<原著>Familial essential myoclonus and epilepsy (FEME) の臨床遺伝学的検討と連鎖解析
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Familial essential myoclonus and epilepsy (FEME) is hereditary epileptic disorder characterized by adult-onset, tremor-like postural myoclonus, spontaneous myoclonus, infrequent convulsive seizures and benign clinical course. Benign adult familial myoclonic epilepsy (BAFME) and Familial adult myoclonic epilepsy (FAME) are autosomal dominant myoclonic epilepsy, and these clinical picture are similar to that of FEME. The causative gene of BAFME and that of FAME were mapped 8q23.3-24.1, but these two candidate area had not overlapped territory. So, to resolve the problem in identity of these three disease concepts and to recognize molecular mechanism of FEME, I started cloning of the causative gene. As the first step clinical information from twenty-seven Japanese FEME families was collected and then detailed clinical genetic analyses including segragation ratio, sex ratio, penetrance, presence of anticipation and distribution of age at onset were conducted. All the families showed complete genetic penetrance without skipping of generation. The mode of inheritance was concluded to be autosomal dominant one. Anticipation of age at onset and potentiation of phenotype were not observed. Distribution of age at onset was unimodel. The collected families had homogenous clinical symptom and age onset, so these families were suitable as families for linkage analysis. Based on the result of these analyses, Given little evidence supporting genetic anticipation that is frequently observed in neurodegenerative diseases caused by expansions CAG repeats, I selected a standard positional cloning strategy to identify the causative gene. Linkage analysis was performed on twenty-one FEME families with informed consent. Pair-wised linkage analysis revealed the highest cumulative maximal lod score of 9.31 at GATA68H01 (θ=0). Observation of obligate recombination events narrowed the candidate region to a 5.1-cM region between D8S1122 and D8S1112. This region had widely overlapped territory on that of BAFME, and not of FAME. These results suggest that FEME and BAFME are genetically identical disorder and the candidate region for the FEME/BAFME gene is located the 3.37-cM region between D8S1122 and D8S1694.
- 2002-11-10