Prenatal Genome-Wide Sequencing analysis (Exome or Genome) in detecting pathogenic Single Nucleotide Variants in fetal Central Nervous System Anomalies: systematic review and meta-analysis

Prenatal Exome (pES) or Genome (pGS) Sequencing analysis showed a significant incremental diagnostic yield over karyotype and chromosomal microarray analysis (CMA) in fetal structural anomalies. Optimized indications and detection rates in different fetal anomalies are still under investigation. The aim of this study was to assess the incremental diagnostic yield in prenatally diagnosed Central Nervous System (CNS) anomalies. A systematic review on antenatal CNS anomalies was performed according to PRISMA guidelines, including n = 12 paper, accounting for 428 fetuses. Results were pooled in a meta-analysis fitting a logistic random mixed-effect model. The effect of interest was the incremental diagnostic rate of pES over karyotype/CMA in detecting likely pathogenic/pathogenic Single Nucleotide Variants (SNVs). A further meta-analysis adding the available pGS studies (including diagnostic coding SNVs only) and submeta-analysis on three CNS subcategories were also performed. The pooled incremental diagnostic yield estimate of pES studies was 38% (95% C.I.: [29%;47%]) and 36% (95% C.I.: [28%;45%]) when including diagnostic SNVs of pGS studies. The point estimate of the effect resulted 22% (95% C.I.: [15%;31%]) in apparently isolated anomalies, 33% (95% C.I.: [22%;46%]) in CNS-only related anomalies (≥1) and 46% (95% C.I.: [38%;55%]) in non-isolated anomalies (either ≥ 2 anomalies in CNS, or CNS and extra-CNS). Meta-analysis showed a substantial diagnostic improvement in performing Prenatal Genome-Wide Sequencing analysis (Exome or Genome) over karyotype and CMA in CNS anomalies.

Prenatal CFAP53-related laterality defect: case report and review of the literature

Laterality defects include morphological anomalies with impaired left-right asymmetry induction, such as dextrocardia, situs inversus abdominis, situs inversus totalis and situs ambiguus. The different arrangement of major organs is called heterotaxy. We describe for the first time a fetus with situs viscerum inversus and azygos continuation of the inferior vena cava, due to previously unreported variants in compound heterozygosity in the CFAP53 gene, whose product is implied in cilial motility. Prenatal trio exome sequencing was performed with turn-around time during the pregnancy. The fetuses with laterality defects are suitable candidates for prenatal exome sequencing due to the emerging high diagnostic rate of this group of morphological anomalies. A timely molecular diagnosis plays a fundamental role in genetic counseling, regarding couple decisions on the ongoing pregnancy, providing recurrence risks, and in predicting possible respiratory complications due to ciliary dyskinesia.

Duplication at 19q13.32q13.33 Segregating with Neuropsychiatric Phenotype in a Three-Generation Family: Towards the Definition of a Critical Region

Chromosomal submicroscopic imbalances represent well-known causes of neurodevelopmental disorders. In some cases, these can cause specific autosomal dominant syndromes, with high-to-complete penetrance and de novo occurrence of the variant. In other cases, they result in non-syndromic neurodevelopmental disorders, often acting as moderate-penetrance risk factors, possibly inherited from unaffected parents. We describe a three-generation family with non-syndromic neuropsychiatric features segregating with a novel 19q13.32q13.33 microduplication. The propositus was a 28-month-old male ascertained for psychomotor delay, with no dysmorphic features or malformations. His mother had Attention-Deficit/Hyperactivity Disorder and a learning disability. The maternal uncle had an intellectual disability. Chromosomal microarray analysis identified a 969 kb 19q13.32q13.33 microduplication in the proband. The variant segregated in the mother, the uncle, and the maternal grandmother of the proband, who also presented neuropsychiatric disorders. Fragile-X Syndrome testing was negative. Exome Sequencing did not identify Pathogenic/Likely Pathogenic variants. Imbalances involving 19q13.32 and 19q13.33 are associated with neurodevelopmental delay. A review of the reported microduplications allowed to propose BICRA (MIM *605690) and KPTN (MIM *615620) as candidates for the neurodevelopmental delay susceptibility in 19q13.32q13.33 copy number gains. The peculiarities of this case are the small extension of the duplication, the three-generation segregation, and the full penetrance of the phenotype.

