Constitutional Chromothripsis on Chromosome 2: A Rare Case with Severe Presentation.

Chromothripsis is characterized by shattering and subsequent reassembly of chromosomes by DNA repair processes, which can give rise to a variety of congenital abnormalities and cancer. Constitutional chromothripsis is a rare occurrence, reported in children presenting with a wide range of birth defects. We present a case of a female child born with multiple major congenital abnormalities including severe microcephaly, ocular dysgenesis, heart defect, and imperforate anus. Chromosomal microarray and mate pair sequencing identified a complex chromosomal rearrangement involving the terminal end of the long arm of chromosome 2, with two duplications (located at 2p25.3-p25.1 and 2q35-q37.2 regions) and two deletions (located at 2q37.2-q37.3 and 2q37.3 regions) along with structural changes including inverted segments. A review of the literature for complex rearrangements on chromosome 2 revealed overlapping features; however, our patient had a significantly more severe phenotype which resulted in early death at the age of 2 years. Breakpoints analysis did not reveal the involvement of any candidate genes. We concluded that the complexity of the genomic rearrangement and the combined dosage/structural effect of these copy number variants are likely explanations for the severe presentation in our patient.

The genomic basis of sporadic and recurrent pregnancy loss: a comprehensive in-depth analysis of 24,900 miscarriages.

RESEARCH QUESTION: What is the genetic cause of sporadic and recurrent pregnancy loss and does the frequency and nature of chromosomal abnormalities play a role? Types and frequency of all identifiable chromosomal abnormalities were determined to inform our understanding, medical management and recurrence risk for patients experiencing pregnancy loss. DESIGN: Genome-wide single-nucleotide polymorphism-based chromosomal microarray (SNP-CMA) were used to evaluate 24,900 products of conception samples from various forms of pregnancy losses. RESULTS: Sporadic miscarriage (64.7%) or recurrent pregnancy loss (RPL) (22%) were the most common referrals. Clinically significant abnormalities were observed in 55.8% (13,910) of samples, variants of uncertain significance in 1.8%, and normal results in 42.4%. In addition to autosomal trisomies (in 36% of samples), polyploidy and large segmental imbalances were identified in 7.8% and 2.8% of samples, respectively. Analysis of sequential samples from 1103 patients who had experienced RPL provided important insight into possible predispositions to RPL. CONCLUSIONS: This expansive chromosomal microarray analyses of pregnancy loss samples illuminates our understanding of the full spectrum, relative frequencies and the role of genomic abnormalities in pregnancy loss. The empiric observations described here provide useful insight for clinicians and highlight the importance of high-resolution genomic testing for comprehensive evaluation and risk assessment of individuals experiencing pregnancy loss.

Heterozygous intragenic deletions of FREM1 are not associated with trigonocephaly.

Recessive mutations in FRAS1-related extracellular matrix 1 (FREM1) are associated with two rare genetic disorders, Manitoba-oculo-tricho-anal (MOTA) and bifid nose with or without anorectal and renal anomalies (BNAR). Fraser syndrome is a more severe disorder that shows phenotypic overlap with both MOTA and anorectal and renal anomalies and results from mutations in FRAS1, FREM2 and GRIP1. Heterozygous missense mutations in FREM1 were reported in association with isolated trigonocephaly with dominant inheritance and incomplete penetrance. Moreover, large deletions encompassing FREM1 have been reported in association with a syndromic form of trigonocephaly and were designated as trigonocephaly type 2. Trigonocephaly results from premature closure of the metopic suture and typically manifests as a form of nonsyndromic craniosynostosis. We report on 20 patients evaluated for developmental delay and without abnormal metopic suture. Chromosomal microarray analysis revealed heterozygous FREM1 deletions in 18 patients and in 4 phenotypically normal parents. Two patients were diagnosed with MOTA and had homozygous FREM1 deletions. Therefore, although our results are consistent with the previous reports of homozygous deletions causing MOTA, we report no association between heterozygous FREM1 deletions and trigonocephaly in this cohort.

Correction: Comprehensive analysis of 204 sporadic hydatidiform moles: revisiting risk factors and their correlations with the molar genotypes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Comprehensive analysis of 204 sporadic hydatidiform moles: revisiting risk factors and their correlations with the molar genotypes.

