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1.
Cell ; 171(5): 1042-1056.e10, 2017 Nov 16.
Article in English | MEDLINE | ID: mdl-29056344

ABSTRACT

We present an extensive assessment of mutation burden through sequencing analysis of >81,000 tumors from pediatric and adult patients, including tumors with hypermutation caused by chemotherapy, carcinogens, or germline alterations. Hypermutation was detected in tumor types not previously associated with high mutation burden. Replication repair deficiency was a major contributing factor. We uncovered new driver mutations in the replication-repair-associated DNA polymerases and a distinct impact of microsatellite instability and replication repair deficiency on the scale of mutation load. Unbiased clustering, based on mutational context, revealed clinically relevant subgroups regardless of the tumors' tissue of origin, highlighting similarities in evolutionary dynamics leading to hypermutation. Mutagens, such as UV light, were implicated in unexpected cancers, including sarcomas and lung tumors. The order of mutational signatures identified previous treatment and germline replication repair deficiency, which improved management of patients and families. These data will inform tumor classification, genetic testing, and clinical trial design.


Subject(s)
Neoplasms/genetics , Adult , Child , Cluster Analysis , DNA Polymerase II/genetics , DNA Polymerase III/genetics , DNA Replication , Humans , Mutation , Neoplasms/classification , Neoplasms/pathology , Neoplasms/therapy , Poly-ADP-Ribose Binding Proteins/genetics
2.
Gastroenterology ; 164(4): 579-592.e8, 2023 04.
Article in English | MEDLINE | ID: mdl-36586540

ABSTRACT

BACKGROUND & AIMS: Constitutional mismatch repair deficiency (CMMRD) is a rare recessive childhood cancer predisposition syndrome caused by germline mismatch repair variants. Constitutional microsatellite instability (cMSI) is a CMMRD diagnostic hallmark and may associate with cancer risk. We quantified cMSI in a large CMMRD patient cohort to explore genotype-phenotype correlations using novel MSI markers selected for instability in blood. METHODS: Three CMMRD, 1 Lynch syndrome, and 2 control blood samples were genome sequenced to >120× depth. A pilot cohort of 8 CMMRD and 38 control blood samples and a blinded cohort of 56 CMMRD, 8 suspected CMMRD, 40 Lynch syndrome, and 43 control blood samples were amplicon sequenced to 5000× depth. Sample cMSI score was calculated using a published method comparing microsatellite reference allele frequencies with 80 controls. RESULTS: Thirty-two mononucleotide repeats were selected from blood genome and pilot amplicon sequencing data. cMSI scoring using these MSI markers achieved 100% sensitivity (95% CI, 93.6%-100.0%) and specificity (95% CI 97.9%-100.0%), was reproducible, and was superior to an established tumor MSI marker panel. Lower cMSI scores were found in patients with CMMRD with MSH6 deficiency and patients with at least 1 mismatch repair missense variant, and patients with biallelic truncating/copy number variants had higher scores. cMSI score did not correlate with age at first tumor. CONCLUSIONS: We present an inexpensive and scalable cMSI assay that enhances CMMRD detection relative to existing methods. cMSI score is associated with mismatch repair genotype but not phenotype, suggesting it is not a useful predictor of cancer risk.


Subject(s)
Brain Neoplasms , Colorectal Neoplasms, Hereditary Nonpolyposis , Colorectal Neoplasms , Neoplastic Syndromes, Hereditary , Humans , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Microsatellite Instability , Neoplastic Syndromes, Hereditary/diagnosis , Neoplastic Syndromes, Hereditary/genetics , Colorectal Neoplasms/genetics , Colorectal Neoplasms/diagnosis , Brain Neoplasms/diagnosis , Genotype , DNA Mismatch Repair/genetics , Mismatch Repair Endonuclease PMS2/genetics
3.
Genet Med ; 26(5): 101101, 2024 05.
Article in English | MEDLINE | ID: mdl-38362852

ABSTRACT

PURPOSE: Females with biallelic CHEK2 germline pathogenic variants (gPVs) more often develop multiple breast cancers than individuals with monoallelic CHEK2 gPVs. This study is aimed at expanding the knowledge on the occurrence of other malignancies. METHODS: Exome sequencing of individuals who developed multiple primary malignancies identified 3 individuals with the CHEK2 (NM_007194.4) c.1100del p.(Thr367MetfsTer15) loss-of-function gPV in a biallelic state. We collected the phenotypes of an additional cohort of individuals with CHEK2 biallelic gPVs (n = 291). RESULTS: In total, 157 individuals (53.4%; 157/294 individuals) developed ≥1 (pre)malignancy. The most common (pre)malignancies next to breast cancer were colorectal- (n = 19), thyroid- (n = 19), and prostate (pre)malignancies (n = 12). Females with biallelic CHEK2 loss-of-function gPVs more frequently developed ≥2 (pre)malignancies and at an earlier age compared with females biallelic for the CHEK2 c.470T>C p.(Ile157Thr) missense variant. Furthermore, 26 males (31%; 26/84 males) with CHEK2 biallelic gPVs developed ≥1 (pre)malignancies of 15 origins. CONCLUSION: Our study suggests that CHEK2 biallelic gPVs likely increase the susceptibility to develop multiple malignancies in various tissues, both in females and males. However, it is possible that a substantial proportion of individuals with CHEK2 biallelic gPVs is missed as diagnostic testing for CHEK2 often is limited to individuals who developed breast cancer.


