Exome sequencing improves genetic diagnosis of structural fetal abnormalities revealed by ultrasound

Trio-whole-exome sequencing and preimplantation genetic diagnosis for unexplained recurrent fetal malformations

Whole-exome sequencing (WES) is widely used to detect genetic mutations that cause Mendelian diseases, and has been successfully applied in combination with preimplantation genetic diagnosis (PGD) to avoid the transmission of genetic defects. We investigated 40 nonconsanguineous families with unexplained, recurrent fetal malformations (two or more malformed fetuses) from May 2016 to December 2018. Using Trio-WES, we identified 32 disease-associated variants in 40 families (80% positive rate), which were subsequently verified. Known Mendelian diseases were identified in 12 families (30%), highly suspected Mendelian diseases in 12 families (30%), variants with uncertain significance in 8 families (20%), and no noticeable variants for 8 families (20%). Further analysis showed variants in 22 genes may cause fetal malformations. Four gene variants were detected in fetuses for the first time, which expanded the spectrum of the disease phenotype. Two novel candidate genes may be related to fetal malformations. Of 26 couples receiving PGD on disease-associated genes, 3 healthy newborns were delivered, and 4 couples are undergoing pregnancies. We reported the fetal data and developed an optimized genetic testing strategy. Our finding strongly suggests the presence of single gene Mendelian disorders in 60% of those families, and PGD services for couples to have healthy babies.

Considerations for whole exome sequencing unique to prenatal care

Whole exome sequencing (WES) is increasingly being used in the prenatal setting. The emerging data support the clinical utility of prenatal WES based on its diagnostic yield, which can be as high as 80% for certain ultrasound findings. However, detailed practice and laboratory guidelines, addressing the indications for prenatal WES and the surrounding technical, interpretation, ethical, and counseling issues, are still lacking. Herein, we review the literature and summarize the most recent findings and applications of prenatal WES. This review offers specialists and clinical genetic laboratorians a body of evidence and expert opinions that can serve as a resource to assist in their practice. Finally, we highlight the emerging technologies that promise a future of prenatal WES without the risks associated with invasive testing.

Next-Generation Sequencing Using a Cardiac Gene Panel in Prenatally Diagnosed Cardiac Anomalies

OBJECTIVE

Most prenatally identified congenital heart defects (CHDs) are the sole structural anomaly detected; however, there is a subgroup of cases where the specific genetic cause will impact prognosis, including chromosome abnormalities and single-gene causes. Next-generation sequencing of all the protein coding regions in the genome or targeted to genes involved in cardiac development is currently possible in the prenatal period, but there are minimal data on the clinical utility of such an approach. This study assessed the outcome of a CHD gene panel that included single-gene causes of syndromic and non-syndromic CHDs.

METHOD

Sixteen cases with a fetal CHD identified on prenatal ultrasound were studied using a 108 CHD gene panel. DNA was extracted from cultured amniocytes.

RESULTS

There was no diagnostic pathogenic variant identified in these cases. There was an average of 2.9 reportable variants identified per case and the majority of them were variants of uncertain significance.

CONCLUSION

Next-generation sequencing has the potential for increased genetic diagnosis for fetal anomalies. However, the large number of variants and the absence of an examinable patient make the interpretation of these variants challenging.

Evaluation of Diagnostic Yield in Fetal Whole-Exome Sequencing: A Report on 45 Consecutive Families

Prenatal ultrasound (US) abnormalities often pose a clinical dilemma and necessitate facilitated investigations in the search of diagnosis. The strategy of pursuing fetal whole-exome sequencing (WES) for pregnancies complicated by abnormal US findings is gaining attention, but the reported diagnostic yield is variable. In this study, we describe a tertiary center's experience with fetal WES from both terminated and ongoing pregnancies, and examine the clinical factors affecting the diagnostic rate. A total of 45 consecutive families of Jewish descent were included in the analysis, for which clinical fetal WES was performed under either single (fetus only), trio (fetus and parents) or quatro (two fetuses and parents) design. Except one, all families were non-consanguineous. In 41 of the 45 families, WES was sought following abnormal fetal US findings, and 18 of them had positive relevant family history (two or more fetuses with US abnormalities, or single fetus with US abnormalities and an affected parent). The overall diagnostic yield was 28.9% (13/45 families), and 31.7% among families with fetal US abnormalities (13/41). It was significantly higher in families with prenatal US abnormalities and relevant family history (10/18, 55.6%), compared to families with prenatal US abnormal findings and lack of such history (3/23, 13%) (p = 0.004). WES yield was relatively high (42.9-60%) among families with involvement of brain, renal or musculoskeletal US findings. Taken together, our results in a real-world setting of genetic counseling demonstrates that fetal WES is especially indicated in families with positive family history, as well as in fetuses with specific types of congenital malformation.

Potential genetic causes of miscarriage in euploid pregnancies: a systematic review

BACKGROUND

Approximately 50% of pregnancy losses are caused by chromosomal abnormalities, such as aneuploidy. The remainder has an apparent euploid karyotype, but it is plausible that there are cases of pregnancy loss with other genetic aberrations that are not currently routinely detected. Studies investigating the use of exome sequencing and chromosomal microarrays in structurally abnormal pregnancies and developmental disorders have demonstrated their clinical application and/or potential utility in these groups of patients. Similarly, there have been several studies that have sought to identify genes that are potentially causative of, or associated with, spontaneous pregnancy loss, but the evidence has not yet been synthesized.

OBJECTIVE AND RATIONALE

The objective was to identify studies that have recorded monogenic genetic contributions to pregnancy loss in euploid pregnancies, establish evidence for genetic causes of pregnancy loss, identify the limitations of current evidence, and make recommendations for future studies. This evidence is important in considering additional research into Mendelian causes of pregnancy loss and appropriate genetic investigations for couples experiencing recurrent pregnancy loss.

SEARCH METHODS

A systematic review was conducted in MEDLINE (1946 to May 2018) and Embase (1974 to May 2018). The search terms ‘spontaneous abortion’, ‘miscarriage’, ‘pregnancy loss’, or ‘lethal’ were used to identify pregnancy loss terms. These were combined with search terms to identify the genetic contribution including ‘exome’, ‘human genome’, ‘sequencing analysis’, ‘sequencing’, ‘copy number variation’, ‘single-nucleotide polymorphism’, ‘microarray analysis’, and ‘comparative genomic hybridization’. Studies were limited to pregnancy loss up to 20 weeks in humans and excluded if the genetic content included genes that are not lethal in utero, PGD studies, infertility studies, expression studies, aneuploidy with no recurrence risk, methodologies where there is no clinical relevance, and complex genetic studies. The quality of the studies was assessed using a modified version of the Newcastle–Ottawa scale.

OUTCOMES

A total of 50 studies were identified and categorized into three themes: whole-exome sequencing studies; copy number variation studies; and other studies related to pregnancy loss including recurrent molar pregnancies, epigenetics, and mitochondrial DNA aberrations. Putatively causative variants were found in a range of genes, including CHRNA1 (cholinergic receptor, nicotinic, alpha polypeptide 1), DYNC2H1 (dynein, cytoplasmic 2, heavy chain 1), and RYR1 (ryanodine receptor 1), which were identified in multiple studies. Copy number variants were also identified to have a causal or associated link with recurrent miscarriage.

