For the first time, scientists have successfully used a method called exome sequencing to quickly discover a previously unknown gene responsible for a mendelian disorder.

Mendelian disorders, such as cystic fibrosis and sickle cell disease, are the result of one or more mutations in a single gene, typically a gene that makes a protein. All of the regions that code for proteins taken together are called the exome. The exome makes up about 1 percent of the genome, but it is in this 1 percent that more than 85 percent of mutations that cause mendelian disorders are found. That is why sequencing the exome is an efficient strategy to search for genes that underlie rare genetic disorders.

The study, "Exome sequencing identifies the cause of a mendelian disorder," was led by University of Washington (UW) researchers and published Nov. 13 in Nature Genetics.

While most mendelian disorders are rare, there are 7,000-plus suspected mendelian disorders that in aggregate affect millions of people in the United States, according to Dr. Michael J. Bamshad, one of the senior authors of the study, a UW professor of genome sciences and pediatrics, and a pediatrician at Seattle Children's. "Our results show that scientists could use exome sequencing to identify the genetic cause for thousands of disorders for which the gene hasn't been discovered."

"One of the reasons that this strategy is so powerful is that the scientists need only use a small number of unrelated cases to find the gene," said the other senior author of the study, Dr. Jay Shendure, UW assistant professor of genome sciences…