Cat eye syndrome: Clinical, cytogenetics and familial findings in a large cohort of 43 patients highlighting the importance of congenital heart disease and inherited cases.

Cat Eye Syndrome (CES) is a rare genetic disease caused by the presence of a small supernumerary marker chromosome derived from chromosome 22, which results in a partial tetrasomy of 22p-22q11.21. CES is classically defined by association of iris coloboma, anal atresia, and preauricular tags or pits, with high clinical and genetic heterogeneity. We conducted an international retrospective study of patients carrying genomic gain in the 22q11.21 chromosomal region upstream from LCR22-A identified using FISH, MLPA, and/or array-CGH. We report a cohort of 43 CES cases. We highlight that the clinical triad represents no more than 50% of cases. However, only 16% of CES patients presented with the three signs of the triad and 9% not present any of these three signs. We also highlight the importance of other impairments: cardiac anomalies are one of the major signs of CES (51% of cases), and high frequency of intellectual disability (47%). Ocular motility defects (45%), abdominal malformations (44%), ophthalmologic malformations (35%), and genitourinary tract defects (32%) are other frequent clinical features. We observed that sSMC is the most frequent chromosomal anomaly (91%) and we highlight the high prevalence of mosaic cases (40%) and the unexpectedly high prevalence of parental transmission of sSMC (23%). Most often, the transmitting parent has mild or absent features and carries the mosaic marker at a very low rate (<10%). These data allow us to better delineate the clinical phenotype associated with CES, which must be taken into account in the cytogenetic testing for this syndrome. These findings draw attention to the need for genetic counseling and the risk of recurrence.

Outcome of partial agenesis of corpus callosum.

BACKGROUND: The diagnosis of corpus callosum anomalies by prenatal ultrasound has improved over the last decade because of improved imaging techniques, scanning skills, and the routine implementation of transvaginal neurosonography. OBJECTIVE: Our aim was to investigate all cases of incomplete agenesis of the corpus callosum and to report the sonographic characteristics, the associated anomalies, and the perinatal outcomes. STUDY DESIGN: We performed a retrospective analysis of cases from January 2007 to December 2017 with corpus callosum anomalies, either referred for a second opinion or derived from the prenatal ultrasound screening program in a single tertiary referral center. Cases with complete agenesis were excluded from the analysis. Standardized investigation included a detailed fetal ultrasound including neurosonogram, fetal karyotyping (standard karyotype or array comparative genomic hybridization) and fetal magnetic resonance imaging. The pregnancy outcome was collected, and pathologic investigation in case of termination of the pregnancy or fetal or neonatal loss was compared with the prenatal findings. The pregnancy and fetal or neonatal outcomes were reported. The neurologic assessment was conducted by a pediatric neurologist using the Bayley Scales of Infant Development-II and the standardized Child Development Inventory when the Bayley investigation was unavailable. RESULTS: Corpus callosum anomalies were diagnosed in 148 cases during the study period, 62 (41.9%) of which were excluded because of complete agenesis, and 86 fetuses had partial agenesis (58.1%). In 20 cases, partial agenesis (23.2%) was isolated, whereas 66 (76.7%) presented with different malformations among which 29 cases (43.9%) were only central nervous system lesions, 21 cases (31.8%) were non-central nervous system lesions, and 16 cases (24.3%) had a combination of central nervous system and non-central nervous system lesions. The mean gestational age at diagnosis for isolated and non-isolated cases was comparable (24.29 [standard deviation, 5.05] weeks and 24.71 [standard deviation, 5.35] weeks, respectively). Of the 86 pregnancies with partial agenesis, 46 patients opted for termination of the pregnancy. Neurologic follow-up data were available for 35 children. The overall neurologic outcome was normal in 21 of 35 children (60%); 3 of 35 (8.6%) showed mild impairment and 6 of 35 (17.1%) showed moderate impairment. The remaining 5 of 35 (14.3%) had severe impairment. The median duration of follow-up for the isolated form was 45.6 months (range, 36-52 months) and 73.3 months (range, 2-138 months) for the nonisolated form. CONCLUSION: Partial corpus callosum agenesis should be accurately investigated by neurosonography and fetal magnetic resonance imaging to describe its morphology and the associated anomalies. Genetic anomalies are frequently present in nonisolated cases. Efforts must be taken to improve ultrasound diagnosis of partial agenesis and to confirm its isolated nature to enhance parental counseling. Although 60% of children with prenatal diagnosis of isolated agenesis have a favorable prognosis later in life, they often have mild to severe disabilities including speech disorders at school age and behavior and motor deficit disorders that can emerge at a later age.

