A team of researchers at the University of Michigan Medical School has identified a new genetic mutation that causes one type of nephronophthisis, a rare pediatric kidney disorder that invariably leads to renal failure.
But in doing so, the group has run into a typical quandary for genetic researchers: What to do when a gene is identified for a disease that is untreatable?
“At present, we can do the diagnostics and confirm for the patient that this is the disease they have, but we cannot offer any treatment,” Friedhelm Hildebrandt, a professor at UMMC and lead author of the study, said in a statement.
“Our only hope is to work out the mechanism to understand where it comes from,” he said. “At least we know where to start asking questions.”
Hildebrandt and his colleagues found nine distinct recessive mutations in the gene, called inversin, in nine infants with early-onset nephronophthisis type 2 from seven families. By contrast, the researchers found no inversin mutations in 100 healthy controls.
To be sure, though Hildebrandt’s finding, which appear in this month’s Nature Genetics, are intriguing, experts agree it will take many more years to understand why and how the inversin mutations lead to renal failure. “But scientists already have some intriguing clues indicating that inversin is required for normal embryonic development,” according to the statement.
Specifically, when Hildebrandt’s team knocked out the inversin gene from embryonic zebrafish, the fish developed severe kidney cysts and heart defects. Alternately, injecting the abnormal embryos with inversin mRNA from mice successfully restored normal development in the fish.
Moreover, studies of mice in whom the inversin gene was knocked out showed that the internal organs in 90 percent of the mice suffered situs inversus, and 10 percent had serious heart defects. According to Hildebrandt, one of the nine infants in the UMMC study “had similar developmental defects.”