Complex genetic disease: can genetic strategies in Alzheimer's disease and new genetic mechanisms be applied to epilepsy?

Apolipoprotein E: Emerging Story in the Pathogenesis of Alzheimer's Disease

Apolipoprotein E (apoE) is implicated in the pathogenesis of Alzheimer's disease. One of the three com mon apoE alleles, apoE4, behaves as an autosomal codominant trait in the majority of late-onset and sporadic Alzheimer's disease, with homozygosity for this allele virtually sufficient to cause disease by the age of 80. In contrast, the apoE2 and apoE3 alleles decrease the probability of disease and increase the age of onset, with the protective effect of apoE2 greater than apoE3. Thus, the inherited alleles of apoE determine, in part, the risk of developing Alzheimer's disease and determine the rate of disease progres sion. Isoform-specific interactions of apoE with other molecules are therefore critical in this disease. ApoE is found in populations of neurons, some of which contain abnormal neurofibrillary tangles assembled from the protein tau. In healthy neurons, tau helps assemble and stabilize microtubules, but in Alzheimer's disease, it forms paired helical filaments of the neurofibrillary tangle. ApoE3 avidly binds tau in vitro, whereas apoE4 does not. Isoform-specific interactions of apoE with tau and other microtubule-associated proteins could contribute to the mechanism of Alzheimer's disease. Uncovering the roles of apoE in the brain, both in health and in disease, will be an exciting area for neuroscience. The Neuroscientist 1:298- 306, 1995

Occurrence of epilepsies in family members of Indian probands with different epileptic syndromes

PURPOSE

Large numbers of families with many members having seizures have been used to understand the role of hereditary factors in the pathogenesis of human epileptic syndromes. We aimed to establish a genetic database to form a hypothesis on the possible genetic contributions in different epileptic syndromes.

METHODS

The occurrence and patterns of different epilepsies and epileptic syndromes in 1,219 Indian probands and their relatives were studied. The concordance of epilepsies between probands and relatives was also analyzed.

RESULTS

Of probands, 231 (19% of 1219) had first- or second-degree relatives affected with seizures. Incidence of family history in probands with generalized epilepsies (GES) and syndrome of single, small, enhancing lesions (SSEL) was comparable and significantly higher than that in probands with localization-related epilepsies (LRES). The ratio of affected first- to second-degree relatives was close to 4:1. Generalized epilepsies were the commonest type of epileptic syndromes seen among all relatives. The proportion of sibs and second-degree relatives with epileptic syndromes similar to probands was significantly greater in the GES group as compared with the concordant relatives of probands with LRES and SSEL.

CONCLUSIONS

A significant percentage of first- and second-degree relatives of probands with all types of epileptic syndromes have seizures. The risk of relatives being affected varied as a function of the relation with the proband. Concordance of epileptic syndromes between probands and relatives was related to the epileptic syndromes in probands. The syndrome of SSEL is probably a benign epileptic syndrome seen in Indians genetically predisposed to seizures. Hereditary factors may play an almost equal role in the predisposition of relatives to epilepsy in families of probands with different epileptic syndromes.