ObjectiveThis study is an example of the contribution of exome sequencing (ES) in selected prenatal indications, while illustrating the complexity of interpreting prenatal genetic testing. Therefore, one of the aims of this study was to better describe antenatal phenotypes.MethodsThis was a multicenter, comparative, prospective study assessing high-throughput sequencing performance (targeted gene panel versus exome sequencing) in selected prenatal indications.ResultsTrio-ES was performed on 86 fetuses, allowed making a definite etiological diagnosis in 28% of cases (24/86). One-third of diagnoses were obtained only after exome analysis (8/24, 33%). The diagnostic yield varied according to the indication and was the highest for vermian hypoplasia (5/12, 42%) and polymalformative syndromes (30%, 8/27) indications. The variants identified were mainly missense variants in ciliopathy (18%, 6/33) and cytoskeleton (15%, 5/33) genes. Among the etiological diagnoses, one fetus carried a postzygotic mosaic variant in RHOA.ConclusionIn selected indications, the diagnostic yield of ES was close to 30% and varied according to the indications, showing the importance of clearly define the malformations justifying this approach. An etiological diagnosis was made in 23 families, within a timeframe compatible with pregnancy, thus improving the management of the pregnancy and/or the unborn child.

PACS1-related disorder (PACS1-RD), also known as Schuurs-Hoeijmakers syndrome, is a rare autosomal dominant neurodevelopmental disorder predominantly caused by the recurrent de novo c.607 C > T p.(Arg203Trp) gain-of-function variant. Although core clinical features have been delineated, systematic data on developmental milestones, growth parameters, and clinical variability remain limited. We assembled a series of 24 previously unreported, unrelated individuals with PACS1-RD and compared their clinical and molecular features with 84 individuals from the literature. Genome-wide DNA methylation profiling was performed on peripheral blood DNA using bisulfite sequencing, interrogating ~860,000 CpG sites. Our study expands the phenotypic spectrum of PACS1-RD by reporting median age at independent walking and first spoken words (both 24 months), cross-sectional growth parameters, and previously undescribed clinical features, including congenital kidney malformations (25%) and feeding difficulties (75%). Compared with the literature, our series showed a higher prevalence of cryptorchidism (77.8%), congenital heart defect (45.8%), and hypotonia (75%). Methylation analysis identified a specific episignature for PACS1-RD, consistently observed in individuals carrying either the canonical p.(Arg203Trp) or the non-recurrent p.(Arg203Gln) variant. This episignature further enabled PACS1-RD diagnosis in one unsolved individual initially suspected of Kabuki syndrome. These findings refine the clinical delineation of PACS1-RD and establish an episignature that will support diagnosis in unresolved neurodevelopmental disorders and guide pathogenicity assessment of non-recurrent PACS1 variants.

PURPOSE:Biallelic variants in the minor spliceosomal gene RNU4ATAC were successively identified in Taybi-Linder/Microcephalic osteodysplastic primordial dwarfism type I, Roifman, and Lowry-Wood syndromes, which are characterized by variable microcephaly, short stature, neurodevelopmental impairment, skeletal dysplasia, and immunodeficiency. Two-thirds of the reported individuals present with Taybi-Linder syndrome, the first-described and most severe form. METHODS:We collected clinical and molecular data from individuals with biallelic RNU4ATAC variants through various French and European networks and clinics to refine the phenotypic spectrum of RNU4ATAC-opathies. RESULTS:We enrolled 69 participants and identified 18 new pathogenic variants. We report a significant proportion of attenuated or atypical presentations, novel rare symptoms, and, unexpectedly, a broad spectrum of autoimmune or inflammatory manifestations, affecting nearly half of the participants. Integrating our data with the 109 published cases, we propose a novel classification based on the main manifestations, immunodeficiency, and microcephalic primordial dwarfism. Using computer-assisted facial analysis, we also demonstrated the existence of a specific dysmorphic pattern in RNU4ATAC-opathies that is distinct among some sub-syndromes. CONCLUSION:We present a large cohort of individuals with RNU4ATAC-opathies and expand the phenotypic spectrum to paucisymptomatic forms, indicating that these diseases are likely to remain underdiagnosed.