Heterozygous Pathogenic Nonsense Variant in the ATM Gene in a Family with Unusually High Gastric Cancer Susceptibility

Germline pathogenic variants (PVs) in the Ataxia Telangiectasia mutated (ATM) gene (MIM* 607585) increase the risk for breast, pancreatic, gastric, and prostatic cancer and, to a reduced extent, ovarian and colon cancer and melanoma, with moderate penetrance and variable expressivity. We describe a family presenting early-onset gastric cancer and harboring a heterozygous pathogenic ATM variant. The proband had gastric cancer (age 45) and reported a sister deceased due to diffuse gastric cancer (age 30) and another sister who developed diffuse gastric cancer (age 52) and ovarian serous cancer. Next generation sequencing for cancer susceptibility genes (APC, ATM, BRD1, BRIP1, CDH1, CDK4, CDKN2A, CHEK2, EPCAM, MLH1, MRE11, MSH2, MSH6, MUTYH, NBN, PALB2, PMS2, PTEN, RAD50, RAD51C, RAD51D, RECQL1, SMAD4, STK11, and TP53) was performed. Molecular analysis identified the truncating c.5944C>T, p.(Gln1982*) variant in the ATM (NM_000051.3; NP_000042.3) in the proband. The variant had segregated in the living affected sister and in the unaffected daughter of the deceased affected sister. Familial early-onset gastric cancer is an unusual presentation for ATM-related malignancies. Individual variants may result in different specific risks. Genotype-phenotype correlations are challenging given the low penetrance and variable expressivity. Careful family history assessments are pivotal for prevention planning and are strengthened by the availability of molecular diagnoses.

Mosaic genome-wide paternal uniparental disomy after discordant results from primary fetal samples and cultured cells

Mosaic genome-wide paternal uniparental disomy (GWpUPD) is a rare condition in which two euploid cell lines coexist in the same individual, one with biparental content and one with genome-wide paternal isodisomy. We report a complex prenatal diagnosis with discordant results from cultured and uncultured samples. A pregnant woman was referred for placental mesenchymal dysplasia and fetal omphalocele. Karyotype, array-CGH and Beckwith-Wiedemann Syndrome (BWS) testing (methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) of 11p15) performed on amniocytes were negative. After intrauterine fetal demise, the clinical suspicion persisted and BWS MS-MLPA was repeated on cultured cells from umbilical cord and amniotic fluid, revealing a mosaicism for KvH19 hypermethylation/KCNQ1OT1:TSS:DMR hypomethylation. These results, along with microsatellite analysis of the BWS region, were consistent with mosaic paternal 11p15 isodisomy. A concurrent maternal contamination exclusion test, analyzing polymorphic microsatellite markers on multiple chromosomes, showed an imbalance in favor of paternal alleles at all examined loci on cultured amniocytes and umbilical cord samples. This led to suspicion of mosaic GWpUPD, later confirmed by SNP-array, identifying a mosaic genome-wide paternal isodisomy affecting 60% of fetal cells. The assessment of mosaic GWpUPD requires multiple approaches beyond the current established diagnostic processes, also entertaining possible low-rate mosaicism. Clinical acumen and an integrated testing approach are the key to a successful diagnosis.

Clinical variability in DYNC2H1-related skeletal ciliopathies includes Ellis-van Creveld syndrome

Deleterious variants of DYNC2H1 gene are associated with a wide spectrum of skeletal ciliopathies (SC). We used targeted parallel sequencing to analyze 25 molecularly unsolved families with different SCs. Deleterious DYNC2H1 variants were found in six sporadic patients and two monozygotic (MZ) twins. Clinical diagnoses included short rib-polydactyly type 3 in two cases, and asphyxiating thoracic dystrophy (ATD) in one case. Remarkably, clinical diagnosis fitted with EvC, mixed ATD/EvC and short rib-polydactyly/EvC phenotypes in three sporadic patients and the MZ twins. EvC/EvC-like features always occurred in compound heterozygotes sharing a previously unreported splice site change (c.6140-5A>G) or compound heterozygotes for two missense variants. These results expand the DYNC2H1 mutational repertoire and its clinical spectrum, suggesting that EvC may be occasionally caused by DYNC2H1 variants presumably acting as hypomorphic alleles.