Hydatidiform mole (HM) is an aberrant human pregnancy characterized by excessive trophoblastic proliferation and abnormal embryonic development. HM has two morphological types, complete (CHM) and partial (PHM), and non-recurrent ones have three genotypic types, androgenetic monospermic, androgenetic dispermic, and triploid dispermic. Most available studies on risk factors predisposing to different types of HM and their malignant transformation mainly suffer from the lack of comprehensive genotypic analysis of large cohorts of molar tissues combined with accurate postmolar hCG follow-up. Moreover, 10-20% of patients with one HM have at least one non-molar miscarriage, which is higher than the frequency of two pregnancy losses in the general population (2-5%), suggesting a common genetic susceptibility to HM and miscarriages. However, the underlying causes of the miscarriages in these patients are unknown. Here, we comprehensively analyzed 204 HM, mostly from patients referred to the Quebec Registry of Trophoblastic Diseases and for which postmolar hCG monitoring is available, and 30 of their non-molar miscarriages. We revisited the risk of maternal age and neoplastic transformation across the different HM genotypic categories and investigated the presence of chromosomal abnormalities in their non-molar miscarriages. We confirm that androgenetic CHM is more prone to gestational trophoblastic neoplasia (GTN) than triploid dispermic PHM, and androgenetic dispermic CHM is more prone to high-risk GTN and choriocarcinoma (CC) than androgenetic monospermic CHM. We also confirm the association between increased maternal age and androgenetic CHM and their malignancies. Most importantly, we demonstrate for the first time that patients with an HM and miscarriages are at higher risk for aneuploid miscarriages [83.3%, 95% confidence interval (CI): 0.653-0.944] than women with sporadic (51.5%, 95% CI: 50.3-52.7%, p value = 0.0003828) or recurrent miscarriages (43.8%, 95% CI: 40.7-47.0%, p value = 0.00002). Our data suggest common genetic female germline defects predisposing to HM and aneuploid non-molar miscarriages in some patients.

Copy-number variants in clinical genome sequencing: deployment and interpretation for rare and undiagnosed disease.

PURPOSE: Current diagnostic testing for genetic disorders involves serial use of specialized assays spanning multiple technologies. In principle, genome sequencing (GS) can detect all genomic pathogenic variant types on a single platform. Here we evaluate copy-number variant (CNV) calling as part of a clinically accredited GS test. METHODS: We performed analytical validation of CNV calling on 17 reference samples, compared the sensitivity of GS-based variants with those from a clinical microarray, and set a bound on precision using orthogonal technologies. We developed a protocol for family-based analysis of GS-based CNV calls, and deployed this across a clinical cohort of 79 rare and undiagnosed cases. RESULTS: We found that CNV calls from GS are at least as sensitive as those from microarrays, while only creating a modest increase in the number of variants interpreted (~10 CNVs per case). We identified clinically significant CNVs in 15% of the first 79 cases analyzed, all of which were confirmed by an orthogonal approach. The pipeline also enabled discovery of a uniparental disomy (UPD) and a 50% mosaic trisomy 14. Directed analysis of select CNVs enabled breakpoint level resolution of genomic rearrangements and phasing of de novo CNVs. CONCLUSION: Robust identification of CNVs by GS is possible within a clinical testing environment.

Causative Mutations and Mechanism of Androgenetic Hydatidiform Moles.

Androgenetic complete hydatidiform moles are human pregnancies with no embryos and affect 1 in every 1,400 pregnancies. They have mostly androgenetic monospermic genomes with all the chromosomes originating from a haploid sperm and no maternal chromosomes. Androgenetic complete hydatidiform moles were described in 1977, but how they occur has remained an open question. We identified bi-allelic deleterious mutations in MEI1, TOP6BL/C11orf80, and REC114, with roles in meiotic double-strand breaks formation in women with recurrent androgenetic complete hydatidiform moles. We investigated the occurrence of androgenesis in Mei1-deficient female mice and discovered that 8% of their oocytes lose all their chromosomes by extruding them with the spindles into the first polar body. We demonstrate that Mei1-/- oocytes are capable of fertilization and 5% produce androgenetic zygotes. Thus, we uncover a meiotic abnormality in mammals and a mechanism for the genesis of androgenetic zygotes that is the extrusion of all maternal chromosomes and their spindles into the first polar body.

The genetics of recurrent hydatidiform moles: new insights and lessons from a comprehensive analysis of 113 patients.