Technologies to Study Genetics and Molecular Pathways.

Over the last few decades, the study of congenital heart disease (CHD) has benefited from various model systems and the development of molecular biological techniques enabling the analysis of single gene as well as global effects. In this chapter, we first describe different models including CHD patients and their families, animal models ranging from invertebrates to mammals, and various cell culture systems. Moreover, techniques to experimentally manipulate these models are discussed. Second, we introduce cardiac phenotyping technologies comprising the analysis of mouse and cell culture models, live imaging of cardiogenesis, and histological methods for fixed hearts. Finally, the most important and latest molecular biotechniques are described. These include genotyping technologies, different applications of next-generation sequencing, and the analysis of transcriptome, epigenome, proteome, and metabolome. In summary, the models and technologies presented in this chapter are essential to study the function and development of the heart and to understand the molecular pathways underlying CHD.

5p13 microduplication in a malformed fetus and his unaffected father.

The 5p13 microduplication syndrome is a contiguous gene syndrome characterized by developmental delay intellectual disability, hypotonia, unusual facies with marked variability, mild limb anomalies, and in some cases brain malformations. The duplication ranges in size from 0.25 to 1.08 Mb and encompasses five genes (NIPBL, SLC1A3, CPLANE1, NUP155, and WDR70), of which NIPBL has been suggested to be the main dose sensitive gene. All patients with duplication of the complete NIPBL gene reported thus far have been de novo. Here, we report a 25-week-old male fetus with hypertelorism, wide and depressed nasal bridge, depressed nasal tip, low-set ears, clenched hands, flexion contracture of elbows, knees, and left wrist, and bilateral clubfeet, bowing and shortening of long bones and brain malformation of dorsal part of callosal body. The fetus had a 667 kb gain at 5p13.2 encompassing SLC1A3, NIPBL and exons 22-52 of CPLANE1. The microduplication was inherited from the healthy father, in whom no indication for mosaicism was detected. The family demonstrates that incomplete penetrance of 5p13 microduplication syndrome may occur which is important in genetic counseling of families with this entity.

The challenges in the interpretation of genetic variants detected by genomics techniques in patients with congenital anomalies.

BACKGROUND: Despite the efforts that have been made to standardize the interpretation of variants, in some cases, their pathogenicity remains vague and confusing, and sometimes their interpretation does not help clinicians to establish clinical correlation using genetic test results. This study aims to shed more lights on these challenging variants. METHODS: In a clinical setting, the variants found from 81 array CGH and 79 whole exome sequencing (WES) in patients with congenital anomalies were interpreted based on American College of Medical Genetics and Genomics guidelines. RESULTS: In this study, the interpretation of the disease-causing variants and the variants with uncertain clinical significance detected by WES was far more challenging than the variants detected by array CGH. The presence of unreported clinical symptoms, incomplete penetrance, variable expressivity, parents' reluctance to analyze segregation in the family, and the limitations of prenatal tests, were among the challenging factors in the interpretation of variants in this study. CONCLUSION: A careful study of the pedigree and disease mode of inheritance, as well as a careful clinical examination of the carrier parents in diseases with autosomal dominant inheritance, are among the primary strategies for determining the clinical significance of the variants. Continued efforts to mitigate these challenges are needed to improve the interpretation of variants.

Array study in fetuses with nuchal translucency above the 95th percentile: a 4-year observational single-centre study.

