Geneticists have long been interested in a phenomenon called epistasis, where two different genes interact to suppress or enhance one another's effects. But deciphering the exact sequences that interact in this way has proved a tricky task. Now scientists have succeeded in demonstrating and dissecting epistasis in Bardet-Biedl syndrome (BBS), an illness often characterized by obesity and learning deficits. The severity of the symptoms varies dramatically among patients with this genetic disorder.
In an article appearing online in Nature, Nicholas Katsanis and his colleagues offer new clues about how and why BBS affects people to different degrees. The team has found that a sequence called MGC1203 interacts with other molecules known to be mutated in BBS. The scientists screened patients with BBS and compared them to control subjects, and found that the former were much more likely to carry a mutation in MGC1203. The researchers also found that, in at least three affected families, the co-incidence of the mutation in MGC1203 with mutations in other BBS genes lead to a more severe form of the disease. But mutations in MGC1203 alone are unlikely to cause the illness. Further evidence from engineered zebrafish supported the idea that MGC1203 has an epistatic effect on other BBS mutations. The findings should help medical experts to better understand disorders that involve interactions between different genes.
Nicholas Katsanis (Johns Hopkins University, Baltimore, MD, USA)
Abstract available online.
(C) Nature press release.
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