Department of Human Genetics, Leiden University Medical Centre, Albinusdreef 2, Leiden, The Netherlands.
Hum Mutat. 2010 May;31(5):578-87. doi: 10.1002/humu.21229.
Heterozygous mutations in PMS2 are involved in Lynch syndrome, whereas biallelic mutations are found in Constitutional mismatch repair-deficiency syndrome patients. Mutation detection is complicated by the occurrence of sequence exchange events between the duplicated regions of PMS2 and PMS2CL. We investigated the frequency of such events with a nonspecific polymerase chain reaction (PCR) strategy, co-amplifying both PMS2 and PMS2CL sequences. This allowed us to score ratios between gene and pseudogene-specific nucleotides at 29 PSV sites from exon 11 to the end of the gene. We found sequence transfer at all investigated PSVs from intron 12 to the 3' end of the gene in 4 to 52% of DNA samples. Overall, sequence exchange between PMS2 and PMS2CL was observed in 69% (83/120) of individuals. We demonstrate that mutation scanning with PMS2-specific PCR primers and MLPA probes, designed on PSVs, in the 3' duplicated region is unreliable, and present an RNA-based mutation detection strategy to improve reliability. Using this strategy, we found 19 different putative pathogenic PMS2 mutations. Four of these (21%) are lying in the region with frequent sequence transfer and are missed or called incorrectly as homozygous with several PSV-based mutation detection methods.
杂合性突变 PMS2 参与林奇综合征，而双等位基因突变则见于先天性错配修复缺陷综合征患者。突变检测因 PMS2 和 PMS2CL 重复区域之间发生序列交换事件而变得复杂。我们使用非特异性聚合酶链反应 (PCR) 策略研究了这种事件的频率，该策略共同扩增 PMS2 和 PMS2CL 序列。这使我们能够在从外显子 11 到基因末端的 29 个 PSV 位点上对基因和假基因特异性核苷酸的比值进行评分。我们发现，在所有研究的 PSV 中，从内含子 12 到基因 3' 端的序列在 4%至 52%的 DNA 样本中发生转移。总体而言，PMS2 和 PMS2CL 之间的序列交换在 69%（83/120）的个体中观察到。我们证明，使用设计在 PSV 上的 PMS2 特异性 PCR 引物和 MLPA 探针进行 3' 重复区域的突变扫描是不可靠的，并提出了一种基于 RNA 的突变检测策略来提高可靠性。使用该策略，我们发现了 19 种不同的潜在致病性 PMS2 突变。其中 4 种（21%）位于频繁发生序列转移的区域，在用几种基于 PSV 的突变检测方法时，这些突变被漏检或错误地被标记为纯合子。
