Array-based technology and recommendations for utilization in medical genetics practice for detection of chromosomal abnormalities

Evaluation of Chromosome Microarray Analysis in a Large Cohort of Females with Autism Spectrum Disorders: A Single Center Italian Study

Autism spectrum disorders (ASD) encompass a heterogeneous group of neurodevelopmental disorders resulting from the complex interaction between genetic and environmental factors. Thanks to the chromosome microarray analysis (CMA) in clinical practice, the accurate identification and characterization of submicroscopic deletions/duplications (copy number variants, CNVs) associated with ASD was made possible. However, the widely acknowledged excess of males on the autism spectrum reflects on a paucity of CMA studies specifically focused on females with ASD (f-ASD). In this framework, we aim to evaluate the frequency of causative CNVs in a single-center cohort of idiopathic f-ASD. Among the 90 f-ASD analyzed, we found 20 patients with one or two potentially pathogenic CNVs, including those previously associated with ASD (located at 16p13.2 16p11.2, 15q11.2, and 22q11.21 regions). An exploratory genotype/phenotype analysis revealed that the f-ASD with causative CNVs had statistically significantly lower restrictive and repetitive behaviors than those without CNVs or with non-causative CNVs. Future work should focus on further understanding of f-ASD genetic underpinnings, taking advantage of next-generation sequencing technologies, with the ultimate goal of contributing to precision medicine in ASD.

Missed diagnoses: Clinically relevant lessons learned through medical mysteries solved by the Undiagnosed Diseases Network

BACKGROUND

Resources within the Undiagnosed Diseases Network (UDN), such as genome sequencing (GS) and model organisms aid in diagnosis and identification of new disease genes, but are currently difficult to access by clinical providers. While these resources do contribute to diagnoses in many cases, they are not always necessary to reach diagnostic resolution. The UDN experience has been that participants can also receive diagnoses through the thoughtful and customized application of approaches and resources that are readily available in clinical settings.

METHODS

The UDN Genetic Counseling and Testing Working Group collected case vignettes that illustrated how clinically available methods resulted in diagnoses. The case vignettes were classified into three themes; phenotypic considerations, selection of genetic testing, and evaluating exome/GS variants and data.

RESULTS

We present 12 participants that illustrate how clinical practices such as phenotype-driven genomic investigations, consideration of variable expressivity, selecting the relevant tissue of interest for testing, utilizing updated testing platforms, and recognition of alternate transcript nomenclature resulted in diagnoses.

CONCLUSION

These examples demonstrate that when a diagnosis is elusive, an iterative patient-specific approach utilizing assessment options available to clinical providers may solve a portion of cases. However, this does require increased provider time commitment, a particular challenge in the current practice of genomics.

A diagnostic approach to syndromic retinal dystrophies with intellectual disability

Inherited retinal dystrophies are a group of monogenic disorders that, as a whole, contribute significantly to the burden of ocular disease in both pediatric and adult patients. In their syndromic forms, retinal dystrophies can be observed in association with intellectual disability, frequently alongside other systemic manifestations. There are now over 80 genes implicated in syndromic retinal dystrophies with intellectual disability. Identifying and accurately characterizing these disorders allows the clinician to narrow the differential diagnosis, evaluate for relevant associated features, arrive at a timely and accurate diagnosis, and address both sight-threatening ocular manifestations and morbidity-causing systemic manifestations. The co-occurrence of retinal dystrophy and intellectual disability in an individual can be challenging to investigate, diagnose, and counsel given the considerable phenotypic and genotypic heterogeneity that exists within this broad group of disorders. We performed a review of the current literature and propose an algorithm to facilitate the evaluation, and clinical and mechanistic classification, of these individuals.

Genetic Basis of Human Congenital Heart Disease

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

Chromosomal Microarray Analysis in Turkish Patients with Unexplained Developmental Delay and Intellectual Developmental Disorders

INTRODUCTION

Aneuploids, copy number variations (CNVs), and single nucleotide variants in specific genes are the main genetic causes of developmental delay (DD) and intellectual disability disorder (IDD). These genetic changes can be detected using chromosome analysis, chromosomal microarray (CMA), and next-generation DNA sequencing techniques. Therefore; In this study, we aimed to investigate the importance of CMA in determining the genomic etiology of unexplained DD and IDD in 123 patients.

METHOD

For 123 patients, chromosome analysis, DNA fragment analysis and microarray were performed. Conventional G-band karyotype analysis from peripheral blood was performed as part of the initial screening tests. FMR1 gene CGG repeat number and methylation analysis were carried out to exclude fragile X syndrome.

RESULTS

CMA analysis was performed in 123 unexplained IDD/DD patients with normal karyotypes and fragile X screening, which were evaluated by conventional cytogenetics. Forty-four CNVs were detected in 39 (39/123=31.7%) patients. Twelve CNV variant of unknown significance (VUS) (9.75%) patients and 7 CNV benign (5.69%) patients were reported. In 6 patients, one or more pathogenic CNVs were determined. Therefore, the diagnostic efficiency of CMA was found to be 31.7% (39/123).

CONCLUSION

Today, genetic analysis is still not part of the routine in the evaluation of IDD patients who present to psychiatry clinics. A genetic diagnosis from CMA can eliminate genetic question marks and thus alter the clinical management of patients. Approximately one-third of the positive CMA findings are clinically intervenable. However, the emergence of CNVs as important risk factors for multiple disorders increases the need for individuals with comorbid neurodevelopmental conditions to be the priority where the CMA test is recommended.

Evaluating the use of a 22-pathogen TaqMan array card for rapid diagnosis of respiratory pathogens in intensive care

Introduction. Pneumonia is highly prevalent in intensive care units (ICUs), with high associated mortality. Empirical treatment prioritizes breadth of coverage while awaiting laboratory diagnosis, often at the expense of antimicrobial stewardship. Microarrays use multiple parallel polymerase chain reactions to enable a rapid syndromic approach to laboratory diagnosis.Aim. To evaluate the clinical and laboratory implications of introducing a bespoke 22-pathogen TaqMan Array Card (TAC) for rapid pathogen detection in deep respiratory samples from adult ICUs.Methodology. TAC results from all ICU patients prospectively tested over a 9-month period at Cambridge's Clinical Microbiology and Public Health Laboratory were compared to those of corresponding conventional microbiological assays (culture-, PCR- or serology-based) in terms of result agreement and time-to-result availability. Clinical impact was assessed by retrospective review of medical records.Results. Seventy-one patients were included [45 (63 %) male, median age 59). Overall result agreement was 94 %, with TAC detecting more pathogens than conventional methods. TAC detected Streptococcus pneumoniae more readily than culture (7 vs 0 cases; P=0.02). TAC did not detect Aspergillus spp. in eight culture- or galactomannan-positive cases. The median turnaround time (1 day) was significantly shorter than that of bacterial/fungal culture, Pneumocystis jirovecii PCR and galactomannan testing (each 3 days; P<0.001), atypical bacteria serology (13 days; P<0.001) and Mycobacterium tuberculosis culture (46 days; P<0.001). Earlier result availability prompted discontinuation of unnecessary antimicrobials in 15/71 (21 %) cases, but had no bearing on patient isolation/deisolation.Conclusion. TAC provided greater overall yield of pathogen detection and faster turnaround times, permitting earlier discontinuation of unnecessary antimicrobials.

Limited diagnostic impact of duplications <1 Mb of uncertain clinical significance: a 10-year retrospective analysis of reporting practices at the Mayo Clinic

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 <1 Mb are found to be inherited and anticipated to be of limited or no clinical significance.

METHODS

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.

RESULTS

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.

CONCLUSION

Our data reveal limited diagnostic utility for duplications of uncertain significance <1 Mb. Considerations for revised reporting criteria are discussed and are applicable to CNVs detected by any genome-wide exploratory methodology, including exome/genome sequencing.