WIDER IMPLICATIONS

Identification of genes that are causative of or predisposing to pregnancy loss will be of significant individual patient impact with respect to counselling and treatment. In addition, knowledge of specific genes that contribute to pregnancy loss could also be of importance in designing a diagnostic sequencing panel for patients with recurrent pregnancy loss and also in understanding the biological pathways that can cause pregnancy loss.

Genetic testing and PGD for unexplained recurrent fetal malformations with MAGEL2 gene mutation

Birth defects are caused by multiple factors, such as chromosome abnormality, environmental factors, and maternal factors. In this study, we focused on exploring the genetic causes of a non-consanguineous couple who suffered from four times of unsuccessful pregnancy due to unexplained recurrent fetal malformations with similar symptoms and normal chromosome copy number variations. Using trio-whole exome sequencing (trio-WES) for this couple and one of the affected fetuses, we found a mutation, c.1996delC on the maternal imprinted gene MAGEL2 that was carried by the affected fetus and husband, leading to Schaaf-Yang syndrome. To screen this mutation, we further performed preimplantation genetic diagnosis (PGD) strategy followed by a gene pedigree validation and pathogenicity analysis. After the transfer of a PGD-screened embryo, a normal newborn without previous abnormal symptoms was born (February 15, 2019). We present the first data that identified a pathogenic gene (MAGEL2 c.1996delC) in a fetus with Schaaf-Yang syndrome in the EAS (East Asian) database and overcame this genetic defect by using processed PGD for this couple based on the WES results.

Update on the use of exome sequencing in the diagnosis of fetal abnormalities

Unexpected fetal abnormalities detected through ultrasound scanning in pregnancy may have a monogenic aetiology but are difficult to diagnose. Next generation sequencing now enables us to sequence fetal exomes, providing increased resolution and broader diagnostic capability compared to traditional cytogenetic prenatal tests, improving the yield and accuracy of diagnoses and allowing better counselling for expectant parents. Here we review published studies of exome sequencing (ES) for prenatal diagnosis over the last 5 years and address important questions for its clinical implementation, including clinical utility, which groups benefit most, and practical and ethical challenges for interpreting and reporting results. We observe that fetal ES substantially improves diagnostic yield relative to cytogenetic techniques. However, diagnostic rates vary widely between studies, largely attributable to differences in case selection. Recently several large studies report variations in diagnostic yield between phenotypic groups, with fetuses with multisystem abnormalities most likely to receive a diagnosis from fetal ES. Challenges for prenatal ES include the limitations of ultrasound-based fetal phenotyping, the need for rapid return of results in pregnancy, and technical limitations compared to whole genome sequencing. We also consider ethical issues around potential secondary findings and variants of uncertain significance and the complex counselling needs these present. Prenatal ES is a valuable tool to diagnose fetal abnormalities and, as it is implemented in the clinic, more large-scale research will serve to further delineate its clinical utility, as well as generating new knowledge about fetal phenotypes and informing guidelines for case selection, reporting results and genetic counselling.

From diagnostic yield to clinical impact: a pilot study on the implementation of prenatal exome sequencing in routine care

PURPOSE

Exome sequencing (ES) is an efficient tool to diagnose genetic disorders postnatally. Recent studies show that it may have a considerable diagnostic yield in fetuses with structural anomalies on ultrasound. We report on the clinical impact of the implementation of prenatal ES (pES) for ongoing pregnancies in routine care.

METHODS

We retrospectively analyzed the impact of pES on pregnancy outcome and pre- or perinatal management in the first 22 patients counseled for pES because of one or more structural anomalies on fetal ultrasound.

RESULTS

In two cases, a diagnosis was made by chromosomal microarray analysis after ES counseling. The remaining 20 cases were divided in three groups: (1) pES to aid parental decision making (n = 12), (2) pES in the context of late pregnancy termination requests (n = 5), and (3) pES to guide pre- or perinatal management (n = 3). pES had a clinical impact in 75% (9/12), 40% (2/5), and 100% (3/3) respectively, showing an overall clinical impact of pES of 70% (14/20).

CONCLUSION

We show that clinical implementation of pES is feasible and affects parental decision making or pre- and perinatal management supporting further implementation of ES in the prenatal setting.

Genetics professionals' attitudes toward prenatal exome sequencing

Prenatal exome sequencing (ES) currently has limited use in the clinical setting, but research suggests that it has added diagnostic utility over karyotyping and array techniques for prenatal diagnosis of fetuses presenting with ultrasound abnormalities. The purpose of this study was to assess the attitudes of genetics professionals toward the clinical implementation of prenatal ES in order to guide development of professional guidelines. A survey was developed using themes identified in previous qualitative studies and was distributed to members of the American College of Medical Genetics and Genomics (ACMG), the American Society of Human Genetics (ASHG), and the National Society of Genetic Counselors (NSGC). A total of 498 participants completed some portion of the survey. There was consensus among participants that there would be clinical utility of prenatal ES when used for diagnosis, pregnancy management, and termination decisions. The majority also agreed that prenatal ES was distinct from its current use in the pediatric and adult settings. There were many areas of contention regarding which types of results should be returned to families and whether or not the current ACMG guidelines for return of incidental findings should also apply to the prenatal setting. Overall, professional guidance is needed to address the continuing concerns surrounding prenatal ES as its utilization in this setting is expected to grow.

Prenatal exome sequencing analysis in fetal structural anomalies detected by ultrasonography (PAGE): a cohort study

BACKGROUND

Fetal structural anomalies, which are detected by ultrasonography, have a range of genetic causes, including chromosomal aneuploidy, copy number variations (CNVs; which are detectable by chromosomal microarrays), and pathogenic sequence variants in developmental genes. Testing for aneuploidy and CNVs is routine during the investigation of fetal structural anomalies, but there is little information on the clinical usefulness of genome-wide next-generation sequencing in the prenatal setting. We therefore aimed to evaluate the proportion of fetuses with structural abnormalities that had identifiable variants in genes associated with developmental disorders when assessed with whole-exome sequencing (WES).

METHODS

In this prospective cohort study, two groups in Birmingham and London recruited patients from 34 fetal medicine units in England and Scotland. We used whole-exome sequencing (WES) to evaluate the presence of genetic variants in developmental disorder genes (diagnostic genetic variants) in a cohort of fetuses with structural anomalies and samples from their parents, after exclusion of aneuploidy and large CNVs. Women were eligible for inclusion if they were undergoing invasive testing for identified nuchal translucency or structural anomalies in their fetus, as detected by ultrasound after 11 weeks of gestation. The partners of these women also had to consent to participate. Sequencing results were interpreted with a targeted virtual gene panel for developmental disorders that comprised 1628 genes. Genetic results related to fetal structural anomaly phenotypes were then validated and reported postnatally. The primary endpoint, which was assessed in all fetuses, was the detection of diagnostic genetic variants considered to have caused the fetal developmental anomaly.

