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Background Monoallelic germline MBD4 pathogenic variants were recently reported to cause a predisposition to uveal melanoma, associated with a specific tumor mutational signature and good response to immunotherapy. Monoallelic tumor pathogenic variants have also been described in brain tumors, breast cancers, and myxofibrosarcomas, whereas biallelic germline MBD4 pathogenic variants have been involved in a recessive hereditary adenomatous polyposis and a specific type of acute myeloid leukemia. Methods We analyzed MBD4 for all patients with a diagnosis of uveal melanoma at Institut Curie since July 2021 and in the 3240 consecutive female probands explored at the Institut Curie for suspicion of predisposition to breast cancer between July 2021 and February 2023. Results We describe 25 families whose probands carry a monoallelic germline pathogenic variant in MBD4. Eighteen of these families presented with uveal melanoma (including a case patient with multiple uveal melanoma), and 7 families presented with breast cancer. Family histories showed the first familial case of uveal melanoma in monoallelic MBD4 pathogenic variant carriers and other various types of cancers in relatives, especially breast, renal, and colorectal tumors. Conclusions Monoallelic MBD4 pathogenic variant may explain some cases of familial and multiple uveal melanoma as well as various cancer types, expanding the tumor spectrum of this predisposition. Further genetic testing in relatives combined with molecular tumor analyses will help define the tumor spectrum and estimate each tumor's risk. [ABSTRACT FROM AUTHOR]

Fanconi anemia (FA) is a recessive genetic disease characterized by congenital abnormalities, chromosome instability, progressive bone marrow failure (BMF), and a strong predisposition to cancer. Twenty FA genes have been identified, and the FANC proteins they encode cooperate in a common pathway that regulates DNA crosslink repair and replication fork stability. We identified a child with severe BMF who harbored biallelic inactivating mutations of the translesion DNA synthesis (TLS) gene REV7 (also known as MAD2L2), which encodes the mutant REV7 protein REV7- V85E. Patient-derived cells demonstrated an extended FA phenotype, which included increased chromosome breaks and [G.sub.2]/M accumulation upon exposure to DNA crosslinking agents, γH2AX and 53BP1 foci accumulation, and enhanced p53/p21 activation relative to cells derived from healthy patients. Expression of WT REV7 restored normal cellular and functional phenotypes in the patient's cells, and CRISPR/Cas9 inactivation of REV7 in a non-FA human cell line produced an FA phenotype. Finally, silencing Rev7 in primary hematopoietic cells impaired progenitor function, suggesting that the DNA repair defect underlies the development of BMF in FA. Taken together, our genetic and functional analyses identified REV7 as a previously undescribed FA gene, which we term FANCV., Introduction Fanconi anemia (FA) is the most frequent cause of inherited bone marrow failure (IBMF) syndromes (1, 2). Twenty FA genes have been identified, including FANCA, FANCB, FANCC, FANCD1 (also [...]

DNA damage checkpoints in the cell cycle may be important barriers against cancer progression in human cells. Fanconi anemia (FA) is an inherited DNA instability disorder that is associated with bone marrow failure and a strong predisposition to cancer. Although FA cells experience constitutive chromosomal breaks, cell cycle arrest at the [G.sub.2] DNA damage checkpoint, and an excess of cell death, some patients do become clinically stable, and the mechanisms underlying this, other than spontaneous reversion of the disease-causing mutation, are not well understood. Here we have defined a clonal phenotype, termed attenuation, in which FA patients acquire an abrogation of the [G.sub.2] checkpoint arrest. Attenuated cells expressed lower levels of CHK1 (also known as CHEK1) and p53. The attenuation could be recapitulated by modulating the ATR/CHK1 pathway, and CHK1 inhibition protected FA cells from cell death. FA patients who expressed the attenuated phenotype had mild bone marrow deficiency and reached adulthood, but several of them eventually developed myelodysplasia or leukemia. Better understanding of attenuation might help predict a patient's clinical course and guide choice of treatment. Our results also highlight the importance of evaluating the cellular DNA damage checkpoint and repair pathways in cancer therapies in general., Introduction Checkpoint pathways are complex biological pathways that regulate responses to DNA damage and other cellular events (1-3). The typical DNA damage checkpoint response triggers cell cycle arrest, allowing time [...]

