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Interpretation of the significance of maternally inherited X chromosome variants in males with neurocognitive phenotypes continues to present a challenge to clinical geneticists and diagnostic laboratories. Here we report 14 males from 9 families with duplications at the Xq13.2-q13.3 locus with a common facial phenotype, intellectual disability (ID), distinctive behavioral features, and a seizure disorder in two cases. All tested carrier mothers had normal intelligence. The duplication arose de novo in three mothers where grandparental testing was possible. In one family the duplication segregated with ID across three generations. RLIM is the only gene common to our duplications. However, flanking genes duplicated in some but not all the affected individuals included the brain-expressed genes NEXMIF, SLC16A2, and the long non-coding RNA gene FTX. The contribution of the RLIM-flanking genes to the phenotypes of individuals with different size duplications has not been fully resolved. Missense variants in RLIM have recently been identified to cause X-linked ID in males, with heterozygous females typically having normal intelligence and highly skewed X chromosome inactivation. We detected consistent and significant increase of RLIM mRNA and protein levels in cells derived from seven affected males from five families with the duplication. Subsequent analysis of MDM2, one of the targets of the RLIM E3 ligase activity, showed consistent downregulation in cells from the affected males. All the carrier mothers displayed normal RLIM mRNA levels and had highly skewed X chromosome inactivation. We propose that duplications at Xq13.2-13.3 including RLIM cause a recognizable but mild neurocognitive phenotype in hemizygous males.

PURPOSE Copy-number variants (CNVs) of uncertain clinical significance are routinely reported in a clinical setting only when exceeding predetermined reporting thresholds, typically based on CNV size. Given that very few genes are associated with triplosensitive phenotypes, it is not surprising that many interstitial duplications

The diagnosis of acute promyelocytic leukemia (APL) relies on the identification of PML::RARA fusion. While the majority of APL cases harbor a typical t(15;17)(q24;q21), atypical genetic mechanisms leading to the oncogenic PML::RARA fusion have been reported yet their frequency and scope remain poorly characterized. We assessed the genetic findings of 831 cases with APL investigated with concurrent chromosome banding analysis and dual-color dual-fusion fluorescence in situ hybridization (D-FISH) analysis at our institution over an 18.5-year timeframe. Seven hundred twenty-three (87%) cases had a typical balanced t(15;17) with both testing modalities. Atypical karyotypic results including complex translocations, unbalanced rearrangements and insertional events occurred in 50 (6%) cases, while 6 (0.7%) cases were cryptic by conventional chromosome studies despite PML::RARA fusion by D-FISH evaluation. Atypical FISH patterns were observed in 48 (6%) cases despite apparently balanced t(15;17) on chromosome banding analysis. Two hundred fifty (30%) cases displayed additional chromosome abnormalities of which trisomy/tetrasomy 8 (37%), del(7q)/add(7q) (12%), and del(9q) (7%) were most frequent. Complex and very complex karyotypes were observed in 81 (10%) and 34 (4%) cases, respectively. In addition, 4 (0.5%) cases presented as an apparently doubled, near-tetraploid stemline clone. This report provides the largest appraisal of cytogenetic findings in APL with conventional chromosome and PML::RARA D-FISH analysis. By characterizing the frequency and breadth of typical and atypical results through the lens of these cytogenetic testing modalities, this study serves as a pragmatic source of information for those involved in the investigation of APL in both the clinical and research laboratory settings.

Understanding whether there is enough evidence to implicate a gene's role in a given disease, as well as the mechanisms by which variants in this gene might cause this disease, are essential in order to determine clinical relevance. The National Institutes of Health-funded Clinical Genome Resource (ClinGen) has developed evaluation frameworks to assess both the strength of evidence supporting a relationship between a gene and disease (gene-disease validity), and whether loss (haploinsufficiency) or gain (triplosensitivity) of individual genes or genomic regions is a mechanism for disease (dosage sensitivity). ClinGen actively applies these frameworks across multiple disease domains, and makes this information publicly available via its website (www.clinicalgenome.org) for use in multiple applications, including clinical variant classification. Here we describe how the results of these curation processes can be utilized to inform proper application of pathogenicity criteria for both sequence and copy number variants, as well as to guide test development and inform genomic filtering pipelines. This article is protected by copyright. All rights reserved.

Copy-number variants (CNVs) of uncertain clinical significance are routinely reported in a clinical setting only when exceeding predetermined reporting thresholds, typically based on CNV size. Given that very few genes are associated with triplosensitive phenotypes, it is not surprising that many interstitial duplications1 Mb are found to be inherited and anticipated to be of limited or no clinical significance.In an effort to further refine our reporting criteria to maximize diagnostic yield while minimizing the return of uncertain variants, we performed a retrospective analysis of all clinical microarray cases reported in a 10-year window. A total of 1112 reported duplications had parental follow-up, and these were compared by size, RefSeq gene content, and inheritance pattern. De novo origin was used as a rough proxy for pathogenicity.Approximately 6% of duplications 500 kb-1 Mb were de novo observations, compared with approximately 14% for 1-2 Mb duplications (p = 0.0005). On average, de novo duplications had higher gene counts than inherited duplications.Our data reveal limited diagnostic utility for duplications of uncertain significance1 Mb. Considerations for revised reporting criteria are discussed and are applicable to CNVs detected by any genome-wide exploratory methodology, including exome/genome sequencing.