Non-Ceruloplasmin Copper Identifies a Subtype of Alzheimer’s Disease (CuAD): Characterization of the Cognitive Profile and Case of a CuAD Patient Carrying an RGS7 Stop-Loss Variant

Alzheimer’s disease (AD) is a type of dementia whose cause is incompletely defined. Copper (Cu) involvement in AD etiology was confirmed by a meta-analysis on about 6000 participants, showing that Cu levels were decreased in AD brain specimens, while Cu and non-bound ceruloplasmin Cu (non-Cp Cu) levels were increased in serum/plasma samples. Non-Cp Cu was advocated as a stratification add-on biomarker of a Cu subtype of AD (CuAD subtype). To further circumstantiate this concept, we evaluated non-Cp Cu reliability in classifying subtypes of AD based on the characterization of the cognitive profile. The stratification of the AD patients into normal AD (non-Cp Cu ≤ 1.6 µmol/L) and CuAD (non-Cp Cu > 1.6 µmol/L) showed a significant difference in executive function outcomes, even though patients did not differ in disease duration and severity. Among the Cu-AD patients, a 76-year-old woman showed significantly abnormal levels in the Cu panel and underwent whole exome sequencing. The CuAD patient was detected with possessing the homozygous (c.1486T > C; p.(Ter496Argext*19) stop-loss variant in the RGS7 gene (MIM*602517), which encodes for Regulator of G Protein Signaling 7. Non-Cp Cu as an add-on test in the AD diagnostic pathway can provide relevant information about the underlying pathological processes in subtypes of AD and suggest specific therapeutic options.

A Pain in the Neck: Lessons Learnt from Genetic Testing in Fetuses Detected with Nuchal Fluid Collections, Increased Nuchal Translucency versus Cystic Hygroma-Systematic Review of the Literature, Meta-Analysis and Case Series

Fetal Nuchal fluid collections can manifest with two distinct presentations attributable to the same phenotypic spectrum: increased nuchal translucency (iNT) and cystic hygroma. The prenatal detection of these findings should prompt an accurate assessment through genetic counseling and testing, including karyotype, chromosomal microarray analysis (CMA) and multigene RASopathy panel. We performed a systematic review of the literature and meta-analysis, to calculate diagnostic yields of genetic testing in fetuses with iNT and cystic hygroma. We compared the results with a cohort of 96 fetuses with these isolated findings. Fetuses with isolated NT ≥ 2.5 mm showed karyotype anomalies in 22.76% of cases and CMA presented an incremental detection rate of 2.35%. Fetuses with isolated NT ≥ 3 mm presented aneuploidies in 14.36% of cases and CMA had an incremental detection rate of 3.89%. When the isolated NT measured at least 3.5 mm the diagnostic yield of karyotyping was 34.35%, the incremental CMA detection rate was 4.1%, the incremental diagnostic rate of the RASopathy panel was 1.44% and it was 2.44% for exome sequencing. Interestingly, CMA presents a considerable diagnostic yield in the group of fetuses with NT ≥ 3.5 mm. Similarly, exome sequencing appears to show promising results and could be considered after a negative CMA result.

Cardiac function in adolescents and young adults with 22q11.2 deletion syndrome without congenital heart disease

BACKGROUND

Diagnosis and treatment of 22q11.2 deletion syndrome (22q11.2DS) have led to improved life expectancy and achievement of adulthood. Limited data on long-term outcomes reported an increased risk of premature death for cardiovascular causes, even without congenital heart disease (CHD). The aim of this study was to assess the cardiac function in adolescents and young adults with 22q11.2DS without CHDs.

METHODS

A total of 32 patients (20M, 12F; mean age 26.00 ± 8.08 years) and a healthy control group underwent transthoracic echocardiography, including Tissue Doppler Imaging (TDI) and 2-dimensional Speckle Tracking Echocardiography (2D-STE).

