Avoidance of pseudogene interference in the detection of 3' deletions in PMS2

Hum Mutat. 2011 Sep;32(9):1063-71. doi: 10.1002/humu.21540.


Lynch syndrome is characterized by mutations in the mismatch repair genes MLH1, MSH2, MSH6, and PMS2. In PMS2, detection of mutations is confounded by numerous pseudogenes. Detection of 3' deletions is particularly complicated by the pseudogene PMS2CL, which has strong similarity to PMS2 exons 9 and 11-15, due to extensive gene conversion. A newly designed multiplex ligation-dependent probe amplification (MLPA) kit incorporates probes for variants found in both PMS2 and PMS2CL. This provides detection of deletions, but does not allow localization of deletions to the gene or pseudogene. To address this, we have developed a methodology incorporating reference samples with known copy numbers of variants, and paired MLPA results with sequencing of PMS2 and PMS2CL. We tested a subset of clinically indicated samples for which mutations were either unidentified or not fully characterized using existing methods. We identified eight unrelated patients with deletions encompassing exons 9-15, 11-15, 13-15, 14-15, and 15. By incorporating specific, characterized reference samples and sequencing the gene and pseudogene it is possible to identify deletions in this region of PMS2 and provide clinically relevant results. This methodology represents a significant advance in the diagnosis of patients with Lynch syndrome caused by PMS2 mutations.

MeSH terms

  • Adenosine Triphosphatases / genetics*
  • Algorithms
  • Colorectal Neoplasms, Hereditary Nonpolyposis / genetics
  • DNA Repair Enzymes / genetics*
  • DNA-Binding Proteins / genetics*
  • Exons / genetics
  • Gene Duplication
  • Humans
  • Mismatch Repair Endonuclease PMS2
  • Multiplex Polymerase Chain Reaction
  • Pseudogenes / genetics*
  • Sequence Deletion / genetics*
  • Sequence Homology, Nucleic Acid


  • DNA-Binding Proteins
  • Adenosine Triphosphatases
  • PMS2 protein, human
  • Mismatch Repair Endonuclease PMS2
  • DNA Repair Enzymes