European guidelines for constitutional cytogenomic analysis

The Need for a Concert of Cytogenomic Methods in Chromosomic Research and Diagnostics

This review focuses on the experimental methods and technologies of cytogenomics and how they can be combined in the process of chromosomic diagnostics and research. It is stressed that no cytogenomic methods can be comprehensive on their own. The strengths and weaknesses of each method have to be considered. This is especially important in a time where the main stream of human genetics diagnostics is actively proclaiming that high throughput methods are able to replace all other established tests.

The CAP/ACMG CYCGH proficiency testing program: 10 years in review

PURPOSE

The College of American Pathologists has offered proficiency testing (PT) for the detection of copy-number variations (CNV) in the constitutional setting (CYCGH) since 2008. We review and summarize data from the CYCGH PT program, including participant performance over time, changes made to the program, and ungraded challenges.

METHODS

The PT challenges from 2011 through 2021 (22 total mailings) and changes to the program over time were reviewed. Laboratory enrollment and performance were assessed.

RESULTS

Overall participation has increased over time, and laboratories have maintained a high level of proficiency. The major changes to the program have occurred twice during the time span examined. Reasons for challenges not meeting consensus were varied. The use of ungraded challenges was also discussed.

CONCLUSION

The CYCGH PT program is challenging because it assesses both analytical performance and interpretation as a single analyte. The program has evolved over time to address the changes in the field of CNV detection. During this time, additional technologies with the ability to detect CNVs have emerged, and the possibility of developing a platform-agnostic CNV PT program is being explored.

Long-Read Whole-Genome Sequencing as a Tool for Variant Detection in Inherited Retinal Dystrophies

Advances in whole-genome sequencing (WGS) have significantly enhanced our ability to detect genomic variants underlying inherited diseases. In this study, we performed long-read WGS on 24 patients with inherited retinal dystrophies (IRDs) to validate the utility of nanopore sequencing in detecting genomic variations. We confirmed the presence of all previously detected variants and demonstrated that this approach allows for the precise refinement of structural variants (SVs). Furthermore, we could perform genotype phasing by sequencing only the probands, confirming that the variants were inherited in trans. Moreover, nanopore sequencing enables the detection of complex variants, such as transposon insertions and structural rearrangements. This comprehensive assessment illustrates the power of long-read sequencing in capturing diverse forms of genomic variation and in improving diagnostic accuracy in IRDs.

Morphology combined with HER2 D-DISH ploidy analysis to diagnose partial hydatidiform mole: an evaluation audit using molecular genotyping

AIMS

A hydatidiform mole (HM) is classified as complete (CHM) or partial (PHM) based on its morphology and genomic composition. Ancillary techniques are often required to confirm a morphologically suspected PHM diagnosis. This study sought to evaluate the clinical accuracy of PHM diagnosis using morphological assessment supported by HER2 dual-colour dual-hapten in situ hybridisation (D-DISH) ploidy determination.

METHODS

Over a 2-year period, our unit examined 1265 products of conception (POCs) from which 103 atypical POCs were diagnosed as PHM or non-molar conceptuses with the assistance of HER2 D-DISH ploidy analysis. We retrospectively audited a sample of 40 of these atypical POCs using short tandem repeat genotyping. DNA extracted from formalin-fixed paraffin-embedded tissue was genotyped using 24 polymorphic loci. Parental alleles in placental villi were identified by comparison to those in maternal decidua. To identify triploid PHM cases, we sought three alleles of equal peak height or two alleles with one allele peak twice the height of the other at each locus.

RESULTS

Thirty-six of the 40 cases (19 PHM and 17 non-molar) were successfully genotyped and demonstrated complete concordance with the original diagnosis. All PHMs were diandric triploid of dispermic origin. In two non-molar diploid cases, we identified suspected trisomies (13 and 18), which potentially explains the pregnancy loss in these cases.

CONCLUSIONS

This study validates the use of HER2 D-DISH ploidy analysis to support the diagnosis of a morphologically suspected PHM in our practice.

Low-pass whole genome sequencing as a cost-effective alternative to chromosomal microarray analysis for low- and middle-income countries

Low-pass whole genome sequencing (LP-WGS) has been applied as alternative method to detect copy number variants (CNVs) in the clinical setting. Compared with chromosomal microarray analysis (CMA), the sequencing-based approach provides a similar resolution of CNV detection at a lower cost. In this study, we assessed the efficiency and reliability of LP-WGS as a more affordable alternative to CMA. A total of 1363 patients with unexplained neurodevelopmental delay/intellectual disability, autism spectrum disorders, and/or multiple congenital anomalies were enrolled. Those patients were referred from 15 nonprofit organizations and university centers located in different states in Brazil. The analysis of LP-WGS at 1x coverage (>50kb) revealed a positive testing result in 22% of the cases (304/1363), in which 219 and 85 correspond to pathogenic/likely pathogenic (P/LP) CNVs and variants of uncertain significance (VUS), respectively. The 16% (219/1363) diagnostic yield observed in our cohort is comparable to the 15%-20% reported for CMA in the literature. The use of commercial software, as demonstrated in this study, simplifies the implementation of the test in clinical settings. Particularly for countries like Brazil, where the cost of CMA presents a substantial barrier to most of the population, LP-WGS emerges as a cost-effective alternative for investigating copy number changes in cytogenetics.

Clinical validation of an abbreviated karyotype analysis protocol for fertility evaluation

Conventional G-banded karyotype is an essential tool for detecting chromosomal variants in patients undergoing fertility evaluation. In Australia, 15 cells are traditionally analysed or counted, to enhance detection of mosaic chromosomal variants. However, this protocol is not backed by clinical evidence. This study aims to assess the test performance of an abbreviated 5-cell karyotype analysis protocol in adult patients undergoing fertility evaluation. A retrospective review of 53,293 blood karyotype tests, performed between 2019 and 2023, was conducted on a patient cohort primarily referred by reproductive endocrinology specialists. There were 513 variants reported in this cohort. Low level mosaic variants, where the variant was observed in less than 40% of cells, were reported in 13 cases, or one in 4,100 patients. Due to reduced sensitivity for low level mosaic variants, a 5-cell protocol is estimated to have a test sensitivity of 97.3% and a negative predictive value of 99.97%. A decision-making flowchart is proposed and we show that additional chromosome analysis and/or counts would be triggered in fewer than one in 10 cases using a 5-cell protocol, whilst remaining appropriate for detecting clinically significant mosaicism. A 5-cell karyotype analysis protocol therefore maintains analytical and clinical validity in adult patients undergoing fertility-related blood karyotyping. Future research is recommended to validate these findings across laboratories and to explore their application to other clinical contexts.

Array Comparative Genomic Hybridization (aCGH) Results among Patients Referred to Invasive Prenatal Testing after First-Trimester Screening: A Comprehensive Cohort Study

Introduction: Invasive prenatal testing with chromosomal microarray analysis after first-trimester screening is a relevant option but there is still debate regarding the indications. Therefore, we evaluated the prevalence of numerical chromosomal aberrations detected by classic karyotype and clinically relevant copy number variants (CNVs) in prenatal samples using array comparative genomic hybridization (aCGH) stratified to NT thickness: 4.5 mm, and by the presence/absence of associated structural anomalies detected by ultrasonography. Materials and Methods: Retrospective cohort study carried out at two tertiary Polish centers for prenatal diagnosis (national healthcare system) in central and south regions from January 2018 to December 2021. A total of 1746 prenatal samples were received. Indications for invasive prenatal testing included high risk of Down syndrome in the first-trimester combined test (n = 1484) and advanced maternal age (n = 69), and, in 193 cases, other reasons, such as parental request, family history of congenital defects, and genetic mutation carrier, were given. DNA was extracted directly from amniotic fluid (n = 1582) cells and chorionic villus samples (n = 164), and examined with classic karyotype and aCGH. Results: Of the entire cohort of 1746 fetuses, classical karyotype revealed numerical chromosomal aberrations in 334 fetuses (19.1%), and aCGH detected CNV in 5% (n = 87). The frequency of numerical chromosomal aberrations increased with NT thickness from 5.9% for fetuses with NT < p95th to 43.3% for those with NT > 4.5 mm. The highest rate of numerical aberrations was observed in fetuses with NT > 4.5 mm having at least one structural anomaly (50.2%). CNVs stratified by NT thickness were detected in 2.9%, 2.9%, 3.5%, 4.3%, 12.2%, and 9.0% of fetuses with NT < 95th percentile, 95th percentile-2.9 mm, 3.0-3.4 mm, 3.5-3.9 mm, 4.0-4.5 mm, and >4.5 mm, respectively. After exclusion of fetuses with structural anomalies and numerical aberrations, aCGH revealed CNVs in 2.0% of fetuses with NT < 95th percentile, 1.5% with NTp95-2.9 mm, 1.3% with NT 3.0-3.4 mm, 5.4% with NT 3.5-3.9 mm, 19.0% with NT 4.0-4.5 mm, and 14.8% with NT > 4.5 mm. Conclusions: In conclusion, our study indicates that performing aCGH in samples referred to invasive prenatal testing after first-trimester screening provides additional clinically valuable information over conventional karyotyping, even in cases with normal NT and anatomy.

