Genetic analyses of samples obtained from two children with mesenchymal hamartomas of the liver (MHLs) implicate variant
DICER1
as a cause and MHL as a phenotype of the DICER1 syndrome. DICER1 is an ...enzyme that processes microRNAs.
Germ-line
RB
-
1
mutations predispose to pineoblastoma (PinB), but other predisposing genetic factors are not well established. We recently identified a germ-line
DICER1
mutation in a child with a ...PinB. This was accompanied by loss of heterozygosity (LOH) of the wild-type allele within the tumour. We set out to establish the prevalence of
DICER1
mutations in an opportunistically ascertained series of PinBs. Twenty-one PinB cases were studied: Eighteen cases had not undergone previous testing for
DICER1
mutations; three patients were known carriers of germ-line
DICER1
mutations. The eighteen PinBs were sequenced by Sanger and/or Fluidigm-based next-generation sequencing to identify
DICER1
mutations in blood gDNA and/or tumour gDNA. Testing for somatic
DICER1
mutations was also conducted on one case with a known germ-line
DICER1
mutation. From the eighteen PinBs, we identified four deleterious
DICER1
mutations, three of which were germ line in origin, and one for which a germ line versus somatic origin could not be determined; in all four, the second allele was also inactivated leading to complete loss of DICER1 protein. No somatic
DICER1
RNase IIIb mutations were identified. One PinB arising in a germ-line
DICER1
mutation carrier was found to have LOH. This study suggests that germ-line
DICER1
mutations make a clinically significant contribution to PinB, establishing
DICER1
as an important susceptibility gene for PinB and demonstrates PinB to be a manifestation of a germ-line
DICER1
mutation. The means by which the second allele is inactivated may differ from other
DICER1
-related tumours.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
No more than almost equal to30% of hereditary breast cancer has been accounted for by mutations in known genes. Most of these genes, such as BRCA1, BRCA2, TP53, CHEK2, ATM, and FANCJ/BRIP1, function ...in DNA repair, raising the possibility that germ line mutations in other genes that contribute to this process also predispose to breast cancer. Given its close relationship with BRCA2, PALB2 was sequenced in affected probands from 68 BRCA1/BRCA2-negative breast cancer families of Ashkenazi Jewish, French Canadian, or mixed ethnic descent. The average BRCAPRO score was 0.58. A truncating mutation (229delT) was identified in one family with a strong history of breast cancer (seven breast cancers in three female mutation carriers). This mutation and its associated breast cancers were characterized with another recently reported but unstudied mutation (2521delA) that is also associated with a strong family history of breast cancer. There was no loss of heterozygosity in tumors with either mutation. Moreover, comparative genomic hybridization analysis showed major similarities to that of BRCA2 tumors but with some notable differences, especially loss of 18q, a change that was previously unknown in BRCA2 tumors and less common in sporadic breast cancer. This study supports recent observations that PALB2 mutations are present, albeit not frequently, in breast cancer families. The apparently high penetrance noted in this study suggests that at least some PALB2 mutations are associated with a substantially increased risk for the disease.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The PALB2 c.2323C>T p.Q775X mutation has been reported in at least three breast cancer families and breast cancer cases of French Canadian descent and this has been attributed to common ancestors. ...The number of mutation-positive cases reported varied based on criteria of ascertainment of index cases tested. Although inherited PALB2 mutations are associated with increased risks of developing breast cancer, risk to ovarian cancer has not been fully explored in this demographically unique population.
We screened the PALB2 p.Q775X variant in 71 families with at least three cases of breast cancer (n=48) or breast and ovarian cancers (n=23) that have previously been found negative for at least the most common BRCA1 and BRCA2 mutations reported in the French Canadian population and in 491 women of French Canadian descent who had invasive ovarian cancer and/or low malignant potential tumors of the major histopathological subtypes.
We identified a PALB2 p.Q775X carrier in a breast cancer family, who had invasive ductal breast carcinomas at 39 and 42 years of age. We also identified a PALB2 p.Q775X carrier who had papillary serous ovarian cystadenocarcinoma at age 58 among the 238 serous subtype ovarian cancer cases investigated, who also had breast cancer at age 52.
Our findings, taken together with previous reports, support adding PALB2 c.2323C>T p.Q775X to the list of cancer susceptibility genes for which founder mutations have been identified in the French Canadian population.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Context
Papillary thyroid carcinoma (PTC) is a common malignancy in adolescence and is molecularly and clinically distinct from adult PTC. Mutations in the DICER1 gene are associated with ...thyroid abnormalities, including multinodular goiter and differentiated thyroid carcinoma.
Objective
In this study, we sought to characterize the prevalence of DICER1 variants in pediatric PTC, specifically in tumors without conventional PTC oncogenic alterations.
Patients
Patients (N = 40) who underwent partial or total thyroidectomy and who were <18 years of age at the time of surgery were selected.
Design
The 40 consecutive thyroidectomy specimens (30 malignant, 10 benign) underwent genotyping for 17 PTC-associated variants, as well as full sequencing of the exons and exon-intron boundaries of DICER1.
Results
Conventional alterations were found in 12 of 30 (40%) PTCs (five BRAFV600E, three RET/PTC1, four RET/PTC3). Pathogenic DICER1 variants were identified in 3 of 30 (10%) PTCs and in 2 of 10 (20%) benign nodules, all of which lacked conventional alterations and did not recur during follow-up. DICER1 alterations thus constituted 3 of 18 (16.7%) PTCs without conventional alterations. The three DICER1-mutated carcinomas each had two somatic DICER1 alterations, whereas two follicular-nodular lesions arose in those with germline DICER1 mutations and harbored characteristic second somatic RNase IIIb “hotspot” mutations.