The non-homologous end joining (NHEJ) pathway is essential to repair DNA double-strand breaks. XRCC4 acts as a stabilizer of the DNA ligase LIG4 in the NHEJ process. In humans, XRCC4 pathogenic variants are responsible for a microcephalic primordial dwarfism syndrome (MPD). Currently, 17 patients have been reported with XRCC4-related MPD and we report 7 new patients from 6 different families, including one fetus. The patients present with short stature, severe microcephaly, neurodevelopmental disorder and additional features, such as transient increase in nuchal translucency, congenital glaucoma, thumb anomalies, hepatic steatosis, seizures, essential tremor and oligodontia which have not been previously described. Hyper- and hypopigmented skin macules, dermatofibrosarcoma, mandibular osteoid osteoma and pancytopenia are also new features, reminiscent of cancer susceptibility syndromes. Functional studies were performed on two patients carrying the known pathogenic p.(Trp43Arg) variant in homozygous state, using a fast, cost-effective and non-invasive approach on PBMCs: (1) Survival analyses after ionizing radiation confirm important radiosensitivity. (2) Flow cytometry showed the lack of TCR-Va7+ T-lymphocytes, suggesting recombination defect of V(D)J coding segments. (3) This was confirmed by multiplexed RT-PCR (PROMIDISα biomarker), analyzing the diversity of V(D)J coding segments in a subset of the TCRα repertoire. We therefore extend the phenotype of XRCC4-related MPD and suggest a combination of three functional assays, based on radiosensitivity and V(D)J recombination defect, to improve the interpretation of XRCC4 variants in fast, cost-effective and non-invasive manner. These findings will improve the diagnosis, genetic counselling, follow-up and management of these patients.

OBJECTIVE:Following the first French multicenter pilot study (AnDDI-Prenatome) focused on the implementation of prenatal exome sequencing (pES), this ancillary study aims to explore the ethical and clinical issues raised by pES within multidisciplinary prenatal diagnosis centers. METHODS:33 healthcare professionals involved in the management of couples undergoing prenatal diagnosis (PND) took part in focus groups (2 with clinical geneticists, 3 with professionals from multidisciplinary prenatal diagnosis centers (MPDC), 1 with biologists). Each focus group was analyzed using the thematic analysis method. RESULTS:Professionals emphasized the importance of having a clear understanding of pES and the criteria for its prescription. Geneticists highlighted the need for a framework to clarify the implications of consent for patients and stressed the importance of offering structured support to assist couples in their decision-making process. Biologists and geneticists expressed a desire for effective multidisciplinary coordination of the care pathway, particularly in situations where the results were uncertain. CONCLUSION:These results will help to establish French recommendations for the prescription of pES.

DDX3X dysfunction causes an X-linked multisystem disorder with high penetrance and variable expressivity. The phenotypic spectrum spans from learning disability without somatic involvement to profound intellectual disability with severe impairments in the central nervous system and other organs. A few multicenter studies and single case reports have previously highlighted some common phenotypic patterns but were unable to delineate correlations between underlying DDX3X variants and phenotypic findings.From the second largest patient cohort published to date, we analysed clinical, psychometric and diagnostic findings of 52 female and 7 male individuals, harbouring de novo and inherited DDX3X variants. These female patients revealed previously unknown quantitative correlations between variant type and localization and specific phenotypic findings (growth features, epilepsy, brain anomalies, dysmorphisms, motor-focused neurological findings). Moreover, by analysing the in silico folding and RNA binding capability of mutant DDX3X monomers, we were able to delineate novel correlations between DDX3X monomer misfolding grade and phenotypic severity.