RESULTS

Compared to controls, 22q11.2DS patients showed a significant increase of the left ventricle (LV) diastolic and systolic diameters (p = 0.029 and p = 0.035 respectively), interventricular septum thickness (p = 0.005), LV mass index (p < 0.001) and aortic root size (p < 0.001). 2D-STE analysis revealed a significant reduction of LV global longitudinal strain (p < 0.001) in 22q11.2DS than controls. Moreover, several LV diastolic parameters were significantly different between groups.

CONCLUSIONS

Our results suggest that an echocardiographic follow-up in 22q11.2DS patients without CHDs can help to identify subclinical impairment of the LV and evaluate a potential progression of aortic root dilation over time, improving outcomes, reducing long-term complications and allowing for a better prognosis.

Crossed pulmonary arteries: An underestimated cardiovascular variant with a strong association with genetic syndromes-A report of 74 cases with systematic review of the literature

Crossed pulmonary arteries (CPAs) represent an uncommon anatomic variant, usually associated with some specific syndromes and conotruncal defects. This finding has been described in 22q11.2 Deletion Syndrome (22q11.2DS). We evaluated the correlation between CPAs and genetic diseases, in order to better define the characteristics of this variant, considered a rare anatomic pattern. An in-depth analysis of CPAs genotype-phenotype correlations was performed via a literature review. We detected 74 CPAs patients through echocardiography. Of these 74 patients, 35.1% of patients showed additional intracardiac malformations, while 29.7% showed extracardiac vascular anomalies, of which 16.2% were associated with intracardiac defects and 13.5% were not. In all, 62.2% of patients were diagnosed with genetic diseases and 52.2% of them were 22q11.2DS patients. In conclusions, CPAs represent a cardiovascular variant, which is detectable in nonsyndromic individuals, but especially in various genetic syndromes and in particular in 22q11.2DS patients. Data on the real prevalence of this morphology is lacking in literature. Knowledge of this anatomic variant is useful to interpret the unusual course of the pulmonary branches and is helpful information before cardiovascular surgical correction. Moreover, due to the strong association of CPAs with some genetic syndromes, the identification of this anatomic pattern can indicate the utility of a genetic assessment of these patients.

Genomic Breakpoints’ Characterization of a Large CHEK2 Duplication in an Italian Family with Hereditary Breast Cancer

CHEK2 (checkpoint kinase 2; MIM# 604373) is a tumor suppressor gene that encodes a serine threonine kinase involved in pathways such as DNA repair, cell cycle arrest, mitosis, and apoptosis. Pathogenic variants in CHEK2 contribute to a moderately increased risk of breast and other cancers. Several variant classes have been reported, either point mutations or large intragenic rearrangements. However, a significant portion of reported variants has an uncertain clinical significance. We report an intragenic CHEK2 duplication, ranging from intron 5 to intron 13, identified in an Italian family with hereditary breast cancer. Using long range PCR, with duplication-specific primers, we were able to ascertain the genomic breakpoint. We also performed a real-time PCR to assess a possible loss-of-function effect. The genomic characterization of large intragenic rearrangements in cancer susceptibility genes is important for the clinical management of the carriers and for a better classification of rare variants. The molecular definition of breakpoints allows for the prediction of the impact of the variant on transcripts and proteins, aiding in its characterization and clinical classification.

Chromosomal Microarray Analysis in Fetuses Detected with Isolated Cardiovascular Malformation: A Multicenter Study, Systematic Review of the Literature and Meta-Analysis

Cardiovascular malformations (CVM) represent the most common structural anomalies, occurring in 0.7% of live births. The CVM prenatal suspicion should prompt an accurate investigation with fetal echocardiography and the assessment through genetic counseling and testing. In particular, chromosomal microarray analysis (CMA) allows the identification of copy number variations. We performed a systematic review and meta-analysis of the literature, studying the incremental diagnostic yield of CMA in fetal isolated CVM, scoring yields for each category of heart disease, with the aim of guiding genetic counseling and prenatal management. At the same time, we report 59 fetuses with isolated CVM with normal karyotype who underwent CMA. The incremental CMA diagnostic yield in fetuses with isolated CVM was 5.79% (CI 5.54–6.04), with conotruncal malformations showing the higher detection rate (15.93%). The yields for ventricular septal defects and aberrant right subclavian artery were the lowest (2.64% and 0.66%). Other CVM ranged from 4.42% to 6.67%. In the retrospective cohort, the diagnostic yield was consistent with literature data, with an overall CMA diagnostic yield of 3.38%. CMA in the prenatal setting was confirmed as a valuable tool for investigating the causes of fetal cardiovascular malformations.