Objective Acute myeloid leukemia (AML) can be subtyped based on recurrent cytogenetic and molecular genetic abnormalities with diagnostic and prognostic significance. Although cytogenetic characterization classically involves conventional chromosome and/or fluorescence in situ hybridization (FISH) assays, limitations of these techniques include poor resolution and the inability to precisely identify breakpoints. Method We evaluated whether an NGS‐based methodology that detects structural abnormalities and copy number changes using mate pair sequencing (MPseq) can enhance the diagnostic yield for patients with AML. Results Using 68 known abnormal and 20 karyotypically normal AML samples, each recurrent primary AML‐specific abnormality previously identified in the abnormal samples was confirmed using MPseq. Importantly, in eight cases with abnormalities that could not be resolved by conventional cytogenetic studies, MPseq was utilized to molecularly define eight recurrent AML‐fusion events. In addition, MPseq uncovered two cryptic abnormalities that were missed by conventional cytogenetic studies. Thus, MPseq improved the diagnostic yield in the detection of AML‐specific structural rearrangements in 10/88 (11%) of cases analyzed. Conclusion Utilization of MPseq represents a precise, molecular‐based technique that can be used as an alternative to conventional cytogenetic studies for newly diagnosed AML patients with the potential to revolutionize the diagnosis of hematologic malignancies.

Wolf-Hirschhorn syndrome (WHS) is a microdeletion syndrome characterized by distinctive facial features consisting of "Greek warrior helmet" appearance, prenatal and postnatal growth deficiency, developmental disability, and seizures. This disorder is caused by heterozygous deletions on chromosome 4p16.3 often identified by cytogenetic techniques. Many groups have attempted to identify the critical region within this deletion to establish which genes are responsible for WHS. Herein, clinical whole exome sequencing (WES) was performed on a child with developmental delays, mild facial dysmorphisms, short stature, failure to thrive, and microcephaly, and revealed a de novo frameshift variant, c.1676_1679del (p.Arg559Tfs*38), in WHSC1 (NSD2). While WHSC1 falls within the WHS critical region, individuals with only disruption of this gene have only recently been described in the literature. Loss-of-function de novo variations in WHSC1 were identified in large developmental delay, autism, diagnostic, and congenital cardiac cohorts, as well as recent case reports, suggesting that de novo loss-of-function WHSC1 variants may be related to disease. These findings, along with our patient suggest that loss-of-function variation in WHSC1 may lead to a mild form of Wolf-Hirschhorn syndrome, and also may suggest that the developmental delays, facial dysmorphisms, and short stature seen in WHS may be due to disruption of WHSC1 gene.

Objective To describe the experience and outcome of performing whole-exome sequencing (WES) for resolution of patients on a diagnostic odyssey in the first 18 months of an individualized medicine clinic (IMC). Patients and Methods The IMC offered WES to physicians of Mayo Clinic practice for patients with suspected genetic disease. DNA specimens of the proband and relatives were submitted to WES laboratories. We developed the Genomic Odyssey Board with multidisciplinary expertise to determine the appropriateness for IMC services, review WES reports, and make the final decision about whether the exome findings explain the disease. This study took place from September 30, 2012, to March 30, 2014. Results In the first 18 consecutive months, the IMC received 82 consultation requests for patients on a diagnostic odyssey. The Genomic Odyssey Board deferred 7 cases and approved 75 cases to proceed with WES. Seventy-one patients met with an IMC genomic counselor. Fifty-one patients submitted specimens for WES testing, and the results have been received for all. There were 15 cases in which a diagnosis was made on the basis of WES findings; thus, the positive diagnostic yield of this practice was 29%. The mean cost per patient for this service was approximately $8000. Medicaid supported 27% of the patients, and 38% of patients received complete or partial insurance coverage. Conclusion The significant diagnostic yield, moderate cost, and notable health marketplace acceptance for WES compared with conventional genetic testing make the former method a rational diagnostic approach for patients on a diagnostic odyssey.

Craniosynostosis, a condition in which the cranial sutures prematurely fuse, can lead to elevated intracranial pressure and craniofacial abnormalities in young children. Currently surgical intervention is the only therapeutic option for patients with this condition. Craniosynostosis has been associated with a variety of different gene mutations and chromosome anomalies. Here we describe three cases of partial deletion of chromosome 19p. Two of the cases present with syndromic craniosynostosis while one has metopic ridging. A review of the genes involved in the rearrangements between the three cases suggests several gene candidates for craniosynostosis. CALR and DAND5, BMP regulators involved in osteoblast differentiation, and MORG1, a mediator of osteoclast dysregulation may play a role in abnormal cranial vault development. Additionally, CACNA1A, a gene that when mutated is associated with epilepsy and CC2D1A, a gene associated with non-syndromic mental retardation may contribute to additional phenotypic features seen in the patients we describe. In addition, these findings further support the need for genetic testing in cases of syndromic craniosynostosis.