Subject(s)
Checkpoint Kinase 2 , Genetic Predisposition to Disease , Germ-Line Mutation , Neoplasms , Adult , Female , Humans , Male , Middle Aged , Alleles , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Checkpoint Kinase 2/genetics , Colorectal Neoplasms/genetics , Colorectal Neoplasms/pathology , Exome Sequencing/methods , Germ-Line Mutation/genetics , Neoplasms/genetics , Phenotype , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology
4.
Clin Chem ; 70(5): 737-746, 2024 May 02.
Article in English | MEDLINE | ID: mdl-38531023

ABSTRACT

BACKGROUND: Constitutional mismatch repair deficiency (CMMRD) is a rare and extraordinarily penetrant childhood-onset cancer predisposition syndrome. Genetic diagnosis is often hampered by the identification of mismatch repair (MMR) variants of unknown significance and difficulties in PMS2 analysis, the most frequently mutated gene in CMMRD. We present the validation of a robust functional tool for CMMRD diagnosis and the characterization of microsatellite instability (MSI) patterns in blood and tumors. METHODS: The highly sensitive assessment of MSI (hs-MSI) was tested on a blinded cohort of 66 blood samples and 24 CMMRD tumor samples. Hs-MSI scores were compared with low-pass genomic instability scores (LOGIC/MMRDness). The correlation of hs-MSI scores in blood with age of cancer onset and the distribution of insertion-deletion (indel) variants in microsatellites were analyzed in a series of 169 individuals (n = 68 CMMRD, n = 124 non-CMMRD). RESULTS: Hs-MSI achieved high accuracy in the identification of CMMRD in blood (sensitivity 98.5% and specificity 100%) and detected MSI in CMMRD-associated tumors. Hs-MSI had a strong positive correlation with whole low-pass genomic instability LOGIC scores (r = 0.89, P = 2.2e-15 in blood and r = 0.82, P = 7e-3 in tumors). Indel distribution identified PMS2 pathogenic variant (PV) carriers from other biallelic MMR gene PV carriers with an accuracy of 0.997. Higher hs-MSI scores correlated with younger age at diagnosis of the first tumor (r = -0.43, P = 0.011). CONCLUSIONS: Our study confirms the accuracy of the hs-MSI assay as ancillary testing for CMMRD diagnosis, which can also characterize MSI patterns in CMMRD-associated cancers. Hs-MSI is a powerful tool to pinpoint PMS2 as the affected germline gene and thus potentially personalize cancer risk.


Subject(s)
Germ-Line Mutation , Microsatellite Instability , Mismatch Repair Endonuclease PMS2 , Humans , Mismatch Repair Endonuclease PMS2/genetics , Neoplastic Syndromes, Hereditary/genetics , Neoplastic Syndromes, Hereditary/diagnosis , Brain Neoplasms/genetics , Brain Neoplasms/diagnosis , Child , Colorectal Neoplasms/genetics , Colorectal Neoplasms/diagnosis , Female , Male , DNA Mismatch Repair/genetics , Child, Preschool , Adolescent , Alleles
5.
J Med Genet ; 60(7): 679-684, 2023 07.
Article in English | MEDLINE | ID: mdl-36411031

ABSTRACT

BACKGROUND: Constitutional mismatch repair deficiency (CMMRD) is a rare autosomal recessively inherited syndrome that is caused by biallelic pathogenic variants of the mismatch repair genes. It is characterised by the development of multiple tumours in the first and second decade of life including brain, gastrointestinal and haematological tumours often resulting in early death. In order to improve the prognosis of these patients, the European collaborative group 'care for CMMRD' developed a surveillance programme in 2014 and established a registry of patients with CMMRD in Paris. The aim of the study was to evaluate the outcome of this programme. METHODS: Twenty-two patients with a definitive diagnosis of CMMRD and with at least one follow-up study were selected from the registry. Medical data on the outcome of surveillance were collected from these patients. RESULTS: During a mean follow-up of 4 years, the programme detected eight malignant tumours including three brain tumours, three upper gastrointestinal cancers and two colorectal cancers. Most tumours could successfully be treated. In addition, many adenomas were detected in the duodenum, and colorectum and subsequently removed. Seven patients developed a symptomatic malignancy, including two brain tumours, one small bowel cancer and four haematological malignancies. At the end of the follow-up, 16 out of 22 patients (73%) who participated in the surveillance programme were still alive. CONCLUSION: The study suggests a beneficial effect of surveillance of the digestive tract and brains.


