Cystic fibrosis mutations in white and black Americans: an approach to identification of unknown mutations with implications for cystic fibrosis screening.

OBJECTIVE: We sought to define the frequency of common cystic fibrosis mutations in white and black American probands from our geographic region. STUDY
DESIGN: Mutation analysis was performed for delta F508, G551D, G542X, R553X, S549N, an d N1303K. For probands with undetermined mutations single-stranded conformational polymorphism analysis was performed.
RESULTS: Among 40 white subjects with cystic fibrosis 26 (65%) were homozygous for delta F508, 10 (25%) were heterozygous for delta F508 and another unknown mutation, and two were homozygous for unknown mutations. Among 10 black probands one was homozygous for delta F508, seven (70%) were heterozygous for delta F508 and another unknown mutation, and one was homozygous for unknown mutations. Single-stranded conformational polymorphism analysis for selected exons was performed for 11 probands with unknown mutations. One mutation was detected in a white proband. Sequencing of this exon showed the mutation to be Q493X.
CONCLUSIONS: Thirty percent of white subjects and 80% of black subjects carried unknown mutations. In one family single-stranded conformational polymorphism was informative in identifying an undetermined cystic fibrosis mutation.