Exon-focused targeted oligonucleotide microarray design increases detection of clinically relevant variants across multiple NHS genomic centres

In recent years, chromosomal microarrays have been widely adopted by clinical diagnostic laboratories for postnatal constitutional genome analysis and have been recommended as the first-line test for patients with intellectual disability, developmental delay, autism and/or congenital abnormalities. Traditionally, array platforms have been designed with probes evenly spaced throughout the genome and increased probe density in regions associated with specific disorders with a resolution at the level of whole genes or multiple exons. However, this level of resolution often cannot detect pathogenic intragenic deletions or duplications, which represent a significant disease-causing mechanism. Therefore, new high-resolution oligonucleotide comparative genomic hybridisation arrays (oligo-array CGH) have been developed with probes targeting single exons of disease relevant genes. Here we present a retrospective study on 27,756 patient samples from a consortium of state-funded diagnostic UK genomic centres assayed by either oligo-array CGH of a traditional design (Cytosure ISCA v2) or by an oligo-array CGH with enhanced exon-level coverage of genes associated with developmental disorders (CytoSure Constitutional v3). The new targeted design used in Cytosure v3 array has been designed to capture intragenic aberrations that would have been missed on the v2 array. To assess the relative performance of the two array designs, data on a subset of samples (n = 19,675), generated only by laboratories using both array designs, were compared. Our results demonstrate that the new high-density exon-focused targeted array design that uses updated information from large scale genomic studies is a powerful tool for detection of intragenic deletions and duplications that leads to a significant improvement in diagnostic yield.

Genetic testing strategies in the newborn

Genetic disorders presenting in the neonatal period can have a significant impact on morbidity and mortality. Early diagnosis can facilitate timely prognostic counseling to families and possibility of precision care, which could improve outcome. As availability of diagnostic testing expands, the required knowledge base of the neonatologist must also expand to include proper application and understanding of genetic testing modalities, especially where availability of clinical genetics consultation is limited. Herein, we review genetic tests utilized in the neonatal intensive care unit (NICU) providing background on the technology, clinical indications, advantages, and limitations of the tests. This review will span from classic cytogenetics to the evolving role of next generation sequencing and its impact on the management of neonatal disease.

Reinterpretation of Chromosomal Microarrays with Detailed Medical History

OBJECTIVE

To investigate the utility of a detailed medical history in the interpretation of chromosomal microarray results for pediatric patients with a constitutional disease.

STUDY DESIGN

A retrospective review and reinterpretation of test results from chromosomal microarrays performed from 2011 to 2013. Previously reported genetic variants were reanalyzed after review of the patient's complete electronic medical record (cEMR). A 3-tier system was used for reclassification of variants: pathogenic or likely pathogenic (P/LP); variant of uncertain significance (VUS); or benign or likely benign (B/LB).

RESULTS

Over an 18-month period, 998 patients with chromosomal microarray results were identified. The most common reasons for chromosomal microarray testing were developmental delay (n = 336), autism spectrum disorder (n = 241), and seizures (n = 143). Chromosomal microarray testing identified 1 or more variants in 48% (482 of 998) of patients; 516 patients had a negative report. For the 482 patients with variants, the original interpretations were composed of 19.3% P/LP (93 of 482), 44.8% VUS (216 of 482), and 35.9% B/LB (173 of 482) variants. After review of the cEMR, 34% of patient results (164 of 482) were changed in interpretation. One case changed from B/LB to VUS, 7 VUS were upgraded to P/LP, and 156 VUS were downgraded to B/LB. No P/LP variants had a change in interpretation.

CONCLUSIONS

Overall, 16.4% (164 of 998) of patients with chromosomal microarray testing had a change in interpretation. Access to the patient's cEMR improves the interpretation of chromosomal microarrays by decreasing the number of uncertain (VUS) interpretations.

State of the Art of Genetic Testing for Patients With Autism: A Practical Guide for Clinicians

The explosion in knowledge, technology, and clinical capabilities regarding genetics and genetic testing has expanded greatly in recent years, and these gains have rapidly been applied to individuals with autism spectrum disorder (ASD). However, most clinicians are unaware or confused in regards to whom to test, what tests to order, and how testing might alter management and improve outcomes. This review will address these issues. Research shows that ASD is highly genetic, and while monogenic cases are common, most patients have multiple genes interacting in disease pathogenesis. However, as genetics dictates disease risk, not outcomes, this does not exclude environmental factors. Clinically actionable genetics test results can be found across the phenotypically-heterogeneous ASD spectrum; thus recommendations are to test everyone. As ASD is also highly genetically heterogeneous, testing should address a wide range of variant types, including both large (historically detected by microarray) and small (detected by sequencing), at least across all genes (exome). Additional specialized testing important in ASD diagnostics includes fragile X, mitochondrial DNA, and pharmacogenetics; the latter often informative for which drug to order, at which dose. Recently, whole genome sequencing has emerged as a favorite since all of the above testing, and more, can be performed at a lower total cost than individual test orders. Trio (child plus parents) sequencing is often indicated, especially in more "severe" cases in order to find new (de novo) variants not present in either parent. Additionally, Angelman syndrome testing should be considered in appropriate cases. Current testing provides a precise diagnosis in many cases with ASD. Beyond diagnosis, genetic testing can oftentimes help elucidate potentially treatable risk factors that predispose the individual patient to develop disease. In this clinician's experience (RGB), this information leads to improved outcomes in as many as one-half of cases. Clinical improvement can occur in common associated ASD symptoms (attention, behavior, and anxiety) and/or in general systemtic symptoms (nausea, fatigue, pain), as demonstrated in brief case reports. Practical guidance is provided regarding assisting clinicians to choose the appropriate test(s) and laboratory, as well as how to get testing paid for. Recent cost reductions now allow for most families to benefit from genetic testing.

Disorders Associated With Diverse, Recurrent Deletions and Duplications at 1q21.1

The subchromosomal region 1q21.1 is one of the hotspots in the human genome for deletions and reciprocal duplications, owing to the existence of hundreds of segmental duplications. Recurrent deletions and duplications in this region are thought to be causative in patients with variable clinical manifestations. Based on the genomic locations, deletions and duplications at the 1q21.1 locus have been associated with distinguishable syndromes: chromosome 1q21.1 deletion syndrome, chromosome 1q21.1 duplication syndrome, and thrombocytopenia-absent radius (TAR) syndrome, which is partially due to deletions at the proximal 1q21.1 region. We report here diverse, recurrent deletions and duplications at the 1q21.1 locus in 36 patients from a cohort of 5,200 individuals. Among the 36 patients, 18 patients carry 1q21.1 deletions, nine individuals have reciprocal duplications at 1q21.1, two patients share an identical short deletion, and the remaining seven possess variable sizes of duplications at the proximal 1q21.1 region. Furthermore, we provide cytogenetic characterization and detailed clinical features for each patient. Notably, duplications at the proximal 1q21.1 region have not been associated with a defined disorder in publications. However, recurrent duplications at the proximal 1q21.1 region among the seven patients strongly suggested that the variants are likely pathogenic. The common phenotypical features of those disorders are also summarized to facilitate clinical diagnoses and genetic counseling.

A Small-Molecule AIE Chromosome Periphery Probe for Cytogenetic Studies

The chromosome periphery (CP) is a complex network that covers the outer surface of chromosomes. It acts as a carrier of nucleolar components, helps maintain chromosome structure, and plays an important role in mitosis. Current methods for fluorescence imaging of CP largely rely on immunostaining. We herein report a small-molecule fluorescent probe, ID-IQ, which possesses aggregation-induced emission (AIE) property, for CP imaging. By labelling the CP, ID-IQ sharply highlighted the chromosome boundaries, which enabled rapid segmentation of touching and overlapping chromosomes, direct identification of the centromere, and clear visualization of chromosome morphology. ID-IQ staining was also compatible with fluorescence in situ hybridization and could assist the precise location of the gene in designated chromosome. Altogether, this study provides a versatile cytogenetic tool for improved chromosome analysis, which greatly benefits the clinical diagnostic testing and genomic research.