Molecular Approaches in Fetal Malformations, Dynamic Anomalies and Soft Markers: Diagnostic Rates and Challenges-Systematic Review of the Literature and Meta-Analysis

Fetal malformations occur in 2-3% of pregnancies. They require invasive procedures for cytogenetics and molecular testing. "Structural anomalies" include non-transient anatomic alterations. "Soft markers" are often transient minor ultrasound findings. Anomalies not fitting these definitions are categorized as "dynamic". This meta-analysis aims to evaluate the diagnostic yield and the rates of variants of uncertain significance (VUSs) in fetuses undergoing molecular testing (chromosomal microarray (CMA), exome sequencing (ES), genome sequencing (WGS)) due to ultrasound findings. The CMA diagnostic yield was 2.15% in single soft markers (vs. 0.79% baseline risk), 3.44% in multiple soft markers, 3.66% in single structural anomalies and 8.57% in multiple structural anomalies. Rates for specific subcategories vary significantly. ES showed a diagnostic rate of 19.47%, reaching 27.47% in multiple structural anomalies. WGS data did not allow meta-analysis. In fetal structural anomalies, CMA is a first-tier test, but should be integrated with karyotype and parental segregations. In this class of fetuses, ES presents a very high incremental yield, with a significant VUSs burden, so we encourage its use in selected cases. Soft markers present heterogeneous CMA results from each other, some of them with risks comparable to structural anomalies, and would benefit from molecular analysis. The diagnostic rate of multiple soft markers poses a solid indication to CMA.

Myoclonic Epilepsy: Case Report of a Mild Phenotype in a Pediatric Patient Expanding Clinical Spectrum of KCNA2 Pathogenic Variants

We report on the rare case of a male toddler presenting with myoclonic epilepsy characterized by daily episodes of upward movements of the eyebrows, and myoclonic jerks of both head and upper limbs. In addition, the child showed speech delay, tremors, and lack of motor coordination. Next Generation Sequencing analysis (NGS) performed in trio revealed in the proband the c.889C>T de novo missense variant in the KCNA2 gene in heterozygous state. This is the first case of myoclonic epilepsy in a toddler due to a c.889C>T KCNA2 missense variant. The patient was treated with valproic acid and ethosuximide with a good clinical response. At 6 years old, follow-up revealed that the proband was seizure-free with tremors and clumsiness in movements. According to the literature, this case supports the correlation between myoclonic epilepsy and KCNA2 alterations. This evidence suggests that performing genomic testing including the KCNA2 gene in preschool patients affected by myoclonic epilepsy, especially when associated with delayed neurodevelopment. Our goal is to expand the phenotypical spectrum of this rare condition and adding clinical features following a genotype-first approach.

External hydrocephalus as a prenatal feature of noonan syndrome

Brain malformations have been reported in RASopathies, including postnatal external hydrocephalus, a nonobstructive form of cerebrospinal fluid accumulation around the brain. It was described in a few patients with mutations of other genes than PTPN11, such as SOS1 and SHOC2 and never in prenatal diagnosis. The aim of this case report is to describe the prenatal presentation of a fetus with Noonan syndrome (NS) and external hydrocephalus. We report on a Noonan syndrome fetus with a de novo pathogenic PTPN11 c.923A>G p.Asn308Ser mutation, showing external hydrocephalus, an extremely rare fetal finding, corpus callosum, and cerebellar vermis under the 10th centile, plus a typical NS cardiopathy. This is the first case of Noonan syndrome prenatal diagnosis in a fetus presenting with external hydrocephalus. Following pathophysiological considerations, we suggest to consider NS in the differential diagnosis of external hydrocephalus, investigating other evocative findings and considering molecular screening for mutations in NS-related genes.

