Unravelling the genetic causes of multiple malformation syndromes: A whole exome sequencing study of the Cypriot population

Dilated aorta in CNOT3 -related neurodevelopmental disorder: 'expanding' the phenotype

INTRODUCTION

Neurodevelopmental disorders (NDDs) comprise conditions that emerge during the child's development and contribute significantly to global health and economic burdens. De novo variants in CNOT3 have been linked to NDDs and understanding the genotype-phenotype relationship between CNOT3 and NDDs will aid in improving diagnosis and management.

METHODS

In this study, we report a case of a patient with CNOT3 -related NDD who presented with progressive aortic dilatation, a feature not reported previously.

RESULTS

Our patient presented with intellectual disorder, dysmorphic facial features, and cardiac anomalies, notably progressive aortic dilatation - a novel finding in CNOT3 -related NDD. Genetic testing identified a de novo 6.3 kbp intragenic deletion in CNOT3 , providing a possible genetic basis for her condition.

CONCLUSION

This study presents the first case of CNOT3 -related NDD in Southeast Asia, expanding the phenotype to include progressive aortic dilatation and suggesting merit in cardiac surveillance of patients with CNOT3 -related NDD. It also emphasizes the importance of genetic testing in diagnosing complex NDD cases as well as reanalysis of 'negative' cases using advanced sequencing technologies to uncover potential hidden genetic etiologies in undiagnosed NDDs.

Diagnostic Utility of Whole Genome Sequencing After Negative Karyotyping/Chromosomal Microarray in Infants Born With Multiple Congenital Anomalies

BACKGROUND

Achieving a definitive genetic diagnosis of unexplained multiple congenital anomalies (MCAs) in neonatal intensive care units (NICUs) infants is challenging because of the limited diagnostic capabilities of conventional genetic tests. Although the implementation of whole genome sequencing (WGS) has commenced for diagnosing MCAs, due to constraints in resources and faculty, many NICUs continue to utilize chromosomal microarray (CMA) and/or karyotyping as the initial diagnostic approach. We aimed to evaluate the diagnostic efficacy of WGS in infants with MCAs who have received negative results from karyotyping and/or CMA.

METHODS

In this prospective study, we enrolled 80 infants with MCAs who were admitted to a NICU at a single center and had received negative results from CMA and/or karyotyping. The phenotypic characteristics were classified according to the International Classification of Diseases and the Human Phenotype Ontology. We assessed the diagnostic yield of trio-WGS in infants with normal chromosomal result and explored the process of diagnosing by analyzing both phenotype and genotype. Also, we compared the phenotype and clinical outcomes between the groups diagnosed with WGS and the undiagnosed group.

RESULTS

The diagnostic yield of WGS was 26% (21/80), of which 76% were novel variants. There was a higher diagnostic yield in cases of craniofacial abnormalities, including those of the eye and ear, and a lower diagnostic yield in cases of gastrointestinal and genitourinary abnormalities. In addition, higher rates of rehabilitation therapy and gastrostomy were observed in WGS-diagnosed infants than in undiagnosed infants.

CONCLUSION

This prospective cohort study assessed the usefulness of trio-WGS following chromosomal analysis for diagnosing MCAs in the NICU and revealed improvements in the diagnostic yield and clinical utility of WGS.

Sepiapterin Reductase Deficiency Misdiagnosed as Neurological Sequelae of Meningitis

Introduction

Sepiapterin reductase deficiency (SRD) is an exceedingly rare neurotransmitter disease caused by an enzyme error involved in the synthesis of tetrahydrobiopterin (BH4). It has been described in nearly 60 cases so far. The clinical manifestations include motor and speech delay, axial hypotonia, dystonia, weakness, oculogyric crises, diurnal fluctuation, and improvement of symptoms during sleep. Molecular genetic analysis can demonstrate pathogenic mutations in the SPR gene, allowing for a definitive diagnosis. Levodopa/carbidopa and 5-hydroxytryptophan are used for treatment.