Parallel Tests of Whole Exome Sequencing and Copy Number Variant Sequencing Increase the Diagnosis Yields of Rare Pediatric Disorders

Background: Both whole exome sequencing and copy number variants sequencing were applied to identify the genetic cause of rare pediatric disorders. In our study, we aimed to investigate the diagnostic yield of parallel tests of trio whole exome sequencing and copy number variants sequencing and its clinical utility. Methods: After collecting detailed clinical information, a total of 60 patients were referred to parallel tests of whole exome sequencing and copy number variants sequencing, which used shared initial libraries. Results: 26 pathogenic or likely pathogenic single nucleotide variants and 11 copy number variants were identified in 32 patients. 65.4% (17/26) of the SNVs were novel. The overall diagnosis rate was 53.3%. For the patients with positive results, 22 (36.7%) patients were diagnosed by whole exome sequencing and 10 (16.7%) patients were diagnosed by copy number variants sequencing. We also reviewed clinical impact on selected cases. Conclusion: We adopted an approach by performing parallel tests of trio whole exome sequencing and copy number variants sequencing with shared initial libraries. This strategy is relatively efficient and cost-effective for the diagnosis of rare pediatric disorders with high heterogeneity.

Application of Whole-Exome Sequencing in Detecting Copy Number Variants in Patients with Developmental Delay and/or Multiple Congenital Malformations

Overcoming challenges for the unambiguous detection of copy number variations is essential to broaden our understanding of the role of genomic variants in the clinical phenotype. With the improvement of software and databases, whole-exome sequencing quickly can become an excellent strategy in the routine diagnosis of patients with a developmental delay and/or multiple congenital malformations. However, even after a detailed analysis of pathogenic single-nucleotide variants and indels in known disease genes, using whole-exome sequencing, some patients with suspected syndromic conditions are left without a conclusive diagnosis. These negative results could be the result of different factors including nongenetic etiologies, lack of knowledge about the genes that cause different disease phenotypes, or, in some cases, a deletion or duplication of genomic information not routinely detectable by whole-exome sequencing variant calling. Although copy number variant detection is possible using whole-exome sequencing data, such analysis presents significant challenges and cannot yet be used to replace chromosomal arrays for identification of deletions or duplications.

Genetic Diagnosis of Rare Diseases: Past and Present

Rare diseases are heterogeneous life-threatening or seriously debilitating conditions that affect < 1 in 2000 individuals, and most have a genetic component. The diagnostic process is usually based on classic clinical practices, such as physical examination, personal and family history (inheritance pattern), laboratory tests and image studies, but diagnosis can be delayed several years after the initiation of symptoms. The advances in molecular genetics that have taken place in recent years have led to an important shift in medical practice and in its approach to the diagnosis and treatment of many rare diseases. The objective of this review is to promote a better understanding of the mechanisms underlying genetic diseases in humans and the tools available for their diagnosis. A practical example of X-linked hypophosphataemic rickets is described.

Exome sequencing compared with standard genetic tests for critically ill infants with suspected genetic conditions

PURPOSE

As exome sequencing (ES) is increasingly used as a diagnostic tool, we aimed to compare ES with status quo genetic diagnostic workup for infants with suspected genetic disorders in terms of identifying diagnoses, survival, and cost of care.

METHODS

We studied newborns and infants admitted to intensive care with a suspected genetic etiology within the first year of life at a US quaternary-referral children's hospital over 5 years. In this propensity-matched cohort study using electronic medical record data, we compared patients who received ES as part of a diagnostic workup (ES cohort, n = 368) with clinically similar patients who did not receive ES (No-ES cohort, n = 368).

RESULTS

Diagnostic yield (27.4% ES, 25.8% No-ES; p = 0.62) and 1-year survival (80.2% ES, 84.8% No-ES; p = 0.10) were no different between cohorts. ES cohort patients had higher cost of admission, diagnostic investigation, and genetic testing (all p < 0.01).

CONCLUSION

ES did not differ from status quo genetic testing collectively in terms of diagnostic yield or patient survival; however, it had high yield as a single test, led to complementary classes of diagnoses, and was associated with higher costs. Further work is needed to define the most efficient use of diagnostic ES for critically ill newborns and infants.

Practice Parameter for the Assessment and Treatment of Psychiatric Disorders in Children and Adolescents With Intellectual Disability (Intellectual Developmental Disorder)

Intellectual disability (intellectual developmental disorder) (ID/IDD) is both a psychiatric disorder and a risk factor for co-occurring psychiatric disorders in children and adolescents. DSM-5 introduced important changes in the conceptualization and diagnosis of ID/IDD, and current research studies clarify assessment and treatment of co-occurring psychiatric disorders in this population. Optimal assessment and treatment of psychiatric illness in children and adolescents with ID/IDD includes modifications in diagnostic and treatment techniques, appreciation of variations in the clinical presentation of psychiatric disorders, an understanding of the spectrum of etiologies of behavioral disturbance, and knowledge of psychosocial and medical interventions.

Factors Associated With Seizure Onset in Children With Autism Spectrum Disorder

BACKGROUND AND OBJECTIVES

Children with autism spectrum disorder (ASD) have a higher prevalence of epilepsy compared with general populations. In this pilot study, we prospectively identified baseline risk factors for the development of seizures in individuals with ASD and also identified characteristics sensitive to seizure onset up to 6 years after enrollment in the Autism Speaks Autism Treatment Network.

METHODS

Children with ASD and no history of seizures at baseline who either experienced onset of seizures after enrollment in the Autism Treatment Network or remained seizure free were included in the analysis.

RESULTS

Among 472 qualifying children, 22 (4.7%) experienced onset of seizures after enrollment. Individuals who developed seizures after enrollment exhibited lower scores at baseline on all domains of the Vineland Adaptive Behavior Scales, greater hyperactivity on the Aberrant Behavior Checklist (25.4 ± 11.8 vs 19.2 ± 11.1; P = .018), and lower physical quality of life scores on the Pediatric Quality of Life Inventory (60.1 ± 24.2 vs 76.0 ± 18.2; P < .001). Comparing change in scores from entry to call-back, adjusting for age, sex, length of follow-up, and baseline Vineland II composite score, individuals who developed seizures experienced declines in daily living skills (-8.38; 95% confidence interval -14.50 to -2.50; P = .005). Adjusting for baseline age, sex, and length of follow-up, baseline Vineland II composite score was predictive of seizure development (risk ratio = 0.95 per unit Vineland II composite score, 95% confidence interval 0.92 to 0.99; P = .007).

CONCLUSIONS

Individuals with ASD at risk for seizures exhibited changes in adaptive functioning and behavior.

Systematic evidence-based review: outcomes from exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability

Purpose

Exome and genome sequencing (ES/GS) are performed frequently in patients with congenital anomalies, developmental delay, or intellectual disability (CA/DD/ID), but the impact of results from ES/GS on clinical management and patient outcomes is not well characterized. A systematic evidence review (SER) can support future evidence-based guideline development for use of ES/GS in this patient population.

Methods

We undertook an SER to identify primary literature from January 2007 to March 2019 describing health, clinical, reproductive, and psychosocial outcomes resulting from ES/GS in patients with CA/DD/ID. A narrative synthesis of results was performed.

Results

We retrieved 2654 publications for full-text review from 7178 articles. Only 167 articles met our inclusion criteria, and these were primarily case reports or small case series of fewer than 20 patients. The most frequently reported outcomes from ES/GS were changes to clinical management or reproductive decision-making. Two studies reported on the reduction of mortality or morbidity or impact on quality of life following ES/GS.