When to test fetuses for RASopathies? Proposition from a systematic analysis of 352 multicenter cases and a postnatal cohort

PURPOSE

Recent studies have identified suggestive prenatal features of RASopathies (e.g., increased nuchal translucency [NT], cystic hygroma [CH], hydrops, effusions, congenital heart diseases [CHD], polyhydramnios, renal anomalies). Our objective is to clarify indications for RASopathy prenatal testing. We compare genotype distributions between pre- and postnatal populations and propose genotype-phenotype correlations.

METHODS

Three hundred fifty-two chromosomal microarray-negative cases sent for prenatal RASopathy testing between 2012 and 2019 were collected. For most, 11 RASopathy genes were tested. Postnatal cohorts (25 patients with available prenatal information and 108 institutional database genotypes) and the NSeuroNet database were used for genotypic comparisons.

RESULTS

The overall diagnostic yield was 14% (50/352), with rates >20% for effusions, hydrops, and CHD. Diagnostic yield was significantly improved in presence of hypertrophic cardiomyopathy (HCM), persistent or associated CH, any suggestive finding combined with renal anomaly or polyhydramnios, or ≥2 ultrasound findings. Largest prenatal contributors of pathogenic variants were PTPN11 (30%), RIT1 (16%), RAF1 (14%), and HRAS (12%), which considerably differ from their prevalence in postnatal populations. HRAS, LZTR1, and RAF1 variants correlated with hydrops/effusions, and RIT1 with prenatal onset HCM.

CONCLUSION

After normal chromosomal microarray, RASopathies should be considered when any ultrasound finding of lymphatic dysplasia or suggestive CHD is found alone or in association.

Fetal early motor neuron disruption and prenatal molecular diagnosis in a severe BICD2-opathy

BICD2 (BICD Cargo Adaptor 2, MIM*609797) mutations are associated with severe prenatal-onset forms of spinal muscular atrophy, lower extremity-predominant 2B (SMALED2B MIM 618291) or milder forms with childhood-onset (SMALED2A MIM 615290). Etiopathogenesis is not fully clarified and a wide spectrum of phenotypic presentations is reported, ranging from extreme prenatal forms with adverse outcome, to slow progressive late-onset forms. We report a fetus at 22 gestational weeks with evidence of Arthrogryposis Multiplex Congenita on ultrasound, presenting with fixed extended lower limbs and flexed upper limbs, bilateral clubfoot and absent fetal movements. A trio-based prenatal Exome Sequencing was performed, disclosing a de novo heterozygous pathogenic in frame deletion (NM_015250.3: c.1636_1638delAAT; p.Asn546del) in BICD2. After pregnancy termination, quantitative analysis on NeuN immunostained spinal cord sections of the ventral horns, revealed that neuronal density was markedly reduced compared to the one of an age-matched normal fetus and an age-matched type-I Spinal Muscular Atrophy sample, used as a comparative model. The present case, the first prenatally diagnosed and neuropathologically characterized, showed an early motor neuron loss in SMALED2B, providing further insight into the pathological basis of BICD2-opathies.

Prenatal Exome Sequencing: Background, Current Practice and Future Perspectives-A Systematic Review

The introduction of Next Generation Sequencing (NGS) technologies has exerted a significant impact on prenatal diagnosis. Prenatal Exome Sequencing (pES) is performed with increasing frequency in fetuses with structural anomalies and negative chromosomal analysis. The actual diagnostic value varies extensively, and the role of incidental/secondary or inconclusive findings and negative results has not been fully ascertained. We performed a systematic literature review to evaluate the diagnostic yield, as well as inconclusive and negative-result rates of pES. Papers were divided in two groups. The former includes fetuses presenting structural anomalies, regardless the involved organ; the latter focuses on specific class anomalies. Available findings on non-informative or negative results were gathered as well. In the first group, the weighted average diagnostic yield resulted 19%, and inconclusive finding rate 12%. In the second group, the percentages were extremely variable due to differences in sample sizes and inclusion criteria, which constitute major determinants of pES efficiency. Diagnostic pES availability and its application have a pivotal role in prenatal diagnosis, though more homogeneity in access criteria and a consensus on clinical management of controversial information management is envisageable to reach widespread use in the near future.

