Researchers at the CHEO Research Institute and the Research Institute of the McGill University Health Centre (RI-MUHC) have discovered a previously unidentified gene variant that causes Primary Ciliary Dyskinesia (PCD), which is present in Inuit populations in both Nunavut and Nunavik. This novel gene variant may play an important role in recurrent pneumonia and chronic lung disease in Inuit.
PCD (also called Kartagener Syndrome) is a genetic disease where cilia (microscopic hairs lining the respiratory passages) fail to move (or move abnormally). The normal movement of cilia is needed to sweep mucus out of the bronchial tubes, nose, sinuses and middle ear. With PCD, mucus becomes trapped and chronically infected, causing chronic inflammation and organ damage. Cilia have many components, each controlled by separate genes.
Until recently, it was believed that Inuit did not have PCD, based on previous research using less-advanced diagnostic techniques than what is now available. The new study “First reports of Primary Ciliary Dyskinesia caused by a shared DNAH11 allele in Canadian Inuit” published in Pediatric Pulmonology indicates that the novel PCD-causing variant, in a gene called DNAH11, was found in seven Inuit individuals, five from Nunavut and two from Nunavik, demonstrating for the first time that PCD is present in the Inuit population of Canada.
“The discovery of the novel gene variant in DNAH11, in widely geographically separated parts of the traditional Inuit homelands, suggests that this gene may be quite common among Inuit and may be an important cause of lung disease in this population,” said Dr. Tom Kovesi, co-senior author and Investigator at the CHEO Research Institute. “Inuit individuals with recurrent pneumonia and/or chronic lung damage should be tested for PCD, and PCD genetic analysis in routine newborn screening should be considered in Inuit regions.”
Previous research at CHEO has shown severe and recurrent lower respiratory tract infections (such as pneumonia and respiratory syncytial virus (RSV), bronchiolitis) are extraordinarily common in young Inuit children, and in most cases, follow severe lung infections early in life. Social determinants of health in Inuit communities, such as overcrowding and reduced ventilation in houses, play an important role in the development of severe lower respiratory tract infections early in life.
Nonetheless, the data in this study strongly suggest that inherited PCD is a considerable cause of respiratory disease in Canadian Inuit and, given that the variant was observed in disparate portions of the traditional Inuit homelands, may be due to a founder effect (a loss of genetic variation that occurs when a small group of individuals is isolated from a larger population).
“This study demonstrates that genetic conditions also need to be considered as a cause of chronic respiratory disease in Inuit patients. Furthermore, it underscores the importance of PCD genetic testing and population analyses in populations with high rates of respiratory infections and lung disease, especially since early disease recognition and timely treatment initiation are important," said the co-senior author, Dr. Adam Shapiro.
An investigator in the Child Health and Human Development Program at the RI-MUHC, pediatric respirologist at the Montreal Children’s Hospital of the MUHC and associate professor of Respiratory Medicine at McGill University, Dr. Shapiro recently found, in another study, identical mutations in another gene causing PCD in four unrelated North American indigenous children from different regions.
“There are many treatment options for PCD,” added Dr. Kovesi, Pediatric Respirologist at CHEO and Professor of Pediatrics at the University of Ottawa. “Understanding the prevalence of PCD caused by variants in DNAH11 as well as discovering possible variants in other PCD genes, and their frequency in the Inuit population, requires more research and are important steps towards improved delivery of care to affected Inuit families.”
Reference: Julia Hunter-Schouela, Michael T. Geraghty, Robert A. Hegele, David A. Dyment, David St. Pierre, Julie Richer, Holden Sheffield, Maimoona A Zariwala, Michael R. Knowles, Anna Lehman, Sharon D. Dell, Adam J. Shapiro, Thomas A. Kovesi. First reports of Primary Ciliary Dyskinesia caused by a shared DNAH11 allele in Canadian Inuit, Pediatric Pulmonology 10.1002/ppul.26414