Exon deletions of the PAH gene in Italian hyperphenylalaninemics

Salvatore Micciche', Valentino Romano, Simone Pozzessere, Valentino Romano, Giuseppa Ruggeri, Mirella Vinci, Francesco Calì, Carla Carducci, Alda Ragalmuto, Valeria Chiavetta, Vincenzo Leuzzi, Concetta Meli, Pietro Schinocca, Mirella Vinci

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Abstract

A consistent finding of many studies describing the spectrum of mutant phenylalanine hydroxylase alleles underlying hyperphenylalaninemia is the impossibility of achieving a 100% mutation ascertainment rate using conventional gene-scanning methods such as Denaturing Gradient Gel Electrophoresis (DGGE), Denaturing High Performance Liquid Chromatography (DHPLC), direct sequencing. In recent years, it has been shown that a significant proportion of these undetermined alleles consist of large deletions overlapping one or more exons. These deletions have been difficult to detect in compound heterozygotes by gene-scanning methods due to the masking effect by the non-deleted allele. To date no systematic search has been carried out for such exon deletions in Italian patients with phenylketonuria or Mild hyperphenylalaninemia. We have used Multiplex Ligation-dependent Probe Amplification (MLPA), Comparative Multiplex Dosage Analysis (CMDA) and Real- Time PCR to search for both large deletions and duplications of the phenylalanine hydroxylase gene in Italian HPA patients. Overall, 4 deletions removing different Phenylalanine Hydroxylase (PAH) gene exons were identified in 12 patients. Two of these deletions involving Exons 4-5-6-7-8 (systematic name c.353-?_912+?del) and Exon 6 (systematic name c.510-?_706+?del) have not been reported previously. In this study we show that exon deletion of the PAH gene account for 1.7% of all mutant PAH alleles in Italian hyperphenylalaninemics. A consistent finding of many studies describing the spectrum of mutant phenylalanine hydroxylase alleles underlying hyperphenylalaninemia is the impossibility of achieving a 100% mutation ascertainment rate using conventional gene-scanning methods such as Denaturing Gradient Gel Electrophoresis (DGGE), Denaturing High Performance Liquid Chromatography (DHPLC), direct sequencing. In recent years, it has been shown that a significant proportion of these undetermined alleles consist of large deletions overlapping one or more exons. These deletions have been difficult to detect in compound heterozygotes by gene-scanning methods due to the masking effect by the non-deleted allele. To date no systematic search has been carried out for such exon deletions in Italian patients with phenylketonuria or Mild hyperphenylalaninemia. We have used Multiplex Ligation-dependent Probe Amplification (MLPA), Comparative Multiplex Dosage Analysis (CMDA) and Real- Time PCR to search for both large deletions and duplications of the phenylalanine hydroxylase gene in Italian HPA patients. Overall, 4 deletions removing different Phenylalanine Hydroxylase (PAH) gene exons were identified in 12 patients. Two of these deletions involving Exons 4-5-6-7-8 (systematic name c.353-?_912+?del) and Exon 6 (systematic name c.510-?_706+?del) have not been reported previously. In this study we show that exon deletion of the PAH gene account for 1.7% of all mutant PAH alleles in Italian hyperphenylalaninemics.
Lingua originaleEnglish
Numero di pagine0
RivistaExperimental and Molecular Medicine
Volume42
Stato di pubblicazionePublished - 2010

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Clinical Biochemistry

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Micciche', S., Romano, V., Pozzessere, S., Romano, V., Ruggeri, G., Vinci, M., Calì, F., Carducci, C., Ragalmuto, A., Chiavetta, V., Leuzzi, V., Meli, C., Schinocca, P., & Vinci, M. (2010). Exon deletions of the PAH gene in Italian hyperphenylalaninemics. Experimental and Molecular Medicine, 42.