New Research for Fast & Reliable Diagnosis of CMT 1A and HNPP

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Am J Med Genet A. 2005 Jun 6

Detection of genomic rearrangements by DHPLC: A prospective study of

90 patients with inherited peripheral neuropathies associated with

17p11.2 rearrangements.

Naimi M, Tardieu S, Depienne C, Ruberg M, Brice A, Dubourg O, Leguern

E.

Departement de Genetique, Cytogenetique et Embryologie, Hopital Pitie-

Salpetriere, AP-HP, Paris, France.

Large genomic duplications and deletions are increasingly recognized

as a cause of human disease. Charcot-Marie-Tooth type 1A (CMT1A) and

hereditary neuropathy with liability to pressure palsy (HNPP) result,

respectively, from a duplication or deletion of a 1.5 Mb genomic

region in 17p11.2-12, containing the PMP22 gene.

In routine diagnostic analysis, CMT1A status is inferred from the

detection of an imbalanced dosage of two alleles or the presence of

three alleles of a polymorphic marker flanking the PMP22 gene. HNPP

is suspected if only one allele is seen, but hemizygosity must be

confirmed by analyzing allele segregation in the family or by other

techniques such as Southern blotting or fluorescence in situ

hybridization (FISH). PCR-based methodologies have also been

developed that allow single-step determination of the PMP22 gene copy

number, wherein amplicons are typically labeled and/or separated by

gel electrophoresis.

We describe here a fast and reliable PCR-based method for the

diagnosis of CMT1A and HNPP in which the PMP22 gene is co-amplified

with a reference gene, and the amplicons are separated according to

their size and quantified by DHPLC. Our results suggest that this

method for quantifying gene dosage could be applied to other genomic

rearrangements.