IMPORTANCE: The exome molecular autopsy may elucidate a pathogenic substrate for sudden unexplained death. OBJECTIVE: To investigate the underlying cause of multiple sudden deaths in young individuals and sudden cardiac arrests that occurred in 2 large Amish families. DESIGN, SETTING, AND PARTICIPANTS: Two large extended Amish families with multiple sudden deaths in young individuals and sudden cardiac arrests were included in the study. A recessive inheritance pattern was suggested based on an extended family history of sudden deaths in young individuals and sudden cardiac arrests, despite unaffected parents. A family with exercise-associated sudden deaths in young individuals occurring in 4 siblings was referred for postmortem genetic testing using an exome molecular autopsy. Copy number variant (CNV) analysis was performed on exome data using PatternCNV. Chromosomal microarray validated the CNV identified. The nucleotide break points of the CNV were determined by mate-pair sequencing. Samples were collected for this study between November 2004 and June 2019. MAIN OUTCOMES AND MEASURES: The identification of an underlying genetic cause for sudden deaths in young individuals and sudden cardiac arrests consistent with the recessive inheritance pattern observed in the families. RESULTS: A homozygous duplication, involving approximately 26 000 base pairs of intergenic sequence, RYR2’s 5′UTR/promoter region, and exons 1 through 4 of RYR2, was identified in all 4 siblings of a family. Multiple distantly related relatives experiencing exertion-related sudden cardiac arrest also had the identical RYR2 homozygous duplication. A second, unrelated family with multiple exertion-related sudden deaths and sudden cardiac arrests in young individuals, with the same homozygous duplication, was identified. Several living, homozygous duplication–positive symptomatic patients from both families had nondiagnostic cardiologic testing, with only occasional ventricular ectopy occurring during exercise stress tests. CONCLUSIONS AND RELEVANCE: In this analysis, we identified a novel, highly penetrant, homozygous multiexon duplication in RYR2 among Amish youths with exertion-related sudden death and sudden cardiac arrest but without an overt phenotype that is distinct from RYR2-mediated catecholaminergic polymorphic ventricular tachycardia. Considering that no cardiac tests reliably identify at-risk individuals and given the high rate of consanguinity in Amish families, identification of unaffected heterozygous carriers may provide potentially lifesaving premarital counseling and reproductive planning.

Perineuriomas are rare nerve sheath tumors, divided into intraneural and extraneural (soft tissue) types. Intraneural perineuriomas frequently contain TRAF7 mutations, and rarely, chr22q12 deletions. While chr22q losses can occur in soft tissue perineuriomas, comprehensive high-resolution molecular profiling has not been reported in these tumors and TRAF7 status is unknown. We used whole-exome sequencing and OncoScan single nucleotide polymorphism (SNP) array to evaluate 14 soft tissue perineuriomas. Thirteen cases showed 2 or more chromosomal abnormalities, composed primarily of large deletions. Recurrent chr22q deletions, containing the NF2 locus (n=6) and the previously unreported finding of chr17q deletions, with the NF1 locus (n=4) were frequent events and were mutually exclusive in all but1 case. In addition, 5 cases had varying chr2 deletions; and 4 cases had chr6 deletions. A chr10 deletion (previously reported in the sclerosing variant of soft tissue perineurioma) was observed in one case and another case had chr7 chromothripsis as the sole chromosomal abnormality. No TRAF7 mutations or alterations were identified in any case and no other evaluated gene (MAF0.0001) had recurrent, deleterious mutations in2 cases. The molecular genetic profiles showed no association with patient sex, age, tumoral histology or anatomic site. OncoScan SNP array analysis was performed on 10 cases and showed high concordance with the whole exome data, validating the large-scale deletions, duplications, and chr7 chromothripsis findings. In soft tissue perineuriomas, recurrent 22q12 deletions (with NF2) and 17q11 deletions (with NF1) appear to be mutually exclusive events, and alterations in NF1 or NF2 likely contribute to perineurioma pathogenesis, similar to other nerve sheath tumors. Moreover, the lack of TRAF7 mutations in soft tissue perineuriomas indicates divergent pathogenetic mechanisms from those of intraneural perineuriomas.

