Three novel CFTR polymorphic repeats improve segregation analysis for cystic fibrosis.
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 1 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 1 or both causal mutations have not been identified. At least 1 of the 4 previously identified microsatellites was informative in 78 of 100 unrelated CF families; at least 1 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.
Elce
Ausilia
A
Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Naples, Italy.
Boccia
Angelo
A
Cardillo
Giuseppe
G
Giordano
Sonia
S
Tomaiuolo
Rossella
R
Paolella
Giovanni
G
Castaldo
Giuseppe
G
D003550:Cystic Fibrosis / Q000175:diagnosis / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D019075:Electrophoresis, Capillary; D005260:Female; D006801:Humans; D008297:Male; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011296:Prenatal Diagnosis; D012091:Repetitive Sequences, Nucleic Acid
D019005:Cystic Fibrosis Transmembrane Conductance Regulator