Subject(s)
Brain Neoplasms , Colorectal Neoplasms , Neoplastic Syndromes, Hereditary , Humans , Follow-Up Studies , Neoplastic Syndromes, Hereditary/diagnosis , Neoplastic Syndromes, Hereditary/epidemiology , Neoplastic Syndromes, Hereditary/genetics , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/epidemiology , Colorectal Neoplasms/genetics , Brain Neoplasms/diagnosis , Brain Neoplasms/genetics , DNA Mismatch Repair , Mismatch Repair Endonuclease PMS2/genetics
6.
Hum Genet ; 142(7): 849-861, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37186028

ABSTRACT

Neurofibromatosis type 1 results from loss-of-function NF1 pathogenic variants (PVs). Up to 30% of all NF1 PVs disrupt mRNA splicing, including deep intronic variants. Here, we retrospectively investigated the spectrum of NF1 deep intronic PVs in a cohort of 8,090 unrelated individuals from the University of Alabama at Birmingham (UAB) dataset with a molecularly confirmed neurofibromatosis type 1. All variants were identified through their effect on the NF1 transcript, followed by variant characterization at the DNA-level. A total of 68 distinct variants, which were ≥ 20 nucleotides away from the closest exon-intron junction, were identified in 2.5% unrelated individuals with NF1 (200/8,090). Nine different pathogenic splice variants, identified in 20 probands, led to exonization of different parts of intron 30 [23.2] or 31 [23a]. The two major NF1 transcript isoforms, distinguished by the absence (type I) or presence (type II) of the alternatively spliced cassette exon 31 [23a], are equally expressed in blood in control individuals without NF1 or NF1-affected individuals carrying their PV not in the introns flanking exon 31 [23a]. By fragment and cloning analysis we demonstrated that the exonization of intron 31 [23a] sequences due to deep intronic PV predominantly affects the NF1 isoform II. Seven additional (likely) pathogenic NF1 deep intronic variants not observed in the UAB dataset were found by classification of 36 variants identified by a literature search. Hence, the unique list of these 75 deep intronic (likely) PVs should be included in any comprehensive NF1 testing strategy.


Subject(s)
Neurofibromatosis 1 , Humans , Neurofibromatosis 1/genetics , Introns/genetics , Retrospective Studies , Exons/genetics , Phenotype , Protein Isoforms/genetics
7.
Hum Mutat ; 43(1): 85-96, 2022 01.
Article in English | MEDLINE | ID: mdl-34816535

ABSTRACT

Heterozygous POLE or POLD1 germline pathogenic variants (PVs) cause polymerase proofreading associated polyposis (PPAP), a constitutional polymerase proofreading deficiency that typically presents with colorectal adenomas and carcinomas in adulthood. Constitutional mismatch-repair deficiency (CMMRD), caused by germline bi-allelic PVs affecting one of four MMR genes, results in a high propensity for the hematological, brain, intestinal tract, and other malignancies in childhood. Nonmalignant clinical features, such as skin pigmentation alterations, are found in nearly all CMMRD patients and are important diagnostic markers. Here, we excluded CMMRD in three cancer patients with highly suspect clinical phenotypes but identified in each a constitutional heterozygous POLE PV. These, and two additional POLE PVs identified in published CMMRD-like patients, have not previously been reported as germline PVs despite all being well-known somatic mutations in hyper-mutated tumors. Together, these five cases show that specific POLE PVs may have a stronger "mutator" effect than known PPAP-associated POLE PVs and may cause a CMMRD-like phenotype distinct from PPAP. The common underlying mechanism, that is, a constitutional replication error repair defect, and a similar tumor spectrum provide a good rationale for monitoring these patients with a severe constitutional polymerase proofreading deficiency according to protocols proposed for CMMRD.


