partial lipomuscular atrophy, and joint contracture. Here, we report a mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit ß5i in patients with NNS. This G201V mutation disrupts the ß-sheet structure, protrudes from the loop that interfaces with the ß4 subunit, and is in close proximity to the catalytic threonine residue. The ß5i mutant is not efficiently incorporated during immunoproteasome biogenesis, resulting in reduced proteasome activity and accumulation of ubiquitinated and oxidized proteins within cells expressing immunoproteasomes. As a result, the level of interleukin (IL)-6 and IFN-γ inducible protein (IP)-10 in patient sera is markedly increased. Nuclear phosphorylated p38 and the secretion of IL-6 are increased in patient cells both in vitro and in vivo, which may account for the inflammatory response and periodic fever observed in these patients. These results show that a mutation within a proteasome subunit is the direct cause of a human disease and suggest that decreased proteasome activity can cause inflammation.

Dystonia and Parkinsonism in COA7-related disorders: expanding the phenotypic spectrum.

BACKGROUND AND OBJECTIVE: Biallelic mutations in the COA7 gene have been associated with spinocerebellar ataxia with axonal neuropathy type 3 (SCAN3), and a notable clinical diversity has been observed. We aim to identify the genetic and phenotypic spectrum of COA7-related disorders. METHODS: We conducted comprehensive genetic analyses on the COA7 gene within a large group of Japanese patients clinically diagnosed with inherited peripheral neuropathy or cerebellar ataxia. RESULTS: In addition to our original report, which involved four patients until 2018, we identified biallelic variants of the COA7 gene in another three unrelated patients, and the variants were c.17A > G (p.D6G), c.115C > T (p.R39W), and c.449G > A (p.C150Y; novel). Patient 1 presented with an infantile-onset generalized dystonia without cerebellar ataxia. Despite experiencing an initial transient positive response to levodopa and deep brain stimulation, he became bedridden by the age of 19. Patient 2 presented with cerebellar ataxia, neuropathy, as well as parkinsonism, and showed a slight improvement upon levodopa administration. Dopamine transporter SPECT showed decreased uptake in the bilateral putamen in both patients. Patient 3 exhibited severe muscle weakness, respiratory failure, and feeding difficulties. A haplotype analysis of the mutation hotspot in Japan, c.17A > G (p.D6G), uncovered a common haplotype block. CONCLUSION: COA7-related disorders typically encompass a spectrum of conditions characterized by a variety of major (cerebellar ataxia and axonal polyneuropathy) and minor (leukoencephalopathy, dystonia, and parkinsonism) symptoms, but may also display a dystonia-predominant phenotype. We propose that COA7 should be considered as a new causative gene for infancy-onset generalized dystonia, and COA7 gene screening is recommended for patients with unexplained dysfunctions of the central and peripheral nervous systems.

Whole-Exome Sequencing Identified a Novel DYRK1A Variant in a Patient With Intellectual Developmental Disorder, Autosomal Dominant 7.

Intellectual developmental disorder, autosomal dominant 7 (MRD7; OMIM 614104) is a rare disease characterized by microcephaly, intellectual disability, speech delay, feeding difficulties, and facial dysmorphisms. This disorder is caused by pathogenic/likely pathogenic variants of the DYRK1A gene, which encodes dual-specificity tyrosine-phosphorylation-regulated kinase 1A. Here, we report a case of MRD7 that was diagnosed using Face2Gene and whole-exome sequencing (WES). A 22-year-old man presented with microcephaly, intellectual disability, slender body, long slender fingers, and facial dysmorphisms. He was previously diagnosed with Cornelia de Lange syndrome (CdLS) at four years of age. However, his CdLS clinical diagnostic score was low at 22 years of age. The Face2Gene application introduced several candidate diseases including MRD7. Finally, by utilizing WES and Sanger sequencing analysis of cloned cDNA, we identified a novel heterozygous duplication variant (c.848dup, p.(Asn283LysfsTer6)) in the DYRK1A gene, which introduces a premature stop codon. This report provides more information about the phenotypic spectrum of a young adult patient with MRD7. Face2Gene helped us introduce candidate diseases of the patient. Registering further genetically confirmed cases with MRD7 will improve the accuracy of the diagnostic recommendations in Face2Gene. Moreover, WES is a powerful tool for diagnosing rare genetic diseases, such as MRD7.

