July 4, 2008
Our laboratory studies the molecular and cellular basis of cystic fibrosis (CF), a common human genetic disease. Cystic fibrosis is caused by defects in a single gene, which has been cloned sequenced, and expressed. The gene product, CFTR, is a small conductance chloride and bicarbonate channel.  Our research projects look at the disease at every level from individual nucleotide changes in DNA to the functioning of individuals who have cystic fibrosis.

   How do submucosal glands work?
    Cystic fibrosis kills people by changing the lungs so that lung infections with normally benign organisms, such as Pseudomonas aeruginosa, become chronic and incapable of being eradicated with any known treatment.  Infecting organisms are confined to the mucus that lines the airways of the lungs, suggesting a defect in the composition and clearance of the mucus.  Most airway mucus is produced by submucosal glands, and CFTR is highly expressed in one type of cell in these glands:  serous cells.  We are using optical methods to study how glands function, using intact glands from animals and from humans.  Human glands are obtained from subjects undergoing lung transplants for cystic fibrosis and other diseases.  We have found profound changes in glands from cystic fibrosis patients; the glands appear to hyposecrete fluid in response to various mediators that would be expected to operate during normal activity, while secretion to strong stimuli that evoke the lung defense reflex are at least partially intact.

  What molecular mechanisms govern how CFTR operates?

    We use patch-clamp methods to determine the single-channel kinetics of endogenous and recombinant wild-type and mutant CFTR channels. 

  How does CFTR function in epithelial--especially in lung epithelia?
    We use Ussing chambers and patch clamping to determine the molecular machinery responsible for electrolyte and fluid secretion and absorption in the airways.  We also use differential interference contrast optics (DIC or Nomarski optics) to study changes in individual cells within glands.
    We then attempt to relate those findings to airways disease.
Can we discover natural animal models of cystic fibrosis?
We attempted to develop model systems that will be useful for developing therapies for cystic fibrosis. We proposed a model using the human sinuses, which has been adopted as the methodology for the first CF gene therapy trials at Stanford. We are now developing a general method for finding natural animal models of recessive genetic diseases. The method is being tested by searching for a primate model of CF. 

The chromatograms to the right show an example of a missense mutation located in exon 20 of the Rhesus monkey CFTR.  Top: normal sequence, note TCAGATC near the middle of the sequence.  Bottom: the animal is heterozygous for a G/C at the normal G position.

This work is on hold pending studies of CF pigs and the expected development of CF ferrets, each of which are expected to have special advantages for studyin CF airway disease.

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