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Exome sequencing reveals MCM8 mutation underlies ovarian failure and chromosomal instability.

ABSTRACT: Premature ovarian failure (POF) is a genetically and phenotypically heterogeneous disorder that includes individuals with manifestations ranging from primary amenorrhea to loss of menstrual function prior to age 40. POF presents as hypergonadotropic hypogonadism and can be part of a syndrome or occur in isolation. Here, we studied 3 sisters with primary amenorrhea, hypothyroidism, and hypergonadotropic hypogonadism. The sisters were born to parents who are first cousins. SNP analysis and whole-exome sequencing revealed the presence of a pathogenic variant of the minichromosome maintenance 8 gene (MCM8, c.446C>G; p.P149R) located within a region of homozygosity that was present in the affected daughters but not in their unaffected sisters. Because MCM8 participates in homologous recombination and dsDNA break repair, we tested fibroblasts from the affected sisters for hypersensitivity to chromosomal breaks. Compared with fibroblasts from unaffected daughters, chromosomal break repair was deficient in fibroblasts from the affected individuals, likely due to inhibited recruitment of MCM8 p.P149R to sites of DNA damage. Our study identifies an autosomal recessive disorder caused by an MCM8 mutation that manifests with endocrine dysfunction and genomic instability.

SUBMITTER: AlAsiri S

PROVIDER: S-EPMC4382257 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Exome sequencing reveals MCM8 mutation underlies ovarian failure and chromosomal instability.

AlAsiri Saleh S Basit Sulman S Wood-Trageser Michelle A MA Yatsenko Svetlana A SA Jeffries Elizabeth P EP Surti Urvashi U Ketterer Deborah M DM Afzal Sibtain S Ramzan Khushnooda K Faiyaz-Ul Haque Muhammad M Jiang Huaiyang H Trakselis Michael A MA Rajkovic Aleksandar A

The Journal of clinical investigation 20141201 1

Premature ovarian failure (POF) is a genetically and phenotypically heterogeneous disorder that includes individuals with manifestations ranging from primary amenorrhea to loss of menstrual function prior to age 40. POF presents as hypergonadotropic hypogonadism and can be part of a syndrome or occur in isolation. Here, we studied 3 sisters with primary amenorrhea, hypothyroidism, and hypergonadotropic hypogonadism. The sisters were born to parents who are first cousins. SNP analysis and whole-e ...[more]

PMID: 25437880

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Project description:STUDY QUESTION:What is the prevalence of somatic chromosomal instability among women with idiopathic primary ovarian insufficiency (POI)? SUMMARY ANSWER:A subset of women with idiopathic POI may have functional impairment in DNA repair leading to chromosomal instability in their soma. WHAT IS KNOWN ALREADY:The formation and repair of DNA double-strand breaks during meiotic recombination are fundamental processes of gametogenesis. Oocytes with compromised DNA integrity are susceptible to apoptosis which could trigger premature ovarian aging and accelerated wastage of the human follicle reserve. Genomewide association studies, as well as whole exome sequencing, have implicated multiple genes involved in DNA damage repair. However, the prevalence of defective DNA damage repair in the soma of women with POI is unknown. STUDY DESIGN, SIZE, DURATION:In total, 46 women with POI and 15 family members were evaluated for excessive mitomycin-C (MMC)-induced chromosome breakage. Healthy fertile females (n = 20) and two lymphoblastoid cell lines served as negative and as positive controls, respectively. PARTICIPANTS/MATERIALS, SETTING, METHODS:We performed a pilot functional study utilizing MMC to assess chromosomal instability in the peripheral blood of participants. A high-resolution array comparative genomic hybridization (aCGH) was performed on 16 POI patients to identify copy number variations (CNVs) for a set of 341 targeted genes implicated in DNA repair. MAIN RESULTS AND THE ROLE OF CHANCE:Array CGH revealed three POI patients (3/16, 18.8%) with pathogenic CNVs. Excessive chromosomal breakage suggestive of a constitutional deficiency in DNA repair was detected in one POI patient with the 16p12.3 duplication. In two patients with negative chromosome breakage analysis, aCGH detected a Xq28 deletion comprising the Centrin EF-hand Protein 2 (CETN2) and HAUS Augmin Like Complex Subunit 7 (HAUS7) genes essential for meiotic DNA repair, and a duplication in the 3p22.2 region comprising a part of the ATPase domain of the MutL Homolog 1 (MLH1) gene. LIMITATIONS REASONS FOR CAUTION:Peripheral lymphocytes, used as a surrogate tissue to quantify induced chromosome damage, may not be representative of all the affected tissues. Another limitation pertains to the MMC assay which detects homologous repair pathway defects and does not test deficiencies in other DNA repair pathways. WIDER IMPLICATIONS OF THE FINDINGS:Our results provide evidence for functional impairment of DNA repair in idiopathic POI, which may predispose the patients to other DNA repair-related conditions such as accelerated aging and/or cancer susceptibility. STUDY FUNDING/COMPETING INTEREST(S):Funding was provided by the National Institute of Child Health and Human Development. There were no competing interests to declare.