FINDINGS

The cohort was recruited between Oct 22, 2014, and June 29, 2017, and clinical data were collected until March 31, 2018. After exclusion of fetuses with aneuploidy and CNVs, 610 fetuses with structural anomalies and 1202 matched parental samples (analysed as 596 fetus-parental trios, including two sets of twins, and 14 fetus-parent dyads) were analysed by WES. After bioinformatic filtering and prioritisation according to allele frequency and effect on protein and inheritance pattern, 321 genetic variants (representing 255 potential diagnoses) were selected as potentially pathogenic genetic variants (diagnostic genetic variants), and these variants were reviewed by a multidisciplinary clinical review panel. A diagnostic genetic variant was identified in 52 (8·5%; 95% CI 6·4-11·0) of 610 fetuses assessed and an additional 24 (3·9%) fetuses had a variant of uncertain significance that had potential clinical usefulness. Detection of diagnostic genetic variants enabled us to distinguish between syndromic and non-syndromic fetal anomalies (eg, congenital heart disease only vs a syndrome with congenital heart disease and learning disability). Diagnostic genetic variants were present in 22 (15·4%) of 143 fetuses with multisystem anomalies (ie, more than one fetal structural anomaly), nine (11·1%) of 81 fetuses with cardiac anomalies, and ten (15·4%) of 65 fetuses with skeletal anomalies; these phenotypes were most commonly associated with diagnostic variants. However, diagnostic genetic variants were least common in fetuses with isolated increased nuchal translucency (≥4·0 mm) in the first trimester (in three [3·2%] of 93 fetuses).

INTERPRETATION

WES facilitates genetic diagnosis of fetal structural anomalies, which enables more accurate predictions of fetal prognosis and risk of recurrence in future pregnancies. However, the overall detection of diagnostic genetic variants in a prospectively ascertained cohort with a broad range of fetal structural anomalies is lower than that suggested by previous smaller-scale studies of fewer phenotypes. WES improved the identification of genetic disorders in fetuses with structural abnormalities; however, before clinical implementation, careful consideration should be given to case selection to maximise clinical usefulness.

FUNDING

UK Department of Health and Social Care and The Wellcome Trust.

Whole-exome sequencing in the evaluation of fetal structural anomalies: a prospective cohort study

BACKGROUND

Identification of chromosomal aneuploidies and copy number variants that are associated with fetal structural anomalies has substantial value. Although whole-exome sequencing (WES) has been applied to case series of a few selected prenatal cases, its value in routine clinical settings has not been prospectively assessed in a large unselected cohort of fetuses with structural anomalies. We therefore aimed to determine the incremental diagnostic yield (ie, the added value) of WES following uninformative results of standard investigations with karyotype testing and chromosomal microarray in an unselected cohort of sequential pregnancies showing fetal structural anomalies.

METHODS

In this prospective cohort study, the parents of fetuses who were found to have a structural anomaly in a prenatal ultrasound were screened for possible participation in the study. These participants were predominantly identified in or were referred to the Columbia University Carmen and John Thain Center for Prenatal Pediatrics (New York, NY, USA). Fetuses with confirmed aneuploidy or a causal pathogenic copy number variant were excluded from WES analyses. By use of WES of the fetuses and parents (parent-fetus trios), we identified genetic variants that indicated an underlying cause (diagnostic genetic variants) and genetic variants that met the criteria of bioinformatic signatures that had previously been described to be significantly enriched among diagnostic genetic variants.

FINDINGS

Between April 24, 2015, and April 19, 2017, 517 sequentially identified pregnant women found to have fetuses with a structural anomaly were screened for their eligibility for inclusion in our study. 71 (14%) couples declined testing, 87 (17%) trios were missing at least one DNA sample (from either parent or the fetus), 69 (13%) trios had a clinically relevant abnormal karyotype or chromosomal microarray finding, 51 (10%) couples did not consent to WES or withdrew consent, and five (1%) samples were not of good enough quality for analysis. DNA samples from 234 (45%) eligible trios were therefore used for analysis of the primary outcome. By use of trio sequence data, we identified diagnostic genetic variants in 24 (10%) families. Mutations with bioinformatic signatures that were indicative of pathogenicity but with insufficient evidence to be considered diagnostic were also evaluated; 46 (20%) of the 234 fetuses assessed were found to have such signatures.

INTERPRETATION

Our analysis of WES data in a prospective cohort of unselected fetuses with structural anomalies shows the value added by WES following the use of routine genetic tests. Our findings suggest that, in cases of fetal anomalies in which assessment with karyotype testing and chromosomal microarray fail to determine the underlying cause of a structural anomaly, WES can add clinically relevant information that could assist current management of a pregnancy. The unique challenges of WES-based prenatal diagnostics require analysis by a multidisciplinary team of perinatal practitioners and laboratory specialists.

FUNDING

Institute for Genomic Medicine (Columbia University Irving Medical Center).

Exome sequencing of fetal anomaly syndromes: novel phenotype-genotype discoveries

The monogenic etiology of most severe fetal anomaly syndromes is poorly understood. Our objective was to use exome sequencing (ES) to increase our knowledge on causal variants and novel candidate genes associated with specific fetal phenotypes. We employed ES in a cohort of 19 families with one or more fetuses presenting with a distinctive anomaly pattern and/or phenotype recurrence at increased risk for lethal outcomes. Candidate variants were identified in 12 families (63%); in 6 of them a definite diagnosis was achieved including known or novel variants in recognized disease genes (MKS1, OTX2, FGFR2, and RYR1) and variants in novel disease genes describing new fetal phenotypes (CENPF, KIF14). We identified variants likely causal after clinical and functional review (SMAD3, KIF4A, and PIGW) and propose novel candidate genes (PTK7, DNHD1, and TTC28) for early human developmental disease supported by functional and cross-species phenotyping evidence. We describe rare and novel fetal anomaly syndromes and highlight the diagnostic utility of ES, but also its contribution to discovery. The diagnostic yield of the future application of prenatal ES will depend on our ability to increase our knowledge on the specific phenotype–genotype correlations during fetal development.

Prenatal Diagnosis by Whole Exome Sequencing in Fetuses with Ultrasound Abnormalities

Whole-exome sequencing (WES) has been used as a standard of care for postnatal diagnosis in the clinical setting in the past few years for children and adults with undiagnosed disease. Many rare disorders have been diagnosed through WES, which is less expensive than the traditional serial genetic testing where patients had previously spent years on an uninformative diagnostic odyssey. Seeking a diagnosis often entails enduring time consuming, and sometimes invasive procedures which may be associated with medical risks that are stressful for families and impose a heavy burden on the health-care system. However, the use of WES is considered impractical in the prenatal and neonatal testing period because of the technical and computational challenges of performing genomic sequencing from small amounts of genetic material, and the need for faster turnaround time (TAT) than the current 6-8 weeks TAT provided by most clinical labs offering postnatal testing. With the rapidly evolving methods of sequence analysis, there are clinical challenges such as the constantly increasing number of genes being identified which are not yet fully phenotypically characterized, especially when ascertained prenatally or neonatally before all the clinical features may be evident. Despite these challenges, there are many clinical benefits to acquiring genomic information in the prenatal and neonatal period. These include superior prognostic information which allows for prenatal planning of mode of delivery and hospital for delivery and optimized neonatal management. We have developed a clinical WES assay using small amounts of DNA with a TAT of 10 days for use in the prenatal or neonatal setting. This test is used to detect small nucleotide variants and indels in fetuses and neonates with structural abnormalities.

Fetal exome sequencing: yield and limitations in a tertiary referral center

OBJECTIVE

To explore the indications for and diagnostic outcomes of fetal exome sequencing in a tertiary referral center.