Currarino syndrome (OMIM 175450) presents with sacral, anorectal, and intraspinal anomalies and presacral meningocele or teratoma. Autosomal dominant loss-of-function mutations in the MNX1 gene cause nearly all familial and 30% of sporadic cases. Less frequently, a complex phenotype of Currarino syndrome can be caused by microdeletions of 7q containing MNX1. Here, we report one familial and three sporadic cases of Currarino syndrome. To determine the most efficient genetic testing approach for these patients, we have compared results from MNX1 sequencing, chromosomal microarray, and performed a literature search with analysis of genotype-phenotype correlation. Based on the relationship between the type of mutation (intragenic MNX1 mutations vs 7q microdeletion) and the presence of intellectual disability, growth retardation, facial dysmorphism, and associated malformations, we propose a testing algorithm. Patients with the classic Currarino triad of malformations but normal growth, intellect, and facial appearance should have MNX1 sequencing first, and only in the event of a normal result should the clinician proceed with chromosomal microarray testing. In contrast, if growth delay and/or facial dysmorphy and/or intellectual disability are present, chromosomal microarray should be the first method of choice for genetic testing.

Single-nucleotide polymorphism (SNP) microarrays can easily identify whole-chromosome isodisomy but are unable to detect whole-chromosome heterodisomy. However, most cases of uniparental disomy (UPD) involve combinations of heterodisomy and isodisomy, visualized on SNP microarrays as long continuous stretches of homozygosity (LCSH). LCSH raise suspicion for, but are not diagnostic of, UPD, and reporting necessitates confirmatory testing. The goal of this study was to define optimal LCSH reporting standards. Eighty-nine individuals with known UPD were analyzed using chromosomal microarray. The LCSH patterns were compared with those in a phenotypically normal population to predict the clinical impact of various reporting thresholds. False-positive and -negative rates were calculated at various LCSH thresholds. Twenty-seven of 84 cases with UPD had no significant LCSH on the involved chromosome. Fifty UPD-positive samples had LCSH of varying sizes: the average size of terminal LCSH was 11.0 megabases while the average size of interstitial LCSH was 24.1 megabases. LCSH in the normal population tended to be much smaller (average 4.3 megabases) and almost exclusively interstitial; however, overlap between the populations was noted. We hope that this work will aid clinical laboratories in the recognition and reporting of LCSH.

Despite the clinical significance of balanced chromosomal abnormalities (BCAs), their characterization has largely been restricted to cytogenetic resolution. We explored the landscape of BCAs at nucleotide resolution in 273 subjects with a spectrum of congenital anomalies. Whole-genome sequencing revised 93% of karyotypes and demonstrated complexity that was cryptic to karyotyping in 21% of BCAs, highlighting the limitations of conventional cytogenetic approaches. At least 33.9% of BCAs resulted in gene disruption that likely contributed to the developmental phenotype, 5.2% were associated with pathogenic genomic imbalances, and 7.3% disrupted topologically associated domains (TADs) encompassing known syndromic loci. Remarkably, BCA breakpoints in eight subjects altered a single TAD encompassing MEF2C, a known driver of 5q14.3 microdeletion syndrome, resulting in decreased MEF2C expression. We propose that sequence-level resolution dramatically improves prediction of clinical outcomes for balanced rearrangements and provides insight into new pathogenic mechanisms, such as altered regulation due to changes in chromosome topology. info:eu-repo/semantics/publishedVersion

Deletion of 15q11.2-q13 results in either Prader-Willi syndrome (PWS) or Angelman syndrome (AS) depending on the parent of origin. Duplication of the PWS/AS critical region (PWASCR) has also been reported in association with developmental delay and autism, and it has been shown that they also show a parent-of-origin effect. It is generally accepted that maternal duplications are pathogenic. However, there is conflicting evidence as to the pathogenicity of paternal duplications. We have identified 35 patients with gain of the PWASCR using array comparative genomic hybridization. Methylation testing was performed to determine parent of origin of the extra copies. Of the 35 cases, 22 had a supernumerary marker chromosome 15 (SMC15), 12 had a tandem duplication, and 1 had a tandem triplication. Only one patient had a paternal duplication; this patient does not have features typical of patients with maternal duplication of the PWASCR. Three of the mothers had a tandem duplication (two were paternal and one was maternal origin). While one of the two mothers with paternal duplication was noted not to have autism, the other was noted to have learning disability and depression. Based on our data, we conclude that SMC15 are almost exclusively maternal in origin and result in an abnormal phenotype. Tandem duplications/triplications are generally of maternal origin when ascertained on the basis of abnormal phenotype; however, tandem duplications of paternal origin have also been identified. Therefore, we suggest that methylation testing be performed for cases of tandem duplications/triplications since the pathogenicity of paternal gains is uncertain.

Chromosomal microarray analysis (CMA) is standard of care, first-tier clinical testing for detection of genomic copy number variation among patients with developmental disabilities. Although diagnostic yield is higher than traditional cytogenetic testing, management impact has not been well studied. We surveyed genetic services providers regarding CMA ordering practices and perceptions about reimbursement. Lack of insurance coverage because of perceived lack of clinical utility was cited among the most frequent reasons why CMA was not ordered when warranted. We compiled a list of genomic regions where haploinsufficiency or triplosensitivity cause genetic conditions with documented management recommendations, estimating that at least 146 conditions potentially diagnosable by CMA testing have published literature supporting specific clinical management implications. Comparison with an existing clinical CMA database to determine the proportion of cases involving these regions showed that CMA diagnoses associated with such recommendations are found in approximately 7% of all cases (n = 28,526). We conclude that CMA impacts clinical management at a rate similar to other genetic tests for which insurance coverage is more readily approved. The information presented here can be used to address barriers that continue to contribute to inequities in patient access and care in regard to CMA testing.