Hydatidiform mole is an aberrant human pregnancy characterized by early embryonic arrest and excessive trophoblastic proliferation. Recurrent hydatidiform moles are defined by the occurrence of at least two hydatidiform moles in the same patient. Fifty to eighty percent of patients with recurrent hydatidiform moles have biallelic pathogenic variants in NLRP7 or KHDC3L. However, in the remaining patients, the genotypic types of the moles are unknown. We characterized 80 new hydatidiform mole tissues, 57 of which were from patients with no mutations in the known genes, and we reviewed the genotypes of a total of 123 molar tissues. We also reviewed mutation analysis in 113 patients with recurrent hydatidiform moles. While all hydatidiform moles from patients with biallelic NLRP7 or KHDC3L mutations are diploid biparental, we demonstrate that those from patients without mutations are highly heterogeneous and only a small minority of them are diploid biparental (8%). The other mechanisms that were found to recur in patients without mutations are diploid androgenetic monospermic (24%) and triploid dispermic (32%); the remaining hydatidiform moles were misdiagnosed as moles due to errors in the analyses and/or their unusual mechanisms. We compared three parameters of genetic susceptibility in patients with and without mutations and show that patients without mutations are mostly from non-familial cases, have fewer reproductive losses, and more live births. Our data demonstrate that patients with recurrent hydatidiform moles and no mutations in the known genes are, in general, different from those with mutations; they have a milder genetic susceptibility and/or a multifactorial etiology underlying their recurrent hydatidiform moles. Categorizing these patients according to the genotypic types of their recurrent hydatidiform moles may facilitate the identification of novel genes for this entity.

ACOG and SMFM guidelines for prenatal diagnosis: Is karyotyping really sufficient?

OBJECTIVE: The American College of Obstetricians and Gynecologists (ACOG) and Society for Maternal-Fetal Medicine (SMFM) recommend chromosomal microarray analysis (CMA) for prenatal diagnosis in cases with 1 or more fetal structural abnormalities. For patients who elect prenatal diagnosis and have a structurally normal fetus, either microarray or karyotype is recommended. This study evaluates the frequency of clinically significant chromosomal abnormalities (CSCA) that would have been missed if all patients offered the choice between CMA and karyotyping chose karyotyping. METHODS: A total of 3223 prenatal samples undergoing CMA were evaluated. Cases were categorized into 2 groups: those that met ACOG guidelines for CMA versus those that met ACOG guidelines for either CMA or karyotype. RESULTS: Of the 3223 cases, 1475 (45.8%) met ACOG recommendations for CMA, and 1748 (54.2%) met recommendations for either CMA or karyotype. In patients who could have elected either CMA or karyotype, 2.5% had CSCA that would have been missed if the patient had elected to pursue karyotype. CONCLUSION: This study suggests that 2.5% of patients will have a CSCA that may be missed if the guidelines continue to suggest that CMA and karyotyping have equivalent diagnostic value for patients without a fetal structural abnormality.

Comprehensive genetic analysis of pregnancy loss by chromosomal microarrays: outcomes, benefits, and challenges.

PURPOSE: Chromosomal microarray analysis (CMA) is currently considered first-tier testing in pediatric care and prenatal diagnosis owing to its high diagnostic sensitivity for chromosomal imbalances. The aim of this study was to determine the efficacy and diagnostic power of CMA in both fresh and formalin-fixed paraffin-embedded (FFPE) samples of products of conception (POCs). METHODS: Over a 44-month period, 8,118 consecutive samples were received by our laboratory for CMA analysis. This included both fresh (76.4%) and FFPE samples (22.4%), most of which were ascertained for recurrent pregnancy loss and/or spontaneous abortion (83%). The majority of samples were evaluated by a whole-genome single-nucleotide polymorphism (SNP)-based array (81.6%); the remaining samples were evaluated by array-comparative genomic hybridization (CGH). RESULTS: A successful result was obtained in 7,396 of 8,118 (91.1%), with 92.4% of fresh tissue samples and 86.4% of FFPE samples successfully analyzed. Clinically significant abnormalities were identified in 53.7% of specimens (3,975 of 7,396), 94% of which were considered causative. CONCLUSION: Analysis of POC specimens by karyotyping fails in 20-40% of cases. SNP-based CMA is a robust platform, with successful results obtained in >90% of cases. SNP-based CMA can identify aneuploidy, polyploidy, whole-genome homozygosity, segmental genomic imbalances, and maternal cell contamination, thus maximizing sensitivity and decreasing false-negative results. Understanding the etiology of fetal loss enables clarification of recurrence risk and assists in determining appropriate management for future family planning.Genet Med 19 1, 83-89.