Cerebellar Hypoperfusion in Two Patients with Cornelia de Lange Syndrome with Novel NIPBL Variants.

Introduction: Cornelia de Lange syndrome (CdLS) is a rare congenital malformation characterized by distinctive facial features, short stature, and limb defects. In addition, half of the patients with CdLS exhibit repetitive self-injurious behaviors (SIBs) related to intellectual disability with autistic traits. CdLS is caused by pathogenic variants of genes encoding the cohesin complex pathway, with 70% of these variants identified in the nipped-B-like (NIPBL) gene. Case Presentation: We report 2 patients with CdLS who exhibited repetitive SIBs. Patient 1, a 40-year-old male, carried a novel heterozygous duplication variant, c.1458dup, p.(Glu487*), in exon 9 of the NIPBL gene. Patient 2, a 49-year-old female, carried a novel heterozygous insertion variant, c.1751_1752ins[A;1652_1751], p.(Asp584Glufs*8), in exon 10 of the NIPBL gene. These variants were predicted to confer loss of function to the protein because of a premature stop codon. In both patients, single-photon emission computed tomography using N-isopropyl-p-[123I] iodoamphetamine (IMP-SPECT) revealed diffuse hypoperfusion in the cerebellum. Discussion: This report identified 2 novel pathogenic variants in the NIPBL gene and the relationship between SIBs and cerebellar hypoperfusion in patients with CdLS. The cerebellar hypoperfusion might have been caused by the dysfunction of the cohesin complex via the downregulation of the NIPBL gene products. Further studies should be conducted to elucidate the contribution of the NIPBL gene to the development of the cerebello-cerebral cortical circuits associated with behavioral disorders.

Phosphorylated Syk expression is enhanced in Nasu-Hakola disease brains.

Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by a loss-of-function mutation of DNAX-activation protein 12 (DAP12) or triggering receptor expressed on myeloid cells 2 (TREM2). TREM2 and DAP12 constitute a receptor/adaptor complex on myeloid cells. The post-receptor signals are transmitted via rapid phosphorylation of the immunoreceptor tyrosine-based activating motif (ITAM) of DAP12, mediated by Src protein tyrosine kinases, followed by binding of phosphorylated ITAM to Src homology 2 (SH2) domains of spleen tyrosine kinase (Syk), resulting in autophosphorylation of the activation loop of Syk. To elucidate the molecular mechanism underlying the pathogenesis of NHD, we investigated Syk expression and activation in the frontal cortex and the hippocampus of three NHD and eight control brains by immunohistochemistry. In NHD brains, the majority of neurons expressed intense immunoreactivities for Syk and Y525/Y526-phosphorylated Syk (pSyk) chiefly located in the cytoplasm, while more limited populations of neurons expressed Src. The levels of pSyk expression were elevated significantly in NHD brains compared with control brains. In both NHD and control brains, substantial populations of microglia and macrophages expressed pSyk, while the great majority of reactive astrocytes and myelinating oligodendrocytes did not express pSyk, Syk or Src. These observations indicate that neuronal expression of pSyk was greatly enhanced in the cerebral cortex and the hippocampus of NHD brains, possibly via non-TREM2/DAP12 signaling pathways involved in Syk activation.

Dyggve-Melchior-Clausen Syndrome Caused by a Novel Frameshift Variant in a Japanese Patient.

Introduction: Dyggve-Melchior-Clausen syndrome (DMC) is a rare autosomal recessive spondyloepimetaphyseal dysplasia characterized by short stature, microcephaly, intellectual disability, and coarse face. This disorder is caused by pathogenic/likely pathogenic variants of the DYM gene which encodes dymeclin. Case Presentation: Herein, we report a 60-year-old Japanese man who was born to consanguineous parents. He presented with abdominal distention and rectal prolapse in addition to the common features of DMC. We identified a novel homozygous frameshift variant [c.1670delT, p.(Leu557Argfs*20)] in the DYM gene, which introduces a premature stop codon. Histological analysis revealed disarrangement of actin filaments in cultured fibroblasts. Discussion: To the best of our knowledge, this is the first Japanese case of DMC with a confirmed variant in the DYM gene. This report provides more information about the geographic distribution and phenotypic spectrum of DMC. Moreover, it presents a novel DYM variant and insights about DMC pathology that may be associated with the disarrangement of actin filaments.

Immunohistochemical characterization of microglia in Nasu-Hakola disease brains.

Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by genetic mutations of DNAX-activation protein 12 (DAP12) or triggering receptor expressed on myeloid cells 2 (TREM2). TREM2 and DAP12 constitute a receptor/adapter signaling complex expressed on osteoclasts, dendritic cells (DC), macrophages and microglia. Previous studies using knockout mice and mouse brain cell cultures suggest that a loss-of-function of DAP12/TREM2 in microglia plays a central role in the neuropathological manifestation of NHD. However, there exist no immunohistochemical studies that focus attention on microglia in NHD brains. To elucidate a role of microglia in the pathogenesis of NHD, we searched NHD-specific biomarkers and characterized their expression on microglia in NHD brains. Here, we identified allograft inflammatory factor 1 (AIF1, Iba1) and sialic acid binding Ig-like lectin 1 (SIGLEC1) as putative NHD-specific biomarkers by bioinformatics analysis of microarray data of NHD DC. We studied three NHD and eight control brains by immunohistochemistry with a panel of 16 antibodies, including those against Iba1 and SIGLEC1. We verified the absence of DAP12 expression in NHD brains and the expression of DAP12 immunoreactivity on ramified microglia in control brains. Unexpectedly, TREM2 was not expressed on microglia but expressed on a small subset of intravascular monocytes/macrophages in control and NHD brains. In the cortex of NHD brains, we identified accumulation of numerous Iba1-positive microglia to an extent similar to control brains, while SIGLEC1 was undetectable on microglia in all the brains examined. These observations indicate that human microglia in brain tissues do not express TREM2 and DAP12-deficient microglia are preserved in NHD brains, suggesting that the loss of DAP2/TREM2 function in microglia might not be primarily responsible for the neuropathological phenotype of NHD.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis with Decrease in Blood Flow in Cerebellum.

In anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, progressive cerebellar atrophy potentially leads to severe sequelae. We encountered a patient with anti-NMDAR antibody encephalitis who showed a decrease of blood flow in the cerebellum. A 15-year-old girl presented with consciousness disturbance. Influenza encephalopathy was suspected, and she was treated with glucocorticoid pulse therapy, high-dose intravenous immunoglobulins, and plasma exchange sequentially. She subsequently underwent left oophorectomy due to the presence of anti-NMDAR antibodies and a left ovarian teratoma. In spite of the surgery, her neuropsychiatric symptoms persisted, and she recovered slowly after the introduction of oral methotrexate (MTX). Sequential cerebral blood flow monitoring with single-photon emission computed tomography showed marked cerebellar hypoperfusion. Although mild impairments including working memory and verbal fluency persisted, she eventually returned to high school 3 years after onset. Profound cerebellar hypoperfusion including lobules VI and VII may be the reason for her working memory impairment and speaking problems. Oral MTX may be a promising alternative treatment for some refractory cases of anti-NMDAR encephalitis.

Frontal Hypoperfusion and the Effectiveness of Perampanel in Long-Lived Patient with Lafora Disease.

We report a long-lived patient with Lafora disease (LD). A 34-year-old woman experienced onset of seizures at the age of 11 years. She was bedridden in her early twenties due to frequent generalized tonic-clonic seizures, myoclonus, and progressive mental deterioration. Her seizures occurred all the time despite administration of multiple anticonvulsants at high doses. At the age of 31, she started perampanel, which resulted in reduction of anticonvulsants after her visible myoclonus and convulsions disappeared. Brain magnetic resonance imaging showed marked cerebral and cerebellar atrophy, and single-photon emission computed tomography using N-isopropyl-p-[123I] iodoamphetamine (IMP-SPECT) revealed significant hypoperfusion of the frontal lobe and cerebellum. We identified a W219R homozygous mutation in exon 1 of the NHLRC1 gene. Because perampanel may not only control seizures but also prevent mental deterioration in LD, we propose that perampanel should be administered from the early stage of LD.

Segmental copy-number gain within the region of isopentenyl diphosphate isomerase genes in sporadic amyotrophic lateral sclerosis.