Recurrent prenatal PIEZO1-related lymphatic dysplasia: Expanding molecular and ultrasound findings

Generalized lymphatic dysplasia (GLD), characterized by lymphedema, lymphangiectasias, chylothorax, effusions, represents a recognized cause of fetal hydrops. We describe for the first time recurrent pregnancies showing different ultrasound presentations of lymphatic dysplasia. The first fetus displayed diffuse subcutaneous cysts and septations while the second one presented fetal hydrops. Exome sequencing results at 18 gestational weeks in the second pregnancy showed compound heterozygosity for two novel PIEZO1 variants, afterwards detected also in the first fetus and in the heterozygous parents. Both ultrasound and genetic findings expand the current knowledge of PIEZO1-related GLD. We suggest exome sequencing in hydropic fetuses with normal cytogenetics and in pregnancies with recurrent hydrops/lymphatic dysplasia.

Role of ductus venosus agenesis in right ventricle development

Ductus venosus agenesis (DVA) results from portal-umbilical and hepatic-systemic venous system connection failure. Despite a large series of DVA was reported, an accurate description of single fetus cardiac trend with hemodynamic consequences is missing. We describe two fetuses with DVA early detection, comparing right ventricle (RV) development in extrahepatic and intrahepatic drainages. In extrahepatic drainage, the RV was larger and slightly hypertrophic. In intrahepatic drainage, the RV showed reduced dimensions. Ventricle dimension differences decreased and became balanced in perinatal period. Detection of non-balanced ventricles in early second trimester should lead to sonographic follow-up. If DVA is hypothesized, it is important to identify other subdiaphragmatic connections that could alter cardiac preload and ventricle development.

A new case of SMABF2 diagnosed in stillbirth expands the prenatal presentation and mutational spectrum of ASCC1

Spinal muscular atrophy with congenital bone fractures 2 (SMABF2) is a rare autosomal recessive neuromuscular disorder characterized by arthrogryposis multiplex congenita and prenatal fractures of the long bones, with poor prognosis. The most affected patients present with biallelic loss-of-function nucleotide variants in ASCC1 gene, coding a subunit of the transcriptional coactivator ASC-1 complex, although the exact pathogenesis is yet unknown. This work describes the first case of SMABF2 in a stillbirth with documented evolution of the disease in the prenatal period. A microdeletion copy number variant (CNV) of about 64 Kb, involving four exons of ASCC1, was firstly detected by microarray analysis, requested for arthrogryposis and hydrops. Subsequent exome analysis disclosed a nucleotide variant of the same gene [c.1027C>T; (p. Arg343*)], resulting in the introduction of a premature termination codon. This stillbirth represents the first case of ASCC1 compound heterozygosity, due to an exonic microdeletion and a nucleotide variant, expanding the mutational spectrum of this gene. It also provides further evidence that exonic CNVs are an underestimated cause of disease-alleles and that the integrated use of the last generation genetic analysis tools, together with careful clinical evaluations, are fundamental for the characterization of rare diseases even in the prenatal setting.

Unusual Segregation of APP Mutations in Monogenic Alzheimer Disease

APP gene mutations causing Alzheimer disease (AD) segregate in an autosomal dominant pattern. We report on a 40-year-old woman with a severe cognitive decline starting at 36 years, while her affected relatives presented symptoms onset in the 6th decade. The proband carried an APP missense variant in homozygous state (NM_000484.4: c.2032G>A; NP_000475.1: p.Asp678Asn; rs63750064) and showed a more severe clinical picture than the other AD relatives, as regards the age of onset and the rate of disease progression. This mutation behaves as a semi-dominant trait. The very rare chance of studying APP mutations in the homozygous state demonstrates they are not always dominant and other segregation models are possible.