Subject(s)
Brain Neoplasms , Colorectal Neoplasms , Neoplastic Syndromes, Hereditary , Adult , Brain Neoplasms/genetics , Colorectal Neoplasms/genetics , DNA Mismatch Repair/genetics , Humans , Mutation , Neoplastic Syndromes, Hereditary/diagnosis , Neoplastic Syndromes, Hereditary/genetics , Phenotype
8.
Genet Med ; 24(9): 1967-1977, 2022 09.
Article in English | MEDLINE | ID: mdl-35674741

ABSTRACT

PURPOSE: Neurofibromatosis type 2 (NF2) and schwannomatosis (SWN) are genetically distinct tumor predisposition syndromes with overlapping phenotypes. We sought to update the diagnostic criteria for NF2 and SWN by incorporating recent advances in genetics, ophthalmology, neuropathology, and neuroimaging. METHODS: We used a multistep process, beginning with a Delphi method involving global disease experts and subsequently involving non-neurofibromatosis clinical experts, patients, and foundations/patient advocacy groups. RESULTS: We reached consensus on the minimal clinical and genetic criteria for diagnosing NF2 and SWN. These criteria incorporate mosaic forms of these conditions. In addition, we recommend updated nomenclature for these disorders to emphasize their phenotypic overlap and to minimize misdiagnosis with neurofibromatosis type 1. CONCLUSION: The updated criteria for NF2 and SWN incorporate clinical features and genetic testing, with a focus on using molecular data to differentiate the 2 conditions. It is likely that continued refinement of these new criteria will be necessary as investigators study the diagnostic properties of the revised criteria and identify new genes associated with SWN. In the revised nomenclature, the term "neurofibromatosis 2" has been retired to improve diagnostic specificity.


Subject(s)
Neurilemmoma , Neurofibromatoses , Neurofibromatosis 1 , Neurofibromatosis 2 , Skin Neoplasms , Consensus , Humans , Neurilemmoma/diagnosis , Neurilemmoma/genetics , Neurilemmoma/pathology , Neurofibromatoses/diagnosis , Neurofibromatoses/genetics , Neurofibromatosis 1/genetics , Neurofibromatosis 2/diagnosis , Neurofibromatosis 2/genetics , Skin Neoplasms/genetics
9.
Genet Med ; 23(8): 1506-1513, 2021 08.
Article in English | MEDLINE | ID: mdl-34012067

ABSTRACT

PURPOSE: By incorporating major developments in genetics, ophthalmology, dermatology, and neuroimaging, to revise the diagnostic criteria for neurofibromatosis type 1 (NF1) and to establish diagnostic criteria for Legius syndrome (LGSS). METHODS: We used a multistep process, beginning with a Delphi method involving global experts and subsequently involving non-NF experts, patients, and foundations/patient advocacy groups. RESULTS: We reached consensus on the minimal clinical and genetic criteria for diagnosing and differentiating NF1 and LGSS, which have phenotypic overlap in young patients with pigmentary findings. Criteria for the mosaic forms of these conditions are also recommended. CONCLUSION: The revised criteria for NF1 incorporate new clinical features and genetic testing, whereas the criteria for LGSS were created to differentiate the two conditions. It is likely that continued refinement of these new criteria will be necessary as investigators (1) study the diagnostic properties of the revised criteria, (2) reconsider criteria not included in this process, and (3) identify new clinical and other features of these conditions. For this reason, we propose an initiative to update periodically the diagnostic criteria for NF1 and LGSS.


Subject(s)
Neurofibromatosis 1 , Cafe-au-Lait Spots/genetics , Consensus , Genetic Testing , Humans , Neurofibromatosis 1/diagnosis , Neurofibromatosis 1/genetics
10.
J Med Genet ; 57(7): 505-508, 2020 07.
Article in English | MEDLINE | ID: mdl-31501241

ABSTRACT

Biallelic mutations in any of the four mismatch repair genes MSH2, MSH6, MLH1 and PMS2 result in one of the most aggressive childhood cancer predisposition syndromes, termed constitutional mismatch repair deficiency (CMMRD) syndrome. In addition to a very high tumour risk, the CMMRD phenotype is often characterised by the presence of signs reminiscent of neurofibromatosis type 1. Although paediatric systemic lupus erythematosus (pSLE) has been reported so far in three patients with CMMRD, it has not been considered a diagnostic feature of the syndrome. We report here two additional female patients with pSLE and CMMRD due to biallelic pathogenic variants in MSH6 Hence, there are a total of five out of approximately 200 (2.5%) currently reported patients with CMMRD that also have pSLE, suggesting pSLE should raise the suspicion of a diagnosis of CMMRD, especially if supported by additional indicative features.