METHODS

Between 2012 and 2017, 77 unrelated fetal samples from pregnancies referred to our center underwent exome sequencing. The cohort included 37 fetuses, 36 products of conception (from cases of pregnancy termination or intrauterine fetal death), one case with DNA from both the fetus and a previous termination of pregnancy, and three cases with DNA of unknown origin. Exome sequencing was performed on DNA extracted from amniocytes or fetal tissue and, in some cases, from parental peripheral blood. Indications, turnaround time, diagnostic rates and pregnancy outcomes were investigated. Diagnostic yield was analyzed according to consanguinity (yes or no), sample type (proband only, or trio or other) and referral indication (malformation or isolated nuchal translucency (NT)).

RESULTS

The most common indication for fetal exome sequencing was multiple malformations (21/77, 27%), followed by isolated brain malformation (15/77, 19%). Twelve (16%) fetuses were referred for isolated increased NT. Exome analysis was diagnostic for 16 fetuses (21%); when subclassified into fetal malformations vs isolated increased NT it became clear that exome analysis did not reveal any known or probable pathogenic variants in cases referred for isolated increased NT, whereas, among the remaining fetuses, a molecular diagnosis was reached in 16/65 (25%). Proband-only cases received a diagnosis more often than did cases that had trio exome sequencing.

CONCLUSIONS

Exome sequencing has the potential to provide molecular diagnoses in cases in which conventional prenatal cytogenetic testing is negative. Referral bias of consanguineous cases could account for the high diagnostic rate of proband-only sequencing. Syndrome-specific prognostic information enables parents to make informed decisions, whereas challenges include time limitations and variant interpretation in the setting of non-specific fetal findings. As we report only established disease-gene associations, further segregation and functional studies in a research setting are expected to increase significantly the diagnostic yield. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Whole exome sequencing for prenatal diagnosis in cases with fetal anomalies: Criteria to improve diagnostic yield

Whole exome sequencing (WES) for prenatal diagnosis has a reported diagnostic yield of 6.2%-57%. Our aim was to identify patients with a high likelihood of genetic diagnosis using WES in cases with fetal ultrasound anomalies. This is a series of five selected cases for prenatal WES at our institution. Pregnant couples were initially identified due to fetal ultrasound anomalies. Candidates for WES for fetal diagnosis had a normal fetal karyotype and negative microarray with at least one of the following: parental consanguinity, large regions of homozygosity on fetal microarray, or high likelihood of single gene disorder based on ultrasound findings. All trios underwent sequencing of parental and fetal samples. WES was diagnostic in four of the five cases (80%). We identified two recessive conditions and two de novo mutations. Four couples consented to secondary findings and in one case, the father was found to have an MSH2 mutation associated with Lynch syndrome. The use of specific selection criteria for WES increased diagnostic yield to 80%. This is higher than previously reported. Wide application of our criteria can help identify those who may benefit most from this testing in prenatal diagnosis.

Identifying the genetic causes for prenatally diagnosed structural congenital anomalies (SCAs) by whole-exome sequencing (WES)

BACKGROUND

Whole-exome sequencing (WES) has become an invaluable tool for genetic diagnosis in paediatrics. However, it has not been widely adopted in the prenatal setting. This study evaluated the use of WES in prenatal genetic diagnosis in fetuses with structural congenital anomalies (SCAs) detected on prenatal ultrasound.

METHOD

Thirty-three families with fetal SCAs on prenatal ultrasonography and normal chromosomal microarray results were recruited. Genomic DNA was extracted from various fetal samples including amniotic fluid, chorionic villi, and placental tissue. Parental DNA was extracted from peripheral blood when available. We used WES to sequence the coding regions of parental-fetal trios and to identify the causal variants based on the ultrasonographic features of the fetus.

RESULTS

Pathogenic mutations were identified in three families (n = 3/33, 9.1%), including mutations in DNAH11, RAF1 and CHD7, which were associated with primary ciliary dyskinesia, Noonan syndrome, and CHARGE syndrome, respectively. In addition, variants of unknown significance (VUSs) were detected in six families (18.2%), in which genetic changes only partly explained prenatal features.

CONCLUSION

WES identified pathogenic mutations in 9.1% of fetuses with SCAs and normal chromosomal microarray results. Databases for fetal genotype-phenotype correlations and standardized guidelines for variant interpretation in prenatal diagnosis need to be established to facilitate the use of WES for routine testing in prenatal diagnosis.

Whole-exome sequencing in fetuses with central nervous system abnormalities

OBJECTIVE

We describe our experience with whole-exome sequencing (WES) in fetuses with central nervous system (CNS) abnormalities following a normal chromosomal microarray result.

METHODS

During the study period (2014-2017) 7 cases (9 fetuses) with prenatally diagnosed CNS abnormality, whose chromosomal microarray analysis was negative, were offered whole-exome sequencing analysis.

RESULTS

A pathogenic or a likely pathogenic variant was found in 5 cases including a previously described, likely pathogenic de novo TUBA1A variant (Case #1); a previously described homozygous VRK1 variant (Case #2); an X-linked ARX variant (Case #3); a likely pathogenic heterozygous variant in the TUBB3 gene (Case #5). Finally, in two fetuses of the same couple (Case #6), a compound heterozygous state was detected, consisting of the NPHP1 gene deletion and a sequence variant of uncertain significance. Two additional cases had normal WES results.

CONCLUSION

Whole-exome sequencing may improve prenatal diagnosis in fetuses with CNS abnormalities.

Clinical exome sequencing for fetuses with ultrasound abnormalities and a suspected Mendelian disorder

Background

Exome sequencing is now being incorporated into clinical care for pediatric and adult populations, but its integration into prenatal diagnosis has been more limited. One reason for this is the paucity of information about the clinical utility of exome sequencing in the prenatal setting.

Methods

We retrospectively reviewed indications, results, time to results (turnaround time, TAT), and impact of exome results for 146 consecutive “fetal exomes” performed in a clinical diagnostic laboratory between March 2012 and November 2017. We define a fetal exome as one performed on a sample obtained from a fetus or a product of conception with at least one structural anomaly detected by prenatal imaging or autopsy. Statistical comparisons were performed using Fisher’s exact test.

Results

Prenatal exome yielded an overall molecular diagnostic rate of 32% (n = 46/146). Of the 46 molecular diagnoses, 50% were autosomal dominant disorders (n = 23/46), 41% were autosomal recessive disorders (n = 19/46), and 9% were X-linked disorders (n = 4/46). The molecular diagnostic rate was highest for fetuses with anomalies affecting multiple organ systems and for fetuses with craniofacial anomalies. Out of 146 cases, a prenatal trio exome option designed for ongoing pregnancies was performed on 62 fetal specimens, resulting in a diagnostic yield of 35% with an average TAT of 14 days for initial reporting (excluding tissue culture time). The molecular diagnoses led to refined recurrence risk estimates, altered medical management, and informed reproductive planning for families.

Conclusion

Exome sequencing is a useful diagnostic tool when fetal structural anomalies suggest a genetic etiology, but other standard prenatal genetic tests did not provide a diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13073-018-0582-x) contains supplementary material, which is available to authorized users.