PWS/AS MS-MLPA Confirms Maternal Origin of 15q11.2 Microduplication.

The proximal region of the long arm of chromosome 15q11.2-q13 is associated with various neurodevelopmental disorders, including Prader-Willi (PWS) and Angelman (AS) syndromes, autism, and other developmental abnormalities resulting from deletions and duplications. In addition, this region encompasses imprinted genes that cause PWS or AS, depending on the parent-of-origin. This imprinting allows for diagnosis of PWS or AS based on methylation status using methylation sensitive (MS) multiplex ligation dependent probe amplification (MLPA). Maternally derived microduplications at 15q11.2-q13 have been associated with autism and other neuropsychiatric disorders. Multiple methods have been used to determine the parent-of-origin for 15q11.2-q13 microdeletions and microduplications. In the present study, a four-year-old nondysmorphic female patient with developmental delay was found to have a de novo ~5 Mb duplication within 15q11.2 by oligonucleotide genomic array. In order to determine the significance of this microduplication to the clinical phenotype, the parent-of-origin needed to be identified. The PWS/AS MS-MLPA assay is generally used to distinguish between deletion and uniparental disomy (UPD) of 15q11.2-q13, resulting in either PWS or AS. However, our study shows that PWS/AS MS-MLPA can also efficiently distinguish the parental origin of duplications of 15q11.2-q13.

Confirmation and further delineation of the 3q26.33-3q27.2 microdeletion syndrome.

Recently, 3 unrelated children with a potentially novel 3q26.33-3q27.2 microdeletion syndrome were reported. We now report a new 9 ½ years old Caucasian boy with a 2 Mb deletion of the same genomic region in combination with Klinefelter syndrome. He presented with facial dysmorphism, developmental delay, Asperger syndrome, thrombocytopenia, recurrent infections and hypogammaglobulinemia. The deletion in our patient improves upon the minimum region of the novel 3q26.33-3q27.2 microdeletion, and provides additional insights into the underlying genetic basis of the observed phenotypes. Consistent with two of three previously described patients, our patient also presents with thrombocytopenia, which we postulate is caused by haploinsufficiency of THPO. In addition, haploinsufficiency of LAMP3, a lymphoid and dendritic cell expressed protein that is implicated in bacterial and viral infections, pulmonary surfactant protein transport and amelogenin degradation, may be a novel cause for the immune deficiency, lung disease and dental abnormalities respectively as seen in these patients.

Chromosomal microarray analysis of consecutive individuals with autism spectrum disorders or learning disability presenting for genetic services.

Chromosomal microarray analysis is now commonly used in clinical practice to identify copy number variants (CNVs) in the human genome. We report our experience with the use of the 105 K and 180K oligonucleotide microarrays in 215 consecutive patients referred with either autism or autism spectrum disorders (ASD) or developmental delay/learning disability for genetic services at the University of Kansas Medical Center during the past 4 years (2009-2012). Of the 215 patients [140 males and 75 females (male/female ratio=1.87); 65 with ASD and 150 with learning disability], abnormal microarray results were seen in 45 individuals (21%) with a total of 49 CNVs. Of these findings, 32 represented a known diagnostic CNV contributing to the clinical presentation and 17 represented non-diagnostic CNVs (variants of unknown significance). Thirteen patients with ASD had a total of 14 CNVs, 6 CNVs recognized as diagnostic and 8 as non-diagnostic. The most common chromosome involved in the ASD group was chromosome 15. For those with a learning disability, 32 patients had a total of 35 CNVs. Twenty-six of the 35 CNVs were classified as a known diagnostic CNV, usually a deletion (n=20). Nine CNVs were classified as an unknown non-diagnostic CNV, usually a duplication (n=8). For the learning disability subgroup, chromosomes 2 and 22 were most involved. Thirteen out of 65 patients (20%) with ASD had a CNV compared with 32 out of 150 patients (21%) with a learning disability. The frequency of chromosomal microarray abnormalities compared by subject group or gender was not statistically different. A higher percentage of individuals with a learning disability had clinical findings of seizures, dysmorphic features and microcephaly, but not statistically significant. While both groups contained more males than females, a significantly higher percentage of males were present in the ASD group.