Subject(s)
Brain Neoplasms/genetics , Colorectal Neoplasms/genetics , DNA-Binding Proteins/genetics , Lupus Erythematosus, Systemic/genetics , Neoplastic Syndromes, Hereditary/genetics , Neurofibromatosis 1/genetics , Brain Neoplasms/complications , Brain Neoplasms/pathology , Child , Child, Preschool , Colorectal Neoplasms/complications , Colorectal Neoplasms/pathology , DNA Mismatch Repair/genetics , Female , Humans , Lupus Erythematosus, Systemic/complications , Lupus Erythematosus, Systemic/pathology , Mutation , Neoplastic Syndromes, Hereditary/complications , Neoplastic Syndromes, Hereditary/pathology , Neurofibromatosis 1/complications , Neurofibromatosis 1/pathology , Pediatrics , Phenotype
11.
J Med Genet ; 57(4): 269-273, 2020 04.
Article in English | MEDLINE | ID: mdl-31494577

ABSTRACT

INTRODUCTION: Lynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are hereditary cancer syndromes associated with mismatch repair (MMR) deficiency. Tumours show microsatellite instability (MSI), also reported at low levels in non-neoplastic tissues. Our aim was to evaluate the performance of high-sensitivity MSI (hs-MSI) assessment for the identification of LS and CMMRD in non-neoplastic tissues. MATERIALS AND METHODS: Blood DNA samples from 131 individuals were grouped into three cohorts: baseline (22 controls), training (11 CMMRD, 48 LS and 15 controls) and validation (18 CMMRD and 18 controls). Custom next generation sequencing panel and bioinformatics pipeline were used to detect insertions and deletions in microsatellite markers. An hs-MSI score was calculated representing the percentage of unstable markers. RESULTS: The hs-MSI score was significantly higher in CMMRD blood samples when compared with controls in the training cohort (p<0.001). This finding was confirmed in the validation set, reaching 100% specificity and sensitivity. Higher hs-MSI scores were detected in biallelic MSH2 carriers (n=5) compared with MSH6 carriers (n=15). The hs-MSI analysis did not detect a difference between LS and control blood samples (p=0.564). CONCLUSIONS: The hs-MSI approach is a valuable tool for CMMRD diagnosis, especially in suspected patients harbouring MMR variants of unknown significance or non-detected biallelic germline mutations.


Subject(s)
Brain Neoplasms/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Colorectal Neoplasms/genetics , DNA-Binding Proteins/genetics , Microsatellite Instability , MutS Homolog 2 Protein/genetics , Neoplastic Syndromes, Hereditary/genetics , Adolescent , Adult , Brain Neoplasms/blood , Brain Neoplasms/pathology , Child , Child, Preschool , Colorectal Neoplasms/blood , Colorectal Neoplasms/pathology , Colorectal Neoplasms, Hereditary Nonpolyposis/blood , Colorectal Neoplasms, Hereditary Nonpolyposis/pathology , DNA Mismatch Repair/genetics , Female , Germ-Line Mutation/genetics , Heterozygote , High-Throughput Nucleotide Sequencing , Humans , Infant , Male , Neoplastic Syndromes, Hereditary/blood , Neoplastic Syndromes, Hereditary/pathology , Young Adult
12.
Hum Mutat ; 41(6): 1145-1156, 2020 06.
Article in English | MEDLINE | ID: mdl-32126153

ABSTRACT

Uncovering frequent motives of action by which variants impair 3' splice site (3'ss) recognition and selection is essential to improve our understanding of this complex process. Through several mini-gene experiments, we demonstrate that the pyrimidine (Y) to purine (R) transversion NM_000267.3(NF1):c.1722-11T>G, although expected to weaken the polypyrimidine tract, causes exon skipping primarily by introducing a novel AG in the AG-exclusion zone (AGEZ) between the authentic 3'ss AG and the branch point. Evaluation of 90 additional noncanonical intronic NF1 3'ss mutations confirmed that 63% of all mutations and 89% (49/55) of the single-nucleotide variants upstream of positions -3 interrupt the AGEZ. Of these AGEZ-interrupting mutations, 24/49 lead to exon skipping suggesting that absence of AG in this region is necessary for accurate 3'ss selection already in the initial steps of splicing. The analysis of 91 noncanonical NF1 3'ss mutations also shows that 90% either introduce a novel AG in the AGEZ, cause a Y>R transversion at position -3 or remove ≥2 Ys in the AGEZ. We confirm in a validation cohort that these three motives distinguish spliceogenic from splice-neutral variants with 85% accuracy and, therefore, are generally applicable to select among variants of unknown significance those likely to affect splicing.


