Human lymphocytes transcribe the cystic fibrosis transmembrane conductance regulator gene and exhibit CF-defective cAMP-regulated chloride current.
Cystic fibrosis (CF) is the most common lethal genetic disease among Caucasians, primarily affecting epithelial tissues of the lung and gut. Mutations in a single gene, the cystic fibrosis transmembrane conductance regulator (CFTR), are responsible for this disease. Whether a physiological defect exists in the immune system of CF patients has remained controversial. A chloride ion transport defect has been described in human CF-derived lymphocytes; however, it has not been possible to detect CFTR mRNA in lymphocytes. We report here that normal human B-lymphoblasts display whole cell Cl- conductances induced by calcium-mediated pathways, volume regulation, and cAMP which are equivalent to currents described in epithelial cells. B-lymphoblasts from CF-affected humans demonstrated defective Cl- conductance regulation by cAMP but preserved regulation by calcium-mediated and volume regulation mechanisms. CFTR involvement in cAMP regulation of Cl- conductance in lymphocytes is further supported by our demonstration of the presence of appropriately spliced CFTR mRNA segments in human B and T lymphocytes as detected by an optimized reverse-transcription and polymerase chain reaction approach. The identity of the amplified products was confirmed by hybridization to CFTR-specific probes and DNA sequencing. Furthermore, the 3'-end of the gene was found in a T cell cDNA library. We conclude that CFTR mRNA is expressed in lymphocytes, consistent with the cAMP regulation of chloride transport present in normal lymphocytes but defective in CF-derived lymphocytes.
Department of Medicine, Falk CVRC, Stanford University School of Medicine, California 94305.
T V
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McDonald
P T
PT
Nghiem
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P
Gardner
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CL
Martens
D001483:Base Sequence; D015139:Blotting, Southern; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology / Q000502:physiology*; D003550:Cystic Fibrosis / Q000235:genetics* / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004594:Electrophysiology; D015723:Gene Library; D006801:Humans; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008214:Lymphocytes / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
C505032:CFTR protein, human; D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004247:DNA; D000242:Cyclic AMP