Whole Exome Sequencing: Applications in Prenatal Genetics

Prenatal whole exome sequencing (WES) has the potential to increase the ability to provide more diagnostic capabilities in fetuses with sonographic abnormalities, which would then improve the ability to counsel families. It is also often the first step in improving the path toward informed diagnosis and treatment, which is especially important in the era of advancing in utero fetal therapy. This article discusses the current literature regarding prenatal WES, clinical indications for WES, challenges with interpretation/counseling (variants of unknown significance), research priorities, ethical issues, and potential future advances.

Next-generation sequencing and prenatal 'omics: advanced diagnostics and new insights into human development

Prenatal genetics has evolved over the last decade to include application of new 'omics technologies to improve perinatal care. The clinical utility of these technologies when applied to direct fetal specimens from amniocentesis or chorionic villus sampling is being explored. In this review, we provide an overview of use of prenatal exome sequencing and role in evaluation of the structurally abnormal fetus, potential applications of genome sequencing, and finally, use of transcriptomics to assess placental and fetal well-being.

Exome sequencing identifies novel ACE splice-site variant in a fetus with renal tubular dysgenesis

We report a 32-week fetus conceived of consanguineous parentage which presented with severe early onset oligohydramnios and history of a similarly affected sibling in previous pregnancy. Ultrasonography and autopsy were inconclusive, prompting exome sequencing on fetal DNA. This resulted in identification of a homozygous novel 3' splice-site variation in intron 17 of the ACE gene (NM_000789.3:c.2642-1G>A), confirming diagnosis of autosomal recessive renal tubular dysgenesis, and facilitating prenatal diagnosis in subsequent pregnancy.

Prenatal diagnosis of skeletal dysplasias using a targeted skeletal gene panel

OBJECTIVE

This study aimed to perform an accurate and precise diagnosis for fetuses with suspected skeletal anomalies based on an incomplete and limited ultrasound phenotype.

METHODS

Proband-only targeted skeletal gene panel sequencing was performed on 12 families who had fetuses with suspected skeletal anomalies based on ultrasound evaluations at a mean gestational age of 24 weeks and 3 days. The fetuses all had normal standard genetic testing yield (karyotyping and microarray).

RESULTS

In 10 of 12 fetuses, panel sequencing provided a diagnosis or possible diagnosis with identification of variants in the following genes: FGFR3, COL1A2, IHH, COL2A1, and DYNC2H1. Two cases revealed novel variants in COL2A1 and DYNC2H1.

CONCLUSIONS

Our study suggests that targeted skeletal gene panel sequencing is highly sensitive for prenatal diagnosis of fetuses presenting with unexpected ultrasound findings suggestive of a skeletal dysplasia.

Two Consecutive Pregnancies with Simpson-Golabi-Behmel Syndrome Type 1: Case Report and Review of Published Prenatal Cases

Fetal overgrowth and numerous congenital malformations can be detected in every trimester of pregnancy. New technologies in molecular testing, such as chromosomal microarray analysis and next-generation sequencing, continually demonstrate advantages for definitive diagnosis in fetal life. Simpson-Golabi-Behmel (SGB) syndrome is a rare but well-known overgrowth condition that is rarely diagnosed in the prenatal setting. We report 3 cases of SGB syndrome in 2 consecutive pregnancies. In our series, distinctive prenatal sonographic findings led to molecular diagnosis. Exome sequencing from fetal DNA revealed a hemizygous splice site variant in the GPC3 gene: NM_004484.3:c.1166+ 1G>T. The mother is a heterozygous carrier. We also provide an overview of the previously published 57 prenatal cases of SGB syndrome with prevalence estimation of the symptoms to aid prenatal differential diagnosis of fetal overgrowth syndromes.

Whole exome sequencing as a diagnostic adjunct to clinical testing in fetuses with structural abnormalities

OBJECTIVES

To evaluate the diagnostic yield of prenatal whole exome sequencing (WES) for monogenic disorders in fetuses with structural malformations and normal results on cytogenetic testing, and to describe information on pathogenic variants that is provided by WES.

METHODS

Karyotyping, chromosomal microarray analysis (CMA) and WES were performed sequentially on stored samples from a cohort of 3949 pregnancies with fetal structural abnormalities detected on ultrasound and/or magnetic resonance imaging, referred between January 2011 and December 2015. Diagnostic rates of the three techniques were investigated overall, for phenotypic subgroups and for proband-only vs fetus-mother-father samples. Information on pathogenic variants was identified by WES.

RESULTS

Overall, 18.2% (720/3949) of fetuses had an abnormal karyotype. Pathogenic copy number variants were detected on CMA in 8.2% (138/1680) of fetuses that had a normal karyotype result. WES performed on a subgroup of 196 fetuses with normal CMA and karyotype results revealed the putative genetic variants responsible for the abnormal phenotypes in 47 cases (24%). The molecular diagnosis rates for fetus-mother-father and proband-only samples were 26.5% (13/49) and 23.1% (34/147), respectively. Variants of uncertain significance were detected in 12.8% (25/196) of fetuses, of which 22 were identified in the fetal proband-only group (15%; 22/147) and three in the fetus-mother-father group (6.1%; 3/49). The incidental finding rate was 6.1% (12/196).

CONCLUSIONS

WES is a promising method for the identification of genetic variants that cause structural abnormalities in fetuses with normal results on karyotyping and CMA. This enhanced diagnostic yield has the potential to improve the clinical management of pregnancies and to inform better the reproductive decisions of affected families. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

A Dysmorphology Based Systematic Approach Toward Perinatal Genetic Diagnosis in a Fetal Autopsy Series

BACKGROUND

This retrospective study assesses the contribution of genetic disorders in fetuses undergoing postmortem evaluation and the performance of a clinical dysmorphology based systematic approach toward genetic diagnosis.

MATERIALS AND METHODS

Ninety fetuses, including spontaneous losses and terminated pregnancies, underwent a postmortem evaluation including dysmorphological examination, radiological studies, and histopathological examination. Genetic testing including karyotyping, biochemical testing, Sanger sequencing, and exome sequencing were performed selectively.

RESULTS

A genetic etiology was concluded in 48 fetuses (55%). As a standalone test, dysmorphological examination was able to ascertain a definite genetic diagnosis in sixteen cases, histopathology in six; and karyotyping, biochemical testing and exome sequencing in two cases each (Total 28). Additionally, dysmorphology findings indicated possible genetic disorder in 20 cases.

CONCLUSION

Genetic etiologies contribute significantly to fetuses undergoing autopsy in this series. A systematic approach to postmortem fetal evaluation guided by dysmorphological examination provides high diagnostic yield toward perinatal genetic diagnosis.