PURPOSE: To evaluate the performance of chromosomal microarray analysis (CMA) in fetuses with nuchal translucency (NT) > 95th percentile. Secondary objectives were to analyze these results according to NT thickness, below or above 3.5 mm, and those without associated anomalies. METHODS: This observational single-cohort study was conducted between 2015 and 2018 in fetuses with NT > 95th percentile. Following an invasive test, quantitative fluorescence-polymerase chain reaction (QF-PCR) was performed, and if normal, CMA was performed. Pathogenic copy number variants (CNVs), non-reported pathogenic CNV, pathogenic autosomal recessive variants and variants of unknown significance (VUS) were analysed. RESULTS: One-hundred and sixty-two fetuses with NT > 95th percentile, normal QF-PCR and CMA were included. Amongst 128 fetuses with NT between the 95th percentile and 3.5 mm, one (0.8%) had a pathogenic CNV, four (3.1%) had non-reported pathogenic CNV, one (0.8%) had pathogenic autosomal recessive variant and 13 (10.2%) had VUS. Amongst 34 fetuses with NT ≥ 3.5 mm, four (11.8%) had pathogenic CNV, one (2.9%) had non-reported pathogenic CNV, one (2.9%) had pathogenic autosomal recessive variant and four (11.8%) had VUS. Four in 162 (2.5%) fetuses had CNVs at the chromosome 16p13.11 region. Amongst 154 fetuses without structural abnormalities and normal QF-PCR, three (1.9%) had a pathogenic CNV, 5 (3.2%) had non-reported pathogenic CNV, one (0.6%) autosomal recessive pathogenic CNV and 16 (10.4%) had VUS. CONCLUSION: Pathogenic CNVs were found in 1% of fetuses with an NT thickness between the 95th percentile and 3.5 mm and in 12% of fetuses with NT ≥ 3.5 mm. CNVs were found at the 16p13.11 region in 2.5% of cases.

AhRR and PPP1R3C: Potential Prognostic Biomarkers for Serous Ovarian Cancer.

The lack of effective screening and successful treatment contributes to high ovarian cancer mortality, making it the second most common cause of gynecologic cancer death. Development of chemoresistance in up to 75% of patients is the cause of a poor treatment response and reduced survival. Therefore, identifying potential and effective biomarkers for its diagnosis and prognosis is a strong critical need. Copy number alterations are frequent in cancer, and relevant for molecular tumor stratification and patients' prognoses. In this study, array-CGH analysis was performed in three cell lines and derived cancer stem cells (CSCs) to identify genes potentially predictive for ovarian cancer patients' prognoses. Bioinformatic analyses of genes involved in copy number gains revealed that AhRR and PPP1R3C expression negatively correlated with ovarian cancer patients' overall and progression-free survival. These results, together with a significant association between AhRR and PPP1R3C expression and ovarian cancer stemness markers, suggested their potential role in CSCs. Furthermore, AhRR and PPP1R3C's increased expression was maintained in some CSC subpopulations, reinforcing their potential role in ovarian cancer. In conclusion, we reported for the first time, to the best of our knowledge, a prognostic role of AhRR and PPP1R3C expression in serous ovarian cancer.

Copy number variants calling from WES data through eXome hidden Markov model (XHMM) identifies additional 2.5% pathogenic genomic imbalances smaller than 30 kb undetected by array-CGH.

It has been estimated that Copy Number Variants (CNVs) account for 10%-20% of patients affected by Developmental Disorder (DD)/Intellectual Disability (ID). Although array comparative genomic hybridization (array-CGH) represents the gold-standard for the detection of genomic imbalances, common Agilent array-CGH 4 × 180 kb arrays fail to detect CNVs smaller than 30 kb. Whole Exome sequencing (WES) is becoming the reference application for the detection of gene variants and makes it possible also to infer genomic imbalances at single exon resolution. However, the contribution of small CNVs in DD/ID is still underinvestigated. We made use of the eXome Hidden Markov Model (XHMM) software, a tool utilized by the ExAC consortium, to detect CNVs from whole exome sequencing data, in a cohort of 200 unsolved DD/DI patients after array-CGH and WES-based single nucleotide/indel variant analyses. In five out of 200 patients (2.5%), we identified pathogenic CNV(s) smaller than 30 kb, ranging from one to six exons. They included two heterozygous deletions in TCF4 and STXBP1 and three homozygous deletions in PPT1, CLCN2, and PIGN. After reverse phenotyping, all variants were reported as causative. This study shows the interest in applying sequencing-based CNV detection, from available WES data, to reduce the diagnostic odyssey of additional patients unsolved DD/DI patients and compare the CNV-detection yield of Agilent array-CGH 4 × 180kb versus whole exome sequencing.

Interstitial 2q24.2q24.3 Microdeletion: Two New Cases with Similar Clinical Features with the Exception of Profound Deafness.

