Two genetic regions that might explain some differences in disease severity in cystic fibrosis (CF) patients have been identified by US and Canadian researchers. The two regions contain genes that can modify lung function.
The findings may help predict disease severity and allow CF treatments to be tailored to patients. The severity of lung disease in CF patients varies more than can be explained by faults in the CFTR gene that causes CF.
'If you look at the lung function of patients, even those that inherited identical mutations in the cystic fibrosis gene, disease severity and lung function decline can differ substantially. We know that these patients all have cystic fibrosis, but the rate at which their lungs are deteriorating is variable', said Dr Peter Durie, a senior author on the research paper.
Dr Durie and colleagues wanted to find out why there is a difference between patients with the same mutation in CFTR. To measure disease severity they looked at how much air a patient could forcefully exhale in one second. This enabled them to develop a standard against which they could compare patients of different ages.
Nearly 3,500 patients with CF, enrolled in three different studies, were genotyped. Two of these studies, the Genetic Modifier Consortium (GMC) and the Canadian Consortium for Genetic Studies (CCGS) involved unrelated people. The Twin and Sibling Study (TSS) didn't.
A genome-wide association study (GWAS) was performed on data from the genomes of the unrelated individuals with a particular mutation in the CFTR gene. From the GWAS the scientists found a region on chromosome 11 linked to more severe CF.
As well as GWAS, researchers used linkage analysis on the genomes of related individuals from the TSS group. This confirmed the same region on chromosome 11, and identified an additional region on chromosome 20.
Further studies are needed to identify which genes located in these regions are influencing lung function. Scientists hope then to use this information to design new treatments.
Dr Durie said: 'If we understand what the genes are, we can find ways to tweak the genes or the protein products using drugs'.
CF is among the UK's most common life-threatening inherited diseases, affecting over 9,000 people. It is an inherited autosomal recessive disease, meaning you have to receive a faulty copy of the gene that causes CF (CFTR) from both of your parents. CF causes scarring of the organs with the lungs and digestive system being the worst affected.
The research was published in the journal Nature Genetics.