Balanced translocations in mental retardation

Hum Genet. 2009 Jul;126(1):133-47. doi: 10.1007/s00439-009-0661-6. Epub 2009 Apr 5.


Over the past few decades, the knowledge on genetic defects causing mental retardation has dramatically increased. In this review, we discuss the importance of balanced chromosomal translocations in the identification of genes responsible for mental retardation. We present a database-search guided overview of balanced translocations identified in patients with mental retardation. We divide those in four categories: (1) balanced translocations that helped to identify a causative gene within a contiguous gene syndrome, (2) balanced translocations that led to the identification of a mental retardation gene confirmed by independent methods, (3) balanced translocations disrupting candidate genes that have not been confirmed by independent methods and (4) balanced translocations not reported to disrupt protein coding sequences. It can safely be concluded that balanced translocations have been instrumental in the identification of multiple genes that are involved in mental retardation. In addition, many more candidate genes were identified with a suspected but (as yet?) unconfirmed role in mental retardation. Some balanced translocations do not disrupt a protein coding gene and it can be speculated that in the light of recent findings concerning ncRNA's and ultra-conserved regions, such findings are worth further investigation as these potentially may lead us to the discovery of novel disease mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Chromosome Breakage
  • Chromosome Mapping
  • Chromosomes, Human, Pair 1
  • Chromosomes, Human, Pair 12
  • Chromosomes, Human, Pair 18
  • Chromosomes, Human, Pair 2
  • Chromosomes, Human, Pair 20
  • Chromosomes, Human, Pair 4
  • Chromosomes, Human, Pair 5
  • Chromosomes, Human, Pair 6
  • Chromosomes, Human, Pair 7
  • Chromosomes, Human, Pair 9
  • Chromosomes, Human, X
  • Cytoskeletal Proteins / genetics
  • Female
  • Forkhead Box Protein L2
  • Forkhead Transcription Factors / genetics
  • Frameshift Mutation
  • GTPase-Activating Proteins / genetics
  • Histone-Lysine N-Methyltransferase / genetics
  • Humans
  • Intellectual Disability / genetics*
  • Kruppel-Like Transcription Factors / genetics
  • Mental Retardation, X-Linked / genetics
  • Nerve Tissue Proteins / genetics
  • Nuclear Proteins / genetics
  • Translocation, Genetic*
  • X Chromosome Inactivation
  • Zinc Finger Protein Gli3


  • ASPM protein, human
  • Cytoskeletal Proteins
  • FOXL2 protein, human
  • Forkhead Box Protein L2
  • Forkhead Transcription Factors
  • GLI3 protein, human
  • GTPase-Activating Proteins
  • Kruppel-Like Transcription Factors
  • Nerve Tissue Proteins
  • Nuclear Proteins
  • OPHN1 protein, human
  • Zinc Finger Protein Gli3
  • EHMT1 protein, human
  • Histone-Lysine N-Methyltransferase