Received on November 6, 2008
Accepted on April 27, 2009

Molecular Diagnostics and Genetics

Three Novel CFTR Polymorphic Repeats Improve Segregation Analysis for Cystic Fibrosis

¹ Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Naples, Italy, and CEINGE-Biotecnologie Avanzate scarl, Naples, Italy
² Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Naples, Italy; CEINGE-Biotecnologie Avanzate scarl, Naples, Italy, and Facoltà di Scienze Biotecnologiche, Università di Napoli Federico II, Naples, Italy
³ Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Naples, Italy; CEINGE-Biotecnologie Avanzate scarl, Naples, Italy; Facoltà di Scienze Biotecnologiche, Università di Napoli Federico II, Naples, Italy, and SEMM, Naples, Italy

^* To whom correspondence should be addressed. E-mail: paolella{at}dbbm.unina.it.

BACKGROUND: Molecular diagnosis for cystic fibrosis (CF) is based on the direct identification of mutations in the CFTR gene [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)] (detection rate about 90% with scanning procedures) and on segregation analysis of intragenic polymorphisms for carrier and prenatal diagnosis in about 20% of CF families in which one or both causal mutations are unknown.

METHODS: We identified 3 novel intragenic polymorphic repeats (IVS3polyA, IVS4polyA, and IVS10CA repeats) in the CFTR gene and developed and validated a procedure based on the PCR followed by capillary electrophoresis for large-scale analysis of these polymorphisms and the 4 previously identified microsatellites (IVS1CA, IVS8CA, IVS17bTA, and IVS17bCA repeats) in a single run. We validated the procedure for both single- and 2-cell samples (for a possible use in preimplantation diagnosis), and on a large number of CF patients bearing different genotypes and non-CF controls.

RESULTS: The allelic distribution and heterozygosity results suggest that the 3 novel polymorphisms strongly contribute to carrier and prenatal diagnosis of CF in families in which one or both causal mutations have not been identified. At least one of the 3 previously identified microsatellites was informative in 78 of 100 unrelated CF families; at least one of all 7 polymorphisms was informative in 98 of the families. Finally, the analysis of haplotypes for the 7 polymorphisms revealed that most CF mutations are associated with different haplotypes, suggesting multiple slippage events but a single origin for most CFTR mutations.

CONCLUSIONS: The analysis of the 7 polymorphisms is a rapid and efficient tool for routine carrier, prenatal, and preimplantation diagnosis of CF.