Interstitial 2q24.2q24.3 microdeletions are rare cytogenetic aberrations associated with heterogeneous clinical features depending on the size of the deletion. Here, we describe 2 patients with overlapping de novo 2q24.2q24.3 deletions, characterized by array-CGH. This is the smallest 2q24.2q24.3 region of overlap described in the literature encompassing only 9 genes (SLC4A10, DPP4, GCG, FAP, IFIH1, GCA, KCNH7, FIGN, GRB14). We focused our attention on SLC4A10, DPP4, and KCNH7, genes associated with neurological features. Our patients presented similar features: intellectual disability, developmental and language delay, hypotonia, joint laxity, and dysmorphic features. Only patient 2 showed profound deafness and also carried a heterozygous mutation of the GJB2 gene responsible for autosomal recessive deafness 1A (DFNB1A: OMIM 220290). Could the disruption of a gene present in the 2q24.2q24.3 deleted region be responsible for her profound hearing loss?

Cytogenomic Analysis of Long-Term Epilepsy-Associated Tumors Using an Array-Based CGH Strategy.

A palette of copy number changes in long-term epilepsy-associated tumors (LEATs) have been reported, but the data are heterogeneous. To better understand the molecular basis underlying the development of LEATs, we performed array-comparative genomic hybridization analysis to investigate chromosomal imbalances across the entire genome in 8 cases of LEATs. A high number of aberrations were found in 4 patients, among which deletions predominated. Both whole-chromosome and regional abnormalities were observed, including monosomy 19, deletion of 1p, deletions of 4p, 12p, and 22q, and gain of 20p. The common altered regions are located mainly on chromosomes 19 and 4p, identifying genes potentially involved in biological processes and cellular mechanisms related to tumorigenesis. Our study highlights new genomic alterations and reinforces others previously reported, offering new molecular insights that may help in diagnosis and therapeutic decision-making.

De novo 4q35.2 duplication containing FAT1 is associated with autism spectrum disorder.

Genetic studies have established a connection between FAT1 (FAT atypical cadherin 1) deletion and variants and autism spectrum disorder (ASD). Here, we describe a 7-year-old girl who sought a neurology consultation in order to be evaluated for ASD and was found to have a de novo 4q35.2 duplication containing the FAT1 gene. Similar to other reported cases of FAT1 variants or deletion, this patient exhibits non-syndromic ASD without facial dysmorphism or brain MRI abnormalities. We suggest also considering FAT1 duplication as a potential ASD cause.

Characterization of Chromosomal Breakpoints in 12 Cases with 8p Rearrangements Defines a Continuum of Fragility of the Region.

Improvements in microarray-based comparative genomic hybridization technology have allowed for high-resolution detection of genome wide copy number alterations, leading to a better definition of rearrangements and supporting the study of pathogenesis mechanisms. In this study, we focused our attention on chromosome 8p. We report 12 cases of 8p rearrangements, analyzed by molecular karyotype, evidencing a continuum of fragility that involves the entire short arm. The breakpoints seem more concentrated in three intervals: one at the telomeric end, the others at 8p23.1, close to the beta-defensin gene cluster and olfactory receptor low-copy repeats. Hypothetical mechanisms for all cases are described. Our data extend the cohort of published patients with 8p aberrations and highlight the need to pay special attention to these sequences due to the risk of formation of new chromosomal aberrations with pathological effects.

A Complex Genomic Rearrangement Resulting in Loss of Function of SCN1A and SCN2A in a Patient with Severe Developmental and Epileptic Encephalopathy.

Complex genomic rearrangements (CGRs) are structural variants arising from two or more chromosomal breaks, which are challenging to characterize by conventional or molecular cytogenetic analysis (karyotype and FISH). The integrated approach of standard and genomic techniques, including optical genome mapping (OGM) and genome sequencing, is crucial for disclosing and characterizing cryptic chromosomal rearrangements at high resolutions. We report on a patient with a complex developmental and epileptic encephalopathy in which karyotype analysis showed a de novo balanced translocation involving the long arms of chromosomes 2 and 18. Microarray analysis detected a 194 Kb microdeletion at 2q24.3 involving the SCN2A gene, which was considered the likely translocation breakpoint on chromosome 2. However, OGM redefined the translocation breakpoints by disclosing a paracentric inversion at 2q24.3 disrupting SCN1A. This combined genomic high-resolution approach allowed a fine characterization of the CGR, which involves two different chromosomes with four breakpoints. The patient's phenotype resulted from the concomitant loss of function of SCN1A and SCN2A.

Genomic Chaos (Multiple Copy Number Variations and Structural Reorganization) Detected in Two Prenatal Cases.