Conclusions
DICER1 is a driver of pediatric thyroid nodules, and DICER1-mutated PTC may represent a distinct class of low-risk malignancies. Given the prevalence of variants in children, we advocate for inclusion of DICER1 sequencing and gene dosage determination in molecular analysis of pediatric thyroid specimens.
In this study, the authors establish DICER1 as a common driver in ATA low-risk pediatric PTC. Of the tumors lacking conventional oncogenic alterations, 16.7% carried pathogenic DICER1 variants.
Genetic variants in folate metabolism have been reported to increase risk for neural tube defects (NTD). The first such sequence change was the 677C
→
T substitution in methylenetetrahydrofolate ...reductase (
MTHFR), but additional sequence changes have been identified in enzymes or transporters for folates. Two recently identified variants are the 1561C
→
T (H475Y) mutation in glutamate carboxypeptidase II (
GCPII) and the 80A
→
G (H27R) change in the reduced folate carrier
RFC-1. We examined a group of mothers of spina bifida offspring, and a group of control women, for the above polymorphisms to assess their impact on NTD risk as well as on homocysteine and nutrient (RBC folate, serum folate, and serum cobalamin) levels. The
GCPII variant (in the heterozygous state) did not influence NTD risk or metabolite levels; homozygous mutant (YY) women were not observed in our study group. The homozygous mutant (RR) genotype for the
RFC-1 gene was not associated with a significant difference in NTD risk (OR=1.39, 95% CI=0.55–3.54), but there was a borderline significant (
p=0.065) decrease in RBC folate levels, compared with the HH genotype. However, the combination of the RR genotype for
RFC-1 and low RBC folate was associated with a significant 4.6-fold increase in NTD risk (OR=4.6, 95% CI=1.47–14.37). Since this small study is the first to demonstrate increased risk for women with the
RFC-1 variant for having a child with a NTD, additional larger studies are required to confirm this change as another potential genetic modifier for spina bifida risk.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Objective Familial multinodular goiter (MNG), with or without ovarian Sertoli-Leydig cell tumor (SLCT), has been linked to DICER1 syndrome. We aimed to search for the presence of a germline DICER1 ...mutation in a large family with a remarkable history of MNG and SLCT, and to further explore the relevance of the identified mutation. Design and methods Sanger sequencing, Fluidigm Access Array and multiplex ligation-dependent probe amplification (MLPA) techniques were used to screen for DICER1 mutations in germline DNA from 16 family members. Where available, tumor DNA was also studied. mRNA and protein extracted from carriers’ lymphocytes were used to characterize the expression of the mutant DICER1. Results Nine of 16 tested individuals carried a germline, in-frame DICER1 deletion (c.4207-41_5364+1034del), which resulted in the loss of exons 23 and 24 from the cDNA. The mutant transcript does not undergo nonsense-mediated decay and the protein is devoid of specific metal ion-binding amino acids (p.E1705 and p.D1709) in the RNase IIIb domain. In addition, characteristic somatic ‘second hit’ mutations in this region were found on the other allele in tumors. Conclusions Patients with DICER1 syndrome usually present a combination of a typically truncating germline DICER1 mutation and a tumor-specific hotspot missense mutation within the sequence encoding the RNase IIIb domain. The in-frame deletion found in this family suggests that the germline absence of p.E1705 and p.D1709, which are crucial for RNase IIIb activity, may be enough to permit DICER1 syndrome to occur.
DICER1 tumor predisposition syndrome is a pleiotropic disorder that gives rise to various mainly pediatric-onset lesions. We report an extraskeletal chondroma (EC) of the great toe occurring in a ...child who, unusually, carries a germline “hotspot” missense
DICER1
variant rather than the more usual loss-of-function (LOF) variant. No heterozygous LOF allele was identified in the EC. We demonstrate this variant impairs 5p cleavage of precursor-miRNA (pre-miRNA) and competes with wild-type (WT) DICER1 protein for pre-miRNA processing. These results suggest a mechanism through which a germline RNase IIIb variant could impair pre-miRNA processing without complete LOF of the WT
DICER1
allele.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Individuals harboring germ-line
DICER1
mutations are predisposed to a rare cancer syndrome, the
DICER1
Syndrome or pleuropulmonary blastoma-familial tumor and dysplasia syndrome online Mendelian ...inheritance in man (OMIM) #601200. In addition, specific somatic mutations in the DICER1 RNase III catalytic domain have been identified in several
DICER1
-associated tumor types. Pituitary blastoma (PitB) was identified as a distinct entity in 2008, and is a very rare, potentially lethal early childhood tumor of the pituitary gland. Since the discovery by our team of an inherited mutation in
DICER1
in a child with PitB in 2011, we have identified 12 additional PitB cases. We aimed to determine the contribution of germ-line and somatic
DICER1
mutations to PitB. We hypothesized that PitB is a pathognomonic feature of a germ-line
DICER1
mutation and that each PitB will harbor a second somatic mutation in
DICER1.
Lymphocyte or saliva DNA samples ascertained from ten infants with PitB were screened and nine were found to harbor a heterozygous germ-line
DICER1
mutation. We identified additional
DICER1
mutations in nine of ten tested PitB tumor samples, eight of which were confirmed to be somatic in origin. Seven of these mutations occurred within the RNase IIIb catalytic domain, a domain essential to the generation of 5p miRNAs from the 5′ arm of miRNA-precursors. Germ-line
DICER1
mutations are a major contributor to PitB. Second somatic
DICER1
“hits” occurring within the RNase IIIb domain also appear to be critical in PitB pathogenesis.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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