Subject(s)
Introns , Neurofibromin 1/genetics , RNA Splice Sites , RNA Splicing , Adult , Alternative Splicing , Base Sequence , Exons , Female , Humans , Mutation , Ribonucleoproteins, Small Nuclear/genetics
13.
Genet Med ; 22(12): 2081-2088, 2020 12.
Article in English | MEDLINE | ID: mdl-32773772

ABSTRACT

PURPOSE: Biallelic germline mismatch repair (MMR) gene pathogenic variants (PVs) cause constitutional MMR deficiency (CMMRD), a highly penetrant childhood cancer syndrome phenotypically overlapping with neurofibromatosis type 1 (NF1). CMMRD testing in suspected NF1 children without NF1/SPRED1 PVs enables inclusion of CMMRD positives into monitoring programs prior to tumor onset. However, testing is associated with potential harms and the prevalence of CMMRD among these children is unknown. METHODS: Using a simple and scalable microsatellite instability (MSI) assay of non-neoplastic leukocyte DNA to detect CMMRD, we retrospectively screened >700 children suspected of sporadic NF1 but lacking NF1/SPRED1 PVs. RESULTS: For three of seven MSI-positive patients germline MMR gene PVs confirmed the diagnosis of CMMRD. Founder variants NM_000535.5(PMS2):c.736_741delinsTGTGTGTGAAG, prevalent in Europe and North America, and NM_000179.2(MSH6):c.10C>G, affecting 1:400 French Canadians, represented two of five PVs. The prevalence of CMMRD was 3/735 (0.41%, 95% confidence interval [CI]: 0.08-1.19%). CONCLUSION: Our empirical data provide reliable numbers for genetic counseling and confirm previous prevalence estimations, on which Care for CMMRD consortium guidelines are based. These advocate CMMRD testing of preselected patients rather than offering reflex testing to all suspected sporadic NF1 children lacking NF1/SPRED1 PVs. The possibility of founder effects should be considered alongside these testing guidelines.


Subject(s)
Colorectal Neoplasms , Neurofibromatosis 1 , Adaptor Proteins, Signal Transducing , Brain Neoplasms , Canada , Child , DNA Mismatch Repair/genetics , Europe , Humans , Mismatch Repair Endonuclease PMS2/genetics , Neoplastic Syndromes, Hereditary , Neurofibromatosis 1/diagnosis , Neurofibromatosis 1/epidemiology , Neurofibromatosis 1/genetics , North America , Retrospective Studies
14.
J Med Genet ; 56(2): 53-62, 2019 02.
Article in English | MEDLINE | ID: mdl-30415209

ABSTRACT

Constitutional mismatch repair deficiency (CMMRD) is a rare childhood cancer predisposition syndrome caused by biallelic germline mutations in one of four mismatch-repair genes. Besides very high tumour risks, CMMRD phenotypes are often characterised by the presence of signs reminiscent of neurofibromatosis type 1 (NF1). Because NF1 signs may be present prior to tumour onset, CMMRD is a legitimate differential diagnosis in an otherwise healthy child suspected to have NF1/Legius syndrome without a detectable underlying NF1/SPRED1 germline mutation. However, no guidelines indicate when to counsel and test for CMMRD in this setting. Assuming that CMMRD is rare in these patients and that expected benefits of identifying CMMRD prior to tumour onset should outweigh potential harms associated with CMMRD counselling and testing in this setting, we aimed at elaborating a strategy to preselect, among children suspected to have NF1/Legius syndrome without a causative NF1/SPRED1 mutation and no overt malignancy, those children who have a higher probability of having CMMRD. At an interdisciplinary workshop, we discussed estimations of the frequency of CMMRD as a differential diagnosis of NF1 and potential benefits and harms of CMMRD counselling and testing in a healthy child with no malignancy. Preselection criteria and strategies for counselling and testing were developed and reviewed in two rounds of critical revisions. Existing diagnostic CMMRD criteria were adapted to serve as a guideline as to when to consider CMMRD as differential diagnosis of NF1/Legius syndrome. In addition, counselling and testing strategies are suggested to minimise potential harms.


Subject(s)
Brain Neoplasms/diagnosis , Brain Neoplasms/genetics , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/genetics , Neoplastic Syndromes, Hereditary/diagnosis , Neoplastic Syndromes, Hereditary/genetics , Neurofibromatosis 1/diagnosis , Adaptor Proteins, Signal Transducing/genetics , Brain Neoplasms/epidemiology , Colorectal Neoplasms/epidemiology , Diagnosis, Differential , Genetic Counseling , Genetic Testing , Humans , Incidence , Mismatch Repair Endonuclease PMS2/genetics , MutL Protein Homolog 1/genetics , Mutation , Neoplastic Syndromes, Hereditary/epidemiology , Neurofibromatosis 1/genetics , Parents , Patient Selection , Practice Guidelines as Topic
15.
Hum Mutat ; 40(5): 649-655, 2019 05.
Article in English | MEDLINE | ID: mdl-30740824

