The researchers then looked for changes in the expression of other genes involved in cyst formation. Surprisingly, they found the expression of the PKHD1 gene was markedly decreased in the mutated mice. Mutations of PKHD1 cause autosomal recessive polycystic kidney disease, a common genetic cystic disease that affects between one in 10,000 to 40,000 babies and is often fatal in the first month of life. In addition, they found that the PKHD1 promoter was directly regulated by the HNF-1 protein.

"Mutations in HNF-1 , the cause of MODY5, interfere with the transcription of PKHD1, a gene known to be mutated in autosomal recessive polycystic kidney disease," said Dr. Thomas Hiesberger, assistant professor of internal medicine and the study's lead author. "This link may allow for similar future therapeutic approaches for both diseases."

At this point, little is known about how inhibition of PKHD1 causes cysts. That is the next step for the researchers and will provide new insight into how both MODY5 and the kidney disease develop.