Conclusion

There is evidence that ES/GS for patients with CA/DD/ID informs clinical and reproductive decision-making, which could lead to improved outcomes for patients and their family members. Further research is needed to generate evidence regarding health outcomes to inform robust guidelines regarding ES/GS in the care of patients with CA/DD/ID.

Genome-Wide Sequencing for Unexplained Developmental Disabilities or Multiple Congenital Anomalies: A Health Technology Assessment

BACKGROUND

People with unexplained developmental disabilities or multiple congenital anomalies might have had many biochemical, metabolic, and genetic tests for a period of years without receiving a diagnosis. A genetic diagnosis can help these people and their families better understand their condition and may help them to connect with others who have the same condition. Ontario Health (Quality), in collaboration with the Canadian Agency for Drugs and Technologies in Health (CADTH) conducted a health technology assessment about the use of genome-wide sequencing for patients with unexplained developmental disabilities or multiple congenital anomalies. Ontario Health (Quality) evaluated the effectiveness, cost-effectiveness, and budget impact of publicly funding genome-wide sequencing. We also conducted interviews with patients and examined the quantitative evidence of preferences and values literature to better understand the patient preferences and values for these tests.

METHODS

Ontario Health (Quality) performed a systematic literature search of the clinical evidence. We assessed the risk of bias of each included study using the Risk of Bias Assessment tool for Non-randomized Studies (RoBANS) and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We also performed a search of the quantitative evidence and undertook direct patient engagement to ascertain patient preferences for genetic testing for unexplained developmental disabilities or multiple congenital anomalies. CADTH performed a review of qualitative literature about patient perspectives and experiences, and a review of ethical issues.Ontario Health (Quality) performed an economic literature review of genome-wide sequencing in people with unexplained developmental disabilities or multiple congenital anomalies. Although we found eight published cost-effectiveness studies, none completely addressed our research question. Therefore, we conducted a primary economic evaluation using a discrete event simulation model. Owing to its high cost and early stage of clinical implementation, whole exome sequencing is primarily used for people who do not have a diagnosis from standard testing (referred to here as whole exome sequencing after standard testing; standard testing includes chromosomal microarray and targeted single-gene tests or gene panels). Therefore, in our first analysis, we evaluated the cost-effectiveness of whole exome sequencing after standard testing versus standard testing alone. In our second analysis, we explored the cost-effectiveness of whole exome and whole genome sequencing used at various times in the diagnostic pathway (e.g., first tier, second tier, after standard testing) versus standard testing. We also estimated the budget impact of publicly funding genome-wide sequencing in Ontario for the next 5 years.

RESULTS

Forty-four studies were included in the clinical evidence review. The overall diagnostic yield of genome-wide sequencing for people with unexplained development disability and multiple congenital anomalies was 37%, but we are very uncertain about this estimate (GRADE: Very Low). Compared with standard genetic testing of chromosomal microarray and targeted single-gene tests or gene panels, genome-wide sequencing could have a higher diagnostic yield (GRADE: Low). As well, for some who are tested, genome-wide sequencing prompts some changes to medications, treatments, and referrals to specialists (GRADE: Very Low).Whole exome sequencing after standard testing cost an additional $3,261 per patient but was more effective than standard testing alone. For every 1,000 persons tested, using whole exome sequencing after standard testing would lead to an additional 240 persons with a molecular diagnosis, 272 persons with any positive finding, and 46 persons with active treatment change (modifications to medications, procedures, or treatment). The resulting incremental cost-effectiveness ratios (ICERs) were $13,591 per additional molecular diagnosis. The use of genome-wide sequencing early in the diagnostic pathway (e.g., as a first- or second-tier test) can save on costs and improve diagnostic yields over those of standard testing. Results remained robust when parameters and assumptions were varied.Our budget impact analysis showed that, if whole exome sequencing after standard testing continues to be funded through Ontario's Out-of-Country Prior Approval Program, its budget impact would range from $4 to $5 million in years 1 to 5. If whole exome sequencing becomes publicly funded in Ontario (not through the Out-of-Country Prior Approval Program), the budget impact would be about $9 million yearly. We also found that using whole exome sequencing as a second-tier test would lead to cost savings ($3.4 million per 1,000 persons tested yearly).Participants demonstrated consistent motivations for and expectations of obtaining a diagnosis for unexplained developmental delay or congenital anomalies through genome-wide sequencing. Patients and families greatly value the support and information they receive through genetic counselling when considering genome-wide sequencing and learning of a diagnosis.

CONCLUSIONS

Genome-wide sequencing could have a higher diagnostic yield than standard testing for people with unexplained developmental disabilities or multiple congenital anomalies. Genome-wide sequencing can also prompt some changes to medications, treatments, and referrals to specialists for some people tested; however, we are very uncertain about this. Genome-wide sequencing could be a cost-effective strategy when used after standard testing to diagnose people with unexplained developmental disabilities or multiple congenital anomalies. It could also lead to cost savings when used earlier in the diagnostic pathway. Patients and families consistently noted a benefit from seeking a diagnosis through genetic testing.

The genetics of isolated congenital heart disease

The genetic mechanisms underlying congenital heart disease (CHD) are complex and remain incompletely understood. The majority of patients with CHD have an isolated heart defect without other organ system involvement, but the genetic basis of isolated CHD has been even more difficult to elucidate compared to syndromic CHD. Our understanding of the genetics of isolated CHD is advancing in large part due to advances in next generation sequencing, and the list of genes associated with CHD is rapidly expanding. Variants in hundreds of genes have been identified that may cause or contribute to CHD, but a genetic cause can still only be identified in about 20-30% of patients. Identifying a genetic cause for CHD can have an impact on clinical outcomes and prognosis and thus it is important for clinicians to understand when and what to test in patients with isolated CHD. This chapter reviews some of the known genetic mechanisms that contribute to isolated inherited and sporadic CHD as well as recommendations for evaluation and genetic testing in patients with isolated CHD.

Overview and Introduction to Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder generally manifesting in the first few years of life and tending to persist into adolescence and adulthood. It is characterized by deficits in communication and social interaction and restricted, repetitive patterns of behavior, interests, and activities. It is a disorder with multifactorial etiology. In this chapter, we will focus on the most important and common epidemiological studies, pathogenesis, screening, and diagnostic tools along with an explication of genetic testing in ASD.

Identification, Evaluation, and Management of Children With Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with reported prevalence in the United States of 1 in 59 children (approximately 1.7%). Core deficits are identified in 2 domains: social communication/interaction and restrictive, repetitive patterns of behavior. Children and youth with ASD have service needs in behavioral, educational, health, leisure, family support, and other areas. Standardized screening for ASD at 18 and 24 months of age with ongoing developmental surveillance continues to be recommended in primary care (although it may be performed in other settings), because ASD is common, can be diagnosed as young as 18 months of age, and has evidenced-based interventions that may improve function. More accurate and culturally sensitive screening approaches are needed. Primary care providers should be familiar with the diagnostic criteria for ASD, appropriate etiologic evaluation, and co-occurring medical and behavioral conditions (such as disorders of sleep and feeding, gastrointestinal tract symptoms, obesity, seizures, attention-deficit/hyperactivity disorder, anxiety, and wandering) that affect the child's function and quality of life. There is an increasing evidence base to support behavioral and other interventions to address specific skills and symptoms. Shared decision making calls for collaboration with families in evaluation and choice of interventions.  This single clinical report updates the 2007 American Academy of Pediatrics clinical reports on the evaluation and treatment of ASD in one publication with an online table of contents and section view available through the American Academy of Pediatrics Gateway to help the reader identify topic areas within the report.

Professionals' accounts of genetic testing in adoption: a qualitative study

OBJECTIVE

To explore social workers' and medical advisors' accounts of genetic testing in adoption.

