March 6 (UPI) -- Researchers at Columbia University Medical Center have found the molecular basis of the rare kidney disease IgA nephropathy, or IgAN, or Berger's disease.
IgAN occurs when the antibody immunoglobulin A, or IgA, collects in the kidneys causing inflammation of the kidney filtering structure glomeruli, which disrupts the kidneys' ability to filter waste from the blood.
There is no cure for IgAN and most patients go on to develop kidney failure.
"Very little is known about the causes of IgAN, genetic or otherwise, so our discovery represents an important step toward developing better therapies for this disease," Dr. Krzysztof Kiryluk, assistant professor of medicine at Columbia, said in a press release.
The main molecular defect in patients with IgAN is abnormal O-glycosylation of IgA antibodies. During O-glycosylation, sugar molecules attach to oxygen atoms in the amino acid residue of a protein. Previous studies have shown issues with O-glycosylation of IgA are genetic, and are common in people with IgAN.
Researchers studied 2,633 people of European and East Asian decent to determine which genes are linked to problems with O-glycosylation.
Results showed that variations in the C1GALT1 and C1GALT1C1 genes were common in people with high levels of Gd-IgA1 markers.
"The genes are found on different chromosomes, but they make proteins that interact to form an enzyme critical for the proper glycosylation of IgA molecules," Kiryluk said.
"Since approximately 50 percent of variability in Gd-IgA1 levels is due to genetic factors, this means that about 43 percent of the genetic variability is still unexplained. We started with a relatively small study population, so explaining 7 percent of variability between individuals with the disease was a good start. As we analyze more patients, we expect that we will find more genetic variants and can begin to piece together how these variants interact with environmental factors to cause disease."
The study was published in PLOS Genetics.