Objective: Ventriculomegaly is the main prenatal imaging feature for diagnosing fetal central nervous system anomalies in humans. Many ventriculomegalies can be related to genetic causes, regardless of their imaging presentations. Among these, MPDZ variants have been reported to cause severe ventriculomegaly inherited in an autosomal recessive manner (OMIM#615219). Several hypotheses have been put forward linking MPDZ variants to ventriculomegaly, but the precise underlying mechanisms, in particular whether its origin is obstructive or non-obstructive, are yet to be elucidated. Methods: To address this question, we retrospectively analyzed pre- and postnatal neuro-imaging and neuropathological data for cases of ventriculomegaly in which MPDZ variants were found through exome or genome sequencing. We performed anti-MPDZ immunostaining on fetal brain samples. Results: We analyzed six cases (four fetuses and two children) of ventriculomegaly of variable severities with MPDZ variants. The precise analysis of brain MRI data, corroborated by fetopathological examinations, demonstrated an obstructive pattern of ventriculomegaly upstream from partial fusion of the thalami, also called diencephalosynapsis, with partial atresia of the third ventricle, which could extend to Sylvius’s aqueduct. Conclusions: The morphological analysis using targeted brain magnetic resonance imaging (MRI) and neuropathological data allowed us to unravel the underlying mechanisms of congenital ventriculomegaly related to MDPZ variants.

Background SATB2-associated syndrome (SAS) results from various mutations of the SATB2 gene and associates a neurodevelopmental disorder including major speech delay, intellectual disability, and behavioral problems with dental anomalies, sometimes a cleft palate, risk of osteoporosis, and facial dysmorphism. The principal objective of this study was to describe the oral phenotype of young children with SATB2-associated syndrome, especially in terms of orofacial malformation of Robin Sequence (RS) spectrum (bifid uvula, cleft palate, or RS, dental malformation, feeding and communication, with data from a national cohort. The secondary objective was to determine whether feeding and communication disorders were more severe when associated with an orofacial malformation of RS spectrum. Methods We conducted a retrospective cross-sectional study among the largest possible cohort of patients with a mutation of the SATB2 gene in France. A questionnaire completed by the referring physicians and by telephone with parents enabled us to collect the following clinical information: (1) orofacial morphology, feeding difficulties, and pharyngeal functioning from birth to 3 years, (2) communication and language from 0 to 6 years, (3) speech development at the last examination. Results The study included 40 patients. Early and persistent feeding difficulties were found in 55% of the children. Communication was abnormal from the first months of life, with poor babbling in 85% of them. A major language delay was described in all patients; 65% had a vocabulary of 10 words or less. An anomaly of RS spectrum was found in half the cases, and dental malformations were described in 90%. Feeding difficulties and language delay were greater in the group with one or more orofacial malformations than the group with none. Conclusion This study confirmed the severity of oral involvement, affecting feeding and speech simultaneously, in individuals with SAS. It raises the question of why the oral phenotype involving feeding and speech is more severe in the presence of cleft palate or RS. We recommend close monitoring of prelanguage communication in infants with apparently isolated cleft palate or RS and the search for SATB2 impairment when a cleft palate or RS is found, especially in the prenatal period.