AIMS: Sporadic amyotrophic lateral sclerosis (SALS) seems to be a multifactorial disease, the pathogenesis of which may involve both genetic and environmental factors. The present study aims at identifying a possible genetic change that confers risk for SALS. METHODS: We performed whole-genome screening of a copy-number variation (CNV) using a CNV beadchip, followed by real-time quantitative polymerase chain reaction (qPCR) and region-targeted high-density oligonucleotide tiling microarray. RESULTS: Within the 40-kb region on 10p15.3 subtelomere, which harbours two genes encoding isopentenyl diphosphate isomerase 1 (IDI1) and IDI2, we found a segmental copy-number gain in a large proportion of SALS patients. qPCR analysis demonstrated the copy-number gain in 46 out of 83 SALS patients, as compared with 10 out of 99 controls (p=4.86×10(-11), Odds Ratio 10.8); subsequent tiling microarray validated qPCR results and elucidated the fine structure of segmental gains. CONCLUSIONS: A segmental copy-number gain in the IDI1/IDI2 gene region may play a significant role in the pathogenesis of SALS.

A case of female adrenoleukodystrophy carrier with insidious neurogenic bladder.

A 65-year-old woman with mutation of the ABCD1 gene for adrenoleukodystrophy (ALD) was admitted to our hospital with a urinary tract infection. Abdominal computed tomography showed dilation of the urinary tract. Although she had noticed pollakisuria since her forties, she had not been followed up by any medical institutions until we diagnosed her as a female carrier with ALD. ALD is an X-linked pattern of inheritance that typically affects males, but many female carriers actually present slowly progressive myelopathy and neuropathy. Therefore, it is important to identify female carriers with ALD and treat them at the earliest stage possible.

The Effectiveness of Perampanel for Myoclonic Seizures in Down Syndrome with Isodicentric Chromosome 21.

Epileptic seizures are common in the elderly Down syndrome population. We encountered a patient with Down syndrome in whom karyotyping showed the rare isodicentric chromosome 21 and who suffered from myoclonic seizures. A 52-year-old woman with Down syndrome experienced sudden onset of drowsiness and frequent myoclonic jerks in the upper body. Video-EEG recordings demonstrated generalized polyspike-wave discharges consistent with myoclonic jerks, which were exacerbated by photo-stimulation. Her myoclonus completely resolved with perampanel administration. Perampanel was effective for myoclonic seizures in our patient. We suggest that perampanel is an option as first-line therapy for epilepsy and myoclonus in elderly Down syndrome patients.

Partial reduced Pi transport function of PiT-2 might not be sufficient to induce brain calcification of idiopathic basal ganglia calcification.

Idiopathic basal ganglia calcification (IBGC) is a rare intractable disease characterized by abnormal mineral deposits, including mostly calcium in the basal ganglia, thalamus, and cerebellum. SLC20A2 is encoding the phosphate transporter PiT-2 and was identified in 2012 as the causative gene of familial IBGC. In this study, we investigated functionally two novel SLC20A2 variants (c.680C > T, c.1487G > A) and two SLC20A2 variants (c.82G > A, c.358G > C) previously reported from patients with IBGC. We evaluated the function of variant PiT-2 using stable cell lines. While inorganic phosphate (Pi) transport activity was abolished in the cells with c.82G > A, c.358G > C, and c.1487G > A variants, activity was maintained at 27.8% of the reference level in cells with the c.680C > T variant. Surprisingly, the c.680C > T variant had been discovered by chance in healthy members of an IBGC family, suggesting that partial preservation of Pi transport activity may avoid the onset of IBGC. In addition, we confirmed that PiT-2 variants could be translocated into the cell membrane to the same extent as PiT-2 wild type. In conclusion, we investigated the PiT-2 dysfunction of four SLC20A2 variants and suggested that a partial reduced Pi transport function of PiT-2 might not be sufficient to induce brain calcification of IBGC.

Expression of caveolar components in primary desminopathy.

Myofibrillar myopathies (MFM) involve accumulation of various proteins in the muscle cytoplasm. In myopathy with a heterozygous A337P mutation of the desmin gene, electron-micrographs showed aggregates of vesicular and tubular structures. Positive cytoplasmic reaction for caveolin-3 immunohistochemistry and cholera toxin B binding suggested that caveolae comprised some of the aggregates. As caveolae occur in the Golgi complex and are transported to the cell surface, the results suggest inhibition of their trafficking to the sarcolemma. Alternatively, they could be trapped during internalization. We hypothesize that the accumulation of multiple proteins in MFM could be partially due to inhibited intracellular trafficking.

Purkinje cell loss in the cerebellar flocculus in patients with ataxia with ocular motor apraxia type 1/early-onset ataxia with ocular motor apraxia and hypoalbuminemia.

