Pathological mutations in TSC1 and TSC2 disrupt the interaction between hamartin and tuberin

Critical functions of hamartin and tuberin, encoded by the TSC1 and TSC2 genes, are likely to be closely linked. The proteins interact directly with one another and mutations affecting either gene result in the tuberous sclerosis phenotype. However, the regions of hamartin and tuberin that interact have not been well defined, and the relationship between their interaction and the pathogenesis of tuberous sclerosis has not been explored. To address these issues a series of hamartin and tuberin constructs were used to assay for interaction in the yeast two-hybrid system. Hamartin (amino acids 302–430) and tuberin (amino acids 1–418) interacted strongly with one another. A region of tuberin encoding a putative coiled-coil (amino acids 346–371) was necessary but not sufficient to mediate the interaction with hamartin, as more N-terminal residues were also required. A region of hamartin (amino acids 719–998) predicted to encode coiled-coils was capable of oligermerization but was not important for the interaction with tuberin. Subtle, non-truncating mutations identified in patients with tuberous sclerosis and located within the putative binding regions of hamartin (N198_F199delinsI;593–595delACT) or tuberin (G294E and I365del), abolished or dramatically reduced interaction of the proteins as assessed by yeast two-hybrid assays and by co-immunoprecipitation of the full-length proteins from Cos7 cells. In contrast, three non-pathogenic missense polymorphisms of tuberin (R261W, M286V, R367Q) in the same region as the disease-causing TSC2 mutations did not. These results indicate a requirement for interaction in critical growth suppressing functions of hamartin and tuberin

Tungiasis: high prevalence, parasite load, and morbidity in a rural community in Lagos State, Nigeria

Background: Tungiasis is common in resource-poor populations throughout Latin America, the Caribbean, and sub-Saharan Africa, but epidemiologic data from Africa on this ectoparasitosis are scarce.\ud \ud Methods: A cross-sectional study was carried out in a representative sample of a rural community in Lagos State, 54 km west of Lagos (Nigeria). In the dry season, 142 households of the community were randomly selected and visited. Family members were examined for the presence of tungiasis. The localization, number, and stage of penetrated fleas, as well as the associated morbidity, were documented.\ud \ud Results: Five hundred and fifty-seven individuals were examined, 299 (53.7%) males and 258 (46.3%) females. In total, 252 (45.2%; 95% confidence interval, 41.1–49.5) were infested with Tunga penetrans. The prevalence was highest between the ages of 5 and 14 years, decreased in adults, and increased again in the elderly. There was no statistically significant difference between the prevalence in males and females (47.2% vs. 43.0%; P = 0.3). Almost 95% of lesions were localized on the feet. Ten per cent of individuals presented with sand fleas on the hands and elbows. The median parasite load was six (interquartile range, 3–16). Individuals aged 60 years or over had significantly more lesions (median of 41 lesions; P < 0.01). About one-third of the study participants found it difficult to walk; in 10% of cases, fissures were present. Superinfection was common.\ud \ud Conclusions: The prevalence of tungiasis and the parasite load were high, and the severity of the disease was considerable. The prevalence and parasite burden showed a characteristic distribution. In western Nigeria, tungiasis needs to be regarded as an important public health problem