METHODS

A qualitative study using semi-structured interviews to gather in-depth accounts of retrospective cases. Data were analysed thematically to identify professionals' knowledge and expectations.

RESULTS

Twenty professionals working in adoption services (including 8 medical advisors and 12 social workers) participated in this study. Social workers adopted an essentialist (single-gene) model to discuss genetic testing in relation to past cases. They assumed that testing was a generic procedure for detecting the presence or absence of a specific aetiology, the results of which were believed to be definitive and mutually exclusive. By contrast, medical advisors were circumspect and agnostic about the meaning of results, especially in relation to chromosomal microarray testing. Whereas social workers believed that genetic testing provided clarity in assessment and therefore assisted adoption, medical advisors emphasised the uncertainties of testing and the possibility that prospective adopters might be misled. Medical advisors also reported inappropriate requests to test children where there was a family history of a genetic condition, or to confirm or exclude a diagnosis of fetal alcohol spectrum disorder in children presenting with non-specific dysmorphic features.

CONCLUSION

Recent advances in genetic technologies are changing the ways in which professionals understand and tolerate uncertainty in adoption. Social workers and medical advisors have different understandings and expectations about the clinical utility of genetic testing. These findings have implications for social work training about genetic testing and enabling effective communication between professional groups.

Prenatal diagnosis of a 5q35.3 microduplication involving part of the ADAMTS2 locus: a likely benign variant without apparent phenotypic abnormality: Case series

RATIONALE

Chromosomal duplications are associated with a series of genetic disorders. However, chromosome 5q duplications, especially pure 5q35.3 microduplications, have rarely been reported in the literature. Clinical phenotypes usually depend on the region of chromosome duplicated, its size, and loci.

PATIENT CONCERNS

From 2011 to 2017, prenatal amniotic fluid samples were obtained from 6 pregnant women diagnosed with pure 5q35.3 microduplications following different prenatal indications at our center. We followed up the children of these pregnancies and determined their postnatal health conditions.

DIAGNOSES

Cytogenetic studies delineated that all patients had normal karyotypes, except for patient 6 who had 46,XX,inv(9)(p11q13). Single-nucleotide polymorphism array results showed 177-269 kb duplications of 5q35.3 (chr5:178728830-178997692) in these cases. All shared similar localization of ADAMTS2.

INTERVENTIONS

All pregnant women chose to continue the pregnancies. Follow-up analysis showed that the children presented normal physical and growth developments.

OUTCOMES

We described six prenatal cases with similar 5q35.3 duplications involving part of the ADAMTS2 locus with no apparent postnatal phenotypic abnormalities.

LESSONS

Our research revealed that partial microduplication of ADAMTS2 (chr5:178728830-178997692) might be benign and not correlate with disorders. And there might exist phenotypic diversities of 5q35.3 duplications.

Noninvasive prenatal testing for chromosome aneuploidies and subchromosomal microdeletions/microduplications in a cohort of 42,910 single pregnancies with different clinical features

Background

Since the discovery of cell-free DNA (cfDNA) in maternal plasma, it has opened up new approaches for non-invasive prenatal testing. With the development of whole-genome sequencing, small subchromosomal deletions and duplications could be found by NIPT. This study is to review the efficacy of NIPT as a screening test for aneuploidies and CNVs in 42,910 single pregnancies.

Methods

A total of 42,910 single pregnancies with different clinical features were recruited. The cell-free fetal DNA was directly sequenced. Each of the chromosome aneuploidies and the subchromosomal microdeletions/microduplications of PPV were analyzed.

Results

A total of 534 pregnancies (1.24%) were abnormal results detected by NIPT, and 403 pregnancies had underwent prenatal diagnosis. The positive predictive value (PPV) for trisomy 21(T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosome aneuploidies (SCAs), and other chromosome aneuploidy was 79.23%, 54.84%, 13.79%, 33.04%, and 9.38% respectively. The PPV for CNVs was 28.99%. The PPV for CNVs ≤ 5 Mb is 20.83%, for within 5–10 Mb 50.00%, for > 10 Mb 27.27% respectively. PPVs of NIPT according to pregnancies characteristics are also different.

Conclusion

Our data have potential significance in demonstrating the usefulness of NIPT profiling not only for common whole chromosome aneuploidies but also for CNVs. However, this newest method is still in its infancy for CNVs. There is still a need for clinical validation studies with accurate detection rates and false positive rates in clinical practice.

A Retrospective Analysis of 10-Year Data Assessed the Diagnostic Accuracy and Efficacy of Cytogenomic Abnormalities in Current Prenatal and Pediatric Settings

Background: Array comparative genomic hybridization (aCGH), karyotyping and fluorescence in situ hybridization (FISH) analyses have been used in a clinical cytogenetic laboratory. A systematic analysis on diagnostic findings of cytogenomic abnormalities in current prenatal and pediatric settings provides approaches for future improvement.

Methods: A retrospective analysis was performed on abnormal findings by aCGH, karyotyping, and FISH from 3,608 prenatal cases and 4,509 pediatric cases during 2008–2017. The diagnostic accuracy was evaluated by comparing the abnormality detection rate (ADR) and the relative frequency (RF) of different types of cytogenomic abnormalities between prenatal and pediatric cases. A linear regression correlation between known prevalence and ADR of genomic disorders was used to extrapolate the prevalence of other genomic disorders. The diagnostic efficacy was estimated as percentage of detected abnormal cases by expected abnormal cases from served population.

Results: The composite ADR for numerical chromosome abnormalities, structural chromosome abnormalities, recurrent genomic disorders, and sporadic pathogenic copy number variants (pCNVs) in prenatal cases were 13.03%, 1.77%, 1.69%, and 0.9%, respectively, and were 5.13%, 2.84%, 7.08%, and 2.69% in pediatric cases, respectively. The chromosomal abnormalities detected in prenatal cases (14.80%) were significantly higher than that of pediatric cases (7.97%) (p < 0.05), while the pCNVs detected in prenatal cases (2.59%) were significantly lower than that of pediatric cases (9.77%) (p < 0.05). The prevalence of recurrent genomic disorders and total pCNVs was estimated to be 1/396 and 1/291, respectively. Approximately, 29% and 35% of cytogenomic abnormalities expected from the population served were detected in current prenatal and pediatric diagnostic practice, respectively.

Conclusion: For chromosomal abnormalities, effective detection of Down syndrome (DS) and Turner syndrome (TS) and under detection of sex chromosome numerical abnormalities in both prenatal and pediatric cases were noted. For pCNVs, under detection of pCNVs in prenatal cases and effective detection of DiGeorge syndrome (DGS) and variable efficacy in detecting other pCNVs in pediatric cases were noted. Extend aCGH analysis to more prenatal cases with fetal ultrasonographic anomalies, enhanced non-invasive prenatal (NIPT) testing screening for syndromic genomic disorders, and better clinical indications for pCNVs are approaches that could improve diagnostic yield of cytogenomic abnormalities.

Chromosomal Aberrations in Pediatric Patients with Developmental Delay/Intellectual Disability: A Single-Center Clinical Investigation

Introduction

Chromosomal microarray analysis (CMA) has currently been considered as the first-tier genetic test for patients with developmental delay/intellectual disability (DD/ID) in many countries. In this study, we performed an extensive assessment of the value of CMA for the diagnosis of children with ID/DD in China.

Methods

A total of 633 patients diagnosed with DD/ID in West China Second University Hospital, Sichuan University, were recruited from January 2014 to March 2019. The patients were classified into 4 subgroups: isolated DD/ID, DD/ID with multiple congenital anomalies (MCA), isolated autism spectrum disorders (ASDs), and DD/ID with epilepsy. CMA was performed on Affymetrix 750K platform.