Case Presentation

We present a 19-year-old male patient who was evaluated for dysarthria, axial hypotonia, limb dystonia, and movement disorder. The parents described the current patient's history with febrile seizures since 9 months of age, as well as speech and neuromotor developmental retardation, which indicated that the disease began in infancy. The basal metabolic work-up was normal except for hyperprolactinemia. The definitive diagnosis of SRD was confirmed by whole exome sequencing (WES) analysis, which revealed a homozygous pathogenic mutation c.655C>T (p.Arg219*) (rs779204655) in the SPR gene. After treatment, we noted significant improvements in dystonia, axial hypotonia, and dysarthria.

Conclusion

WES analysis offers a more expeditious and dependable method for diagnosing difficult cases exhibiting neurodevelopmental problems and thus renders the possibilities of early management.

Optimal Protocols and Management of Clinical and Genomic Data Collection to Assist in the Early Diagnosis and Treatment of Multiple Congenital Anomalies

Standardized protocols have been designed and developed specifically for clinical information collection and obtaining trio genomic information from infants affected with congenital anomalies (CA) and their parents, as well as securing human biological resources. The protocols include clinical and genomic information collection on multiple CA that were difficult to diagnose using pre-existing screening methods. We obtained human-derived resources and genomic information from 138 cases, including 45 families of infants with CA and their parent trios. For the clinical information collection protocol, criteria for target patient selection and a consent system for collecting and utilizing research resources are crucial. Whole genome sequencing data were generated for all participants, and standardized protocols were developed for resource collection and manufacturing. We recorded the phenotype information according to the Human Phenotype Ontology term, and epidemiological information was collected through an environmental factor questionnaire. Updating and recording of clinical symptoms and genetic information that have been newly added or changed over time are significant. The protocols enabled long-term tracking by including the growth and development status that reflect the important characteristics of newborns. Using these clinical and genetic information collection protocols for CA, an essential platform for early genetic diagnosis and diagnostic research can be established, and new genetic diagnostic guidelines can be presented in the near future.

Novel mutation causing Zellweger syndrome

Genetic conditions have varied presentations, and one of them is the association with multiple malformation syndrome (MMS), which has a high mortality rate in the immediate postnatal period. Here, we describe a neonate born with multiple anomalies-wide anterior and posterior fontanelle, metopic suture, flat nasal bridge, hypertelorism, low set dysplastic ears, corneal cloudiness, micrognathia, webbed neck, simian crease, undescended testis, hypospadias, congenital talipes equinovarus, hypoplastic inferior cerebellar vermis, poor reflexes, hypotonia and ventricular septal defect. There was a history of sibling death with similar malformations, pointing towards a genetic aetiology. Clinical exome sequencing yielded the diagnosis of Zellweger syndrome with a rare mutation in PEX-19 gene. Inherited metabolic syndromes frequently masquerade as malformations, but family history of an affected sibling and clinical suspicion aided diagnosis of the infant.

First splicing variant in HECW2 with an autosomal recessive pattern of inheritance and associated with NDHSAL

We report the clinical and genetic features of a Caucasian girl who presented a severe neurodevelopmental disorder with drug-resistant epilepsy, hypotonia, severe gastro-esophageal reflux and brain MRI anomalies. WES uncovered a novel variant in homozygosis (g.197092814_197092824delinsC) in HECW2 gene that encodes the E3 ubiquitin-protein ligase HECW2. This protein induces ubiquitination and is implicated in the regulation of several important pathways involved in neurodevelopment and neurogenesis. Furthermore, de novo heterozygous missense variants in this gene have been associated with NDHSAL. The homozygous variant of our patient disrupts the splice donor site of intron 22 and causes the elimination of exon 22 (r.3766_3917+1del) leading to an in-frame deletion of the protein (p.Leu1256_Trp1306del). Functional studies showed a two-fold increase of its RNA expression, while the protein expression level was reduced by 60%, suggesting a partial LOF mechanism of pathogenesis. Thus, this is the first patient with NDHSAL caused by an autosomal recessive splicing variant in HECW2. This article is protected by copyright. All rights reserved.