The use of new technologies in the routine diagnosis of constitutional abnormalities, such as high-resolution chromosomal microarray and next-generation sequencing, has unmasked new mechanisms for generating structural variation of the human genome. For example, complex chromosome rearrangements can originate by a chromosome catastrophe phenomenon in which numerous genomic rearrangements are apparently acquired in a single catastrophic event. This phenomenon is named chromoanagenesis (from the Greek "chromo" for chromosome and "anagenesis" for rebirth). Herein, we report 2 cases of genomic chaos detected at prenatal diagnosis. The terms "chromothripsis" and "chromoanasynthesis" and the challenge of genetic counseling are discussed.

Molecular Cytogenetic Characterization of the Murine Melanoma Cell Lines S91 Clone M3 and B16-F1 with Variant B16-4A5.

Melanoma is considered to be one of the most aggressive human tumors. Thus, early molecular diagnosis with risk factor stratification could be an efficacious strategy to increase the survival rates in affected patients. Murine cell lines B16-F1, B16-4A5, and S91 clone M3 are the ones most commonly applied in melanoma research. However, genetic peculiarities of these 3 cell lines have not been studied in detail before. Here, we closed this gap by molecular cytogenetic and array-comparative genomic hybridization studies and the translation of the characterized imbalances into the human genome. This study revealed severely rearranged karyotypes with in parts similar imbalances for all 3 cell lines. Interestingly, they involve genes known to play major roles in human melanoma. These are specifically the oncogenes and tumor suppressor genes, being associated with aggressive forms of melanoma. B16-F1, B16-4A5, and S91 clone M3 revealed aberrations which were similarly observed in human eye and skin but not in human uveal melanoma. Thus, they can be considered as model systems for advanced eye and skin melanoma.

Mosaicism for copy number variations in the placenta is even more difficult to interpret than mosaicism for whole chromosome aneuploidy.

OBJECTIVE: To compare mosaicisms in prenatal chorionic villus samples (CVSs) with corresponding postpartum placental samples. METHOD: We collected placentas from 15 consecutive cases of mosaicism detected in CVSs and obtained five standardized samples on each placenta after delivery. All pre- and postnatal placental samples were uncultured and analyzed by high-resolution chromosomal microarray. RESULTS: Ten cases of mosaicism for whole chromosome aneuploidy (mWC) and five cases with mosaicism for (sub)chromosomal copy number variations (mCNVs) were included. In 5/10 mWC cases and in 4/5 mCNV cases the prenatally detected aberration was confirmed in the postpartum placenta. Three postpartum placentas revealed various complex aberrations differing from the prenatal results: (1) mosaicisms for different deletions/duplications on 9p and 9q in all samples (prenatal: mosaic 5.3 Mb duplication on 9p24), (2) different regions with deletions/duplications/loss of heterozygosity on 1p in all samples (prenatal: mosaic 2.3 Mb 1p36 duplication), and (3) mosaicism for a duplication on 5q and a deletion on 6p in one out of five samples (prenatal: mosaic trisomy 7). CONCLUSION: CNVs constitute a complex subgroup in placental mosaicism. Counseling of these couples after chorionic villus sampling should not focus on the specific CNV involved, but on the nature of mosaicism and the option of amniocentesis and ultrasound.

A 343 Italian cohort of patients analysed with array-comparative genomic hybridization: unsolved problems and genetic counselling difficulties.

BACKGROUND: The recent introduction of microarrays for genetic analyses has allowed higher etiological diagnostic rates in patient with intellectual disability (ID), autism spectrum disorders (ASD), epilepsy and multiple congenital anomalies (MCA), because of its resolution. This approach still results of high complexity and some limitations have been reported. In fact, it discloses several variants of unknown significance (VOUS) or incidental findings. In all cases, a massive amount of data is generated, because of this, the analysis and the interpretation is very difficult and often without a definitive conclusion. METHOD: We analysed an Italian cohort of 343 patients with ID, MCA and ASD by array-comparative genomic hybridization. The purpose of this work was to consider the proportion of the chromosomal abnormalities in such cohort and to assess the distribution of the different type of the chromosomal abnormalities concerning their pathogenic significance, their origin and their correlation to these clinical phenotypes. RESULTS: Array-comparative genomic hybridization analysis revealed 76 positive results. Abnormalities were detected in 27.8% of patients with ID, 11.1% with ASD, 10.7% with epilepsy and 19.4% with multiple congenital anomalies. The anomalies were classified in three major groups: group 1 (27 patients) with pathogenic alterations (P group); group 2 (34 patients) with VOUS potentially pathogenic (PP group); and group 3 (13 patients) with VOUS potentially benign (PB group). As expected, comparing the diagnostic groups, we observed a greater number of deletions in the P group and that all the abnormalities of the PB group were inherited. CONCLUSIONS: Our retrospective study resulted in confirming the high detection rate of microarrays. CNV classification remains a complex procedure. The difficulty in CNV classification points out the importance of the patient selection, helping the interpretation of the molecular cytogenetic results.

