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Spinocerebellar ataxia 36 is caused by the expansion of the intronic GGCCTG hexanucleotide repeat in NOP56. The original article describing this condition demonstrated that patients with spinocerebellar ataxia 36 present with tongue atrophy, a finding that had not been seen in previous types of spinocerebellar ataxias. A total of 2121 patients with clinically diagnosed spinocerebellar ataxia participated in the study. We screened our patient samples for spinocerebellar ataxia 36 using the repeat-primed polymerase chain reaction method and also determined the clinical features of spinocerebellar ataxia 36. Of the ataxia cases examined, 12 were identified as spinocerebellar ataxia 36. Of these, 7 cases (6 families) were autosomal dominant, 4 cases (three families) had a positive family history but were not autosomal dominant, and 1 case was sporadic. The average age of onset was 51.7 years, and disease progression was slow. The main symptoms and signs of disease included ataxia, dysarthria, and hyperreflexia. Approximately half the affected patients demonstrated nystagmus, bulging eyes, and a positive pathological reflex, although dysphagia, tongue atrophy, and hearing loss were rare. Moreover, the observed atrophy of the cerebellum and brain stem was not severe. The patients identified in this study were concentrated in western Japan. The frequency of spinocerebellar ataxia 36 was approximately 1.2% in the autosomal dominant group, and the age of onset for this condition was later in comparison with other spinocerebellar ataxia subtypes.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common genetic determinant of Parkinson's disease (PD) in European-derived populations, but far less is known about LRRK2 mutations and susceptibility alleles in Asians. To address this issue, we sequenced the LRRK2 coding region in 36 patients with familial PD, then genotyped variants of interest in an additional 595 PD cases and 1,641 controls who were all of Japanese ancestry. We also performed a meta-analysis of studies on G2385R, a polymorphism previously reported to associate with PD. One pathogenic (G2019S) and one putative pathogenic (R1067Q) mutation were each observed in two patients with sporadic PD. The overall mutation frequency among patients was 0.6%. G2385R was highly associated with PD under a dominant model in our dataset (adjusted OR, 1.83; 95% CI, 1.31-2.54; P = 3.3 x 10(-4)) and similar results were seen in the meta-analysis (summary OR assuming fixed effects, 2.55; 95% CI, 2.10-3.10). G2385R represents the first consistently replicated common PD susceptibility variant in a non-European population and its effect size is substantially greater than that reported for other well-validated genetic risk factors for the disease. However, LRRK2 mutations appear to be rare among Japanese patients with PD.

Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia and intermittent axial myoclonus. Various mutations have been found in the PRKCG gene encoding protein kinase C gamma in SCA14 families. Most of those mutations have been found in exon 4 of the PRKCG gene. We performed polymerase chain reaction (PCR)-based screening to clarify the approximate morbidity rate of the disease in the Japanese SCA population. We screened exon 4 of the PRKCG gene in 882 SCA patients with undefined etiologies using denaturing high-performance liquid chromatography and subsequent direct sequencing. We found a novel C/T missense mutation with a Ser119-to-Phe substitution (S119F) in 2 patients and subsequently found that they belonged to the same family. This S119F mutation was not found in 259 control individuals. Further PCR-based analysis revealed an additional 5 members with the same mutation in this family. Cerebellar ataxia was manifested in 5 of those 7 members. The main symptom in 4 of the 5 affected members was pure cerebellar ataxia with late onset. They had no myoclonus, extrapyramidal signs, ophthalmoplegia, or intellectual disturbance, some of which were found in previously reported SCA families. One patient showed intractable epilepsy, severe walking disturbance, and trunk ataxia with early onset. The results of this study suggest that the frequency of SCA14 in the Japanese SCA population is very low.