Importance of complete phenotyping in prenatal whole exome sequencing

Whole exome sequencing (WES) is an emerging technique in prenatal diagnosis. In this retrospective study, we examined diagnostic utility and limitations of WES in prenatal cases with structural birth defects. DNA from 20 trios (fetal and parental), with normal karyotype and microarray findings, underwent WES and variant interpretation at a reference laboratory. The WES results were later re-evaluated in our academic center utilizing prenatal and postnatal phenotyping. Initial analysis using only prenatal ultrasound findings revealed no pathogenic or likely pathogenic variants in 20 pregnancies with structural birth defects. Re-analysis of WES variants and combination of prenatal and postnatal phenotyping yielded pathogenic variants in at least 20% of cases including PORCN gene in a fetus with split-hand/foot malformation, as well as variants of uncertain significance in NEB and NOTCH1 in fetuses with postnatal muscle weakness and Adams-Oliver syndrome, respectively. Furthermore, Sanger sequencing in a patient with holoprosencephaly, elucidated by postnatal MRI, revealed a pathogenic 47-base pairs deletion in ZIC2 which was missed by prenatal WES. This study suggests that incomplete prenatal phenotyping and lack of prenatal ultrasound-genotype databases are the limiting factors for current interpretation of WES data in prenatal diagnosis. Development of prenatal phenotype-genotype databases would significantly help WES interpretation in this setting. Patients who underwent prenatal clinical WES may benefit from the re-analysis based on detailed postnatal findings.

Promises, pitfalls and practicalities of prenatal whole exome sequencing

Prenatal genetic diagnosis provides information for pregnancy and perinatal decision-making and management. In several small series, prenatal whole exome sequencing (WES) approaches have identified genetic diagnoses when conventional tests (karyotype and microarray) were not diagnostic. Here, we review published prenatal WES studies and recent conference abstracts. Thirty-one studies were identified, with diagnostic rates in series of five or more fetuses varying between 6.2% and 80%. Differences in inclusion criteria and trio versus singleton approaches to sequencing largely account for the wide range of diagnostic rates. The data suggest that diagnostic yields will be greater in fetuses with multiple anomalies or in cases preselected following genetic review. Beyond its ability to improve diagnostic rates, we explore the potential of WES to improve understanding of prenatal presentations of genetic disorders and lethal fetal syndromes. We discuss prenatal phenotyping limitations, counselling challenges regarding variants of uncertain significance, incidental and secondary findings, and technical problems in WES. We review the practical, ethical, social and economic issues that must be considered before prenatal WES could become part of routine testing. Finally, we reflect upon the potential future of prenatal genetic diagnosis, including a move towards whole genome sequencing and non-invasive whole exome and whole genome testing. © 2017 John Wiley & Sons, Ltd.

Advanced genomic testing may aid in counseling of isolated agenesis of the corpus callosum on prenatal ultrasound

OBJECTIVE

Isolated agenesis of the corpus callosum on fetal ultrasound has a varied prognosis. Microarray and exome sequencing (ES) might aid in prenatal counseling.

METHOD

This study includes 25 fetuses with apparently isolated complete corpus callosum (cACC) on ultrasound. All cases were offered single nucleotide polymorphism array. Complementary ES was offered postnatally in selected cases. Clinical physical and neurodevelopmental follow-up was collected.

RESULTS

Eighteen cases opted for single nucleotide polymorphism array testing, which detected a causal anomaly in 2/18 (11.1%; 95% CI 2.0%-31%). Among ongoing pregnancies without a causal anomaly on microarray, 30% (95% CI 8.5%-60%) showed intellectual disability. Postnatal magnetic resonance imaging and physical examination often (64%; 95% CI 38%-85%, and 64%; 95% CI 38%-85%, respectively) revealed additional physical anomalies in cases without a causal anomaly on microarray. Two cases appeared truly isolated after birth. Postnatal sequencing in 4 of 16 cases without a causal anomaly on microarray but with intellectual disability and/or additional postnatal physical anomalies revealed 2 single-gene disorders. Therefore, the estimated diagnostic yield of ES in chromosomally normal cACC fetuses is between 2/4 (50%; 95% CI 11%-89%) and 2/16 (13.3%; 95% CI 2.4%-36%).

CONCLUSION

In accordance with current guidelines, we conclude that microarray should be offered in case of isolated cACC on ultrasound. ES is likely to be informative for prenatal counseling and should be offered if microarray is normal.

Intersociety policy statement on the use of whole-exome sequencing in the critically ill newborn infant

The rapid advancement of next-generation sequencing (NGS) technology and the decrease in costs for whole-exome sequencing (WES) and whole-genome sequening (WGS), has prompted its clinical application in several fields of medicine. Currently, there are no specific guidelines for the use of NGS in the field of neonatal medicine and in the diagnosis of genetic diseases in critically ill newborn infants. As a consequence, NGS may be underused with reduced diagnostic success rate, or overused, with increased costs for the healthcare system. Most genetic diseases may be already expressed during the neonatal age, but their identification may be complicated by nonspecific presentation, especially in the setting of critical clinical conditions. The differential diagnosis process in the neonatal intensive care unit (NICU) may be time-consuming, uncomfortable for the patient due to repeated sampling, and ineffective in reaching a molecular diagnosis during NICU stay. Serial gene sequencing (Sanger sequencing) may be successful only for conditions for which the clinical phenotype strongly suggests a diagnostic hypothesis and for genetically homogeneous diseases. Newborn screenings with Guthrie cards, which vary from country to country, are designed to only test for a few dozen genetic diseases out of the more than 6000 diseases for which a genetic characterization is available. The use of WES in selected cases in the NICU may overcome these issues. We present an intersociety document that aims to define the best indications for the use of WES in different clinical scenarios in the NICU. We propose that WES is used in the NICU for critically ill newborn infants when an early diagnosis is desirable to guide the clinical management during NICU stay, when a strong hypothesis cannot be formulated based on the clinical phenotype or the disease is genetically heterogeneous, and when specific non-genetic laboratory tests are not available. The use of WES may reduce the time for diagnosis in infants during NICU stay and may eventually result in cost-effectiveness.

Prenatal exome sequencing in anomalous fetuses: new opportunities and challenges

PurposeWe investigated the diagnostic and clinical performance of exome sequencing in fetuses with sonographic abnormalities with normal karyotype and microarray and, in some cases, normal gene-specific sequencing.MethodsExome sequencing was performed on DNA from 15 anomalous fetuses and from the peripheral blood of their parents. Parents provided consent to be informed of diagnostic results in the fetus, medically actionable findings in the parents, and their identification as carrier couples for significant autosomal recessive conditions. We assessed the perceptions and understanding of exome sequencing using mixed methods in 15 mother-father dyads.ResultsIn seven (47%) of 15 fetuses, exome sequencing provided a diagnosis or possible diagnosis with identification of variants in the following genes: COL1A1, MUSK, KCTD1, RTTN, TMEM67, PIEZO1 and DYNC2H1. One additional case revealed a de novo nonsense mutation in a novel candidate gene (MAP4K4). The perceived likelihood that exome sequencing would explain the results (5.2 on a 10-point scale) was higher than the approximately 30% diagnostic yield discussed in pretest counseling.ConclusionExome sequencing had diagnostic utility in a highly select population of fetuses where a genetic diagnosis was highly suspected. Challenges related to genetics literacy and variant interpretation must be addressed by highly tailored pre- and posttest genetic counseling.

Genomic study of severe fetal anomalies and discovery of GREB1L mutations in renal agenesis

PURPOSE

Fetal anomalies represent a poorly studied group of developmental disorders. Our objective was to assess the impact of whole-exome sequencing (WES) on the investigation of these anomalies.

METHODS

We performed WES in 101 fetuses or stillborns who presented prenatally with severe anomalies, including renal a/dysgenesis, VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities), brain anomalies, suspected ciliopathies, multiple major malformations, and akinesia.