BACKGROUND:Pathogenic gain-of-function or dominant-negative effect missense variations in ACTB are associated with a neurodevelopmental disorder characterised by intellectual disability (ID), seizures, sensorineural hearing loss, cerebral, renal and ocular abnormalities and dysmorphic features (Baraitser-Winter cerebrofrontofacial syndrome). ACTB encodes beta-actin, a highly conserved protein involved in cell motility, structure and integrity. Deletions including ACTB, and, more rarely, single-nucleotide loss-of-function variants in ACTB have been described in patients with a distinct phenotype including developmental delay, ID, microcephaly, growth restriction, cardiac and renal abnormalities and dysmorphic features. METHODS:We collected 14 individuals and 1 fetus carrying a heterozygous deletion including ACTB, and 4 individuals with a heterozygous truncating variant. Genotypic and phenotypic data were analysed. Furthermore, a comprehensive review of all cases reported to date was also undertaken. RESULTS:Twelve out of 17 individuals presented with ID, and 3 out of 17 with learning disabilities. Speech delay and behavioural abnormalities were observed in 15 out of 17 and 12 out of 17 individuals, respectively, motor delay in 9 out of 17 and growth restriction in 9 out of 18. Most of the individuals (13/18) had recognisable dysmorphic features. 11 anomalies were de novo, except for 1 deletion inherited from the mother. The size of the deletion varied from 125 kb to 1.6 Mb and could result from a fork stalling and template switching. CONCLUSION:This study allowed us to better characterise the phenotype associated with the haploinsufficiency of ACTB, underlying the high prevalence of neurodevelopmental disorders (ID, speech and motor delay, behavioural abnormalities) and growth restriction in this recognisable syndrome.

In 30-40% of fetuses with structural defects, the causal variant remains undiagnosed after karyotype, chromosomal microarray, and exome sequencing. This study presents the results of a reanalysis of unsolved prenatal ES (pES) cases and investigates how postnatal/postmortem phenotyping contributes to identifying relevant variants. pES data was prospectively reanalyzed for unsolved cases enrolled in the AnDDI-Prénatome cohort study. Postnatal/postmortem data were included with prenatal features using Human Phenotype Ontology terms up to 3 years after pES. The reanalysis involved updating bioinformatic processing and querying raw data using a GREP query. We reanalyzed 58/94 (62%) unsolved pES cases, including 8 variants of unknown significance. Data for clinical examination at birth was available for all live newborns, and postmortem examination was available in 12 terminated fetuses. Additional features were identified at birth in 27/58 cases (44%): 9 terminated fetuses, 2 stillbirths, and 16 live newborns. One diagnosis (SNAPC4) was obtained through a periodic query following recent associations with human disease, and without additional clinical data. Three additional VUS were identified through reanalysis with the addition of new clinical features, illustrating the limited contribution of updated postnatal/postmortem phenotyping in identifying relevant variants after negative pES. In conclusion, the benefit of prospective reanalysis of unsolved pES is limited, even over time. Postnatal genome sequencing may be a more appropriate option than reanalysis with postnatal/postmortem phenotyping to establish a causal diagnosis.

