Functional and phenotypic consequences of an unusual inversion in MSH2.

Lynch syndrome is an autosomal dominant disorder that usually results from a pathogenic germline variant in one of four genes (MSH2, MSH6, MLH1, PMS2) involved in DNA mismatch repair. Carriers of such variants are at risk of developing numerous cancers during adulthood. Here we report on a family suspected of having Lynch syndrome due to a history of endometrial adenocarcinoma, ovarian clear cell carcinoma, and adenocarcinoma of the duodenum in whom we identified a germline 29 nucleotide in-frame inversion in exon 3 of MSH2. We further show that this variant is almost completely absent at the protein level, and that the associated cancers have complete loss of MSH2 and MSH6 expression by immunohistochemistry. Functional investigation of this inversion in a laboratory setting revealed a resultant abnormal protein function. Thus, we have identified an unusual, small germline inversion in a mismatch repair gene that does not lead to a premature stop codon yet appears likely to be causal for the observed cancers.

Reclassification of a frequent African-origin variant from PMS2 to the pseudogene PMS2CL.

Genomic analysis has become a mainstay in the investigation of cancer patients, especially for those suspected of harboring a heritable cancer predisposition syndrome. With ubiquitous short-read next-generation sequencing (NGS) technologies, these analyses can be complicated by the inappropriate alignment of variants to homologous genomic regions or pseudogenes. Using distinct primer sets specific to the gene and pseudogene, a nonspecific primer set, and a highly gene-specific long-range polymerase chain reaction primer set, we have shown that in at least a subset of patients, the common African PMS2 variant NM_000535.5:c.2182_2184delACTinsG, classified as pathogenic in ClinVar, has been incorrectly assigned to PMS2 from its well-documented pseudogene, PMS2CL. This result is not only important for patients but also highlights a weakness in short-read NGS technologies and the racial inequity in genomic analysis.

DGCR8 microprocessor defect characterizes familial multinodular goiter with schwannomatosis.

BACKGROUNDDICER1 is the only miRNA biogenesis component associated with an inherited tumor syndrome, featuring multinodular goiter (MNG) and rare pediatric-onset lesions. Other susceptibility genes for familial forms of MNG likely exist.METHODSWhole-exome sequencing of a kindred with early-onset MNG and schwannomatosis was followed by investigation of germline pathogenic variants that fully segregated with the disease. Genome-wide analyses were performed on 13 tissue samples from familial and nonfamilial DGCR8-E518K-positive tumors, including MNG, schwannomas, papillary thyroid cancers (PTCs), and Wilms tumors. miRNA profiles of 4 tissue types were compared, and sequencing of miRNA, pre-miRNA, and mRNA was performed in a subset of 9 schwannomas, 4 of which harbor DGCR8-E518K.RESULTSWe identified c.1552G>A;p.E518K in DGCR8, a microprocessor component located in 22q, in the kindred. The variant identified is a somatic hotspot in Wilms tumors and has been identified in 2 PTCs. Copy number loss of chromosome 22q, leading to loss of heterozygosity at the DGCR8 locus, was found in all 13 samples harboring c.1552G>A;p.E518K. miRNA profiling of PTCs, MNG, schwannomas, and Wilms tumors revealed a common profile among E518K hemizygous tumors. In vitro cleavage demonstrated improper processing of pre-miRNA by DGCR8-E518K. MicroRNA and RNA profiling show that this variant disrupts precursor microRNA production, impacting populations of canonical microRNAs and mirtrons.CONCLUSIONWe identified DGCR8 as the cause of an unreported autosomal dominant mendelian tumor susceptibility syndrome: familial multinodular goiter with schwannomatosis.FUNDINGCanadian Institutes of Health Research, Compute Canada, Alex's Lemonade Stand Foundation, the Mia Neri Foundation for Childhood Cancer, Cassa di Sovvenzioni e Risparmio fra il Personale della Banca d'Italia, and the KinderKrebsInitiative Buchholz/Holm-Seppensen.

PTPRD copy number variants and Ewing's sarcoma: Strengthening the association and therapeutic implications.

Ewing sarcoma (ES), a common pediatric primary bone neoplasm, has a well-defined genomic landscape with various predisposing genomic elements including TP53, PMS2 and RET. Additionally, germline and somatic variants in protein tyrosine phosphatase delta (PTPRD), a tumor suppressor gene, have been identified in a limited number of ES patients. Here we present an ES patient, remarkable in terms of his young age and extent at presentation, found to have a PTPRD CNV. We explore the pathogenicity of this CNV, describe the patient's clinical course and touch upon the potential therapeutic implications in this subset of patients.