Small 7p22.3 microdeletion: Case report of Snx8 haploinsufficiency and neurological findings

Some cases of chromosome 7p22.3 deletions have been reported, but the genotype-phenotype correlation is still uncertain. Neurodevelopmental delay and heart anomalies have been recorded as the most recurrent defects. We describe the clinical features of a four-year-old male child with a 139 kb deletion at 7p22.3 involving SNX8 gene, inherited from a mosaic mother. The same deletion is also present in the fetus on the ongoing third pregnancy of the couple with normal fetal ultrasound assessment. The proband was prenatally diagnosed with left kidney agenesis. He does not show any congenital heart disease, but mild intellectual disability, learning and language delay, and severe behavioral problems related to the hyperactive-impulsive and inattentive area. These clinical features are also evident in other 7p22 deletions cases involving the SNX8 gene, supporting the role of this gene in neurodevelopment. Conversely, the revision of all published cases with small 7p22 deletions and the absence of heart malformations in the present family confirm that this region is involved in heart development, anyway did not confirm the role of SNX8 in cardiac phenotypes, either due to the reduced penetrance or the involvement of other candidate genes.

Clinical and functional characterization of a novel RASopathy-causing SHOC2 mutation associated with prenatal-onset hypertrophic cardiomyopathy

SHOC2 is a scaffold protein mediating RAS-promoted activation of mitogen-activated protein kinase (MAPK) signaling in response to extracellular stimuli. A recurrent activating mutation in SHOC2 (p.Ser2Gly) causes Mazzanti syndrome, a RASopathy characterized by features resembling Noonan syndrome and distinctive ectodermal abnormalities. A second mutation (p.Met173Ile) supposed to cause loss-of-function was more recently identified in two individuals with milder phenotypes. Here, we report on the third RASopathy-causing SHOC2 mutation (c.807_808delinsTT, p.Gln269_His270delinsHisTyr), which was found associated with prenatal-onset hypertrophic cardiomyopathy. Structural analyses indicated a possible impact of the mutation on the relative orientation of the two SHOC2's leucine-rich repeat domains. Functional studies provided evidence of its activating role, revealing enhanced binding of the mutant protein to MRAS and PPP1CB, and increased signaling through the MAPK cascade. Differing from SHOC2 ^S2G , SHOC2 ^{Q269_H270delinsHY} is not constitutively targeted to the plasma membrane. These data document that diverse mechanisms in SHOC2 functional dysregulation converge toward MAPK signaling upregulation.

Left pulmonary artery in 22q11.2 deletion syndrome. Echocardiographic evaluation in patients without cardiac defects and role of Tbx1 in mice

Introduction and hypothesis

Patients with 22q11 deletion syndrome (22q11.2DS) present, in about 75% of cases, typical patterns of cardiac defects, with a particular involvement on the ventricular outflow tract and great arteries. However, in this genetic condition the dimensions of the pulmonary arteries (PAs) never were specifically evaluated.

We measured both PAs diameter in patients with 22q11.2DS without cardiac defects, comparing these data to a normal control group. Moreover, we measured the PAs diameter in Tbx1 mutant mice. Finally, a cell fate mapping in Tbx1 mutants was used to study the expression of this gene in the morphogenesis of PAs.

Methods

We evaluated 58 patients with 22q11.2DS without cardiac defects. The control group consisted of 54 healthy subjects, matched for age and sex. All cases underwent a complete transthoracic echocardiography. Moreover, we crossed Tbx1^+/- mice and harvested fetuses. We examined the cardiovascular phenotype of 8 wild type (WT), 37 heterozygous (Tbx1^+/-) and 6 null fetuses (Tbx1^-/-). Finally, we crossed Tbx1^Cre/+mice with R26R^mT-mG Cre reporter mice to study Tbx1 expression in the pulmonary arteries.

Results

The echocardiographic study showed that the mean of the LPA/RPA ratio in 22q11.2DS was smaller (0.80 ± 0.12) than in controls (0.97 ± 0.08; p < 0.0001).

Mouse studies resulted in similar data as the size of LPA and RPA was not significantly different in WT embryos, but in Tbx1^+/- and Tbx1^-/- embryos the LPA was significantly smaller than the RPA in both mutants (P = 0.0016 and 0.0043, respectively). We found that Tbx1 is expressed near the origin of the PAs and in their adventitia.

Conclusions

Children with 22q11.2DS without cardiac defects show smaller LPA compared with healthy subjects. Mouse studies suggest that this anomaly is due to haploinsufficiency of Tbx1. These data may be useful in the clinical management of children with 22q11.2DS and should guide further experimental studies as to the mechanisms underlying PAs development.