14-A, 14-B, 14-C, 14-D, 15, 16-A, 16-B, 16-C, 16-D, 16-E, 16-F, 19, 20 and 22) in the 5-HTTLPR was 14 in our populations (Japanese: n = 131; Caucasian: n = 74) in the present study. In addition, a significant ethnic difference between Japanese and Caucasian populations was observed for distributions of alleles and genotypes (P Ͻ 0.0001 and P Ͻ 0.0001, respectively). Our results suggest that the analyses of the 5-HTTLPR should be revised by genotyping with a more complete subdivision of alleles. Molecular Psychiatry (2000) 5, 32-38.

Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterized by combined systemic degeneration of the dentatofugal and pallidofugal pathways. We investigated a candidate gene and found that DRPLA patients had an expanded CAG trinucleotide repeat in a gene on the short arm of chromosome 12. The repeat size varied from 7-23 in normal individuals. In patients one allele was expanded to between 49-75 repeats or occasionally even more. Expansion was usually associated with paternal transmission and only occasionally with maternal transmission. Repeat size showed a close correlation with age of onset of symptoms and disease severity. We conclude that DRPLA is the seventh genetic disorder known to be associated with expansion of an unstable trinucleotide repeat.

Epilepsy is a common neurological disorder, and mutations in genes encoding ion channels or neurotransmitter receptors are frequent causes of monogenic forms of epilepsy. Here we show that abnormal expansions of TTTCA and TTTTA repeats in intron 4 of SAMD12 cause benign adult familial myoclonic epilepsy (BAFME). Single-molecule, real-time sequencing of BAC clones and nanopore sequencing of genomic DNA identified two repeat configurations in SAMD12. Intriguingly, in two families with a clinical diagnosis of BAFME in which no repeat expansions in SAMD12 were observed, we identified similar expansions of TTTCA and TTTTA repeats in introns of TNRC6A and RAPGEF2, indicating that expansions of the same repeat motifs are involved in the pathogenesis of BAFME regardless of the genes in which the expanded repeats are located. This discovery that expansions of noncoding repeats lead to neuronal dysfunction responsible for myoclonic tremor and epilepsy extends the understanding of diseases with such repeat expansion.

Chorea-acanthocytosis is a neurodegenerative disorder with peripheral red cell acanthocytosis. Linkage of chorea-acanthocytosis to chromosome 9q21 has been found. We refined the locus region and identified a previously unknown, full-length cDNA encoding a presumably structural protein, which we called chorein. We found a deletion in the coding region of the cDNA leading to a frame shift resulting in the production of a truncated protein in both alleles of patients and in single alleles of obligate carriers.

No abstract

Benign adult familial myoclonic epilepsy is an autosomal dominant idiopathic epileptic syndrome characterized by adult-onset tremulous finger movement, myoclonus, epileptic seizures, and nonprogressive course. It was recently recognized in Japanese families. In this study, we report that the gene locus is assigned to the distal long arm of chromosome 8, by linkage analysis in a large Japanese kindred with a maximum two-point LOD score of 4.31 for D8S555 at recombination fraction of 0 (maximum multipoint LOD score of 5.42 for the interval between D8S555 and D8S1779). Analyses of recombinations place the locus within an 8-cM interval, between D8S1784 and D8S1694, in which three markers, D8S1830, D8S555, and D8S1779, show no recombination with the phenotypes. Although three other epilepsy-related loci on chromosome 8q have been recognized-one on chromosome 8q13-21 (familial febrile convulsion) and two others on chromosome 8q24 (KCNQ3 and childhood absence epilepsy)-the locus assigned here is distinct from these three epilepsy-related loci. This study establishes the presence of a new epilepsy-related locus on 8q23.3-q24.11.

The term "neuroacanthocytosis" is normally used to refer to autosomal recessive chorea-acanthocytosis and X-linked McLeod syndrome, but there are other movement disorders in which erythrocyte acanthocytosis may also be seen, such as Huntington disease-like 2 and pantothenate kinase-associated neurodegeneration. Disorders of serum lipoproteins such as Bassen-Kornzweig disease form a distinct group of neuroacanthocytosis syndromes in which ataxia is observed, but movement disorders are not seen. Genetic testing has enabled us to distinguish between these disorders, even when there are considerable similarities between phenotypes. Improved detection is important for accurate genetic counseling, for monitoring for complications, and, it is hoped, for implementing causal treatments, once these become available. As in other neurodegenerative conditions, animal models are a promising strategy for the development of such therapies.

No abstract