DICER1 syndrome is a rare paediatric autosomal dominant inherited disorder predisposing to various benign and malignant tumours. It is caused by a germline pathogenic variant in DICER1, and the second hit for tumour development is usually a missense hotspot pathogenic variant in the DICER1 ribonuclease IIIb domain. While DICER1 predisposing variants account for about 60% of ovarian Sertoli-Leydig cell tumours, no DICER1-related testicular stromal tumours have been described. Here we report the first two cases of testicular stromal tumours in children carrying a DICER1 germline pathogenic variant: a case of Sertoli cell tumour and a case of Leydig cell tumour diagnosed at 2 and 12 years of age, respectively. A somatic DICER1 hotspot pathogenic variant was detected in the Sertoli cell tumour. This report extends the spectrum of DICER1-related tumours to include testicular Sertoli cell tumour and potentially testicular Leydig cell tumour. Diagnosis of a testicular Sertoli cell tumour should prompt DICER1 genetic testing so that patients with a DICER1 germline pathogenic variant can benefit from established surveillance guidelines. DICER1 genetic evaluation may be considered for testicular Leydig cell tumour. Our findings suggest that miRNA dysregulation underlies the aetiology of some testicular stromal tumours. [ABSTRACT FROM AUTHOR]

Ataxia telangiectasia (A-T) is a rare autosomal recessive disorder characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, immune defects and predisposition to malignancies. A-T is caused by biallelic inactivation of the ATM gene, in most cases by frameshift or nonsense mutations. More rarely, ATM missense mutations with unknown consequences on ATM function are found, making definitive diagnosis more challenging. In this study, a series of 15 missense mutations, including 11 not previously reported, were identified in 16 patients with clinical diagnosis of A-T belonging to 14 families and 1 patient with atypical clinical features. ATM function was evaluated in patient lymphoblastoid cell lines by measuring H2AX and KAP1 phosphorylation in response to ionizing radiation, confirming the A-T diagnosis for 16 cases. In accordance with previous studies, we showed that missense mutations associated with A-T often lead to ATM protein underexpression (15 out of 16 cases). In addition, we demonstrated that most missense mutations lead to an abnormal cytoplasmic localization of ATM, correlated with its decreased expression. This new finding highlights ATM mislocalization as a new mechanism of ATM dysfunction, which may lead to therapeutic strategies for missense mutation associated A-T. [ABSTRACT FROM AUTHOR]

DNA damage checkpoints in the cell cycle may be important barriers against cancer progression in human cells. Fanconi anemia (FA) is an inherited DNA instability disorder that is associated with bone marrow failure and a strong predisposition to cancer. Although FA cells experience constitutive chromosomal breaks, cell cycle arrest at the G2 DNA damage checkpoint, and an excess of cell death, some patients do become clinically stable, and the mechanisms underlying this, other than spontaneous reversion of the disease-causing mutation, are not well understood. Here we have defined a clonal phenotype, termed attenuation, in which FA patients acquire an abrogation of the G2 checkpoint arrest. Attenuated cells expressed lower levels of CHK1 (also known as CHEK1) and p53. The attenuation could be recapitulated by modulating the ATR/CHK1 pathway, and CHK1 inhibition protected FA cells from cell death. FA patients who expressed the attenuated phenotype had mild bone marrow deficiency and reached adulthood, but several of them eventually developed myelodysplasia or leukemia. Better understanding of attenuation might help predict a patient's clinical course and guide choice of treatment. Our results also highlight the importance of evaluating the cellular DNA damage checkpoint and repair pathways in cancer therapies in general. [ABSTRACT FROM AUTHOR]

Ataxia Telangiectasia (A-T) is caused by biallelic inactivation of the Ataxia Telangiectasia Mutated (ATM) gene, due to nonsense or missense mutations, small insertions/deletions (indels), splicing alterations, and large genomic rearrangements. After establishing A-T clinical diagnosis, a molecular confirmation is needed, based on the detection of one of these loss-of-function mutations in at least one allele. In most cases, the pathogenicity of the detected mutations is sufficient to make a definitive diagnosis. More rarely, mutations of unknown consequences are identified and direct biological analyses are required to establish their pathogenic characters. In such cases, complementary analyses of ATM expression, localization, and activity allow fine characterization of these mutations and facilitate A-T diagnosis. Here, we present genetic and biochemical protocols currently used in the laboratory that have proven to be highly accurate, reproducible, and quantitative. We also provide additional discussion on the critical points of the techniques presented here.