ABSTRACT Microcephaly with simplified gyral pattern (MSG) is an intrinsic genetic central nervous system disorder, characterized by microcephaly (a reduction of brain volume) and a simplified gyral pattern (a reduced number of gyri and shallow sulci associated with normal cortical thickness and neuroanatomical architecture), related to a reduced number of neuronal progenitors in the germinal matrix. We report the first prenatal series of MSG and define the prenatal imaging pattern, which should inform diagnosis and guide prenatal counseling in cases of fetal microcephaly. In this single‐center retrospective study of fetuses with MSG, we assessed features on ultrasound and magnetic resonance imaging (MRI), as well as genetic and neuropathological/postnatal data. We included eight patients who had been referred following observation of microcephaly. Ultrasound examination confirmed microcephaly, with a mean growth delay in head circumference of 3.4 weeks, associated with both a lack of gyration and a lack of opercularization of the Sylvian fissure and without any extracephalic anomaly. Fetal brain MRI confirmed lack of gyration with normal cortical thickness and normal intensity of the white matter in all cases. These MRI features led to exclusion of migration/corticogenesis disorders (lissencephaly/polymicrogyria), instead suggesting MSG. The posterior fossa was normal in seven of the eight cases. The corpus callosum was thin in four cases, hypoplastic in two and dysgenetic in two. In four cases, the pregnancy was terminated. The diagnosis of MSG was confirmed from neuropathological and postnatal MRI data. MSG was associated with a genetic diagnosis of RTTN ( n = 1) and ASPM ( n = 2) biallelic variants in three of the six cases in which genetic work‐up was performed. Mild or moderate intellectual deficit with speech delay was present in the three surviving children who were at least 5 years of age at their last examination, without seizures. In conclusion, in the presence of isolated fetal microcephaly with lack of gyration on ultrasound, fetal cerebral MRI is key to diagnosing MSG, which, in the majority of cases, affects the supratentorial space exclusively, and to ruling out other cortical malformations that show a similar sonographic pattern. In addition to imaging, genetic assessment may guide prenatal counseling, since the prenatal prognosis of MSG is different from that of both diffuse polymicrogyria and lissencephaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Microcephalic osteodysplastic primordial dwarfism type I (MOPDI) is a very rare and severe autosomal recessive disorder characterized by marked intrauterine growth retardation, skeletal dysplasia, microcephaly and brain malformations. MOPDI is caused by biallelic mutations in RNU4ATAC, a non-coding gene involved in U12-type splicing of 1% of the introns in the genome, which are recognized by their specific splicing consensus sequences. Here, we describe a unique observation of immunodeficiency in twin sisters with mild MOPDI, who harbor a novel n.108_126del mutation, encompassing part of the U4atac snRNA 3' stem-loop and Sm protein binding site, and the previously reported n.111G>A mutation. Interestingly, both twin sisters show mild B-cell anomalies, including low naive B-cell counts and increased memory B-cell and plasmablasts counts, suggesting partial and transitory blockage of B-cell maturation and/or excessive activation of naive B-cells. Hence, the localization of a mutation in stem II of U4atac snRNA, as observed in another RNU4ATAC-opathy with immunodeficiency, that is, Roifman syndrome (RFMN), is not required for the occurrence of an immune deficiency. Finally, we emphasize the importance of considering immunodeficiency in MOPDI management to reduce the risk of serious infectious episodes.

The shift to a genotype-first approach in genetic diagnostics has revolutionized our understanding of neurodevelopmental disorders, expanding both their molecular and phenotypic spectra. Kleefstra syndrome (KLEFS1) is caused by EHMT1 haploinsufficiency and exhibits broad clinical manifestations. EHMT1 encodes euchromatic histone methyltransferase-1-a pivotal component of the epigenetic machinery. We have recruited 209 individuals with a rare EHMT1 variant and performed comprehensive molecular in silico and in vitro testing alongside DNA methylation (DNAm) signature analysis for the identified variants. We (re)classified the variants as likely pathogenic/pathogenic (molecularly confirming Kleefstra syndrome) in 191 individuals. We provide an updated and broader clinical and molecular spectrum of Kleefstra syndrome, including individuals with normal intelligence and familial occurrence. Analysis of the EHMT1 variants reveals a broad range of molecular effects and their associated phenotypes, including distinct genotype-phenotype associations. Notably, we showed that disruption of the "reader" function of the ankyrin repeat domain by a protein altering variant (PAV) results in a KLEFS1-specific DNAm signature and milder phenotype, while disruption of only "writer" methyltransferase activity of the SET domain does not result in KLEFS1 DNAm signature or typical KLEFS1 phenotype. Similarly, N-terminal truncating variants result in a mild phenotype without the DNAm signature. We demonstrate how comprehensive variant analysis can provide insights into pathogenesis of the disorder and DNAm signature. In summary, this study presents a comprehensive overview of KLEFS1 and EHMT1, revealing its broader spectrum and deepening our understanding of its molecular mechanisms, thereby informing accurate variant interpretation, counseling, and clinical management.