Array comparative genomic hybridization (aCGH) technology is commonly used to estimate genome-wide copy-number variation and to evaluate associations between copy number and disease. Although aCGH technology is well developed and there are numerous algorithms available for estimating copy number, little attention has been paid to the important issue of the statistical experimental design. Herein, we review classical statistical experimental designs and discuss their relevance to aCGH technology as well as their importance for downstream statistical analyses. Furthermore, we provide experimental design guidance for various study objectives.

A challenge in clinical genomics is to predict whether copy number variation (CNV) affecting a gene or multiple genes will manifest as disease. Increasing recognition of gene dosage effects in neurodevelopmental disorders prompted us to develop a computational approach based on critical-exon (highly expressed in brain, highly conserved) examination for potential etiologic effects. Using a large CNV dataset, our updated analyses revealed significant (P −15) enrichment of critical-exons within rare CNVs in cases compared to controls. Separately, we used a weighted gene co-expression network analysis (WGCNA) to construct an unbiased protein module from prenatal and adult tissues and found it significantly enriched for critical exons in prenatal (P −50, OR = 2.11) and adult (P −18, OR = 1.55) tissues. WGCNA yielded 1,206 proteins for which we prioritized the corresponding genes as likely to have a role in neurodevelopmental disorders. We compared the gene lists obtained from critical-exon and WGCNA analysis and found 438 candidate genes associated with CNVs annotated as pathogenic, or as variants of uncertain significance (VOUS), from among 10,619 developmental delay cases. We identified genes containing CNVs previously considered to be VOUS to be new candidate genes for neurodevelopmental disorders (GIT1, MVB12B and PPP1R9A) demonstrating the utility of this strategy to index the clinical effects of CNVs.

Background Loss of expression of imprinted genes in the 15q11.2-q13 region is known to cause either Prader-Willi syndrome (PWS) or Angelman syndrome (AS), depending on the parent of origin. In some patients (1 % in PWS and 2–4 % in AS), the disease is due to aberrant imprinting or gene silencing, or both. Results We report here a 4-year-old boy on whom a chromosomal microarray (CMA) was performed due to mild hand tremors, mild developmental delays, and clumsiness. CMA revealed absence of heterozygosity (AOH) spanning the entire chromosome 15, suggesting uniparental isodisomy 15. The patient had no definitive phenotypic features of PWS or AS. Methylation-sensitive multiplex ligation-dependent probe amplification (MS-MLPA) was performed to determine the parent of origin of the uniparental disomy (UPD) by examining methylation status at maternally imprinted sites. Interestingly, our patient had a mosaic methylation pattern. We identified nine additional previously tested patients with a similar mosaic methylation pattern. CMA was performed on these individuals retrospectively to test whether patients with mosaic methylation are more likely to have UPD of chromosome 15. Of the nine patients, only one had regions of AOH on chromosome 15; however, this patient had numerous regions of AOH on multiple chromosomes suggestive of consanguinity. Conclusion The patients with mosaic methylation had milder or atypical features of AS, and the majority also had some features characteristic of PWS. We suggest that quantitative methylation analysis be performed for cases of atypical PWS or AS. It is also important to follow up with methylation testing when whole-chromosome isodisomy is detected.

The evidence-based review (EBR) process has been widely used to develop standards for medical decision-making and to explore complex clinical questions. This approach can be applied to genetic tests, such as chromosomal microarrays, in order to assist in the clinical interpretation of certain copy number variants (CNVs), particularly those that are rare, and guide array design for optimal clinical utility. To address these issues, the International Standards for Cytogenomic Arrays Consortium has established an EBR Work Group charged with building a framework to systematically assess the potential clinical relevance of CNVs throughout the genome. This group has developed a rating system enumerating the evidence supporting or refuting dosage sensitivity for individual genes and regions that considers the following criteria: number of causative mutations reported; patterns of inheritance; consistency of phenotype; evidence from large-scale case-control studies; mutational mechanisms; data from public genome variation databases; and expert consensus opinion. The system is designed to be dynamic in nature, with regions being reevaluated periodically to incorporate emerging evidence. The evidence collected will be displayed within a publically available database, and can be used in part to inform clinical laboratory CNV interpretations as well as to guide array design.