Genomic and Epigenomic Profile of Uterine Smooth Muscle Tumors of Uncertain Malignant Potential (STUMPs) Revealed Similarities and Differences with Leiomyomas and Leiomyosarcomas.

Uterine smooth muscle tumors of uncertain malignant potential (STUMPs) represent a heterogeneous group of tumors that cannot be histologically diagnosed as unequivocally benign or malignant. For this reason, many authors are working to obtain a better definition of diagnostic and prognostic criteria. In this work, we analyzed the genomic and epigenomic profile of uterine smooth muscle tumors (USMTs) in order to find similarities and differences between STUMPs, leiomyosarcomas (LMSs) and leiomyomas (LMs), and possibly identify prognostic factors in this group of tumors. Array-CGH data on 23 USMTs demonstrated the presence of a more similar genomic profile between STUMPs and LMSs. Some genes, such as PRKDC and PUM2, with a potential prognostic value, were never previously associated with STUMP. The methylation data appears to be very promising, especially with regards to the divergent profile found in the sample that relapsed, characterized by an overall CGI hypomethylation. Finally, the Gene Ontology analysis highlighted some cancer genes that could play a pivotal role in the unexpected aggressive behavior that can be found in some of these tumors. These genes could prove to be prognostic markers in the future.

QNBC Is Associated with High Genomic Instability Characterized by Copy Number Alterations and miRNA Deregulation.

Triple-negative breast cancer (TNBC) can be further classified into androgen receptor (AR)-positive TNBC and AR-negative TNBC or quadruple-negative breast cancer (QNBC). Here, we investigated genomic instability in 53 clinical cases by array-CGH and miRNA expression profiling. Immunohistochemical analysis revealed that 64% of TNBC samples lacked AR expression. This group of tumors exhibited a higher level of copy number alterations (CNAs) and a higher frequency of cases affected by CNAs than TNBCs. CNAs in genes of the chromosome instability 25 (CIN25) and centrosome amplification (CA) signatures were more frequent in the QNBCs and were similar between the groups, respectively. However, expression levels of CIN25 and CA20 genes were higher in QNBCs. miRNA profiling revealed 184 differentially expressed miRNAs between the groups. Fifteen of these miRNAs were mapped at cytobands with CNAs, of which eight (miR-1204, miR-1265, miR-1267, miR-23c, miR-548ai, miR-567, miR-613, and miR-943), and presented concordance of expression and copy number levels. Pathway enrichment analysis of these miRNAs/mRNAs pairings showed association with genomic instability, cell cycle, and DNA damage response. Furthermore, the combined expression of these eight miRNAs robustly discriminated TNBCs from QNBCs (AUC = 0.946). Altogether, our results suggest a significant loss of AR in TNBC and a profound impact in genomic instability characterized by CNAs and deregulation of miRNA expression.

Increased Frequency of Copy Number Variations Revealed by Array Comparative Genomic Hybridization in the Offspring of Male Mice Exposed to Low Dose-Rate Ionizing Radiation.

There is very little information on the transgenerational or genetic effects of low dose-rate ionizing radiation. We report the detection of the transgenerational effects of chronic low dose-rate irradiation in mice, at the molecular level in the whole genome, using array comparative genomic hybridization technology. We observed that the number of the mice with de novo copy number variations (specifically, deletions) was significantly increased in the offspring of C57BL/6J male mice exposed to 20 mGy/day gamma-rays for 400 days (total dose: 8000 mGy), as compared to non-irradiated controls. We did not detect any difference in the size of the de novo deletions between the irradiated and the non-irradiated groups. An analysis of the life span of the offspring suggested a possibility that de novo copy-number variations may be associated with shorter life spans.