ABSTRACT

Constitutional mismatch repair deficiency (CMMRD) is caused by germline pathogenic variants in both alleles of a mismatch repair gene. Patients have an exceptionally high risk of numerous pediatric malignancies and benefit from surveillance and adjusted treatment. The diversity of its manifestation, and ambiguous genotyping results, particularly from PMS2, can complicate diagnosis and preclude timely patient management. Assessment of low-level microsatellite instability in nonneoplastic tissues can detect CMMRD, but current techniques are laborious or of limited sensitivity. Here, we present a simple, scalable CMMRD diagnostic assay. It uses sequencing and molecular barcodes to detect low-frequency microsatellite variants in peripheral blood leukocytes and classifies samples using variant frequencies. We tested 30 samples from 26 genetically-confirmed CMMRD patients, and samples from 94 controls and 40 Lynch syndrome patients. All samples were correctly classified, except one from a CMMRD patient recovering from aplasia. However, additional samples from this same patient tested positive for CMMRD. The assay also confirmed CMMRD in six suspected patients. The assay is suitable for both rapid CMMRD diagnosis within clinical decision windows and scalable screening of at-risk populations. Its deployment will improve patient care, and better define the prevalence and phenotype of this likely underreported cancer syndrome.


Subject(s)
Brain Neoplasms/diagnosis , Brain Neoplasms/genetics , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/genetics , DNA Mismatch Repair , Genetic Association Studies , Genetic Predisposition to Disease , Leukocytes/metabolism , Microsatellite Instability , Neoplastic Syndromes, Hereditary/diagnosis , Neoplastic Syndromes, Hereditary/genetics , Alleles , Genetic Association Studies/methods , Germ-Line Mutation , Humans , Microsatellite Repeats
16.
Genet Med ; 21(12): 2706-2712, 2019 12.
Article in English | MEDLINE | ID: mdl-31204389

ABSTRACT

PURPOSE: Biallelic pathogenic variants in the mismatch repair (MMR) genes cause a recessive childhood cancer predisposition syndrome known as constitutional mismatch repair deficiency (CMMRD). Family members with a heterozygous MMR variant have Lynch syndrome. We aimed at estimating cancer risk in these heterozygous carriers as a novel approach to avoid complicated statistical methods to correct for ascertainment bias. METHODS: Cumulative colorectal cancer incidence was estimated in a cohort of PMS2- and MSH6-associated families, ascertained by the CMMRD phenotype of the index, by using mutation probabilities based on kinship coefficients as analytical weights in a proportional hazard regression on the cause-specific hazards. Confidence intervals (CIs) were obtained by bootstrapping at the family level. RESULTS: The estimated cumulative colorectal cancer risk at age 70 years for heterozygous PMS2 variant carriers was 8.7% (95% CI 4.3-12.7%) for both sexes combined, and 9.9% (95% CI 4.9-15.3%) for men and 5.9% (95% CI 1.6-11.1%) for women separately. For heterozygous MSH6 variant carriers these estimates are 11.8% (95% CI 4.5-22.7%) for both sexes combined, 10.0% (95% CI 1.83-24.5%) for men and 11.7% (95% CI 2.10-26.5%) for women. CONCLUSION: Our findings are consistent with previous reports that used more complex statistical methods to correct for ascertainment bias. These results underline the need for MMR gene-specific surveillance protocols for Lynch syndrome.


Subject(s)
Colorectal Neoplasms, Hereditary Nonpolyposis/complications , Colorectal Neoplasms/etiology , Risk Assessment/methods , Adult , Aged , Cohort Studies , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/metabolism , DNA Mismatch Repair , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Female , Genetic Predisposition to Disease/genetics , Germ-Line Mutation , Humans , Incidence , Male , Middle Aged , Mismatch Repair Endonuclease PMS2/genetics , Mismatch Repair Endonuclease PMS2/metabolism , Mutation , Risk Factors
18.
Am J Hum Genet ; 97(2): 238-49, 2015 Aug 06.
Article in English | MEDLINE | ID: mdl-26189818

ABSTRACT

Genomic rearrangements can cause both Mendelian and complex disorders. Currently, several major mechanisms causing genomic rearrangements, such as non-allelic homologous recombination (NAHR), non-homologous end joining (NHEJ), fork stalling and template switching (FoSTeS), and microhomology-mediated break-induced replication (MMBIR), have been proposed. However, to what extent these mechanisms contribute to gene-specific pathogenic copy-number variations (CNVs) remains understudied. Furthermore, few studies have resolved these pathogenic alterations at the nucleotide-level. Accordingly, our aim was to explore which mechanisms contribute to a large, unique set of locus-specific non-recurrent genomic rearrangements causing the genetic neurocutaneous disorder neurofibromatosis type 1 (NF1). Through breakpoint-spanning PCR as well as array comparative genomic hybridization, we have identified the breakpoints in 85 unrelated individuals carrying an NF1 intragenic CNV. Furthermore, we characterized the likely rearrangement mechanisms of these 85 CNVs, along with those of two additional previously published NF1 intragenic CNVs. Unlike the most typical recurrent rearrangements mediated by flanking low-copy repeats (LCRs), NF1 intragenic rearrangements vary in size, location, and rearrangement mechanisms. We propose the DNA-replication-based mechanisms comprising both FoSTeS and/or MMBIR and serial replication stalling to be the predominant mechanisms leading to NF1 intragenic CNVs. In addition to the loop within a 197-bp palindrome located in intron 40, four Alu elements located in introns 1, 2, 3, and 50 were also identified as intragenic-rearrangement hotspots within NF1.