Purpose: Copy number variants have emerged as a major cause of human disease such as autism and intellectual disabilities. Because copy number variants are common in normal individuals, determining the functional and clinical significance of rare copy number variants in patients remains challenging. The adoption of whole-genome chromosomal microarray analysis as a first-tier diagnostic test for individuals with unexplained developmental disabilities provides a unique opportunity to obtain large copy number variant datasets generated through routine patient care. Methods: A consortium of diagnostic laboratories was established (the International Standards for Cytogenomic Arrays consortium) to share copy number variant and phenotypic data in a central, public database. We present the largest copy number variant case-control study to date comprising 15,749 International Standards for Cytogenomic Arrays cases and 10,118 published controls, focusing our initial analysis on recurrent deletions and duplications involving 14 copy number variant regions. Results: Compared with controls, 14 deletions and seven duplications were significantly overrepresented in cases, providing a clinical diagnosis as pathogenic. Conclusion: Given the rapid expansion of clinical chromosomal microarray analysis testing, very large datasets will be available to determine the functional significance of increasingly rare copy number variants. This data will provide an evidencebased guide to clinicians across many disciplines involved in the diagnosis, management, and care of these patients and their families. Genet Med 2011:13(9):777–784.

Genomic microarrays used to assess DNA copy number are now recommended as first-tier tests for the postnatal evaluation of individuals with intellectual disability, autism spectrum disorders, and/or multiple congenital anomalies. Application of this technology has resulted in the discovery of widespread copy number variation in the human genome, both polymorphic variation in healthy individuals and novel pathogenic copy number imbalances. To assist clinical laboratories in the evaluation of copy number variants and to promote consistency in interpretation and reporting of genomic microarray results, the American College of Medical Genetics has developed the following professional guidelines for the interpretation and reporting of copy number variation. These guidelines apply primarily to evaluation of constitutional copy number variants detected in the postnatal setting.

Ataxia telangiectasia (A-T) is a rare genetic disorder characterized by progressive cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency, chromosomal instability, and radiation sensitivity (Peterson et al. Lancet 283:1189–1193, 1964; Boder and Sedgwick Pediatrics 21:526–554, 1958; Taylor et al. Nature 258:427–429, 1975). Compared to the general population, patients with primary immunodeficiencies such as A-T have an increased rate of malignancy and an earlier age at presentation (Loeb et al. J Pediatr Hematol/Oncol 22:464–467, 2000; Taylor et al. Blood 87:423–438, 1996). We report the clinical, histopathologic, and molecular features of a 6-year-old child who presented with EBV-positive Hodgkin lymphoma (HL), which led to the diagnosis of ataxia telangiectasia. The diagnosis of HL at this unusually young age prompted further clinical, immunologic and cytogenetic evaluations, all of which supported a diagnosis of A-T. Because A-T patients are exquisitely sensitive to radiation, the patient was put on a modified chemotherapeutic regimen; however, 14 months later, he experienced a relapse and passed away by age 9. Classical HL is relatively rare among A-T patients, and this is the first documented case of an EBER-1 positive Hodgkin lymphoma in an ataxia telangiectasia patient. A review of the literature examining cases of HL in A-T is provided.

Purpose: The purpose of this study was to assess the variability in interpretation and reporting of copy number changes that are detected by array-based technology in the clinical laboratory. Methods: Thirteen different copy number changes, detected by array comparative genomic hybridization, that have not been associated with an abnormal phenotype in the literature were evaluated by directors from 11 different clinical laboratories to determine how they would interpret and report the findings. Results: For none of the thirteen copy number changes was there complete agreement in the interpretation of the clinical significance of the deletion or duplication. For some cases, the interpretations ranged from normal to abnormal. Conclusion: There is a need for more specific guidelines for interpreting and reporting copy number changes detected by array-based technology to clearly and more consistently communicate the clinical significance of these findings to ordering providers.

OBJECTIVE To use fluorescence in situ hybridization (FISH) to visualize genetic abnormalities in interphase cell nuclei (interphase FISH) of acinar cell carcinoma, ductal adenocarcinoma, and islet cell carcinoma of the pancreas. PATIENTS AND METHODS Between April 4, 2007, and December 4, 2008, interphase FISH was used to study paraffin-embedded preparations of tissue obtained from 18 patients listed in the Mayo Clinic Biospecimen Resource for Pancreas Research with a confirmed diagnosis of acinar cell carcinoma, ductal adenocarcinoma, islet cell carcinoma, or pancreas without evidence of neoplasia. FISH probes were used for chromosome loci of APC (see glossary at end of article for expansion of all gene symbols), BRCA2, CTNNB1, EGFR, ERBB2, CDKN2A, TP53, TYMP, and TYMS . These FISH probes were used with control probes to distinguish among various kinds of chromosome abnormalities of number and structure. RESULTS FISH abnormalities were observed in 12 (80%) of 15 patients with pancreatic cancer: 5 of 5 patients with acinar cell carcinoma, 5 of 5 patients with ductal adenocarcinoma, and 2 (40%) of 5 patients with islet cell carcinoma. All 3 specimens of pancreatic tissue without neoplasia had normal FISH results. Gains of CTNNB1 due to trisomy 3 occurred in each tumor with acinar cell carcinoma but in none of the other tumors in this study. FISH abnormalities of all other cancer genes studied were observed in all forms of pancreatic tumors in this investigation. CONCLUSION FISH abnormalities of CTNNB1 due to trisomy 3 were observed only in acinar cell carcinoma. FISH abnormalities of genes implicated in familial cancer, tumor progression, and the 5-fluorouracil pathway were common but were not associated with specific types of pancreatic cancer.