RESULTS

A molecular diagnosis was obtained in 19 cases (19%). In 13 of these cases, the diagnosis was not initially suspected by the clinicians because the phenotype was nonspecific or atypical, corresponding in some cases to the severe end of the spectrum of a known disease (e.g., MNX1-, RYR1-, or TUBB-related disorders). In addition, we identified likely pathogenic variants in genes (DSTYK, ACTB, and HIVEP2) previously associated with phenotypes that were substantially different from those found in our cases. Finally, we identified variants in novel candidate genes that were associated with perinatal lethality, including de novo mutations in GREB1L in two cases with bilateral renal agenesis, which represents a significant enrichment of such mutations in our cohort.

CONCLUSION

Our study opens a window on the distinctive genetic landscape associated with fetal anomalies and highlights the power-but also the challenges-of WES in prenatal diagnosis.

Diagnostic application of a capture based NGS test for the concurrent detection of variants in sequence and copy number as well as LOH

Whole exome sequencing (WES) has made the identification of causative SNVs/InDels associated with rare Mendelian conditions increasingly accessible. Incorporation of softwares allowing CNVs detection into the WES bioinformatics pipelines may increase the diagnostic yield. However, no standard protocols for this analysis are so far available and CNVs in non-coding regions are totally missed by WES, in spite of their possible role in the regulation of the flanking genes expression. So, in a number of cases the diagnostic workflow contemplates an initial investigation by genomic arrays followed, in the negative cases, by WES. The opposite workflow may also be applied, according to the familial segregation of the disease. We show preliminary results for a diagnostic application of a single next generation sequencing panel permitting the concurrent detection of LOH and variations in sequences and copy number. This approach allowed us to highlight compound heterozygosity for a CNV and a sequence variant in a number of cases, the duplication of a non-coding region responsible for sex reversal, and a whole-chromosome isodisomy causing reduction to homozygosity for a WFS1 variant. Moreover, the panel enabled us to detect deletions, duplications, and amplifications with sensitivity comparable to that of the most widely used array-CGH platforms.

Congenital diaphragmatic hernias: from genes to mechanisms to therapies

Congenital diaphragmatic hernias (CDHs) and structural anomalies of the diaphragm are a common class of congenital birth defects that are associated with significant morbidity and mortality due to associated pulmonary hypoplasia, pulmonary hypertension and heart failure. In ∼30% of CDH patients, genomic analyses have identified a range of genetic defects, including chromosomal anomalies, copy number variants and sequence variants. The affected genes identified in CDH patients include transcription factors, such as GATA4, ZFPM2, NR2F2 and WT1, and signaling pathway components, including members of the retinoic acid pathway. Mutations in these genes affect diaphragm development and can have pleiotropic effects on pulmonary and cardiac development. New therapies, including fetal endoscopic tracheal occlusion and prenatal transplacental fetal treatments, aim to normalize lung development and pulmonary vascular tone to prevent and treat lung hypoplasia and pulmonary hypertension, respectively. Studies of the association between particular genetic mutations and clinical outcomes should allow us to better understand the origin of this birth defect and to improve our ability to predict and identify patients most likely to benefit from specialized treatment strategies.

Molecular autopsy in maternal-fetal medicine

PurposeThe application of genomic sequencing to investigate unexplained death during early human development, a form of lethality likely enriched for severe Mendelian disorders, has been limited.MethodsIn this study, we employed exome sequencing as a molecular autopsy tool in a cohort of 44 families with at least one death or lethal fetal malformation at any stage of in utero development. Where no DNA was available from the fetus, we performed molecular autopsy by proxy, i.e., through parental testing.ResultsPathogenic or likely pathogenic variants were identified in 22 families (50%), and variants of unknown significance were identified in further 15 families (34%). These variants were in genes known to cause embryonic or perinatal lethality (ALPL, GUSB, SLC17A5, MRPS16, THSD1, PIEZO1, and CTSA), genes known to cause Mendelian phenotypes that do not typically include embryonic lethality (INVS, FKTN, MYBPC3, COL11A2, KRIT1, ASCC1, NEB, LZTR1, TTC21B, AGT, KLHL41, GFPT1, and WDR81) and genes with no established links to human disease that we propose as novel candidates supported by embryonic lethality of their orthologs or other lines of evidence (MS4A7, SERPINA11, FCRL4, MYBPHL, PRPF19, VPS13D, KIAA1109, MOCS3, SVOPL, FEN1, HSPB11, KIF19, and EXOC3L2).ConclusionOur results suggest that molecular autopsy in pregnancy losses is a practical and high-yield alternative to traditional autopsy, and an opportunity for bringing precision medicine to the clinical practice of perinatology.

Clinical diagnostic exome evaluation for an infant with a lethal disorder: genetic diagnosis of TARP syndrome and expansion of the phenotype in a patient with a newly reported RBM10 alteration

Background

Diagnostic Exome Sequencing (DES) has been shown to be an effective tool for diagnosis individuals with suspected genetic conditions.

Case Presentation

We report a male infant born with multiple anomalies including bilateral dysplastic kidneys, cleft palate, bilateral talipes, and bilateral absence of thumbs and first toes. Prenatal testing including chromosome analysis and microarray did not identify a cause for the multiple congenital anomalies. Postnatal diagnostic exome studies (DES) were utilized to find a molecular diagnosis for the patient.

Exome sequencing of the proband, mother, and father showed a previously unreported maternally inherited RNA binding motif protein 10 (RBM10) c.1352_1353delAG (p.E451Vfs*66) alteration. Mutations in RBM10 are associated with TARP syndrome, an X-linked recessive disorder originally described with cardinal features of talipes equinovarus, atrial septal defect, Robin sequence, and persistent left superior vena cava.

Conclusion

DES established a molecular genetic diagnosis of TARP syndrome for a neonatal patient with a poor prognosis in whom traditional testing methods were uninformative and allowed for efficient diagnosis and future reproductive options for the parents. Other reported cases of TARP syndrome demonstrate significant variability in clinical phenotype. The reported features in this infant including multiple hemivertebrae, imperforate anus, aplasia of thumbs and first toes have not been reported in previous patients, thus expanding the clinical phenotype for this rare disorder.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0426-3) contains supplementary material, which is available to authorized users.

Prenatal and pre-implantation genetic diagnosis

The past decade has seen the development of technologies that have revolutionized prenatal genetic testing; that is, genetic testing from conception until birth. Genome-wide single-cell arrays and high-throughput sequencing analyses are dramatically increasing our ability to detect embryonic and fetal genetic lesions, and have substantially improved embryo selection for in vitro fertilization (IVF). Moreover, both invasive and non-invasive mutation scanning of the genome are helping to identify the genetic causes of prenatal developmental disorders. These advances are changing clinical practice and pose novel challenges for genetic counselling and prenatal care.

