Journal
JOURNAL OF MEDICAL GENETICS
Volume 48, Issue 8, Pages 513-519Publisher
B M J PUBLISHING GROUP
DOI: 10.1136/jmedgenet-2011-100050
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Funding
- Wilhelm-Sander Foundation
- German Cancer Aid (Deutsche Krebshife)
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Background A positive family history, germline mutations in DNA mismatch repair genes, tumours with high microsatellite instability, and loss of mismatch repair protein expression are the hallmarks of hereditary non-polyposis colorectal cancer (Lynch syndrome). However, in similar to 10-15% of cases of suspected Lynch syndrome, no disease-causing mechanism can be detected. Methods Oligo array analysis was performed to search for genomic imbalances in patients with suspected mutation-negative Lynch syndrome with MLH1 deficiency in their colorectal tumours. Results and conclusion A deletion in the LRRFIP2 (leucine-rich repeat flightless-interacting protein 2) gene flanking the MLH1 gene was detected, which turned out to be a paracentric inversion on chromosome 3p22.2 creating two new stable fusion transcripts between MLH1 and LRRFIP2. A single-nucleotide polymorphism in MLH1 exon 8 was expressed from both alleles, initially pointing to appropriate MLH1 function at least in peripheral cells. In a second case, an inherited duplication of the MLH1 gene region resulted in constitutional MLH1 promoter methylation. Constitutional MLH1 promoter methylation may therefore in rare cases be a heritable disease mechanism and should not be overlooked in seemingly sporadic patients.
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