Two groups of researchers have independently discovered a new, rare type of lung cell.
These cells, which make up only 1 percent of all cells in the lung, express a large amount of the protein responsible for cystic fibrosis, which could help researchers develop brand-new treatments in the future.
Cystic fibrosis is a genetic disorder caused by mutations in both copies of a gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein.
CFTR is involved in the production and release of body fluids like mucus and sweat, and when the gene is non-functional, secretions that are usually thin become thick.
This is what causes a number of symptoms of the disease, including frequent lung and sinus infections.
"Cystic fibrosis is an amazingly well-studied disease, and we're still discovering completely new biology that may alter the way we approach it," said Jayaraj Rajagopal, senior author of one of the studies and medical doctor at Massachusetts General Hospital, Boston.
"We have the framework now for a new cellular narrative of lung disease."
Both sets of researchers started by trying to build an atlas of the cells that make up the airway.
They analysed the gene expression of tens of thousands of individual cells, one at a time.
Once they'd been analysed, the teams were able to compare the gene expression patterns and catalogue the different cell types, states, abundance, and distribution through the airway.
One of the cells they identified had never been seen before, which they called a pulmonary ionocyte.
The standard wisdom when it comes to CFTR is that it is expressed at low levels in ciliated cells, a common lung cell type.
But the researchers found that this new pulmonary ionocyte has exceptionally high levels of CFTR expression, meaning that these cells - if mutated - could be causing cystic fibrosis.
Rajagopal's team then disrupted a critical molecular process in the pulmonary ionocytes in mice, finding that some features associated with cystic fibrosis – like thick mucus – occurred.
Although this isn't a definite confirmation that cystic fibrosis is caused by pulmonary ionocytes, it is a solid piece of research pointing in that direction.
And this is a big deal, according to Amy Ryan, a lung biologist at the University of Southern California, who was not involved in either study.
"These papers are extremely exciting," says Ryan in an interview with The Scientist.
"They've interrogated the cellular composition and the cellular hierarchy of the airways by using a single-cell RNA-sequencing technique. That kind of information is going to have a significant impact on advancing the research that we can do, and hopefully the derivation of new therapeutic approaches for any number of airway diseases."
The researchers hope they can look at a number of diseases with this new information and atlas of cells.
"So much that we found rewrites the way we think about lung biology and lung cells," says Rajagopal.
"I think the entire community of pulmonologists and lung biologists will have to take a step back and think about their problems with respect to all these new cell types."