Copy-number variants (CNVs) are substantial contributors to human disease. A central challenge in CNV-disease association studies is to characterize the pathogenicity of rare and possibly incompletely penetrant events, which requires the accurate detection of rare CNVs in large numbers of individuals. Cost and throughput issues limit our ability to perform these studies. We have adapted the Illumina BeadXpress SNP genotyping assay and developed an algorithm, SNP-Conditional OUTlier detection (SCOUT), to rapidly and accurately detect both rare and common CNVs in large cohorts. This approach is customizable, cost effective, highly parallelized, and largely automated. We applied this method to screen 69 loci in 1105 children with unexplained intellectual disability, identifying pathogenic variants in 3.1% of these individuals and potentially pathogenic variants in an additional 2.3%. We identified seven individuals (0.7%) with a deletion of 16p11.2, which has been previously associated with autism. Our results widen the phenotypic spectrum of these deletions to include intellectual disability without autism. We also detected 1.65–3.4 Mbp duplications at 16p13.11 in 1.1% of affected individuals and 350 kbp deletions at 15q11.2, near the Prader-Willi/Angelman syndrome critical region, in 0.8% of affected individuals. Compared to published CNVs in controls they are significantly (P = 4.7 × 10−5 and 0.003, respectively) enriched in these children, supporting previously published hypotheses that they are neurocognitive disease risk factors. More generally, this approach offers a previously unavailable balance between customization, cost, and throughput for analysis of CNVs and should prove valuable for targeted CNV detection in both research and diagnostic settings.

To describe the experience and outcome of performing whole-exome sequencing (WES) for resolution of patients on a diagnostic odyssey in the first 18 months of an individualized medicine clinic (IMC).The IMC offered WES to physicians of Mayo Clinic practice for patients with suspected genetic disease. DNA specimens of the proband and relatives were submitted to WES laboratories. We developed the Genomic Odyssey Board with multidisciplinary expertise to determine the appropriateness for IMC services, review WES reports, and make the final decision about whether the exome findings explain the disease. This study took place from September 30, 2012, to March 30, 2014.In the first 18 consecutive months, the IMC received 82 consultation requests for patients on a diagnostic odyssey. The Genomic Odyssey Board deferred 7 cases and approved 75 cases to proceed with WES. Seventy-one patients met with an IMC genomic counselor. Fifty-one patients submitted specimens for WES testing, and the results have been received for all. There were 15 cases in which a diagnosis was made on the basis of WES findings; thus, the positive diagnostic yield of this practice was 29%. The mean cost per patient for this service was approximately $8000. Medicaid supported 27% of the patients, and 38% of patients received complete or partial insurance coverage.The significant diagnostic yield, moderate cost, and notable health marketplace acceptance for WES compared with conventional genetic testing make the former method a rational diagnostic approach for patients on a diagnostic odyssey.

Loss of tumor protein 53 ( TP53 ) has been associated with aggressive disease and poor response to therapy in B-cell chronic lymphocytic leukemia (B-CLL). TP53 is located at chromosome band 17p13 and its absence can be detected by fluorescence in situ hybridization (FISH) in the interphase nuclei of 8–10% patients with B-CLL. To study the cytogenetic mechanism for loss of TP53 , metaphase and interphase FISH studies were conducted on 16 B-CLL patients to investigate 17p10 to 17p12, a chromosome region known to be rich in low-copy DNA repeats. Loss of TP53 was caused by an isochromosome with breakpoints between 17p10 and 17p11.2 in four patients, an unbalanced translocation involving 17p10 to 17p11.2 in nine patients, and an unbalanced translocation involving 17p11.2 to 17p12 in three patients. These findings indicate that loss of TP53 results from the absence of nearly the entire chromosome 17 p-arm rather than to monosomy 17 or deletions of TP53 . Translocations or isochromosome formations at sites of low-copy DNA repeats in 17p10 to 17p12 appear to be the mechanism for the loss of TP53 in B-CLL.

Purpose: Validation of fluorescence in situ hybridization assays is required before using them in clinical practice. Yet, there are few published examples that describe the validation process, leading to inconsistent and sometimes inadequate validation practices. The purpose of this article is to describe a broadly applicable preclinical validation process. Methods: Validation is performed using four consecutive experiments. The Familiarization experiment tests probe performance on metaphase cells to measure analytic sensitivity and specificity for normal blood specimens. The Pilot Study tests a variety of normal and abnormal specimens, using the intended tissue type, to set a preliminary normal cutoff and establish the analytic sensitivity. The Clinical Evaluation experiment tests these parameters in a series of normal and abnormal specimens to simulate clinical practice, establish the normal cutoff and abnormal reference ranges, and finalize the standard operating procedure. The Precision experiment measures the reproducibility of the new assay over 10 consecutive working days. To illustrate documentation and analysis of data with this process, the results for a new assay to detect fusion of IGH and BCL3 associated with t(14;19)(q32;q13.3) in lymphoproliferative disorders are provided in this report. Results: These four experiments determine the analytic sensitivity and specificity, normal values, precision, and reportable reference ranges for validation of the new test. Conclusion: This report describes a method for preclinical validation of fluorescence in situ hybridization studies of metaphase cells and interphase nuclei using commercial or home brew probes.