Genetic landscape of thrombophilia in recurrent miscarriages

The etiology of recurrent miscarriage (RM) is extremely heterogeneous, encompassing genetic, immunological, anatomical, endocrine, thrombophilic, infectious, and uterine abnormalities. Thrombophilia is a major contributor to pregnancy complications, potentially harming the fetus and jeopardizing the continuation of pregnancy. Therefore, successful pregnancy outcomes depend on maintaining a delicate balance between coagulation and fibrinolytic factors, crucial for ensuring the adjustment of the basal plate to facilitate adequate placental perfusion. Despite numerous studies shedding light on the role of thrombophilic factors and genetic variations in RM, the exact pathogenesis remains unclear. It is imperative to systematically rule out thrombophilia and other related factors responsible for pregnancy disorders and RMs to guide appropriate and active management strategies. Addressing thrombophilia continues to present challenges in terms of effective treatment. The current review aims to address the heterogeneity of RM as a therapeutic challenge, emphasizing the need for standardized diagnostic tests and welldesigned multicenter research trials to gather robust, evidence-based data on thrombophilic causes of RM and provide effective treatment. The goal is to enhance the understanding of thrombophilic factors and genetic landscapes associated with RM through various approaches, including candidate gene studies, genome-wide association studies, and high-throughput sequencing. Meta-analyses have underscored the significance of genetic aberrations in RM, highlighting the necessity for identifying critical mutations implicated in the etiopathogenesis of miscarriages to pave the way for implementation of targeted clinical therapies.

Analysis of parental origin of de novo pathogenic CNVs in patients with intellectual disability

Chromosomal Microarray Analysis (CMA) has increased the comprehension of the mechanisms of copy number variation (CNV) formation, classification of these rearrangements, type of recurrence, and its origin, and has also been a powerful approach to identifying CNVs in individuals with intellectual disability. The aim of this study was to establish the parental origin of de novo pathogenic CNV in a cohort of patients with intellectual disability from the public health system of Goiás-Brazil. CMA was done in 76 trios and we identified 15 de novo pathogenic CNVs in 12 patients with intellectual disability. In a total of 15 de novo pathogenic CNV, 60% were derived from the maternal germline and 40% from the paternal germline. CNV flanked by low copy repeats (LCR) were identified in 46.7% and most of them were of maternal origin. No significant association was observed between paternal age and the mutation rate of de novo CNVs. The presence of high-identity LCRs increases the occurrence of CNV formation mediated by non-allelic homologous recombination and the majority of paternal CNVs are non-recurrent. The mechanism of formation of these CNV may have been by microhomology-mediated break-induced replication or non-homologous end joining.

Performance of Massive Parallel Sequencing-Based Cell-Free DNA Testing in Compromised Pregnancies

Background/Objectives: Non-Invasive prenatal test (NIPT) is used as a universal or contingent test after prior risk assessment. Screening is mainly performed for common trisomies (T21, T13, T18), although other chromosomal anomalies may be detected. Our objective was to study the performance of GWNIPT in the detection of chromosomal abnormalities in pregnancies in which an invasive prenatal study was performed and in early pregnancy losses, in comparison with the reference test. Method: VeriSeqTM NIPT Solution v2, a genome-wide NIPT (GWNIPT), was performed prior to invasive testing in fetal diagnostic study cases (FDS, n = 155) and in early pregnancy losses (EPL, n = 68). Results: In the FDS group, the diagnostic test (QFPCR, array and karyotype) detected anomalies in 32 pregnancies (21%), in twenty of them (61%) also detected by GWNIPT. Eleven of the twelve cases undetected by GWNIPT were balanced translocations (n = 4) or deletions/duplications <7 Mb (n = 7). In the EPL group, GWNIPT detected anomalies in 46% of cases (31/68) but comparison with reference test (QFPCR and karyotype) in products of conception (POC) was only possible in 18 cases. Concordant results between POC and GWNIPT test were obtained in 16 of the 18 cases. In EPL, with GWNIPT testing, common trisomies accounted for 25.8% of cases (8/31), rare trisomies 54.8% (17/31) and microdeletions/duplications 16.1% (5/31). Conclusions: The GWNIPT test may be useful in clinical practice in prenatal and in EPL's genetic diagnosis when the appropriate sample is not available.

Clinical practice guidelines for the care of girls and women with Turner syndrome

Turner syndrome (TS) affects 50 per 100 000 females. TS affects multiple organs through all stages of life, necessitating multidisciplinary care. This guideline extends previous ones and includes important new advances, within diagnostics and genetics, estrogen treatment, fertility, co-morbidities, and neurocognition and neuropsychology. Exploratory meetings were held in 2021 in Europe and United States culminating with a consensus meeting in Aarhus, Denmark in June 2023. Prior to this, eight groups addressed important areas in TS care: (1) diagnosis and genetics, (2) growth, (3) puberty and estrogen treatment, (4) cardiovascular health, (5) transition, (6) fertility assessment, monitoring, and counselling, (7) health surveillance for comorbidities throughout the lifespan, and (8) neurocognition and its implications for mental health and well-being. Each group produced proposals for the present guidelines, which were meticulously discussed by the entire group. Four pertinent questions were submitted for formal GRADE (Grading of Recommendations, Assessment, Development and Evaluation) evaluation with systematic review of the literature. The guidelines project was initiated by the European Society for Endocrinology and the Pediatric Endocrine Society, in collaboration with members from the European Society for Pediatric Endocrinology, the European Society of Human Reproduction and Embryology, the European Reference Network on Rare Endocrine Conditions, the Society for Endocrinology, and the European Society of Cardiology, Japanese Society for Pediatric Endocrinology, Australia and New Zealand Society for Pediatric Endocrinology and Diabetes, Latin American Society for Pediatric Endocrinology, Arab Society for Pediatric Endocrinology and Diabetes, and the Asia Pacific Pediatric Endocrine Society. Advocacy groups appointed representatives for pre-meeting discussions and the consensus meeting.

The Approach to a Child with Dysmorphic Features: What the Pediatrician Should Know

The advancement of genetic knowledge and the discovery of an increasing number of genetic disorders has made the role of the geneticist progressively more complex and fundamental. However, most genetic disorders present during childhood; thus, their early recognition is a challenge for the pediatrician, who will be also involved in the follow-up of these children, often establishing a close relationship with them and their families and becoming a referral figure. In this review, we aim to provide the pediatrician with a general knowledge of the approach to treating a child with a genetic syndrome associated with dysmorphic features. We will discuss the red flags, the most common manifestations, the analytic collection of the family and personal medical history, and the signs that should alert the pediatrician during the physical examination. We will offer an overview of the physical malformations most commonly associated with genetic defects and the way to describe dysmorphic facial features. We will provide hints about some tools that can support the pediatrician in clinical practice and that also represent a useful educational resource, either online or through apps downloaded on a smartphone. Eventually, we will offer an overview of genetic testing, the ethical considerations, the consequences of incidental findings, and the main indications and limitations of the principal technologies.

Optimizing peripheral blood chromosome analysis: effects of refrigeration time and blood volume

OBJECTIVE

This study aims to investigate the impact of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis using response surface methodology (RSM).

METHODS

Peripheral blood samples from 30 volunteers were subjected to chromosomal analysis under different refrigeration duration periods (≤7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days) along with different blood volumes (0.2 mL, 0.3 mL, 0.4 mL, 0.5 mL, 0.6 mL, 0.7 mL, and 0.8 mL). The effects of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis were determined using the Chi-square test for trend, followed with Spearman's rank correlation coefficient, and RSM analysis to identify the optimal combination of refrigeration time and blood volume.

