Genetic disorder traced to cilia.

• Position: Obesity - Bardet-Biedl syndrome

A potential new contributor to obesity--faulty cilia--has been discovered by researchers at Johns Hopkins University, Baltimore, Md. Many a high school biology student has glanced into a microscope to see the planet's smallest animals--paramecium and the like--being propelled by the waving, hair-like projections known as cilia. Yet, cilia also are found in human cells, helping move fluid and mucous around in the brain, lungs, eyes, and kidneys, or sticking out from cells to act like antennae. Studying families with a relatively rare condition called Bardet-Biedl syndrome (BBS), characterized by obesity, learning disabilities, and eye and kidney problems, the researchers uncovered a new gene. Furthermore, the gene's protein, BBS8, is found only at the base of cilia.

Bardet-Biedl syndrome (pronounced BAR-day BEED-el) "is a relatively rare genetic disorder, but it has traits common to many people," declares Nicholas Katsanis, assistant professor in the McKusick-Nathans Institute of Genetic Medicine. "We don't know yet how the ciliary defect might lead to obesity or learning disabilities, but the finding provides a new avenue to studying these genetically murky traits. It is very difficult to translate genetic understanding into a cellular mechanism that explains what is seen in a disease."

Some aspects of BBS have been linked to ciliary defects in other conditions. Cilia are known to play key roles in mammalian development...