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Related Experiment Videos

Diagnostic genome profiling in mental retardation.

Bert B A de Vries1, Rolph Pfundt, Martijn Leisink

  • 1Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. b.devries@antrg.umcn.nl

American Journal of Human Genetics
|September 22, 2005
PubMed
Summary

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Array comparative genomic hybridization (array CGH) significantly improves the diagnosis of unexplained mental retardation (MR). This molecular karyotyping method detects submicroscopic chromosomal alterations, doubling the diagnostic yield compared to conventional karyotyping.

Area of Science:

  • Genetics
  • Molecular Biology
  • Developmental Biology

Background:

  • Mental retardation (MR) affects 2%-3% of the population.
  • Conventional karyotyping detects chromosomal alterations in only ~5% of individuals with unexplained MR.
  • The frequency of submicroscopic chromosomal alterations in MR patients remains largely unknown.

Purpose of the Study:

  • To investigate the utility of array comparative genomic hybridization (array CGH) for detecting submicroscopic chromosomal alterations in patients with unexplained MR.
  • To determine the diagnostic yield of array CGH compared to standard karyotyping for MR diagnosis.

Main Methods:

  • 100 patients with unexplained MR underwent array CGH using a novel tiling-resolution genomewide microarray.
  • DNA copy-number changes were analyzed.

Related Experiment Videos

  • Alterations were validated using fluorescence in situ hybridization and/or multiplex ligation-dependent probe amplification.
  • Parental testing was performed to identify de novo alterations.

    • Main Results:

    • Reproducible DNA copy-number changes were identified in 97% of patients.
    • Clinically relevant de novo alterations (deletions and duplications) were found in 10% of patients.
    • These de novo alterations ranged from 540 kb to 12 Mb and were distributed across the genome.
    • The majority of detected alterations were inherited from phenotypically normal parents.

    Conclusions:

    • Array CGH significantly increases the diagnostic yield for unexplained MR, identifying submicroscopic chromosomal alterations missed by conventional methods.
    • This molecular karyotyping approach offers at least double the diagnostic yield of standard GTG-banded karyotyping for MR patients.
    • Array CGH is a powerful tool for identifying the genetic causes of unexplained mental retardation.