RESULTS

The refrigeration time within 10 days had a minor impact on the success rate, while refrigeration time more than 11 days significantly decreased the success rate. An increase in blood volume slightly improved the success rate. The success rate showed both linear and nonlinear changes with refrigeration time, while the effect of blood volume was primarily linear. The highest success rate was observed at a refrigeration time of ≤7 days and a blood volume of 0.8 mL. The interaction between refrigeration time and blood volume had a significant impact on the success rate.

CONCLUSION

It is recommended to keep the refrigeration time of blood samples within 7 days and control the blood volume at 0.8 mL to maximize the success rate of chromosomal analysis.

Low-pass whole genome sequencing is a reliable and cost-effective approach for copy number variant analysis in the clinical setting

INTRODUCTION

Next generation sequencing technology has greatly reduced the cost and time required for sequencing a genome. An approach that is rapidly being adopted as an alternative method for CNV analysis is the low-pass whole genome sequencing (LP-WGS). Here, we evaluated the performance of LP-WGS to detect copy number variants (CNVs) in clinical cytogenetics.

MATERIALS AND METHODS

DNA samples with known CNVs detected by chromosomal microarray analyses (CMA) were selected for comparison and used as positive controls; our panel included 44 DNA samples (12 prenatal and 32 postnatal), comprising a total of 55 chromosome imbalances. The selected cases were chosen to provide a wide range of clinically relevant CNVs, the vast majority being associated with intellectual disability or recognizable syndromes. The chromosome imbalances ranged in size from 75 kb to 90.3 Mb, including aneuploidies and two cases of mosaicism.

RESULTS

All CNVs were successfully detected by LP-WGS, showing a high level of consistency and robust performance of the sequencing method. Notably, the size of chromosome imbalances detected by CMA and LP-WGS were compatible between the two different platforms, which indicates that the resolution and sensitivity of the LP-WGS approach are at least similar to those provided by CMA.

DISCUSSION

Our data show the potential use of LP-WGS to detect CNVs in clinical diagnosis and confirm the method as an alternative for chromosome imbalances detection. The diagnostic effectiveness and feasibility of LP-WGS, in this technical validation study, were evidenced by a clinically representative dataset of CNVs that allowed a systematic assessment of the detection power and the accuracy of the sequencing approach. Further, since the software used in this study is commercially available, the method can easily be tested and implemented in a routine diagnostic setting.

Practical guidelines of the EOTTD for pathological and genetic diagnosis of hydatidiform moles

Hydatidiform moles are rare and thus most pathologists and geneticists have little experience with their diagnosis. It is important to promptly and correctly identify hydatidiform moles given that they are premalignant disorders associated with a risk of persistent gestational trophoblastic disease and gestational trophoblastic neoplasia. Improvement in diagnosis can be achieved with uniformization of diagnostic criteria and establishment of algorithms. To this aim, the Pathology and Genetics Working Party of the European Organisation for Treatment of Trophoblastic Diseases has developed guidelines that describe the pathological criteria and ancillary techniques that can be used in the differential diagnosis of hydatidiform moles. These guidelines are based on the best available evidence in the literature, professional experience and consensus of the experts' group involved in its development.

Exome sequencing improves the molecular diagnostics of paediatric unexplained neurodevelopmental disorders

BACKGROUND

Neurodevelopmental disorders (NDDs) and/or associated multiple congenital abnormalities (MCAs) represent a genetically heterogeneous group of conditions with an adverse prognosis for the quality of intellectual and social abilities and common daily functioning. The rapid development of exome sequencing (ES) techniques, together with trio-based analysis, nowadays leads to up to 50% diagnostic yield. Therefore, it is considered as the state-of-the-art approach in these diagnoses.

RESULTS

In our study, we present the results of ES in a cohort of 85 families with 90 children with severe NDDs and MCAs. The interconnection of the in-house bioinformatic pipeline and a unique algorithm for variant prioritization resulted in a diagnostic yield of up to 48.9% (44/90), including rare and novel causative variants (41/90) and intragenic copy-number variations (CNVs) (3/90). Of the total number of 47 causative variants, 53.2% (25/47) were novel, highlighting the clinical benefit of ES for unexplained NDDs. Moreover, trio-based ES was verified as a reliable tool for the detection of rare CNVs, ranging from intragenic exon deletions (GRIN2A, ZC4H2 genes) to a 6-Mb duplication. The functional analysis using PANTHER Gene Ontology confirmed the involvement of genes with causative variants in a wide spectrum of developmental processes and molecular pathways, which form essential structural and functional components of the central nervous system.

CONCLUSION

Taken together, we present one of the first ES studies of this scale from the central European region. Based on the high diagnostic yield for paediatric NDDs in this study, 48.9%, we confirm trio-based ES as an effective and reliable first-tier diagnostic test in the genetic evaluation of children with NDDs.

Lessons learned from rapid exome sequencing for 575 critically ill patients across the broad spectrum of rare disease

Introduction: Rapid exome sequencing (rES) has become the first-choice genetic test for critically ill patients, mostly neonates, young infants, or fetuses in prenatal care, in time-sensitive situations and when it is expected that the genetic test result may guide clinical decision making. The implementation of rES has revolutionized medicine by enabling timely identification of genetic causes for various rare diseases. The utilization of rES has increasingly been recognized as an essential diagnostic tool for the identification of complex and undiagnosed genetic disorders. Methods: We conducted a retrospective evaluation of our experiences with rES performed on 575 critically ill patients from various age groups (prenatal to adulthood), over a four-year period (2016-2019). These patients presented with a wide spectrum of rare diseases, including but not limited to neurological disorders, severe combined immune deficiency, and cancer. Results: During the study period, there was a significant increase in rES referrals, with a rise from a total of two referrals in Q1-2016 to 10 referrals per week in Q4-2019. The median turnaround time (TAT) decreased from 17 to 11 days in the period 2016-2019, with an overall median TAT of 11 days (IQR 8-15 days). The overall diagnostic yield for this cohort was 30.4%, and did not significantly differ between the different age groups (e.g. adults 22.2% vs children 31.0%; p-value 0.35). However, variability in yield was observed between clinical entities: craniofacial anomalies yielded 58.3%, while for three clinical entities (severe combined immune deficiency, aneurysm, and hypogonadotropic hypogonadism) no diagnoses were obtained. Discussion: Importantly, whereas clinical significance is often only attributed to a conclusive diagnosis, we also observed impact on clinical decision-making for individuals in whom no genetic diagnosis was established. Hence, our experience shows that rES has an important role for patients of all ages and across the broad spectrum of rare diseases to impact clinical outcomes.

Unbiased assessment of genome integrity and purging of adverse outcomes at the target locus upon editing of CD4+ T-cells for the treatment of Hyper IgM1

Hyper IgM1 is an X-linked combined immunodeficiency caused by CD40LG mutations, potentially treatable with CD4+ T-cell gene editing with Cas9 and a "one-size-fits-most" corrective template. Contrary to established gene therapies, there is limited data on the genomic alterations following long-range gene editing, and no consensus on the relevant assays. We developed drop-off digital PCR assays for unbiased detection of large on-target deletions and found them at high frequency upon editing. Large deletions were also common upon editing different loci and cell types and using alternative Cas9 and template delivery methods. In CD40LG edited T cells, on-target deletions were counter-selected in culture and further purged by enrichment for edited cells using a selector coupled to gene correction. We then validated the sensitivity of optical genome mapping for unbiased detection of genome wide rearrangements and uncovered on-target trapping of one or more vector copies, which do not compromise functionality, upon editing using an integrase defective lentiviral donor template. No other recurring events were detected. Edited patient cells showed faithful reconstitution of CD40LG regulated expression and function with a satisfactory safety profile. Large deletions and donor template integrations should be anticipated and accounted for when designing and testing similar gene editing strategies.

Prevalence of chromosomal alterations in first-trimester spontaneous pregnancy loss

Pregnancy loss is often caused by chromosomal abnormalities of the conceptus. The prevalence of these abnormalities and the allocation of (ab)normal cells in embryonic and placental lineages during intrauterine development remain elusive. In this study, we analyzed 1,745 spontaneous pregnancy losses and found that roughly half (50.4%) of the products of conception (POCs) were karyotypically abnormal, with maternal and paternal age independently contributing to the increased genomic aberration rate. We applied genome haplarithmisis to a subset of 94 pregnancy losses with normal parental and POC karyotypes. Genotyping of parental DNA as well as POC extra-embryonic mesoderm and chorionic villi DNA, representing embryonic and trophoblastic tissues, enabled characterization of the genomic landscape of both lineages. Of these pregnancy losses, 35.1% had chromosomal aberrations not previously detected by karyotyping, increasing the rate of aberrations of pregnancy losses to 67.8% by extrapolation. In contrast to viable pregnancies where mosaic chromosomal abnormalities are often restricted to chorionic villi, such as confined placental mosaicism, we found a higher degree of mosaic chromosomal imbalances in extra-embryonic mesoderm rather than chorionic villi. Our results stress the importance of scrutinizing the full allelic architecture of genomic abnormalities in pregnancy loss to improve clinical management and basic research of this devastating condition.

