Sequana Therapeutics Inc. has begun studying blood samples from 300closely related residents on a remote island in the South Atlantic Oceanto identify the genetic causes of asthma.The La Jolla, Calif.-based company is collaborating with the SamuelLunenfield Research Institute of the Toronto-based Mount SinaiHospital, whose researchers acquired the blood samples in 1993 fromresidents of Tristan da Cunha. The island is located about midwaybetween Brazil and South Africa and 30 percent of the residents haveasthma.The Tristans are descended from seven original families dating to theearly 1800s and the incidence of asthma is among the highest foundanywhere in the world.Scott Salka, Sequana's director of business operations, said asthma isbelieved to be a polygenic disease and should be easier to track in theislanders than in the general population, where asthma affects about 5percent of adults and up to 15 percent of children in Western countries."First of all we have everybody's relationships," Salka said. "We'll belooking for a small number of mutations that lead to the disease. In thegeneral population, there could be many mutations that manifestthemselves as asthma."Salka said Sequana has completed the initial genome-wide scan of theTristan families and the company's bioinformatics researchers willanalyze the data to identify genetic regions common to the islandersafflicted with asthma."Basically we'll be using the same technique used to discover thegenetic causes of Huntington's disease and cystic fibrosis: positionalcloning," he said.Because asthma is considered a polygenic disease, Salka said theresearchers will be looking for a major gene that accounts for morethan 10 percent of the asthma cases."If there's a major gene effect, we might find it before the end of thisfall," he added. "If not, it will take longer."Salka said Sequana also intends to conduct obesity and hypertensionstudies on the islanders' blood samples.Terms of the agreement between Sequana and Mount Sinai Hospitalwere not disclosed. n

-- Charles Craig

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