A novel familial 11p15.4 microduplication associated with intellectual disability, dysmorphic features, and obesity with involvement of the ZNF214 gene.

We evaluated a patient with mild intellectual disability, obesity, overgrowth, and dysmorphic features. Array comparative genomic hybridization (aCGH) analysis showed a single copy number increase of a BAC clone in the 11p15.4 region. Oligonucleotide aCGH refined the duplication to approximately 2.29 megabases (Mb) in size. Testing the parents revealed that the father, who had learning disabilities and overgrowth, also had the 11p15.4 duplication, and the mother had a normal microarray. In addition, the patient's brother and grandmother all share clinical features with the proband and tested positive for the duplication. The duplicated region (Chr11:6,934,067-9,220,605) encompasses 29 genes, including the ZNF214 gene, which has been postulated to play a role in Beckwith-Wiedemann syndrome [Alders et al., 2000]. This three-generation pedigree outlines features of a novel microduplication syndrome.

Structural Chromosome Abnormalities Associated with Obesity: Report of Four New subjects and Review of Literature.

Obesity in humans is a complex polygenic trait with high inter-individual heritability estimated at 40-70%. Candidate gene, DNA linkage and genome-wide association studies (GWAS) have allowed for the identification of a large set of genes and genomic regions associated with obesity. Structural chromosome abnormalities usually result in congenital anomalies, growth retardation and developmental delay. Occasionally, they are associated with hyperphagia and obesity rather than growth delay. We report four new individuals with structural chromosome abnormalities involving 10q22.3-23.2, 16p11.2 and Xq27.1-q28 chromosomal regions with early childhood obesity and developmental delay. We also searched and summarized the literature for structural chromosome abnormalities reported in association with childhood obesity.

Inversion and deletion of 16q22 defined by array CGH, FISH, and RT-PCR in a patient with AML.

Acute myelomonocytic leukemia with eosinophilia is commonly associated with pericentric inversions of chromosome 16, involving the core binding factor beta gene (CBFB) on 16q22 and the myosin heavy chain gene (MYH11) on 16p13. The inv(16)(p13q22) results in a fusion gene comprising the 5'CBFB gene and the 3'MYH11 gene on the short arm of chromosome 16. The fusion gene interferes with the normal transcription of the CBFA/CBFB heterodimer and disrupts myeloid differentiation. The inv(16) is associated with a good prognosis. The inv(16) with deletion of the 3'CBFB region of the gene is a very rare occurrence. Although the number of cases is small, inv(16) with a deleted 3'CBFB seems to be associated with a poorer prognosis than that generally associated with inv(16). Our patient was a 30-year-old man with newly diagnosed acute myeloid leukemia who was found to have a CBFB-MYH11 fusion by reverse transcriptase-polymerase chain reaction. The high blast count and lack of differentiation were not typical for this entity and suggested clonal progression. The initial karyotype by conventional cytogenetic analysis, in all metaphases examined, was 46,XY,del(7)(q32),del(16)(q22). Fluorescence in situ hybridization analysis with a dual-color, break-apart probe corresponding to the CBFB gene locus (Abbott, Des Plaines, IL) showed a derivative chromosome 16 resulting from an inversion of the CBFB gene with a deletion of the 3'CBFB probe region. Oligonucleotide array comparative genetic hybridization analysis was performed on this patient's diagnostic bone marrow DNA referenced to a normal male control DNA by using the DNAarray Heme Profile (CombiMatrix Diagnostics, Irvine, CA) microarray. This analysis showed a 1.2 Mb loss of 16q22.1, which did not include loss of the 3'CBFB gene locus, but rather sequences distal to this locus. The DNAarray Heme Profile results illustrate the importance of microarray in the correct identification of abnormalities that will affect prognosis.

The 3q29 microdeletion syndrome: report of three new unrelated patients and in silico "RNA binding" analysis of the 3q29 region.

The human 3q29 microdeletion syndrome is associated with mild facial dysmorphism, developmental delay and variable congenital malformations. We report three new unrelated patients with this syndrome. We also performed in silico RNA binding analysis in silico on the 3q29 critical region genes. Several genes within this genomic region including DLG1 and RNF168 are predicted to bind RNA. While recessive mutations in RNF168 cause RIDDLE syndrome, an immune deficiency and radiosensitivity disorder, the potential impact of heterozygous deletion of RNF168 on patients with the 3q29 deletion syndrome is still unknown.