Reanalysis of Chromosomal Microarray Data Using a Smaller Copy Number Variant Call Threshold Identifies Four Cases with Heterozygous Multiexon Deletions of ARID1B, EHMT1, and FOXP1 Genes

Introduction

Chromosomal microarray (CMA) is a highly accurate and established method for detecting copy number variations (CNVs) in clinical genetic testing. CNVs are important etiological factors for disorders such as intellectual disability, developmental delay, and multiple congenital anomalies. Recently developed analytical methods have facilitated the identification of smaller CNVs. Therefore, reanalyzing CMA data using a smaller CNV calling threshold may yield useful information. However, this method was left to the discretion of each institution.

Methods

We reanalyzed the CMA data of 131 patients using a smaller CNV call threshold: 50 kb 50 probes for gain and 25 kb 25 probes for loss. We interpreted the reanalyzed CNVs based on the most recently available information. In the reanalysis, we filtered the data using the Clinical Genome Resource dosage sensitivity gene list as an index to quickly and efficiently check morbid genes.

Results

The number of copy number loss was approximately 20 times greater, and copy number gain was approximately three times greater compared to those in the previous analysis. We detected new likely pathogenic CNVs in four participants: a 236.5 kb loss within ARID1B, a 50.6 kb loss including EHMT1, a 46.5 kb loss including EHMT1, and an 89.1 kb loss within the FOXP1 gene.

Conclusion

The method employed in this study is simple and effective for CMA data reanalysis using a smaller CNV call threshold. Thus, this method is efficient for both ongoing and repeated analyses. This study may stimulate further discussion of reanalysis methodology in clinical laboratories.

A rare ring chromosome 21 abnormality is associated with azoospermia in two different phenotypically normal cases

Azoospermia can be diagnosed with spermiogram analysis, and karyotyping is the golden standard to explain the etiology. In this study, we investigated two male cases with azoospermia and male infertility for chromosomal abnormalities. Their phenotypes and physical and hormonal examinations were both normal. In karyotyping G-banding and NOR staining, a rare ring chromosome 21 abnormality was detected in the cases and no microdeletion in chromosome Y. Ring abnormality, deletion size, and deleted regions were shown with subtelomeric FISH (.ish r(21)(p13q22.3?)(D21S1446-)) and array CGH analyses. Due to the findings, bioinformatics, protein, and pathway analyses were done to detect a candidate gene through common genes in two cases' deleted regions or ring chromosome 21.

The role of a multidisciplinary team in managing variants of uncertain clinical significance in prenatal genetic diagnosis

BACKGROUND

Although in general prenatal exome sequencing only reports (likely) pathogenic variants, in some cases a variant of uncertain significance (VUS) is disclosed. The aims of this retrospective study were to evaluate the types of VUS that have been reported to prospective parents, possible reclassification and to design a standard flow chart to determine which types of VUS could be considered for reporting in prenatal settings. Furthermore, we investigated what the crucial elements are to facilitate rapid management of uncertain results in a prenatal setting.

MATERIAL AND METHODS

We reviewed exome results from 451 pregnancies performed in 2019-2021. We analyzed which factors that were taken into account by the multidisciplinary team (MDT) contributed towards decision making on reporting VUS after prenatal exome sequencing.

RESULTS

In 9/451 (2%) pregnancies tested with exome sequencing using a broad panel analysis a VUS was reported. After birth 3/9 VUS could be reclassified to likely pathogenic variants based on new clinical follow up data. We considered reporting VUS in genes: 1) matching the fetal phenotype, 2) associated with a severe disorder when a functional test is available or 3) possibly associated with a disorder where early post-partum diagnosis and treatment are crucial for a better prognosis. Two flowcharts were designed to guide first the laboratory specialist and then the MDT in decisions on reporting VUS. The crucial elements that enabled timely decisions on VUS disclosure were regular meetings, appropriate expertise, professional connections with other experts and psychological safety within the MDT.

CONCLUSION

In this study three out of nine VUS could be re-classified as likely pathogenic after clinical follow-up. In order to protect pregnant couples from the burden of uncertain results, the genetic professionals have to take the responsibility to limit the reporting of VUS. This can be done not only by automated filtering of data, by following professional guidelines and by building standardized decision flows, but also by discussing individual cases considering personal situations and the involved disease and by sharing professional experience and responsibility in a multidisciplinary prenatal team setting.

Loss of function of FIGNL1, a DNA damage response gene, causes human ovarian dysgenesis

Ovarian dysgenesis (OD), an XX disorder of sex development, presents with primary amenorrhea, hypergonadotrophic hypogonadism, and infertility. In an Ashkenazi Jewish patient with OD, whole exome sequencing identified compound heterozygous frameshifts in FIGNL1, a DNA damage response (DDR) gene: c.189del and c.1519_1523del. Chromosomal breakage was significantly increased in patient cells, both spontaneously, and following mitomycin C exposure. Transfection of DYK-tagged FIGNL1 constructs in HEK293 cells showed no detectable protein in FIGNL1c.189del and truncation with reduced expression in FIGNL1c.1519_1523del (64% of wild-type [WT], P = .003). FIGNL1 forms nuclear foci increased by phleomycin treatment (20.6 ± 1.6 vs 14.8 ± 2.4, P = .02). However, mutant constructs showed reduced DYK-FIGNL1 foci formation in non-treated cells (0.8 ± 0.9 and 5.6 ± 1.5 vs 14.8 ± 2.4 in DYK-FIGNL1WT, P < .001) and no increase with phleomycin treatment. In conclusion, FIGNL1 loss of function is a newly characterized OD gene, highlighting the DDR pathway's role in ovarian development and maintenance and suggesting chromosomal breakage as an assessment tool in XX-DSD patients.

Incidence of sex chromosome aneuploidy in a prenatal population: 27-year longitudinal study in Northern Italy

OBJECTIVES

The availability of cell-free (cf) DNA as a prenatal screening tool affords an opportunity for non-invasive identification of sex chromosome aneuploidy (SCA). The aims of this longitudinal study were to investigate the evolution and frequency of both invasive prenatal diagnostic testing, using amniocentesis and chorionic villus sampling (CVS), and the detection of SCA in cfDNA samples from a large unselected cohort in Northern Italy.

METHODS

The results of genetic testing from CVS and amniotic fluid samples received from public and private centers in Italy from 1995 to 2021 were collected. Chromosomal analysis was performed by routine Q-banding karyotype. Regression analyses and descriptive statistics were used to determine population data trends regarding the frequency of prenatal diagnostic testing and the identification of SCA, and these were compared with the changes in indication for prenatal diagnostic tests and available screening options.

RESULTS

Over a period of 27 years, there were 13 939 526 recorded births and 231 227 invasive procedures were performed, resulting in the prenatal diagnosis of 933 SCAs. After the commercial introduction of cfDNA use in 2015, the frequency of invasive procedures decreased significantly (P = 0.03), while the frequency of prenatal SCA detection increased significantly (P = 0.007). Between 2016 and 2021, a high-risk cfDNA result was the indication for 31.4% of detected sex chromosome trisomies, second only to advanced maternal age.

CONCLUSIONS

Our findings suggest that the inclusion of SCA in prenatal cfDNA screening tests can increase the prenatal diagnosis of affected individuals. As the benefits of early ascertainment are increasingly recognized, it is essential that healthcare providers are equipped with comprehensive and evidence-based information regarding the associated phenotypic differences and the availability of targeted effective interventions to improve neurodevelopmental and health outcomes for affected individuals. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal Chromosomal Microarray Analysis: Does Increased Resolution Equal Increased Yield?