Results

Among the 633 patients, 127 cases were identified as having pathogenic copy number variations (pCNVs) with an overall positive rate of 20.06%. Of the 127 cases with abnormal results, 76 cases had 35 types of microdeletion/microduplication syndromes (59.84%) including 5 cases caused by uniparental disomy (UPD), and 18 cases had unbalanced rearrangements (14.17%) including 10 cases inherited from parental balanced translocations or pericentric inversions. The diagnostic yields of pCNVs for the subgroups of isolated DD/ID, DD/ID with MCA, isolated ASD, and DD/ID with epilepsy were 18.07% (60/332), 34.90% (52/149), 3.70% (3/81), and 16.90% (12/71), respectively. The diagnostic yield of pCNVs in DD/ID patients with MCA was significantly higher than that of the other three subgroups, and the diagnostic yield of pCNVs in isolated ASD patients was significantly lower than that of the other three subgroups (p < 0.05).

Conclusion

Microdeletion/microduplication syndromes and unbalanced rearrangements are probably the main genetic etiological factors for DD/ID. DD/ID patients with MCA have a higher rate of chromosomal aberrations. Parents of DD/ID children with submicroscopic unbalance rearrangements are more likely to have chromosome balanced translocations or pericentric inversions, which might have been missed by karyotyping. CMA can significantly improve the diagnostic rate for patients with DD/ID, which is of great value for medical management and clinical guidance for genetic counseling.

Technical standards for the interpretation and reporting of constitutional copy-number variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resource (ClinGen)

Copy number analysis to detect disease-causing losses and gains across the genome is recommended for the evaluation of individuals with neurodevelopmental disorders and/or multiple congenital anomalies, as well as for fetuses with ultrasound abnormalities. In the decade that this analysis has been in widespread clinical use, tremendous strides have been made in understanding the effects of copy number variants (CNVs) in both affected individuals and the general population. However, continued broad implementation of array- and next-generation sequencing-based technologies will expand the types of CNVs encountered in the clinical setting, as well as our understanding of their impact on human health. To assist clinical laboratories in the classification and reporting of CNVs, irrespective of the technology used to identify them, the American College of Medical Genetics and Genomics has developed the following professional standards in collaboration with the NIH-funded Clinical Genome Resource (ClinGen) project. This update introduces a quantitative, evidence-based scoring framework; encourages the implementation of the 5-tier classification system widely used in sequence variant classification; and recommends “uncoupling” the evidence-based classification of a variant from its potential implications for a particular individual. These professional standards will guide the evaluation of constitutional CNVs and encourage consistency and transparency across clinical laboratories.

Epidemiology of fetal cerebral ventriculomegaly and evaluation of chromosomal microarray analysis versus karyotyping for prenatal diagnosis in a Chinese hospital

Objective

To evaluate the efficiency and incremental value of chromosomal microarray analysis as compared with standard karyotyping for the identification of genomic abnormalities in fetal DNA.

Methods

This retrospective study enrolled female patients with ultrasonographically diagnosed fetal ventriculomegaly. The prevalence, associated anomalies and clinical outcomes of ventriculomegaly were evaluated based on data from a single maternal and child health hospital in southwest China.

Results

A total of 943 cases of ventriculomegaly were analysed in this study, which were diagnosed at a mean ± SD gestational age of 23.8 ± 8.2 weeks. Non-isolated ventriculomegaly cases had a significantly higher maternal age than isolated cases (29.6 ± 5.5 versus 27.9 ± 4.2 years, respectively) and were also associated with a larger proportion of bilateral (56.1% versus 46.7%, respectively) and severe (12.8% versus 3.7%, respectively) ventriculomegaly. There were 97 cases detected by both karyotyping and microarray analysis. All apparent chromosome abnormalities identified upon karyotyping were detected with the use of microarray analysis. Microarray analysis also reported genetic abnormalities in 20 additional cases not detected by karyotyping. Of these additional 20 cases, 9.3% of pregnancies reported standard genetic variants for clinically relevant information, whereas 11.3% reported uncertain genetic abnormalities.

Conclusion

Chromosomal microarray analysis is an efficient tool, significantly increasing the diagnostic power for prenatal diagnosis.

Prenatal diagnosis of Desbuquois dysplasia Type 1: Utilization of high-density SNP array to map homozygosity and identify the gene

Desbuquois dysplasia (DBQD1 [MIM 251450]) is an autosomal recessive chondrodysplasia with micromelia, severe joint laxity and dislocations, and a characteristic radiographic "monkey wrench" appearance at the proximal femur. Type 1 Desbuquois dysplasia is caused by mutations in CANT1 and is distinct from Type 2, caused by mutations in XYLT1, in that the former has unique hand anomalies including accessory phalangeal ossification centers, advanced carpal bone maturation, and/or axial phalangeal deviation. Severe prenatal presentations have been rarely reported. We report a Pakistani female in a consanguineous relationship with a diagnosis of Type 1 Desbuquois dysplasia in three consecutive pregnancies. Multiple similar severe fetal limb anomalies were detected by ultrasound in Pregnancy 1 and 2. Regions of homozygosity within the single nucleotide polymorphism (SNP)-microarray from both terminated fetuses were compared, revealing CANT1 as a likely disease-causing candidate gene. Insufficient fetal DNA precluded confirmatory testing, therefore parents were tested; both had a previously reported heterozygous CANT1 mutation (c.643G>T; Glu215Term). The patient presented with a third pregnancy revealing similarly abnormal limb position and probable polysyndactyly by ultrasound. Targeted testing of CANT1 revealed homozygous c.643G>T CANT1 mutations and this pregnancy was terminated. In clinical situations in which ample DNA is not available or more expensive testing (e.g., whole exome sequencing) with a longer turnaround time is not feasible, utilization of SNP-microarray in consanguineous families at risk for rare autosomal recessive disorders may dramatically narrow the list of candidate genes.

Diagnostic interpretation of genetic studies in patients with primary immunodeficiency diseases: A working group report of the Primary Immunodeficiency Diseases Committee of the American Academy of Allergy, Asthma & Immunology

Genetic testing has become an integral component of the diagnostic evaluation of patients with suspected primary immunodeficiency diseases. Results of genetic testing can have a profound effect on clinical management decisions. Therefore clinical providers must demonstrate proficiency in interpreting genetic data. Because of the need for increased knowledge regarding this practice, the American Academy of Allergy, Asthma & Immunology Primary Immunodeficiency Diseases Committee established a work group that reviewed and summarized information concerning appropriate methods, tools, and resources for evaluating variants identified by genetic testing. Strengths and limitations of tests frequently ordered by clinicians were examined. Summary statements and tables were then developed to guide the interpretation process. Finally, the need for research and collaboration was emphasized. Greater understanding of these important concepts will improve the diagnosis and management of patients with suspected primary immunodeficiency diseases.

Detection of copy number disorders associated with congenital anomalies of the kidney and urinary tract in fetuses via single nucleotide polymorphism arrays

Background

While congenital anomalies of the kidney and urinary tract (CAKUT) constitute one‐third of all congenital malformations, the mechanisms underlying their development are poorly understood. Some studies have reported an association between CAKUT and copy number variations (CNVs) in children and adults, but few have focused on chromosomal microarray analysis (CMA) findings in fetuses with CAKUT. Therefore, we aimed to perform a CMA on fetuses with CAKUT and normal karyotypes in the presence and absence of other structural anomalies.

Method

The study was conducted in 147 fetuses with CAKUT and normal karyotypes between January 2016 and January 2019 in the Fujian Provincial Maternal and Child Health Hospital. Single nucleotide polymorphism (SNP) analysis was performed using the Affymetrix CytoScan HD platform.

