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An intronic polymorphic deletion in the PTEN gene: implications for molecular diagnostic testing.

ABSTRACT: A cohort of 629 patients with suspected Bannayan-Riley-Ruvalcaba syndrome or Cowden syndrome was tested for mutations in the PTEN gene.Dosage analysis of PTEN was carried out using a PTEN-specific multiplex ligation-dependent probe amplification (MLPA) kit, whereas point mutation analysis was performed using direct sequencing.Approximately 4% of the patients from the testing cohort were heterozygously deleted for the two MLPA probe-binding sites situated in intron 1. The same deletion was subsequently seen in ?3% of 220 normal controls, and in patients from the testing cohort with a causative mutation elsewhere in the PTEN gene. Sequencing of the variant revealed an 899 bp deletion, the 3' breakpoint of which is only 58 bp from the start of exon 2.Although all evidence suggests that the 899 bp deletion is a polymorphism with no clinical effect, it removes the binding sites of almost all published PTEN exon 2 forward primers, resulting in allelic loss during PCR.

SUBMITTER: Sandell S

PROVIDER: S-EPMC3566822 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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An intronic polymorphic deletion in the PTEN gene: implications for molecular diagnostic testing.

Sandell S S Schuit R J L RJ Bunyan D J DJ

British journal of cancer 20130108 2

<h4>Background</h4>A cohort of 629 patients with suspected Bannayan-Riley-Ruvalcaba syndrome or Cowden syndrome was tested for mutations in the PTEN gene.<h4>Methods</h4>Dosage analysis of PTEN was carried out using a PTEN-specific multiplex ligation-dependent probe amplification (MLPA) kit, whereas point mutation analysis was performed using direct sequencing.<h4>Results</h4>Approximately 4% of the patients from the testing cohort were heterozygously deleted for the two MLPA probe-binding sites ...[more]

PMID: 23299532

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Project description:The identification of numerous genetically based epilepsies has resulted in the widespread use of genetic testing to inform epilepsy etiology. Our study aims to investigate whether a difference exists in the diagnostic evaluation and healthcare-related cost expenditures of pediatric patients with epilepsy of unknown etiology who receive a genetic diagnosis through multigene epilepsy panel (MEP) testing and comparing those who underwent early (EGT) versus late genetic testing (LGT). Testing was defined as early (less than 1 year), or late (more than 1 year), following clinical epilepsy diagnosis. A retrospective chart review of pediatric individuals (1-17 years) with epilepsy of unknown etiology who underwent multigene epilepsy panel (MEP) testing identified 28 of 226 (12%) individuals with a pathogenic epilepsy variant [EGT n = 8 (29%); LGT n = 20 (71%)]. The average time from clinical epilepsy diagnosis to genetic diagnosis was 0.25 years (EGT), compared with 7.1 years (LGT). The EGT cohort underwent fewer metabolic tests [EGT n = 0 (0%); LGT n = 16 (80%) (P < 0.01)] and invasive procedures [EGT n = 0 (0%); LGT n = 5 (25%) (P = 0.06)]. Clinical management changes implemented due to genetic diagnosis occurred in 10 (36%) patients [EGT n = 2 (25%); LGT n = 8 (40%) (P = 0.76)]. Early genetic testing with a MEP in pediatric patients with epilepsy of unknown etiology who receive a genetic diagnosis is associated with fewer non-diagnostic tests and invasive procedures and reduced estimated overall healthcare-related costs. PLAIN LANGUAGE SUMMARY: This study aims to investigate whether a difference exists in the diagnostic evaluation and cost expenditures of pediatric patients (1-17 years) with epilepsy of unknown cause who are ultimately diagnosed with a genetic cause of epilepsy through multigene epilepsy panel testing and comparing those who underwent early testing (less than 1 year) versus late testing (more than 1 year) after clinical epilepsy diagnosis. Of the 28 of 226 individuals with a confirmed genetic cause of epilepsy on multigene epilepsy panel testing, performing early testing was associated with fewer non-diagnostic tests, fewer invasive procedures and reduced estimated overall healthcare-related costs.

Project description:To investigate the genetic basis for autosomal recessive cone-rod dystrophy (CRD) in a consanguineous Israeli Jewish family.Patients underwent a detailed ophthalmic evaluation, including eye examination, visual field testing, optical coherence tomography (OCT), and electrophysiological tests, electroretinography (ERG) and visual evoked potential (VEP). Genome-wide homozygosity mapping using a single nucleotide polymorphism (SNP) array was performed to identify homozygous regions shared among two of the affected individuals. Mutation screening of the underlying gene was performed with direct sequencing. In silico and in vitro analyses were used to predict the effect of the identified mutation on splicing.The affected family members are three siblings who have various degrees of progressive visual deterioration, glare, color vision abnormalities, and night vision difficulties. Visual field tests revealed central scotomas of different extension. Cone and rod ERG responses were reduced, with cones more severely affected. Homozygosity mapping revealed several homozygous intervals shared among two of the affected individuals. One included the PROM1 gene. Sequence analysis of the 26 coding exons of PROM1 in one affected individual revealed no mutations in the coding sequence or in intronic splice sites. However, in intron 21, proximate to the intron-exon junction, we observed a homozygous 10 bp deletion between positions -26 and -17 (c.2281-26_-17del). The deletion was linked to a known SNP, c.2281-6C>G. The deletion cosegregated with the disease in the family, and was not detected in public databases or in 101 ethnically-matched control individuals. In silico analysis predicted that this deletion would lead to altered intron 21 splicing. Bioinformatic analysis predicted that a recognition site for the SRSF2 splicing factor is located within the deleted sequence. The in vitro splicing assay demonstrated that c.2281-26_-17del leads to complete exon 22 skipping.A novel and unique intronic mutation of PROM1, underlying autosomal recessive CRD in a consanguineous Israeli family, was found. This report expands the spectrum of pathogenic mutations of PROM1 and further demonstrates the importance of intronic mutations.

Dataset Information

An intronic polymorphic deletion in the PTEN gene: implications for molecular diagnostic testing.

Publications

An intronic polymorphic deletion in the PTEN gene: implications for molecular diagnostic testing.

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