Chromosomal microarray analysis (CMA) is considered a first-tier test for patients with developmental disabilities and congenital anomalies and is also routinely applied in prenatal diagnosis. The current consensus size cut-off for reporting copy number variants (CNVs) in the prenatal setting ranges from 200 Kb to 400 Kb, with the intention of minimizing the impact of variants of uncertain significance (VUS). Very limited data are currently available on the application of higher resolution platforms prenatally. The aim of this study is to investigate the feasibility and impact of applying high-resolution CMA in the prenatal setting. To that end, we report on the outcomes of applying CMA with a size cut-off of 20 Kb in 250 prenatal samples and discuss the findings and diagnostic yield and also provide follow-up for cases with variants of uncertain significance. Overall, 19.6% (49) showed one or more chromosomal abnormalities, with the findings classified as Pathogenic (P) or Likely Pathogenic (LP) in 15.6% and as VUS in 4%. When excluding the cases with known familial aberrations, the diagnostic yield was 12%. The smallest aberration detected was a 32 Kb duplication of the 16p11.2 region. In conclusion, this study demonstrates that prenatal diagnosis with a high-resolution aCGH platform can reliably detect smaller CNVs that are often associated with neurodevelopmental phenotypes while providing an increased diagnostic yield, regardless of the indication for testing, with only a marginal increase in the VUS incidence. Thus, it can be an important tool in the prenatal setting.

Challenges and Pragmatic Solutions in Pre-Test and Post-Test Genetic Counseling for Prenatal Exome Sequencing

The yield of genetic prenatal diagnosis has been notably improved by introducing whole genome chromosomal microarray (CMA) and prenatal exome sequencing (pES). However, together with increased numbers of diagnoses made, the need to manage challenging findings such as variants of unknown significance (VUS) and incidental findings (IF) also increased. We have summarized the current guidelines and recommendations and we have shown current solutions used in our tertiary center in the Netherlands. We discuss four of the most common clinical situations: fetus with normal pES results, fetus with a pathogenic finding explaining the fetal phenotype, fetus with a variant of uncertain clinical significance fitting the phenotype and fetus with a variant leading to an incidental diagnosis. Additionally, we reflect on solutions in order to facilitate genetic counseling in an NGS-era.

Inversions on human chromosomes

Human chromosome inversions are types of balanced structural variations, making them difficult to analyze. Thanks to PEM (paired-end sequencing and mapping), there has been tremendous progress in studying inversions. Inversions play an important role as an evolutionary factor, contributing to the formation of gonosomes, speciation of chimpanzees and humans, and inv17q21.3 or inv8p23.1 exhibit the features of natural selection. Both inversions have been related to pathogenic phenotype by directly affecting a gene structure (e.g., inv5p15.1q14.1), regulating gene expression (e.g., inv7q21.3q35) and by predisposing to other secondary arrangements (e.g., inv7q11.23). A polymorphism of human inversions is documented by the InvFEST database (a database that stores information about clinical predictions, validations, frequency of inversions, etc.), but only a small fraction of these inversions is validated, and a detailed analysis is complicated by the frequent location of breakpoints within regions of repetitive sequences.

The performance of genome sequencing as a first-tier test for neurodevelopmental disorders

Genome sequencing (GS) can identify novel diagnoses for patients who remain undiagnosed after routine diagnostic procedures. We tested whether GS is a better first-tier genetic diagnostic test than current standard of care (SOC) by assessing the technical and clinical validity of GS for patients with neurodevelopmental disorders (NDD). We performed both GS and exome sequencing in 150 consecutive NDD patient-parent trios. The primary outcome was diagnostic yield, calculated from disease-causing variants affecting exonic sequence of known NDD genes. GS (30%, n = 45) and SOC (28.7%, n = 43) had similar diagnostic yield. All 43 conclusive diagnoses obtained with SOC testing were also identified by GS. SOC, however, required integration of multiple test results to obtain these diagnoses. GS yielded two more conclusive diagnoses, and four more possible diagnoses than ES-based SOC (35 vs. 31). Interestingly, these six variants detected only by GS were copy number variants (CNVs). Our data demonstrate the technical and clinical validity of GS to serve as routine first-tier genetic test for patients with NDD. Although the additional diagnostic yield from GS is limited, GS comprehensively identified all variants in a single experiment, suggesting that GS constitutes a more efficient genetic diagnostic workflow.

EOSAL-CNV for Easy and Rapid Detection of CNVs by Fragment Analysis : EOSAL: A Fast and Reliable New Method for CNV Detection

Copy number variations (CNVs) are a type of genetic variation involving from 50 base pairs (bps) to millions of bps and, in a general point of view, can include alterations of complete chromosomes. As CNVs mean the gain or loss of DNA sequences, their detection requires specific techniques and analysis. We have developed Easy One-Step Amplification and Labeling for CNV Detection (EOSAL-CNV) by fragment analysis in a DNA sequencer. The procedure is based on a single PCR reaction for amplification and labeling of all fragments included. The protocol includes specific primers for the amplification of the regions of interest with a tail in each of the primers (one for forward and another for the reverse primers) together with primers for tail amplification. One of the primers for tail amplification is labeled with a fluorophore, allowing the amplification and labeling in the same reaction. Combination of several tail pairs and labels allows the detection of DNA fragment by different fluorophores and increases the number of fragments that can be analyzed in one reaction. PCR products can be analyzed without any purification on a DNA sequencer for fragment detection and quantification. Finally, simple and easy calculations allow the detection of fragments with deletions or extra copies. The use of EOSAL-CNV allows simplifying and reducing costs in sample analysis for CNV detection.

Dual Molecular Diagnoses of Recessive Disorders in a Child from Consanguineous Parents: Case Report and Literature Review

The widespread use of whole exome sequencing (WES) resulted in the discovery of multilocus pathogenic variations (MPV), defined as two or more distinct or overlapping Mendelian disorders occurring in a patient, leading to a blended phenotype. In this study, we report on a child with autosomal recessive primary microcephaly-5 (MCPH5) and nephropathic cystinosis. The proband is the first child of consanguineous parents, presenting a complex phenotype including neurodevelopmental delay, microcephaly, growth restriction, significant delay of bone maturation, lissencephaly, and abnormality of neuronal migration, photophobia, and renal tubular acidosis. WES revealed two pathogenic and homozygous variants: a c.4174C>T variant in the ASPM gene and a c.382C>T variant in the CTNS gene, explaining the complex phenotype. The literature review showed that most of the patients harboring two variants in recessive disease genes are born to consanguineous parents. To the best of our knowledge, the patient herein described is the first one harboring pathogenic variants in both the ASPM and CTNS genes. These findings highlight the importance of searching for MPV in patients with complex phenotypes investigated by genome-wide testing methods, especially for those patients born to consanguineous parents.

Gomoiu” Hospital Group, Shelby ES, Albeanu A, Burada F, Ioana M. Pathogenic Copy Number Variations Involved in the Genetic Etiology of Syndromic and Non-Syndromic Intellectual Disability-Data from a Romanian Cohort

The investigation of unexplained global developmental delay (GDD)/intellectual disability (ID) is challenging. In low resource settings, patients may not follow a standardized diagnostic process that makes use of the benefits of advanced technologies. Our study aims to explore the contribution of chromosome microarray analysis (CMA) in identifying the genetic etiology of GDD/ID. A total of 371 Romanian patients with syndromic or non-syndromic GDD/ID, without epilepsy, were routinely evaluated in tertiary clinics. A total of 234 males (63.07%) and 137 (36.93%) females, with ages ranging from 6 months to 40 years (median age of 5.5 years), were referred for genetic diagnosis between 2015 and 2022; testing options included CMA and/or karyotyping. Agilent Technologies and Oxford Gene Technology CMA workflows were used. Pathogenic/likely pathogenic copy number variations (pCNVs) were identified in 79 patients (21.29%). Diagnosis yield was comparable between mild ID (17.05%, 22/129) and moderate/severe ID 23.55% (57/242). Higher rates were found in cases where facial dysmorphism (22.97%, 71/309), autism spectrum disorder (ASD) (19.11%, 26/136) and finger anomalies (20%, 27/96) were associated with GDD/ID. GDD/ID plus multiple congenital anomalies (MCA) account for the highest detection rates at 27.42% (17/62). pCNVs represent a significant proportion of the genetic causes of GDD/ID. Our study confirms the utility of CMA in assessing GDD/ID with an uncertain etiology, especially in patients with associated comorbidities.