Results

The SNP array identified abnormal CNVs in 13 cases (8.8%): Six were pathogenic, and seven were variations of uncertain clinical significance (VOUS). The detection rate of abnormal CNVs in non‐isolated CAKUT was higher than that in isolated CAKUT (22.7% vs 6.4%, P = .038). Within the abnormal CNV groups, the highest frequency of CNVs was identified in fetuses with polycystic kidney dysplasia (13.5%), followed by those with renal agenesis (10.5%).

Conclusion

SNP array is effective for identifying chromosomal abnormalities in CNVs in fetuses with CAKUT and normal karyotypes, and help counseling.

A Novel Homozygous Deletion within the FRY Gene Associated with Nonsyndromic Developmental Delay

The role of autosomal recessive (AR) variants in clinically heterogeneous conditions such as intellectual disability and developmental delay (ID/DD) has been difficult to uncover. Implication of causative pathogenic AR variants often requires investigation within large and consanguineous families, and/or identifying rare biallelic variants in affected individuals. Furthermore, detection of homozygous gene-level copy number variants during first-line genomic microarray testing in the pediatric population is a rare finding. We describe a 6.7-year-old male patient with ID/DD and a novel homozygous deletion involving the FRY gene identified by genomic SNP microarray. This deletion was observed within a large region of homozygosity on the long arm of chromosome 13 and in a background of increased low-level (2.6%) autosomal homozygosity, consistent with a reported common ancestry in the family. FRY encodes a protein that regulates cell cytoskeletal dynamics, functions in chromosomal alignment in mitosis in vitro, and has been shown to function in the nervous system in vivo. Homozygous mutation of FRY has been previously reported in 2 consanguineous families from studies of autosomal recessive ID in Middle Eastern and Northern African populations. This report provides additional supportive evidence that deleterious biallelic mutation of FRY is associated with ID/DD and illustrates the utility of genomic SNP microarray detection of low-level homozygosity.

Prenatal detection of interstitial 18p11.31-p11.22 microduplications: Phenotypic diversity and literature review

INTRODUCTION

Pure duplication of chromosome 18p is rare, with clinical phenotypes ranging from normal or slight abnormalities to various degrees of mental retardation. It remains difficult to establish a clear genotype-phenotype correlation.

METHODS

Chromosomal karyotyping analysis was performed on cultured amniotic fluid cells from three cases. Single nucleotide polymorphism (SNP) array analysis was carried out using the Illumina Human CytoSNP-12 BeadChip. We also carried out a review of the literature regarding 18p11 microduplication.

RESULTS

G-banding analysis showed that the three cases had normal karyotypes. SNP array results showed 0.48- to 1.6-Mb microduplications of 18p11.31-p11.22 (chr18: 6995739-8713088) in these cases, encompassing different degrees of LAMA1 duplication. Follow-up analysis showed that the parents of both cases 1 and 2 chose termination of pregnancy. Case 3 presented with normal growth and physical development. Currently, there is not enough evidence supporting the pathogenicity of LAMA1 triplosensitivity.

CONCLUSION

We described three prenatal cases with 18p11.31-p11.22 microduplications involving part of the LAMA1 locus. There might be phenotypic diversity associated with 18p11.31-p11.22 microduplications. To avoid unnecessary abortions for pregnancies such as these, comprehensive genetic counseling should be offered.

Genetic testing in fetuses with isolated agenesis of the corpus callosum

PURPOSE

The objectives of this study were to explore genetics pathogenesis of isolated agenesis of corpus callosum (ACC) and assess the utility of chromosomal microarray analysis (CMA) for genetic diagnosis of isolated ACC.

METHODS

We analyzed the genomes of 16 fetuses with isolated ACC using Afymetrix CytoScan HD arrays and conducted further bioinformatic analysis for one proband fetus with an abnormal copy number variation (CNV).

RESULTS

Of the 16 fetal samples examined, two (12.5%) had pathogenic CNVs and three (18.75%) had variants of unknown significance. Two cases, case 2 and case 9, were found to have pathogenic CNVs. Bioinformatic analyses indicated that the CNV of one fetus (case 9) contained 115 annotated coding genes, five of which (SLC6A5, BDNF, ELP4, PAX6, and SLC1A2) have been associated with neurodevelopment. Three of these genes (SLC1A2, BDNF, and PAX6) may play a key role in ACC development. GO cluster analysis of the implicated genes revealed strong representations of protein binding and metal ion binding functions. KEGG pathway analysis pointed to four pathways: longevity regulating pathway, amyotrophic lateral sclerosis, cocaine addiction, and autophagy-animal.

CONCLUSIONS

BDNF, SLC1A2, and PAX6 may be involved in the development of isolated ACC. CMA is a feasible technology for prenatal diagnosis of isolated ACC.

Fabrication of Inverted High-Density DNA Microarrays in a Hydrogel

Current techniques for making high-resolution, photolithographic DNA microarrays suffer from the limitation that the 3' end of each sequence is anchored to a hard substrate and hence is unavailable for many potential enzymatic reactions. Here, we demonstrate a technique that inverts the entire microarray into a hydrogel. This method preserves the spatial fidelity of the original pattern while simultaneously removing incorrectly synthesized oligomers that are inherent to all other microarray fabrication strategies. First, a standard 5'-up microarray on a donor wafer is synthesized, in which each oligo is anchored with a cleavable linker at the 3' end and an Acrydite phosphoramidite at the 5' end. Following the synthesis of the array, an acrylamide monomer solution is applied to the donor wafer, and an acrylamide-silanized acceptor wafer is placed on top. As the polyacrylamide hydrogel forms between the two wafers, it covalently incorporates the acrydite-terminated sequences into the matrix. Finally, the oligos are released from the donor wafer upon immersing in an ammonia solution that cleaves the 3'-linkers, thus freeing the oligos at the 3' end. The array is now presented 3'-up on the surface of the gel-coated acceptor wafer. Various types of on-gel enzymatic reactions demonstrate a versatile and robust platform that can easily be constructed with far more molecular complexity than traditional photolithographic arrays by endowing the system with multiple enzymatic substrates. We produce a new generation of microarrays where highly ordered, purified oligos are inverted 3'-up, in a biocompatible soft hydrogel, and functional with respect to a wide variety of programable enzymatic reactions.

Preserved expressive language as a phenotypic determinant of Mosaic Angelman Syndrome

Background

Angelman Syndrome (AS) is a neurodevelopmental disorder with core features of intellectual disability, speech impairment, movement disorders, and a unique behavioral profile. Typically, AS results from absent maternal expression of UBE3A, but some individuals have imprinting defects in a portion of their cells. These individuals are mosaic for normal and defective UBE3A expression, resulting in mosaic AS (mAS) with a partial loss of gene expression.

Methods

This study aims to contrast the mAS phenotype to that of AS. Clinical characteristics of mAS were obtained from a parental survey of 22 mAS patients and from the Angelman Natural History study. These were contrasted with those of AS using historical data.

Results

Developmental delay was present in nearly all mAS patients, whereas the core features of AS were reported in less than 40%. While language and ability to manage activities of daily living were markedly improved over that expected in AS, mAS patients demonstrated a high incidence of behavioral challenges.

Conclusion

Clinical work‐up of an individual with developmental delay, hyperactivity, anxiety, and an uncharacteristically happy demeanor should prompt methylation studies to rule out mAS. We expand the phenotypic spectrum of AS to include features that overlap with Prader‐Willi such as hyperphagia.

The clinical benefit of array-based comparative genomic hybridization for detection of copy number variants in Czech children with intellectual disability and developmental delay

BACKGROUND

Chromosomal microarray analysis has been shown to be a valuable and cost effective assay for elucidating copy number variants (CNVs) in children with intellectual disability and developmental delay (ID/DD).

METHODS

In our study, we performed array-based comparative genomic hybridization (array-CGH) analysis using oligonucleotide-based platforms in 542 Czech patients with ID/DD, autism spectrum disorders and multiple congenital abnormalities. Prior to the array-CGH analysis, all the patients were first examined karyotypically using G-banding. The presence of CNVs and their putative derivation was confirmed using fluorescence in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA) and predominantly relative quantitative polymerase chain reaction (qPCR).