Subject(s)
DNA Copy Number Variations/genetics , Neurofibromatosis 1/genetics , Neurofibromin 1/genetics , Chromosome Breakpoints , Comparative Genomic Hybridization , DNA Mutational Analysis , Humans , In Situ Hybridization, Fluorescence , Polymerase Chain Reaction/methods
19.
Hum Mutat ; 38(7): 889-897, 2017 07.
Article in English | MEDLINE | ID: mdl-28449315

ABSTRACT

Targeted next-generation-sequencing (NGS) panels have largely replaced Sanger sequencing in clinical diagnostics. They allow for the detection of copy-number variations (CNVs) in addition to single-nucleotide variants and small insertions/deletions. However, existing computational CNV detection methods have shortcomings regarding accuracy, quality control (QC), incidental findings, and user-friendliness. We developed panelcn.MOPS, a novel pipeline for detecting CNVs in targeted NGS panel data. Using data from 180 samples, we compared panelcn.MOPS with five state-of-the-art methods. With panelcn.MOPS leading the field, most methods achieved comparably high accuracy. panelcn.MOPS reliably detected CNVs ranging in size from part of a region of interest (ROI), to whole genes, which may comprise all ROIs investigated in a given sample. The latter is enabled by analyzing reads from all ROIs of the panel, but presenting results exclusively for user-selected genes, thus avoiding incidental findings. Additionally, panelcn.MOPS offers QC criteria not only for samples, but also for individual ROIs within a sample, which increases the confidence in called CNVs. panelcn.MOPS is freely available both as R package and standalone software with graphical user interface that is easy to use for clinical geneticists without any programming experience. panelcn.MOPS combines high sensitivity and specificity with user-friendliness rendering it highly suitable for routine clinical diagnostics.


Subject(s)
Computational Biology , DNA Copy Number Variations , Databases, Genetic , Algorithms , Computer Graphics , Gene Library , High-Throughput Nucleotide Sequencing , Humans , Quality Control , Reproducibility of Results , Sensitivity and Specificity , Sequence Analysis, DNA , Software , User-Computer Interface
20.
Arch Gynecol Obstet ; 296(1): 123-127, 2017 Jul.
Article in English | MEDLINE | ID: mdl-28510097

ABSTRACT

PURPOSE: This manuscript reports the consensus recommendations on screening and diagnosis of Lynch syndrome (LS) in patients with endometrial or ovarian cancer as well as on possible preventive measures in effectively LS-diagnosed women. The recommendations are issued by the Austrian Arbeitsgemeinschaft für Gynäkologische Onkologie (AGO) of the Österreichischen Gesellschaft für Gynäkologie und Geburtshilfe (OEGGG) after consultation of the most recent and relevant literature and following deliberation by the Genetic Task-Force convoked May, 2015 by the AGO Council. RESULTS AND CONCLUSION: The Austrian AGO recommends immunohistochemical tissue screening for type-I and type-II endometrial cancers in all patients below the age of 70 years, and for all endometrioid and clear-cell ovarian cancers independently of the patient's age. If needed immunohistochemistry should be complemented by tissue MLH1 promotor hypermethylation testing and/or microsatellite instability (MSI) analysis. The diagnosis LS requires confirmation through identification of a germline mutation by a molecular genetic examination in the mismatch repair genes using the patient's blood. This should be performed without preceding tissue screening when in LS-associated cancer patients the family history fulfills the Amsterdam II or the revised Bethesda criteria. In LS-diagnosed women, the age for prophylactic surgery should be set flexibly based on an informed consent. Regarding the monitoring of these women, chemo-preventive measures as well as screening procedures either to avoid or to early detect LS-related tumors are discussed with a special light on their specific limitations.


Subject(s)
Colorectal Neoplasms, Hereditary Nonpolyposis/diagnosis , Adult , Austria , Colorectal Neoplasms, Hereditary Nonpolyposis/complications , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , DNA Mismatch Repair/genetics , Endometrial Neoplasms/complications , Endometrial Neoplasms/genetics , Endometrial Neoplasms/pathology , Female , Germ-Line Mutation , Humans , Immunohistochemistry , Microsatellite Instability , Middle Aged , Ovarian Neoplasms/complications , Ovarian Neoplasms/genetics , Ovarian Neoplasms/pathology , Promoter Regions, Genetic
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