Cytogenetic Investigation of Infertile Patients in Hungary: A 10-Year Retrospective Study

Chromosome abnormalities play a crucial role in reproductive failure. The presence of numerical or structural aberrations may induce recurrent pregnancy loss or primary infertility. The main purpose of our study was to determine the types and frequency of chromosomal aberrations in infertile patients and to compare the frequency of structural aberrations to a control group. Karyotyping was performed in 1489 men and 780 women diagnosed with reproductive failure between 2010 and 2020. The control group included 869 male and 1160 female patients having cytogenetic evaluations for reasons other than infertility. Sex chromosomal aberrations were detected in 33/1489 (2.22%) infertile men and 3/780 (0.38%) infertile women. Structural abnormalities (e.g., translocation, inversion) were observed in 89/1489 (5.98%) infertile men and 58/780 (7.44%) infertile women. The control population showed structural chromosomal abnormalities in 27/869 (3.11%) men and 39/1160 (3.36%) women. There were significant differences in the prevalence of single-cell translocations between infertile individuals (males: 3.5%; females: 3.46%) and control patients (males: 0.46%; females: 0.7%). In summary, this is the first report of cytogenetic alterations in infertile patients in Hungary. The types of chromosomal abnormalities were comparable to previously published data. The prevalence of less-studied single-cell translocations was significantly higher in infertile patients than in the control population, supporting an earlier suggestion that these aberrations may be causally related to infertility.

The past, present, and future for constitutional ring chromosomes: A report of the international consortium for human ring chromosomes

Human ring chromosomes (RCs) are rare diseases with an estimated newborn incidence of 1/50,000 and an annual occurrence of 2,800 patients globally. Over the past 60 years, banding cytogenetics, fluorescence in situ hybridization (FISH), chromosome microarray analysis (CMA), and whole-genome sequencing (WGS) has been used to detect an RC and further characterize its genomic alterations. Ring syndrome featuring sever growth retardation and variable intellectual disability has been considered as general clinical presentations for all RCs due to the cellular losses from the dynamic mosaicism of RC instability through mitosis. Cytogenomic heterogeneity ranging from simple complete RCs to complex rearranged RCs and variable RC intolerance with different relative frequencies have been observed. Clinical heterogeneity, including chromosome-specific deletion and duplication syndromes, gene-related organ and tissue defects, cancer predisposition to different types of tumors, and reproductive failure, has been reported in the literature. However, the patients with RCs reported in the literature accounted for less than 1% of its occurrence. Current diagnostic practice lacks laboratory standards for analyzing cellular behavior and genomic imbalances of RCs to evaluate the compound effects on patients. Under-representation of clinical cases and lack of comprehensive diagnostic analysis make it a challenge for evidence-based interpretation of clinico-cytogenomic correlations and recommendation of follow-up clinical management. Given recent advancements in genomic technologies and organized efforts by international collaborations and patient advocacy organizations, the prospective of standardized cytogenomic diagnosis and evidence-based clinical management for all patients with RCs could be achieved at an unprecedented global scale.

Chromosomal microarray analyses from 5778 patients with neurodevelopmental disorders and congenital anomalies in Brazil

Chromosomal microarray analysis (CMA) has been recommended and practiced routinely since 2010 both in the USA and Europe as the first-tier cytogenetic test for patients with unexplained neurodevelopmental delay/intellectual disability, autism spectrum disorders, and/or multiple congenital anomalies. However, in Brazil, the use of CMA is still limited, due to its high cost and complexity in integrating the results from both the private and public health systems. Although Brazil has one of the world’s largest single-payer public healthcare systems, nearly all patients referred for CMA come from the private sector, resulting in only a small number of CMA studies in Brazilian cohorts. To date, this study is by far the largest Brazilian cohort (n = 5788) studied by CMA and is derived from a joint collaboration formed by the University of São Paulo and three private genetic diagnostic centers to investigate the genetic bases of neurodevelopmental disorders and congenital abnormalities. We identified 2,279 clinically relevant CNVs in 1886 patients, not including the 26 cases of UPD found. Among detected CNVs, the corresponding frequency of each category was 55.6% Pathogenic, 4.4% Likely Pathogenic and 40% VUS. The diagnostic yield, by taking into account Pathogenic, Likely Pathogenic and UPDs, was 19.7%. Since the rational for the classification is mostly based on Mendelian or highly penetrant variants, it was not surprising that a second event was detected in 26% of those cases of predisposition syndromes. Although it is common practice to investigate the inheritance of VUS in most laboratories around the world to determine the inheritance of the variant, our results indicate an extremely low cost–benefit of this approach, and strongly suggest that in cases of a limited budget, investigation of the parents of VUS carriers using CMA should not be prioritized.

Cardiovascular Anomalies among 1005 Fetuses Referred to Invasive Prenatal Testing-A Comprehensive Cohort Study of Associated Chromosomal Aberrations

This retrospective cohort study comprehensively evaluates cardiovascular anomalies (CVAs) and associated extracardiac structural malformations (ECMs) among 1005 fetuses undergoing invasive prenatal testing at a single tertiary Polish center in the context of chromosomal aberrations detected in them by array comparative genomic hybridization (aCGH) and G-band karyotyping. The results of our study show that CVAs are among the most common malformations detected in fetuses undergoing invasive prenatal testing, as they affected 20% of all cases seen in our department. Septal defects predominated among fetuses with numerical aberrations, while conotruncal defects were the most common findings among fetuses with pathogenic copy number variants (CNVs). In 61% of cases, CVAs were associated with ECMs (the diagnosis was confirmed postnatally or in cases of pregnancy termination by means of autopsy). The most common ECMs were anomalies of the face and neck, followed by skeletal defects. In total, pathogenic chromosomal aberrations were found in 47.5% of CVAs cases, including 38.6% with numerical chromosomal aberrations. Pathogenic CNVs accounted for 14.5% of cases with CVAs and normal karyotype. Thus, our study highlights the importance of assessing the anatomy of the fetus, and of the genetic testing (preferably aCGH) that should be offered in all CVA and ECM cases.

DNA Methylation Episignatures in Neurodevelopmental Disorders Associated with Large Structural Copy Number Variants: Clinical Implications

Large structural chromosomal deletions and duplications, referred to as copy number variants (CNVs), play a role in the pathogenesis of neurodevelopmental disorders (NDDs) through effects on gene dosage. This review focuses on our current understanding of genomic disorders that arise from large structural chromosome rearrangements in patients with NDDs, as well as difficulties in overlap of clinical presentation and molecular diagnosis. We discuss the implications of epigenetics, specifically DNA methylation (DNAm), in NDDs and genomic disorders, and consider the implications and clinical impact of copy number and genomic DNAm testing in patients with suspected genetic NDDs. We summarize evidence of global methylation episignatures in CNV-associated disorders that can be used in the diagnostic pathway and may provide insights into the molecular pathogenesis of genomic disorders. Finally, we discuss the potential for combining CNV and DNAm assessment into a single diagnostic assay.

Reanalysis of exome negative patients with rare disease: a pragmatic workflow for diagnostic applications

Background

Approximately two third of patients with a rare genetic disease remain undiagnosed after exome sequencing (ES). As part of our post-test counseling procedures, patients without a conclusive diagnosis are advised to recontact their referring clinician to discuss new diagnostic opportunities in due time. We performed a systematic study of genetically undiagnosed patients 5 years after their initial negative ES report to determine the efficiency of diverse reanalysis strategies.

Methods

We revisited a cohort of 150 pediatric neurology patients originally enrolled at Radboud University Medical Center, of whom 103 initially remained genetically undiagnosed. We monitored uptake of physician-initiated routine clinical and/or genetic re-evaluation (ad hoc re-evaluation) and performed systematic reanalysis, including ES-based resequencing, of all genetically undiagnosed patients (systematic re-evaluation).

Results

Ad hoc re-evaluation was initiated for 45 of 103 patients and yielded 18 diagnoses (including 1 non-genetic). Subsequent systematic re-evaluation identified another 14 diagnoses, increasing the diagnostic yield in our cohort from 31% (47/150) to 53% (79/150). New genetic diagnoses were established by reclassification of previously identified variants (10%, 3/31), reanalysis with enhanced bioinformatic pipelines (19%, 6/31), improved coverage after resequencing (29%, 9/31), and new disease-gene associations (42%, 13/31). Crucially, our systematic study also showed that 11 of the 14 further conclusive genetic diagnoses were made in patients without a genetic diagnosis that did not recontact their referring clinician.

Conclusions

We find that upon re-evaluation of undiagnosed patients, both reanalysis of existing ES data as well as resequencing strategies are needed to identify additional genetic diagnoses. Importantly, not all patients are routinely re-evaluated in clinical care, prolonging their diagnostic trajectory, unless systematic reanalysis is facilitated. We have translated our observations into considerations for systematic and ad hoc reanalysis in routine genetic care.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01069-z.