Glucocorticoid resistance syndrome caused by a novel NR3C1 point mutation.

Glucocorticoid resistance syndrome (GRS) is a rare genetic disorder caused by inactivating mutations of the NR3C1 gene which encodes the glucocorticoid receptor. The phenotypic spectrum is broad but typically include symptoms of adrenal insufficiency, mineralocorticoid excess and hyperandrogenism. We report a new case associated with a novel NR3C1 mutation. A 55-year-old woman with lifelong history of low body weight, hyperandrogenism and anxiety was seen at the endocrine clinic after left adrenalectomy and salpingoophorectomy for lesions suspicious of ovarian cancer and adrenal metastasis. The tumors turned out to be a 3.5 cm benign ovarian serous adenofibroma and a 3.5 cm multinodular adrenal mass. She complained of worsened fatigue and inability to recover weight lost with surgery. Pre-operative serum and urinary cortisol were elevated, but she had no stigma of Cushing's syndrome. Plasma ACTH was elevated and a 1-mcg cosyntropin stimulation test was normal. Her fatigue persisted over ensuing years and ACTH-dependent hypercortisolemia remained stable. Low dose oral dexamethasone failed to suppress endogenous cortisol. A pituitary MRI was normal but revealed incidental brain aneurysms. Bone densitometry showed profound osteoporosis. On the bases of this contradictory clinical picture, glucocorticoid resistance syndrome (GRS) was suspected. Using next generation sequencing technology, a novel heterozygous pathogenic variant in the NR3C1 gene was detected. We speculate that vascular malformations and profound osteoporosis, findings associated to cortisol excess, reflect in our patient a variable tissue sensitivity to glucocorticoids. In conclusion, in patients with clinically unexpected ACTH-dependent hypercortisolemia, primary glucocorticoid resistance (GRS) should be considered.

A case of neuroblastoma in DICER1 syndrome: Chance finding or noncanonical causation?

DICER1 syndrome is an inherited disorder associated with at least a dozen rare, mainly pediatric-onset tumors. Its characterization remains incomplete. Some studies suggested that neuroblastoma (NB) may be involved in this syndrome. Here, we describe the case of a 14-year-old female presenting with a multinodular goiter (MNG) and a collision tumor composed of NB and cystic nephroma (CN). She is a carrier of a deleterious germline mutation in exon 23 of DICER1 and harbored different somatic mutations in the CN and MNG. However, no second hit was found in the NB, questioning its status as a DICER1-related tumor.

Prevalence of four Mendelian disorders associated with autism in 2392 affected families.

Autism spectrum disorder (ASD) is a neurobehavioral disorder with a heterogeneous genetic etiology. Based on the literature, several single-gene disorders, including Rett syndrome, Smith-Lemli-Opitz syndrome, PTEN hamartoma tumor syndrome and tuberous sclerosis, are associated with a high prevalence of ASD. We estimated the prevalence of these four conditions in a large cohort of patients using whole-exome sequencing data from 2392 families (1800 quads and 592 trios) with ASD from the National Database for Autism Research. Seven patients carried a pathogenic or likely pathogenic variant in either TSC1, TSC2, PTEN, DHCR7 or MECP2, with 6 out of 7 reportable variants occurring in PTEN (1 in 399).

Germline and somatic SMARCA4 mutations characterize small cell carcinoma of the ovary, hypercalcemic type.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is the most common undifferentiated ovarian malignancy in women under 40 years of age. We sequenced the exomes of six individuals from three families with SCCOHT. After discovering segregating deleterious germline mutations in SMARCA4 in all three families, we tested DNA from a fourth affected family, which also carried a segregating SMARCA4 germline mutation. All the familial tumors sequenced harbored either a somatic mutation or loss of the wild-type allele. Immunohistochemical analysis of these cases and additional familial and non-familial cases showed loss of SMARCA4 (BRG1) protein in 38 of 40 tumors overall. Sequencing of cases with available DNA identified at least one germline or somatic deleterious SMARCA4 mutation in 30 of 32 cases. Additionally, the SCCOHT cell line BIN-67 had biallelic deleterious mutations in SMARCA4. Our findings identify alterations in SMARCA4 as the major cause of SCCOHT, which could lead to improvements in genetic counseling and new treatment approaches.