[Linkage study of hereditary olivopontocerebellar atrophy: genetic evidence for locus heterogeneity in Japanese cases].
Spinocerebellar ataxial 1 (SCA1) is the locus name of autosomal dominant olivopontocerebellar atrophy (OPCA), and is assigned to the short arm of chromosome 6. The tight linkage between SCA1 and D6S89 has recently been reported. In order to examine possible locus heterogeneity, we studied linkage for D6S89 to disease loci in 16 pedigrees of dominant OPCA. D6S89 polymorphism was analysed with PCR amplification of genomic DNA by using specific oligonucleotide primers. Lod scores were computed by LIPED program with the correction of age-dependent penetrance. Homogeneity test was performed by using HOMOG program. Fifteen out of 16 pedigrees were informative to D6S89. Among them, 7 pedigrees showed positive and 8 pedigrees showed negative lod scores throughout all recombination fractions. Homogeneity testing disclosed that approximately 55% of pedigrees are linked to D6S89, and others were not linked. Our results provide evidences that dominant OPCA in Japan are genetically heterogenous. At now, it has been still unknown whether there are any clinico-pathological differences among OPCA genotypes. Based on the alpha-constant from homogeneity testing, we divided our pedigrees into linked-pedigree (SCA1) and nonlinked-pedigrees (nonSCA1). Then, clinical features were compared between these two groups. Hyperactive DTR was more common in SCA1 than nonSCA1 group. On the other hand, hypoactive DTR was more significantly dominated in nonSCA1 than SCA1. Slow saccade and Babinski sign were common in both groups. Although not statistically significant, nystagmus, exteral ophthalmoparesis, mydriasis, ptosis, facio-lingual twitching, and limb spasticity were more frequently observed in SCA1 than nonSCA1. These results indicate that there are possible correlation between disease genotype and phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)
Sasaki
H
H
Department of Neurology, Hokkaido University School of Medicine.
Wakisaka
A
A
Tashiro
K
K
Hamada
T
T
Shima
K
K
D000328:Adult; D002874:Chromosome Mapping; D002896:Chromosomes, Human, Pair 6; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D009849:Olivopontocerebellar Atrophies / Q000235:genetics*; D010375:Pedigree; D013132:Spinocerebellar Degenerations / Q000235:genetics