Prenatal Diagnosis of Fetal Trisomy 5 Mosaicism with Congenital Pulmonary Airway Malformation Type 3: A Case Report

Background: Trisomy mosaicism of chromosome 5 is uncommon with few cases described. Case report: A 41-year-old woman underwent ultrasound (US) at 16 weeks, which showed oligohydramnios and intrauterine growth restriction (IUGR). Amniocentesis discovered a karyotype of 47,XX,+5/46,XX. US at 19 weeks disclosed IUGR, enlargement of right side of heart, main pulmonary artery dilatation, and a suspected congenital pulmonary airway malformation (CPAM) in the inferior lobe of the left lung. Due to poor fetal prognosis, the parents opted for legal termination of pregnancy. At postmortem, a wide ventricular septal defect and CPAM type 3 were found. Cytogenetic analyses on fetal tissues detected mosaic trisomy 5 in skin, thymus, kidneys and CPAM. Placenta and fetal peripheral blood revealed normal female karyotype. Discussion/conclusion: These results suggest that if a fetus presents normal phenotypic features, mosaicism may be confined to extraembryonic structures, otherwise, in case of malformations, it may be carried by affected organs.

Genetic investigation of syndromic forms of obesity

BACKGROUND

Syndromic obesity (SO) refers to obesity with additional phenotypes, including intellectual disability (ID)/developmental delay (DD), dysmorphic features, or organ-specific abnormalities. SO is rare, has high phenotypic variability, and frequently follows a monogenic pattern of inheritance. However, the genetic etiology of most cases of SO has not been elucidated.

SUBJECTS AND METHODS

In this study, we investigated 20 SO patients by whole-exome sequencing (WES) trios to identify causal genetic variants.

RESULTS

4/20 patients had negative results for array comparative genomic hybridization (aCGH) analyses. In the remaining 15 patients, in addition to SNVs and indels, CNVs were also evaluated. Pathogenic/likely pathogenic (P/LP) SNVs/indels were detected in 6/20 patients (involving MED13L, AHDC1, EHMT1, MYT1L, GRIA3, and SETD1A), while two patients carried an inherited VUS. In addition, P/LP CNVs were observed in 3/15 patients (involving SATG2, KIAA0442, and MEIS2).

CONCLUSIONS

All nine detected P/LP variants involved genes already known to lead to syndromic ID/DD; however, for only two genes (EHMT1 and MYT1L) is the link with obesity well established. This is the first study applying a comprehensive genomic investigation of an SO cohort, showing a high diagnostic yield (~47%). Additionally, our findings suggested that several known ID/DD genes may also predispose individuals to SO.

Enhancing DLG2 Implications in Neuropsychiatric Disorders: Analysis of a Cohort of Eight Patients with 11q14.1 Imbalances

Neurodevelopmental disorders (NDDs) are considered synaptopathies, as they are due to anomalies in neuronal connectivity during development. DLG2 is a gene involved insynaptic function; the phenotypic effect of itsalterations in NDDs has been underestimated since few cases have been thoroughly described.We report on eight patients with 11q14.1 imbalances involving DLG2, underlining its potential effects on clinical presentation and its contribution to NDD comorbidity by accurate neuropsychiatric data collection. DLG2 is a very large gene in 11q14.1, extending over 2.172 Mb, with alternative splicing that gives rise to numerous isoforms differentially expressed in brain tissues. A thorough bioinformatic analysis of the altered transcripts was conducted for each patient. The different expression profiles of the isoforms of this gene and their influence on the excitatory–inhibitory balance in crucial brain structures could contribute to the phenotypic variability related to DLG2 alterations. Further studies on patients would be helpful to enrich clinical and neurodevelopmental findings and elucidate the molecular mechanisms subtended to NDDs.

Third-Generation Cytogenetic Analysis: Diagnostic Application of Long-Read Sequencing

Copy number variants (CNVs) play important roles in the pathogenesis of several genetic syndromes. Traditional and molecular karyotyping are considered the first-tier diagnostic tests to detect macroscopic and cryptic deletions/duplications. However, their time-consuming and laborious experimental protocols protract diagnostic times from 3 to 15 days. Nanopore sequencing has the ability to reduce time to results for the detection of CNVs with the same resolution of current state-of-the-art diagnostic tests. Nanopore sequencing was compared to molecular karyotyping for the detection of pathogenic CNVs of seven patients with previously diagnosed causative CNVs of different sizes and cellular fractions. Larger chromosomal anomalies included trisomy 21 and mosaic tetrasomy 12p. Among smaller CNVs, two genomic imbalances of 1.3 Mb, a small deletion of 170 kb, and two mosaic deletions (1.2 Mb and 408 kb) were tested. DNA was sequenced and data generated during runs were analyzed in online mode. All pathogenic CNVs were identified with detection time inversely proportional to size and cellular fraction. Aneuploidies were called after only 30 minutes of sequencing, whereas 30 hours were needed to call small CNVs. These results demonstrate the clinical utility of our approach that allows the molecular diagnosis of genomic disorders within a 30-minute to 30-hour time frame and its easy implementation as a routinary diagnostic tool.

Extended genetic testing in fetuses with sonographic skeletal system abnormalities

OBJECTIVES

To analyze genetic causes of skeletal system abnormalities diagnosed by prenatal sonography and to establish a diagnostic protocol with regard to extended genetic testing in this group of patients.

METHODS

This prospective observational cohort study included all singleton pregnancies with a sonographic abnormality of the skeletal system evaluated in a single ultrasound department during a 1-year period (2019). Fetuses underwent routine genetic testing by chromosomal microarray analysis (CMA) supplemented with polyploidy testing, and those with either a normal result or an abnormal result not consistent with the observed phenotype underwent exome sequencing (ES). Interpretation of variants was discussed by a panel of specialists to identify pathogenic/likely pathogenic variants.

RESULTS

The study group comprised 55 fetuses. A chromosomal abnormality consistent with the observed phenotype was detected in 24 (43.6%) cases. After exclusions, 26 (47.3%) cases underwent further molecular testing by ES, of which 18 (69.2%) were classified as having abnormal ES results, thus increasing the diagnostic yield by a further 18 (32.7%) cases and giving an abnormal genetic test result in 42/55 (76.4%) fetuses overall. Pathogenic or likely pathogenic sequence variants in 14 different genes were detected across 18 fetuses. Seven genes are already listed in the International Skeletal Dysplasia Society Nosology and seven are not typically found to be causal for skeletal dysplasias and are not listed in the Nosology.

CONCLUSIONS

In fetuses with skeletal system anomalies, chromosomal abnormality was the most common genetic diagnosis. Exome sequencing increased the diagnostic yield over that of CMA and polyploidy testing. Fetuses with skeletal abnormalities should undergo extended genetic testing following routine testing, as many genetic anomalies responsible for skeletal defects may otherwise be missed. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

MLPA analysis of 32 foetuses with a congenital heart defect and 1 foetus with renal defects - pilot study. The significant frequency rate of presented pathological CNV

AIMS

The aim of this retrospective study was to determine the detection rate of the pathogenic copy number variants (CNVs) in a cohort of 33 foetuses - 32 with CHD (congenital heart defects) and 1 with kidney defect, after exclusion of common aneuploidies (trisomy 13, 18, 21, and monosomy X) by karyotyping, Multiplex ligation - dependent probe amplification (MLPA) and chromosomal microarray analysis (CMA). We also assess the effectivity of MLPA as a method of the first tier for quick and inexpensive detection of mutations, causing congenital malformations in foetuses.

METHODS

MLPA with probe mixes P070, P036 - Telomere 3 and 5, P245 - microdeletions, P250 - DiGeorge syndrome, and P311 - CHD (Congenital heart defects) was performed in 33 samples of amniotic fluid and chorionic villi. CMA was performed in 10 relevant cases.

RESULTS

Pathogenic CNVs were found in 5 samples: microdeletions in region 22q11.2 (≈2 Mb) in two foetuses, one distal microdeletion of the 22q11.2 region containing genes LZTR1, CRKL, AIFM3 and SNAP29 (≈416 kb) in the foetus with bilateral renal agenesis, 8p23.1 (3.8 Mb) microdeletion syndrome and microdeletion in area 9q34.3 (1.7 Mb, Kleefstra syndrome). MLPA as an initial screening method revealed unambiguously pathogenic CNVs in 15.2 % of samples.

CONCLUSION

Our study suggests that MLPA and CMA are a reliable and high-resolution technology and should be used as the first-tier test for prenatal diagnosis of congenital heart disease. Determination of the cause of the abnormality is crucial for genetic counselling and further management of the pregnancy.