Whole-exome sequencing on deceased fetuses with ultrasound anomalies: expanding our knowledge of genetic disease during fetal development

PurposeThe aim of this study was to determine the diagnostic yield of whole-exome sequencing (WES) in fetuses with ultrasound anomalies that resulted in fetal demise or pregnancy termination. The results were also utilized to aid in the identification of candidate genes for fetal development and to expand the clinical phenotype of known genetic conditions.MethodsWES was performed on specimens from 84 deceased fetuses. Data were analyzed and final results were classified into one of four categories: positive, possible, negative, and candidate gene only. WES analysis was predominantly performed in fetus-parent trios or quads (61%, n=52).ResultsOverall, 20% (n = 17) of cases were positive, 45% (n=38) were possible, 9% (n=7) had only candidate gene variants and 26% (n = 22) tested negative. The diagnostic yield for definitive findings for trio analysis was 24% (n = 11) compared to 14% (n = 4) for singletons. The most frequently reported ultrasound anomalies were central nervous system (37%, n = 31), hydrops/edema (36%, n = 30), and cardiovascular anomalies (31%, n = 26).ConclusionOur experience supports the use of WES to identify the molecular etiology of fetal ultrasound anomalies, to identify candidate genes involved in fetal development, and to expand our knowledge of the clinical phenotype of known genetic conditions.

Prenatal DNA Sequencing: Clinical, Counseling, and Diagnostic Laboratory Considerations

Clinical diagnostic laboratories are producing next-generation sequencing-based test results that are becoming increasingly incorporated into patient care. Whole genome and exome sequencing on fetal material derived from amniocytes, chorionic villi, or products of conception is starting to be offered clinically in specialized centers, but it has not yet become routine practice. The technical, interpretation, and ethical challenges are greatest in the area of prenatal medicine because the fetus has a limited health history, and the physical examination is only indirectly available via prenatal sonography. Here, we provide an overview of these challenges and highlight the clinical utility, reporting, and counseling issues associated with prenatal DNA sequencing. Future considerations are also discussed. © 2017 John Wiley & Sons, Ltd.

Prenatal and postnatal findings in small-for-gestational-age fetuses without structural ultrasound anomalies at 18-24 weeks

OBJECTIVE

To assess phenotypic and genotypic characteristics of small-for-gestational-age (SGA) fetuses without structural anomalies at 18-24 weeks' gestation.

METHODS

This retrospective study included structurally normal singleton fetuses with an abdominal circumference ≤ 5^th percentile on detailed ultrasound examination between 18 and 24 weeks' gestation. Cases were stratified according to the absence or presence of other abnormal ultrasound findings, such as abnormal amniotic fluid or soft markers. All patients were offered invasive prenatal testing with rapid aneuploidy detection by qualitative fluorescence polymerase chain reaction (QF-PCR) and, if normal, consecutive single nucleotide polymorphism (SNP) array was also offered. Detailed postnatal follow-up (≥ 5 months) was performed. In cases in which a syndromic phenotype became apparent within 5 months after birth and SNP array had not been performed prenatally, it was performed postnatally.

RESULTS

A total of 211 pregnancies were eligible for inclusion. Of the 158 cases with isolated SGA on ultrasound, 36 opted for invasive prenatal testing. One case of trisomy 21 and one case of a submicroscopic abnormality (a susceptibility locus for neurodevelopmental disease) were detected. Postnatal follow-up showed a postnatal apparent syndromic phenotype in 10 cases. In one case this was due to trisomy 21 and the other nine (5.8%; 95% CI, 2.8-10.0%) cases had normal SNP array results. In 32/53 cases with SGA and associated ultrasound abnormalities, parents opted for invasive testing. One case of trisomy 21 and one of triploidy were found. In 11 cases a syndromic phenotype became apparent after birth. One was due to trisomy 21 and in one case a submicroscopic anomaly (a susceptibility locus) was found. The remaining syndromic cases (17.3%; 95% CI, 8.7-29.0%) had normal SNP array results.

CONCLUSION

Testing for chromosomal anomalies should be offered in cases of SGA between 18 and 24 weeks' gestation. Whole chromosome anomalies occur in 1.3% (95% CI, 0.2-3.9%) of isolated SGA and 5.8% (95% CI, 1.5-14.0%) of associated SGA. In 0.6% (95% CI, 0.1-2.8%) and 1.9% (95% CI, 0.2-8.2%), respectively, SNP array detected a susceptibility locus for neurodevelopmental disease that would not be detected by karyotyping, QF-PCR or non-invasive prenatal testing. Therefore, and because the genetic causes of SGA are diverse, we suggest SNP array testing in cases of SGA. Thorough postnatal examination and follow-up of infants that presented with reduced fetal growth is important because chromosomally normal syndromic phenotypes occur frequently in SGA fetuses. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Novel Pathogenic Variant (c.580C>T) in the CPS1 Gene in a Newborn With Carbamoyl Phosphate Synthetase 1 Deficiency Identified by Whole Exome Sequencing

Diagnosis of the urea cycle disorder (USD) carbamoyl-phosphate synthetase 1 (CPS1) deficiency (CPS1D) based on only the measurements of biochemical intermediary metabolites is not sufficient to properly exclude other UCDs with similar symptoms. We report the first Korean CPS1D patient using whole exome sequencing (WES). A four-day-old female neonate presented with respiratory failure due to severe metabolic encephalopathy with hyperammonemia (1,690 µmol/L; reference range, 11.2-48.2 µmol/L). Plasma amino acid analysis revealed markedly elevated levels of alanine (2,923 µmol/L; reference range, 131-710 µmol/L) and glutamine (5,777 µmol/L; reference range, 376-709 µmol/L), whereas that of citrulline was decreased (2 µmol/L; reference range, 10-45 µmol/L). WES revealed compound heterozygous pathogenic variants in the CPS1 gene: one novel nonsense pathogenic variant of c.580C>T (p.Gln194*) and one known pathogenic frameshift pathogenic variant of c.1547delG (p.Gly516Alafs*5), which was previously reported in Japanese patients with CPS1D. We successfully applied WES to molecularly diagnose the first Korean patient with CPS1D in a clinical setting. This result supports the clinical applicability of WES for cost-effective molecular diagnosis of UCDs.

Prenatal diagnosis of X-linked myopathy associated with a VMA21 gene mutation afforded through a novel targeted exome sequencing strategy applied in fetuses with abnormal ultrasound findings

Fetal malformations detected through routine prenatal ultrasound examination comprise a heterogeneous group potentially associated with genetic disorders where the underlying cause is difficult to establish. We present the prenatal diagnosis of a rare X‐linked myopathy involving a new VMA21 gene mutation, detected through a novel prenatal exome sequencing‐based approach.

Unsolved challenges in pediatric whole-exome sequencing: A literature analysis

Whole-exome sequencing (WES) has been instrumental in the discovery of novel genes and mechanisms causing Mendelian diseases. While this technology is now being successfully applied in a number of clinics, particularly to diagnose patients with rare diseases, it also raises a number of ethical, legal and social issues. In order to identify what challenges were directly foreseen by technology users, we performed a systematic review of the literature. In this paper, we focus on recent publications related to the use of WES in the pediatric context and analyze the most prominent challenges raised by technology users. This is particularly relevant considering that a) most patients currently undergoing testing using WES to identify the genetic basis for rare diseases are children and b) their lack of capacity to consent for themselves makes them a vulnerable population and generates the need for specific ethical, legal and regulatory procedures. We identified key challenges that related to four main categories: (1) intake; (2) sequence production and analysis; (3) reporting of results and counseling considerations and (4) collaborative data interpretation and data sharing. We then contextualize these challenges in light of the recent recommendations and guidelines, published by professional societies that have significant potential to impact the field.