Dysfunctional RNA processing caused by genetic defects in RNA processing enzymes has a profound impact on the nervous system, resulting in neurodevelopmental conditions. We characterized a recessive neurological disorder in 18 children and young adults from 10 independent families typified by intellectual disability, motor developmental delay and gait disturbance. In some patients peripheral neuropathy, corpus callosum abnormalities and progressive basal ganglia deposits were present. The disorder is associated with rare variants in NUDT2, a mRNA decapping and Ap4A hydrolysing enzyme, including novel missense and in-frame deletion variants. We show that these NUDT2 variants lead to a marked loss of enzymatic activity, strongly implicating loss of NUDT2 function as the cause of the disorder. NUDT2-deficient patient fibroblasts exhibit a markedly altered transcriptome, accompanied by changes in mRNA half-life and stability. Amongst the most up-regulated mRNAs in NUDT2-deficient cells, we identified host response and interferon-responsive genes. Importantly, add-back experiments using an Ap4A hydrolase defective in mRNA decapping highlighted loss of NUDT2 decapping as the activity implicated in altered mRNA homeostasis. Our results confirm that reduction or loss of NUDT2 hydrolase activity is associated with a neurological disease, highlighting the importance of a physiologically balanced mRNA processing machinery for neuronal development and homeostasis.

OBJECTIVE:Prenatal exome sequencing (pES) is now commonly used in clinical practice. It can be used to identifiy an additional diagnosis in around 30% of fetuses with structural defects and normal chromosomal microarray analysis (CMA). However, interpretation remains challenging due to the limited prenatal data for genetic disorders. METHOD:We conducted an ancillary study including fetuses with pathogenic/likely pathogenic variants identified by trio-pES from the "AnDDI-Prenatome" study. The prenatal phenotype of each patient was categorized as typical, uncommon, or unreported based on the comparison of the prenatal findings with documented findings in the literature and public phenotype-genotype databases (ClinVar, HGMD, OMIM, and Decipher). RESULTS:Prenatal phenotypes were typical for 38/56 fetuses (67.9%). For the others, genotype-phenotype associations were challenging due to uncommon prenatal features (absence of recurrent hallmark, rare, or unreported). We report the first prenatal features associated with LINS1 and PGM1 variants. In addition, a double diagnosis was identified in three fetuses. CONCLUSION:Standardizing the description of prenatal features, implementing longitudinal prenatal follow-up, and large-scale collection of prenatal features are essential steps to improving pES data interpretation.

PURPOSE:Valproic acid or valproate is an effective antiepileptic drug; however, embryonic exposure to valproate can result in a teratogenic disorder referred to as fetal valproate syndrome (OMIM #609442). Currently there are no diagnostic biomarkers for the condition. This study aims to define an episignature biomarker for teratogenic antenatal exposure to valproate. METHODS:DNA extracted from peripheral blood of individuals with teratogenic antenatal exposure to valproate was processed using DNA methylation microarrays. Subsequently, methylation profiling and construction of support vector machine classifiers were performed in R. RESULTS:Genomic DNA methylation analysis was applied, and a distinct DNA methylation profile was identified in the majority of affected individuals. This profile was used to develop a diagnostic episignature classifier. The valproate exposure episignature exhibited high sensitivity and specificity relative to a large reference data set of unaffected controls and individuals with a wide spectrum of syndromic disorders with episignatures. Gene set enrichment analysis demonstrated an enrichment for terms associated with cell adhesion, including significant overrepresentation of the cadherin superfamily. CONCLUSION:This study provides evidence of a robust peripheral blood-based diagnostic epigenetic biomarker for a prenatal teratogenic disorder.

INTRODUCTION AND METHODS:We report two series of individuals with DDX3X variations, one (48 individuals) from physicians and one (44 individuals) from caregivers. RESULTS:These two series include several symptoms in common, with fairly similar distribution, which suggests that caregivers' data are close to physicians' data. For example, both series identified early childhood symptoms that were not previously described: feeding difficulties, mean walking age, and age at first words. DISCUSSION:Each of the two datasets provides complementary knowledge. We confirmed that symptoms are similar to those in the literature and provides more details on feeding difficulties. Caregivers considered that the symptom attention-deficit/hyperactivity disorder were most worrisome. Both series also reported sleep disturbance. Recently, anxiety has been reported in individuals with DDX3X variants. We strongly suggest that attention-deficit/hyperactivity disorder, anxiety, and sleep disorders need to be treated.