RESULTS

In total, 5.9% (32/542) patients were positive for karyotypic abnormalities. Pathogenic/likely pathogenic CNVs were identified in 17.7% of them (96/542), variants of uncertain significance (VOUS) were detected in 4.8% (26/542) and likely benign CNVs in 9.2% of cases (50/542). We identified 6.6% (36/542) patients with known recurrent microdeletion (24 cases) and microduplication (12 cases) syndromes, as well as 4.8% (26/542) patients with non-recurrent rare microdeletions (21 cases) and microduplications (5 cases). In the group of patients with submicroscopic pathogenic/likely pathogenic CNVs (13.3%; 68/510) we identified 91.2% (62/68) patients with one CNV, 5.9% (4/68) patients with two likely independent CNVs and 2.9% (2/68) patients with two CNVs resulting from cryptic unbalanced translocations. Of all detected CNVs, 21% (31/147) had a de novo origin, 51% (75/147) were inherited and 28% (41/147) of unknown origin. In our cohort pathogenic/likely pathogenic microdeletions were more frequent than microduplications (69%; 51/74 vs. 31%; 23/74) ranging in size from 0.395 Mb to 10.676 Mb (microdeletions) and 0.544 Mb to 8.156 Mb (microduplications), but their sizes were not significantly different (P = 0.83). The pathogenic/likely pathogenic CNVs (median 2.663 Mb) were significantly larger than benign CNVs (median 0.394 Mb) (P < 0.00001) and likewise the pathogenic/likely pathogenic CNVs (median 2.663 Mb) were significantly larger in size than VOUS (median 0.469 Mb) (P < 0.00001).

CONCLUSIONS

Our results confirm the benefit of array-CGH in the current clinical genetic diagnostics leading to identification of the genetic cause of ID/DD in affected children.

The rare 13q33-q34 microdeletions: eight new patients and review of the literature

The objective of this study is to shed light on the phenotype and inheritance pattern of rare 13q33-q34 microdeletions. Appropriate cases were retrieved using local databases of two largest Israeli centers performing CMA analysis. In addition, literature search in PubMed, DECIPHER and ClinVar databases was performed. Local database search yielded eight new patients with 13q33.1-q34 microdeletions (three of which had additional copy number variants). Combined with 15 cases detected by literature search, an additional 23 cases were reported in DECIPHER database, and 17 cases from ClinVar, so overall 60 patients with isolated 13q33.1-q34 microdeletions were described. Developmental delay and/or intellectual disability were noted in the vast majority of affected individuals (81.7% = 49/60). Of the 23 deletions involving the 13q34 cytoband only, in 3 cases, developmental delay and/or intellectual disability was not reported. Interestingly, in two of these cases (66.7%), the deletions did not involve the terminal CHAMP1 gene, as opposed to 3/20 (15%) of patients with 13q34 deletions and neurocognitive disability. Facial dysmorphism and microcephaly were reported in about half of the overall cases, convulsions were noted in one-fifth of the patients, while heart anomalies, short stature and hypotonia each involved about 10-30% of the cases. None of the 13q33-q34 deletions were inherited from a reported healthy parent. 13q33-q34 microdeletions are rare chromosomal aberrations, associated with high risk for neurodevelopmental disability. The rarity of this chromosomal aberration necessitates continuous reporting and collection of available evidence, to improve the ability to provide accurate genetic counseling, especially in the context of prenatal setting.

Additive Diagnostic Yield of Homozygosity Regions Identified During Chromosomal microarray Testing in Children with Developmental Delay, Dysmorphic Features or Congenital Anomalies

Chromosomal microarray (CMA) has emerged as a robust tool for identifying microdeletions and microduplications, termed copy number variants (CNVs). Nevertheless, data regarding its utility in different patient populations with developmental delay (DD), dysmorphic features (DF) and congenital anomalies (CA), is a matter of dense debate. Although regions of homozygosity (ROH) are not diagnostic of a specific condition, they may have pathogenic implications. Certain CNVs and ROH have ethnically specific occurrences and frequencies. We aimed to determine whether CMA testing offers additional diagnostic information over classical cytogenetics for identifying genomic imbalances in a pediatric cohort with idiopathic DD, DF, or CA. One hundred sixty-nine patients were offered cytogenetics and CMA simultaneously for etiological diagnosis of DD (n = 67), DF (n = 52) and CA (n = 50). CMA could identify additional, clinically significant anomalies as compared with cytogenetics. CMA detected 61 CNVs [21 (34.4%) pathogenic CNVs, 37 (60.7%) variants of uncertain clinical significance and 3 (4.9%) benign CNVs] in 44 patients. CMA identified one or more ROH in 116/169 (68.6%) patients. When considering pathogenic CNVs and aneuploidies as positive findings, 9/169 (5.3%) received a genetic diagnosis from cytogenetics, while 25/169 (14.8%) could have a genetic diagnosis from CMA. The identification of ROH was clinically significant in two cases (2/169), thereby, adding 1.2% to the diagnostic yield of CMA (16% vs. 5.3%, p < 0.001). CMA uncovers additional genetic diagnoses over cytogenetics, thereby, offering a much higher diagnostic yield. Our findings convincingly demonstrate the additive diagnostic value of clinically significant ROH identified during CMA testing, highlighting the need for careful clinical interpretation of these ROH.

[Application of single nucleotide polymorphism microarray in clinical diagnosis of intellectual disability or retardation]

OBJECTIVE

To assess the clinical application of single nucleotide polymorphism microarray (SNP array) in patients with intellectual disability/developmental delay(ID/DD).

METHODS

SNP array was performed to detect genome-wide DNA copy number variants (CNVs) for 145 patients with ID/DD in Women's Hospital, Zhejiang University School of Medicine from January 2013 to June 2018. The CNVs were analyzed by CHAS software and related databases.

RESULTS

Among 145 patients, pathogenic chromosomal abnormalities were detected in 32 cases, including 26 cases of pathogenic CNVs and 6 cases of likely pathogenic CNVs. Meanwhile, 18 cases of uncertain clinical significance and 14 cases of likely benign were identified, no significant abnormalities were found in 81 cases (including benign).

CONCLUSIONS

SNP array is effective for detecting chromosomal abnormalities in patients with ID/DD with high efficiency and resolution.

Meta-analysis and multidisciplinary consensus statement: exome sequencing is a first-tier clinical diagnostic test for individuals with neurodevelopmental disorders

Purpose

For neurodevelopmental disorders (NDDs), etiological evaluation can be a diagnostic odyssey involving numerous genetic tests, underscoring the need to develop a streamlined algorithm maximizing molecular diagnostic yield for this clinical indication. Our objective was to compare the yield of exome sequencing (ES) with that of chromosomal microarray (CMA), the current first-tier test for NDDs.

Methods

We performed a PubMed scoping review and meta-analysis investigating the diagnostic yield of ES for NDDs as the basis of a consensus development conference. We defined NDD as global developmental delay, intellectual disability, and/or autism spectrum disorder. The consensus development conference included input from genetics professionals, pediatric neurologists, and developmental behavioral pediatricians.

Results

After applying strict inclusion/exclusion criteria, we identified 30 articles with data on molecular diagnostic yield in individuals with isolated NDD, or NDD plus associated conditions (such as Rett-like features). Yield of ES was 36% overall, 31% for isolated NDD, and 53% for the NDD plus associated conditions. ES yield for NDDs is markedly greater than previous studies of CMA (15–20%).

Conclusion

Our review demonstrates that ES consistently outperforms CMA for evaluation of unexplained NDDs. We propose a diagnostic algorithm placing ES at the beginning of the evaluation of unexplained NDDs.