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 re gion. STUDY DESIGN: Mutation analysis was performed for DELTAF508, G55 1D, G542X, R553X, S549N, and N1303K. For probands with undetermined mu tations single-stranded conformational polymorphism analysis was perfo rmed. RESULTS: Among 40 white subjects with cystic fibrosis 26 (65%) w ere homozygous for DELTAF508, 10 (25%) were heterozygous for DELTAF508 and another unknown mutation, and two were homozygous for unknown mut ations. Among 10 black probands one was homozygous for DELTAF508, seve n (70%) were heterozygous for DELTAF508 and another unknown mutation, and one was homozygous for unknown mutations. Single-stranded conforma tional polymorphism analysis for selected exons was performed for 11 p robands with unknown mutations. One mutation was detected in a white p roband. Sequencing of this exon showed the mutation to be Q493X. CONCL USIONS: Thirty percent of white subjects and 80% of black subjects car ried unknown mutations. In one family single-stranded conformational p olymorphism was informative in identifying an undetermined cystic fibr osis mutation.