Project description:BackgroundIntra-tumor heterogeneity stems from genetic, epigenetic, functional, and environmental differences among tumor cells. A major source of genetic heterogeneity comes from DNA sequence differences and/or whole chromosome and focal copy number variations (CNVs). Whole chromosome CNVs are caused by chromosomal instability (CIN) that is defined by a persistently high rate of chromosome mis-segregation. Accordingly, CIN causes constantly changing karyotypes that result in extensive cell-to-cell genetic heterogeneity. How the genetic heterogeneity caused by CIN influences gene expression in individual cells remains unknown.MethodsWe performed single-cell RNA sequencing on a chromosomally unstable glioblastoma cancer stem cell (CSC) line and a control normal, diploid neural stem cell (NSC) line to investigate the impact of CNV due to CIN on gene expression. From the gene expression data, we computationally inferred large-scale CNVs in single cells. Also, we performed copy number adjusted differential gene expression analysis between NSCs and glioblastoma CSCs to identify copy number dependent and independent differentially expressed genes.ResultsHere, we demonstrate that gene expression across large genomic regions scales proportionally to whole chromosome copy number in chromosomally unstable CSCs. Also, we show that the differential expression of most genes between normal NSCs and glioblastoma CSCs is largely accounted for by copy number alterations. However, we identify 269 genes whose differential expression in glioblastoma CSCs relative to normal NSCs is independent of copy number. Moreover, a gene signature derived from the subset of genes that are differential expressed independent of copy number in glioblastoma CSCs correlates with tumor grade and is prognostic for patient survival.ConclusionsThese results demonstrate that CIN is directly responsible for gene expression changes and contributes to both genetic and transcriptional heterogeneity among glioblastoma CSCs. These results also demonstrate that the expression of some genes is buffered against changes in copy number, thus preserving some consistency in gene expression levels from cell-to-cell despite the continuous change in karyotype driven by CIN. Importantly, a gene signature derived from the subset of genes whose expression is buffered against copy number alterations correlates with tumor grade and is prognostic for patient survival that could facilitate patient diagnosis and treatment.

Project description:Introduction: The majority of pulmonary carcinoid (PC) tumors can be cured by surgical resection alone, but a significant proportion of patients experience recurrences. PC is insensitive to conventional chemotherapy, and it would be necessary to reveal the molecular mechanisms of metastasis and develop targeted therapeutics. Methods: We performed the comprehensive whole-exome sequencing (WES) of primary tumors and corresponding normal lung tissues from 14 PC patients (including 4 patients who developed postsurgical distant metastasis) and the RNA sequencing of primary tumors from 6 PC patients (including 4 patients who developed postsurgical distant metastasis). Exon array-based gene expression analysis was performed in 25 PC. Results: We identified a total of 139 alterations in 136 genes. MUC6 and SPTA1 were recurrently mutated with the frequency of 21 % (3/14) and 14% (2/14), respectively. The mucin protein family genes including MUC2, MUC4 and MUC6 were mutated in 36% (5/14) in a mutually exclusive manner. The pathway analysis of mutated genes revealed the enrichment of genes involved in the mitogen-activated protein kinase (MAPK) signaling, regulation of actin cytoskeleton and focal adhesion, and transforming growth factor (TGF)-β signaling pathways. RNA sequencing reveals a total of 8 novel fusion transcripts including one derived from chromosomal translocation between the TRIB2 and PRKCE genes. All the 8 fusion genes were detected in primary PC that had developed metastasis after surgical resection. We identified 14 genes (DENND1B, GRID1, CLMN, DENND1B, NRP1, SEL1L3, C5orf13, TNFRSF21, TES, STK39, MTHFD2, OPN3, MET, and HIST1H3C) up-regulated in 5 PC that had relapsed after surgical resection. Conclusions: In this study we identified novel somatic mutations and chromosomal rearrangements by examining clinically aggressive cases that had developed postsurgical metastasis. It is essential to validate their clinical significance in an independent larger patient cohort.

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Exome sequencing reveals MCM8 mutation underlies ovarian failure and chromosomal instability.

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Exome sequencing reveals MCM8 mutation underlies ovarian failure and chromosomal instability.

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