By comparing the genomes of an alga, a weed and humans, a team of researchers has identified a new gene behind Bardet-Biedl syndrome (BBS), a complex condition marked by learning disabilities, vision loss and obesity.
"Finding this gene underscores the power of comparing organisms' complete genetic information," says Nicholas Katsanis, Ph.D., an assistant professor in the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins. "We can use this technique to look for new genes and proteins involved in specific cellular structures and their roles in health and disease."
That's because even very distantly related organisms -- the alga and humans, for example -- may share genes and proteins for common cellular structures that have been conserved by nature.
The genetic comparisons, done by researchers at Washington University in St. Louis, revealed 688 genes in humans and the alga that are involved in building cells' hair-like projections called cilia, the team reports in the May 14 issue of Cell.
In people, cilia help push fluid and molecules around outside certain cells, including some in the lung, eye, brain and kidney. Johns Hopkins researchers and their colleagues have reported that genetic mutations in BBS cause problems at least in part by rendering cilia and related structures useless.
Two of the identified genes turned out to be located in a region of human chromosome 2 that already had been linked to BBS. Stimulated by the St. Louis researchers, the international BBS team sequenced the two genes in families with BBS and discovered mutations in one of the two genes.
"There were 230 possible genes in the region of chromosome 2 linked to BBS, and this genomic comparison immediately narrowed down the most likely possibilities to just two," says Katsanis, also an assistant professor of ophthalmology. "Using comparative genomics in this way is a big, big deal.
It would have been nearly impossible to find this gene in any other way."
He adds, "This study should be a massive springboard for using comparative genomics, and it proves without a doubt the value of sequencing the genomes of a wide variety of species."
The Washington University researchers, led by Susan Dutcher, Ph.D., a professor of genetics, study cilia in an alga called Chlamydomonas. The alga provides easier access than other organisms to examine cilia and related structures called flagella, which also help with cells' own movement.