Comparative Genomic Hybridization to Microarrays in Fetuses with High-Risk Prenatal Indications: Polish Experience with 7400 Pregnancies

The aim of this study was to determine the suitability of the comparative genomic hybridization to microarray (aCGH) technique for prenatal diagnosis, but also to assess the frequency of chromosomal aberrations that may lead to fetal malformations but are not included in the diagnostic report. We present the results of the aCGH in a cohort of 7400 prenatal cases, indicated for invasive testing due to ultrasound abnormalities, high-risk for serum screening, thickened nuchal translucency, family history of genetic abnormalities or congenital abnormalities, and advanced maternal age (AMA). The overall chromosomal aberration detection rate was 27.2% (2010/7400), including 71.2% (1431/2010) of numerical aberrations and 28.8% (579/2010) of structural aberrations. Additionally, the detection rate of clinically significant copy number variants (CNVs) was 6.8% (505/7400) and 0.7% (57/7400) for variants of unknown clinical significance. The detection rate of clinically significant submicroscopic CNVs was 7.9% (334/4204) for fetuses with structural anomalies, 5.4% (18/336) in AMA, 3.1% (22/713) in the group of abnormal serum screening and 6.1% (131/2147) in other indications. Using the aCGH method, it was possible to assess the frequency of pathogenic chromosomal aberrations, of likely pathogenic and of uncertain clinical significance, in the groups of cases with different indications for an invasive test.

Diagnostic yield of patients with undiagnosed intellectual disability, global developmental delay and multiples congenital anomalies using karyotype, microarray analysis, whole exome sequencing from Central Brazil

Intellectual Disability (ID) is a neurodevelopmental disorder that affects approximately 3% of children and adolescents worldwide. It is a heterogeneous and multifactorial clinical condition. Several methodologies have been used to identify the genetic causes of ID and in recent years new generation sequencing techniques, such as exome sequencing, have enabled an increase in the detection of new pathogenic variants and new genes associated with ID. The aim of this study was to evaluate exome sequencing with analysis of the ID gene panel as a tool to increase the diagnostic yield of patients with ID/GDD/MCA in Central Brazil, together with karyotype and CMA tests. A retrospective cohort study was carried out with 369 patients encompassing both sexes. Karyotype analysis was performed for all patients. CMA was performed for patients who did not present structural and or numerical alterations in the karyotype. Cases that were not diagnosed after performing karyotyping and CMA were referred for exome sequencing using a gene panel for ID that included 1,252 genes. The karyotype identified chromosomal alterations in 34.7% (128/369). CMA was performed in 83 patients who had normal karyotype results resulting in a diagnostic yield of 21.7% (18/83). Exome sequencing with analysis of the ID gene panel was performed in 19 trios of families that had negative results with previous methodologies. With the ID gene panel analysis, we identified mutations in 63.1% (12/19) of the cases of which 75% (9/12) were pathogenic variants,8.3% (1/12) likely pathogenic and in 16.7% (2/12) it concerned a Variant of Uncertain Significance. With the three methodologies applied, it was possible to identify the genetic cause of ID in 42.3% (156/369) of the patients. In conclusion, our studies show the different methodologies that can be useful in diagnosing ID/GDD/MCA and that whole exome sequencing followed by gene panel analysis, when combined with clinical and laboratory screening, is an efficient diagnostic strategy.

QF-PCR: a valuable first-line prenatal and postnatal test for common aneuploidies in South Africa

Quantitative fluorescence-polymerase chain reaction (QF-PCR) is useful for the detection of aneuploidies involving chromosomes 13, 18, 21, X and Y. Due to the rapid turn-around time and reduced cost compared to traditional karyotyping, QF-PCR has been used as an alternative test for both pre- and postnatal aneuploidy detection in Johannesburg, South Africa since 2001. An internal review of 13,396 aneuploidy tests processed using QF-PCR between January 2015 and December 2019 was performed, and the results showed that the majority (~ 88%) of cases were postnatal tests, with prenatal samples accounting for only ~ 12% of cases. The most common aneuploidies detected were Trisomy 21 (20.6%), Trisomy 18 (3.7%) and Trisomy 13 (2.4%), while sex chromosome aneuploidies were only detected in < 1% of cases. The average percentage of positive cases over the 5-year period was 32.1% for postnatal samples and 11.3% for prenatal samples. QF-PCR testing of the common aneuploidies is being used appropriately, and the high percentage of positive cases demonstrates the value of QF-PCR as prenatal and postnatal tests, particularly in limited resource settings. The higher proportion of positive postnatal cases suggests that referrals are clinically appropriate. However, there is under- and uneven utilization of genetic services in many provinces in South Africa, and the state of prenatal genetic services is poor, as reflected by the low number of prenatal referrals. These results demonstrate the need for programs which will improve the genetic knowledge of referring doctors and the general public, thereby improving the broader utilisation of QF-PCR aneuploidy diagnostic testing, so that patients receive appropriate diagnoses and subsequent management.

Increased runs of homozygosity in the autosomal genome of Brazilian individuals with neurodevelopmental delay/intellectual disability and/or multiple congenital anomalies investigated by chromosomal microarray analysis

Runs of homozygosity (ROH) in the human genome may be clinically relevant. The aim of this study was to report the frequency of increased ROH of the autosomal genome in individuals with neurodevelopmental delay/intellectual disability and/or multiple congenital anomalies, and to compare these data with a control group. Data consisted of calls of homozygosity from 265 patients and 289 controls. In total, 7.2% (19/265) of the patients showed multiple ROH exceeding 1% of autosomal genome, compared to 1.4% (4/289) in the control group (p=0.0006). Homozygosity ranged from 1.38% to 22.12% among patients, and from 1.53 to 2.40% in the control group. In turn, 1.9% (5/265) of patients presented ROH ≥10Mb in a single chromosome, compared to 0.3% (1/289) of individuals from the control group (p=0.0801). By excluding cases with reported consanguineous parents (15/24), the frequency of increased ROH was 3.4% (9/250) among patients and 1.7% (5/289) in the control group, considering multiple ROH exceeding 1% of the autosome genome and ROH ≥10Mb in a single chromosome together, although not statistically significant (p=0.1873). These results reinforce the importance of investigating ROH, which with complementary diagnostic tests can improve the diagnostic yield for patients with such conditions.

Genes To Mental Health (G2MH): A Framework to Map the Combined Effects of Rare and Common Variants on Dimensions of Cognition and Psychopathology

Rare genomic disorders (RGDs) confer elevated risk for neurodevelopmental psychiatric disorders. In this era of intense genomics discoveries, the landscape of RGDs is rapidly evolving. However, there has not been comparable progress to date in scalable, harmonized phenotyping methods. As a result, beyond associations with categorical diagnoses, the effects on dimensional traits remain unclear for many RGDs. The nature and specificity of RGD effects on cognitive and behavioral traits is an area of intense investigation: RGDs are frequently associated with more than one psychiatric condition, and those studied to date affect, to varying degrees, a broad range of developmental and cognitive functions. Although many RGDs have large effects, phenotypic expression is typically influenced by additional genomic and environmental factors. There is emerging evidence that using polygenic risk scores in individuals with RGDs offers opportunities to refine prediction, thus allowing for the identification of those at greatest risk of psychiatric illness. However, translation into the clinic is hindered by roadblocks, which include limited genetic testing in clinical psychiatry, and the lack of guidelines for following individuals with RGDs, who are at high risk of developing psychiatric symptoms. The Genes to Mental Health Network (G2MH) is a newly funded National Institute of Mental Health initiative that will collect, share, and analyze large-scale data sets combining genomics and dimensional measures of psychopathology spanning diverse populations and geography. The authors present here the most recent understanding of the effects of RGDs on dimensional behavioral traits and risk for psychiatric conditions and discuss strategies that will be pursued within the G2MH network, as well as how expected results can be translated into clinical practice to improve patient outcomes.

Clinical exome sequencing - mistakes and caveats

Massive parallel sequencing technology has become the predominant technique for genetic diagnostics and research. Many genetic laboratories have wrestled with the challenges of setting up genetic testing workflows based on a completely new technology. The learning curve we went through as a laboratory was accompanied by growing pains while we gained new knowledge and expertise. Here we discuss some important mistakes that have been made in our laboratory through 10 years of clinical exome sequencing but that have given us important new insights on how to adapt our working methods. We provide these examples and the lessons that we learned to help other laboratories avoid to make the same mistakes.