Published July 16, 2010
WASHINGTON – A gene that appears to protect people from sleeping sickness in Africa also appears to make black Americans four times more likely to develop kidney disease, U.S. and Belgian researchers reported on Thursday.
Their findings shed light on why U.S. blacks are far more likely than whites to suffer from kidney disease and could potentially lead to new treatments or even preventive measures.
More than 30 percent of African Americans carry at least one copy of the risky gene sequences, the researchers reported in the journal Science, and people with two copies of them had 10 times the usual risk of kidney disease.
The gene involved is called APOL1.
Dr. Martin Pollak of Harvard Medical School and Beth Israel Deaconess Medical Center and colleagues at the Universite Libre de Bruxelles in Belgium used data from the 1,000 Genomes Project that is sequencing the gene maps of people around the world.
They found two variants of APOL1, called G1 and G2, that raised the risk of two types of serious kidney diseases.
"G1 and G2 both changed the coding sequence of APOL1," Pollak said in a statement. "Further analyses revealed that these very same genetic variants conferred human immunity against the parasite responsible for sleeping sickness."
The findings are parallel to another disease that is more common in blacks -- sickle cell disease. People with one copy of the sickle cell gene appear to be less likely to be infected by malaria, but those with two versions develop misshapen red blood cells and have a range of often deadly symptoms.
Tests in the lab showed that APOL1 protein made by the G1 and G2 versions of the gene killed Trypanosoma brucei rhodesiense, which causes African sleeping sickness.
Kidney disease affects about 500,000 people in the United States and is becoming more common. High blood pressure is a common cause, and the rate of kidney disease in U.S. blacks is four times that of European-Americans.
"We were excited that our findings appeared to relate kidney disease in the United States with human evolution and parasite infection in Africa," Pollak said. "We hope that these new findings will not only lead us to a better understanding of the underlying mechanisms leading to kidney failure, but will also help us develop new ways to treat trypanosome infection and kidney disease."
Drug companies can exploit such niche markets. In 2005, the U.S. Food and Drug Administration approved NitroMed heart failure drug BiDil for marketing to African Americans after clinical trials showed it especially benefited blacks.