We describe a new cause of congenital disorder of glycosylation-Ic (CDG-Ic) in a young girl with a rather mild CDG phenotype. Her cells accumulated lipid-linked oligosaccharides lacking three glucose residues, and sequencing of the ALG6 gene showed what initially appeared to be a homozygous novel point mutation (338G > A). However, haplotype analysis showed that the patient does not carry any paternal DNA markers extending 33 kb in the telomeric direction from the ALG6 region, and microsatellite analysis extended the abnormal region to at least 2.5 Mb. We used high-resolution karyotyping to confirm a deletion (10–12 Mb) [del(1)(p31.2p32.3)] and found no structural abnormalities in the father, suggesting a de novo event. Our findings extend the causes of CDG to larger DNA deletions and identify the first Japanese CDG-Ic mutation.

For decades, conventional chromosome analysis using G-banded karyotyping has been the gold standard for detecting cytogenetic abnormalities in fetuses for prenatal diagnosis and pregnancy loss. Although chromosome studies easily identify such chromosome abnormalities as aneuploidy (gain or loss of an entire chromosome), balanced rearrangements, and large unbalanced structural rearrangements, they have limited resolution. Pathogenic copy number changes smaller than approximately 5–10 Mb are not detectable; however, recent advances in chromosomal microarray (CMA)2 analysis now allow the detection of chromosomal deletions and duplications at much higher resolutions (down to only a few kilobases, depending on the microarray), producing a higher diagnostic yield. In fact, a recently published study that compared standard karyotyping with postnatal CMA testing for patients with unexplained developmental delay, autism spectrum disorders, or multiple congenital anomalies demonstrated an increased diagnostic yield of about 12%–15% with CMA analysis, vs. 4% with karyotyping. These findings led to the recommendation by the American College of Medical Genetics that CMA testing replace chromosome analysis as the first-tier test for such patients (1, 2). Given these findings in the postnatal setting, the incremental diagnostic yields of CMA analysis and chromosome analysis are now being evaluated for prenatal genetic testing. Recent publications in the New England Journal of Medicine have described approaches to answering this question, not only with prenatal samples (3) but also with stillbirths (defined as pregnancy loss at or after 20 weeks' gestation) (4). The multicenter study by Wapner et al. successfully analyzed 4182 samples of amniotic fluid and chorionic villi with both chromosome and CMA analysis (3). The women were tested for indications that included advanced maternal age, a positive result in maternal-serum screening, and fetal anomalies detected on ultrasonography. CMA was equally efficacious in identifying all aneuploidies and unbalanced rearrangements that had been identified by karyotyping. …

Chromosome 22, particularly band 22q11.2, is predisposed to rearrangements due to misalignments of low-copy repeats (LCRs). DiGeorge/velocardiofacial syndrome (DG/VCFS) is a common disorder resulting from microdeletion within the same band. Although both deletion and duplication are expected to occur in equal proportions as reciprocal events caused by LCR-mediated rearrangements, very few microduplications have been identified. We have identified 13 cases of microduplication 22q11.2, primarily by interphase fluorescence in situ hybridization (FISH). The size of the duplications, determined by FISH probes from bacterial artificial chromosomes and P(1) artificial chromosomes, range from 3-4 Mb to 6 Mb, and the exchange points seem to involve an LCR. Molecular analysis based on 15 short tandem repeats confirmed the size of the duplications and indicated that at least 1 of 15 loci has three alleles present. The patients' phenotypes ranged from mild to severe, sharing a tendency for velopharyngeal insufficiency with DG/VCFS but having other distinctive characteristics, as well. Although the present series of patients was ascertained because of some overlapping features with DG/VCF syndromes, the microduplication of 22q11.2 appears to be a new syndrome.

The development of cervical cancer is highly associated with human papillomavirus (HPV) infection. Greater than 99% of all cervical tumors contain HPV DNA. Integration of high-risk HPV has been temporally associated with the acquisition of a malignant phenotype. Recent work from our lab has shown that HPV16, the most common high-risk HPV associated with cervical carcinoma, preferentially integrates at loci containing human common fragile sites (CFSs). CFSs are regions of genomic instability that have also been associated with deletions, translocations, and gene amplification during cancer development. The current work shows that HPV18, the second most prevalent high-risk HPV type found in cervical tumors, preferentially targets the CFSs. We identified 27 unique HPV18 integrations in cervical tumors, of which 63% (P