Variable deletion of exon 9 coding sequences in cystic fibrosis transmembrane conductance regulator gene mRNA transcripts in normal bronchial epithelium

EMBO J. 1991 Jun;10(6):1355-63.


The predicted protein domains coded by exons 9-12 and 19-23 of the 27 exon cystic fibrosis transmembrane conductance regulator (CFTR) gene contain two putative nucleotide-binding fold regions. Analysis of CFTR mRNA transcripts in freshly isolated bronchial epithelium from 12 normal adult individuals demonstrated that all had some CFTR mRNA transcripts with exon 9 completely deleted (exon 9- mRNA transcripts). In most (9 of 12), the exon 9- transcripts represented less than or equal to 25% of the total CFTR transcripts. However, in three individuals, the exon 9- transcripts were more abundant, comprising 39, 62 and 66% of all CFTR transcripts. Re-evaluation of the same individuals 2-4 months later showed the same proportions of exon 9- transcripts. Of the 24 CFTR alleles in the 12 individuals, the sequences of the exon-intron junctions relevant to exon 9 deletion (exon 8-intron 8, intron 8-exon 9, exon 9-intron 9, and intron 9-exon 10) were identical except for the intron 8-exon 9 region sequences. Several individuals had varying lengths of a TG repeat in the region between splice branch and splice acceptor consensus sites. Interestingly, one allele in each of the two individuals with 62 and 66% exon 9- transcripts had a TT deletion in the splice acceptor site for exon 9. These observations suggest either the unlikely possibility that sequences in exon 9 are not critical for the functioning of the CFTR or that only a minority of the CFTR mRNA transcripts need to contain exon 9 sequences to produce sufficient amounts of a normal CFTR to maintain a normal clinical phenotype.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Bronchi / physiology*
  • Cystic Fibrosis
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Epithelium
  • Female
  • Humans
  • Male
  • Membrane Proteins / genetics*
  • Molecular Sequence Data
  • Oligonucleotides / chemistry
  • Polymerase Chain Reaction
  • RNA Processing, Post-Transcriptional
  • RNA Splicing
  • RNA, Messenger / genetics


  • CFTR protein, human
  • Membrane Proteins
  • Oligonucleotides
  • RNA, Messenger
  • Cystic Fibrosis Transmembrane Conductance Regulator