We genetically screened patients with ataxia with ocular motor apraxia type 1 (AOA1)/early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH), with a Japanese variant form of Friedreich's ataxia. Three patients were found to have a homozygous insertion mutation of the aprataxin gene (689insT). An elder sister of a patient in this series died of cerebral hemorrhage at the age of 45, and underwent autopsy. In her cerebellar cortex, the mean density of Purkinje cells in the flocculus had predominantly decreased to 6.7% of normal controls, whereas the Purkinje cells in the other areas of the cerebellar hemisphere had decreased to 78.2%. This suggests that the cerebellar flocculus is the primary affected lesion in AOA1/EAOH, which should be associated with ocular motor apraxia.

[Nationwide questionnaire study in "the Model Core Curriculum" and current status for the undergraduate education in neurology].

To investigate the current state of education for undergraduates, the subcommittee of the Japanese Society of Neurology for undergraduate education sent a questionnaire on the 2001-version of Model Core Curriculum to the department of neurology in 80 medical universities and their 7 associate medical institutes throughout Japan. Answers were obtained from 56 out of those 87 institutes (64.4%). According to the answers, the Core Curriculum was introduced to the program of undergraduate education in 93% of those 56 universities. For the revision of neurology part in the current Core Curriculum, there are number of requests for improving the description on the neurological examination, list of common symptoms and disorders, and addition of therapeutics. Despite application of the Model Core Curriculum in medical education, the present study disclosed that there were considerable difference in the number and content of the lectures, and the duration of clinical clerkship in neurology ward. These differences of the curriculum and training program depends on not only the number of staffs, but also whether they are working as staffs in a department of neurology or as a small group of neurologists within a department other than neurology.

Medical Attitudes Survey for Female Dystrophinopathy Carriers in Japan.

Objective This study attempted to clarify the current status of female dystrophinopathy carriers, including the numbers of patients, the status of genetic screening, the status of counseling, physicians' understanding, and barriers to registration. Methods We sent out questionnaires to 402 physicians registered in the Remudy dystrophinopathy registry. The total number of responses received was 130 (response rate: 32%). Result In total, 1,212 cases of Duchenne muscular dystrophy, 365 cases of Becker muscular dystrophy, and 132 cases of female dystrophinopathy with a confirmed genetic mutation were encountered, and genetic testing was performed in the mother in 137, 23, and 12 cases, respectively. With respect to the risk of the onset of health problems, 25% of physicians always explained, 29% usually explained, 29% sometimes explained, and 13% never explained the risk to the mothers and female siblings of dystrophinopathy patients. The most common reason for not explaining the risk was a lack of knowledge/information. Thirty-five percent were familiar with the guidelines for testing the heart function of carriers. Conclusion Fewer mothers of dystrophinopathy patients have undergone genetic testing in Japan than in other countries. A significant portion of doctors did not explain the risks of health problems due to a lack of knowledge. We hope this survey will lead to an increased discussion of female dystrophinopathy patients.

The role of G-protein-coupled receptor kinase 5 in pathogenesis of sporadic Parkinson's disease.

Sporadic Parkinson's disease (sPD) is a common neurodegenerative disorder, characterized by selective degeneration of dopaminergic neurons in the substantia nigra. Although the pathogenesis of the disease remains undetermined, phosphorylation of alpha-synuclein and its oligomer formation seem to play a key role. However, the protein kinase(s) involved in the phosphorylation in the pathogenesis of sPD has not been identified. Here, we found that G-protein-coupled receptor kinase 5 (GRK5) accumulated in Lewy bodies and colocalized with alpha-synuclein in the pathological structures of the brains of sPD patients. In cotransfected cells, GRK5 phosphorylated Ser-129 of alpha-synuclein at the plasma membrane and induced translocation of phosphorylated alpha-synuclein to the perikaryal area. GRK5-catalyzed phosphorylation also promoted the formation of soluble oligomers and aggregates of alpha-synuclein. Genetic association study revealed haplotypic association of the GRK5 gene with susceptibility to sPD. The haplotype contained two functional single-nucleotide polymorphisms, m22.1 and m24, in introns of the GRK5 gene, which bound to YY1 (Yin Yang-1) and CREB-1 (cAMP response element-binding protein 1), respectively, and increased transcriptional activity of the reporter gene. The results suggest that phosphorylation of alpha-synuclein by GRK5 plays a crucial role in the pathogenesis of sPD.