PURPOSE:Biallelic variants in RDH11, encoding retinol dehydrogenase 11, have been associated with a syndromic disorder, based on 4 individuals from 2 unrelated families. We aimed to profile the clinical variability, natural history and associated molecular spectrum of this condition. METHODS:In the frame of a collaborative effort, clinical and molecular data were collected using a semistructured survey. Structural modeling of RDH11 with NADH(P) was used to assess the functional impact of missense variants. RESULTS:Sixteen affected individuals from 9 unrelated families with biallelic RDH11 variants were assembled, frequently showing juvenile-onset progressive myopathy with vacuolar degeneration and prodromic asymptomatic hyperCKemia. Neurodevelopmental impairment, juvenile-onset cataract, and retinal dystrophy were confirmed as common features. Microcephaly and distinct craniofacial traits were also recurrent, whereas short stature was less frequent than previously reported. Most pathogenic variants were truncating, supporting RDH11 loss of function as the mechanism of disease. Consistently, the identified missense changes were predicted to affect RDH11 catalytic function. CONCLUSION:We refine the clinical and molecular spectra of RDH11-related disorder, reclassifying it as syndromic intellectual disability with muscular (juvenile myopathy) and ocular (retinal dystrophy) involvement. These insights are expected to improve diagnostic accuracy and patient care, guiding clinical evaluation, and genetic counseling.

Nucleotide sequences in the FASTQ or BAM format are widely shared, yet derived from platform-specific raw data outputs that differ across sequencing platforms. In Oxford Nanopore Technologies (ONT) sequencing, raw signal data contain valuable biological information and enable basecaller optimization and modification detection. These raw signals also underpin algorithms that could improve ONT device portability and enhance target enrichment efficiency through adaptive sampling. Nevertheless, the storage and sharing of raw nanopore data remain limited due to technical constraints and the lack of standardized and centralized infrastructure. To address this challenge, we developed SquiDBase (https://squidbase.org), a dedicated repository for raw microbial nanopore sequencing data with linked processed data and metadata. To maximize immediate utility, we built SquiDPipe, a Nextflow pipeline for the automated removal of human reads from raw nanopore data, sequenced 24 clinically relevant viruses and incorporated them into SquiDBase, and added publicly available reference datasets and new community contributions. By offering a centralized, open-access raw data collection platform, SquiDBase facilitates data sharing, enhances reproducibility, and supports the development and benchmarking of computational tools, reinforcing open science in nanopore sequencing.

OBJECTIVE:Prenatal cell-free DNA screening is widely used to assess the risk of fetal trisomy 21, 18, and 13. Although commercial and laboratory-developed tests (LDTs) show high accuracy in validation studies, real-world longitudinal performance data are lacking. METHOD:In Belgium, prenatal cell-free DNA screening is a population screening offered to all pregnant people, regardless of their a priori risk. Over 3 years, all confirmatory diagnostic tests after a positive prenatal cell-free DNA screening result were recorded along with the technologies used and their outcomes. Positive predictive values (PPVs) for the three common fetal trisomies were calculated per technology. RESULTS:A total of 1158 diagnostic tests were performed after a positive prenatal cell-free DNA screening. Of these, 58.5% came from an LDT, 15.7% from VeriSeq (Illumina), 6.6% from Harmony (Roche), 5% from Vanadis (Perkin-Elmer); for 14.2% the technology could not be traced. PPVs ranged from 92.2% to 65.7% for trisomy 21, from 82.8% to 44.4% for trisomy 18, and from 40% to 18.2% for trisomy 13. Overall, the LDT performed better than the commercial tests. CONCLUSION:This study confirms the reported accuracy of commercial tests and LDT, while showing that LDT generally outperforms commercial tests. Despite high specificities across tests, differences in PPVs significantly impact pregnant people and the national health care system.

The CCR4-NOT complex, crucial in gene expression regulation, includes CNOT3, a subunit linked to neurodevelopmental disorders when mutated. This study investigates 51 patients from 42 families with heterozygous CNOT3 variants, aiming to expand the understanding of CNOT3-related neurodevelopmental disorders and explore genotype-phenotype correlations. Patients originated from various countries, reflecting the disorder’s global significance. All patients exhibited developmental delays, particularly in the language area. Intellectual disability was found in 87% of patients and was typically mild to moderate. Behavioral issues, including autism spectrum disorders and attention deficits, were common, affecting over half of the patients. Dysmorphic features were highlighted and may help establishing the diagnosis. Epilepsy was uncommon (10%). Twenty-eight novel variants were identified, including missense, nonsense, frameshift, intronic variations and a deletion of 12 exons. Missense variants clustered at the N- and C-terminal regions of the protein, indicating critical functional roles. No clear genotype-phenotype correlation was observed, suggesting that all identified variants resulted in a loss-of-function effect. Finally, this work delineates the clinical and molecular spectrum of CNOT3-related disorders thanks to an in-depth characterization of a large cohort. Further research will be necessary to understand the functional consequences of the variants and enhance patient long-term outcomes.

Congenital titinopathy has recently emerged as one of the most common congenital muscle disorders.ObjectiveTo better understand the presentation and clinical needs of the under‐characterized extreme end of the congenital titinopathy severity spectrum.MethodsWe comprehensively analyzed the clinical, imaging, pathology, autopsy, and genetic findings in 15 severely affected individuals from 11 families.ResultsPrenatal features included hypokinesia or akinesia and growth restriction. Six pregnancies were terminated. Nine infants were born at or near term with severe‐to‐profound weakness and required resuscitation. Seven died following withdrawal of life support. Two surviving children require ongoing respiratory support. Most cohort members had at least 1 disease‐causing variant predicted to result in some near‐normal‐length titin expression. The exceptions, from 2 unrelated families, had homozygous truncating variants predicted to induce complete nonsense mediated decay. However, subsequent analyses suggested that the causative variant in each family had an additional previously unrecognized impact on splicing likely to result in some near‐normal‐length titin expression. This impact was confirmed by minigene assay for 1 variant.InterpretationThis study confirms the clinical variability of congenital titinopathy. Severely affected individuals succumb prenatally/during infancy, whereas others survive into adulthood. It is likely that this variability is because of differences in the amount and/or length of expressed titin. If confirmed, analysis of titin expression could facilitate clinical prediction and increasing expression might be an effective treatment strategy. Our findings also further‐support the hypothesis that some near‐normal‐length titin expression is essential to early prenatal survival. Sometimes expression of normal/near‐normal‐length titin is due to disease‐causing variants having an additional impact on splicing. ANN NEUROL 2025

Next generation sequencing has revolutionized the diagnostic approach for patients with neurodevelopmental disorders (NDDs), yields are however highly variable depending on the patient's phenotype. It is often challenging to predict which indications are likely to lead to a molecular diagnosis and which will benefit less from genetic testing. To identify phenotypic characteristics associated with higher diagnostic yields we conducted detailed phenotyping of a cohort of 868 children with NDD, who underwent clinical exome sequencing between 2016 and 2021. A molecular diagnosis was reached in 27 % of cases. Significantly higher yields of respectively 34 % and 32 % were observed in patients with intellectual disability (ID) or global developmental delay (GDD). Autism spectrum disorders (ASD) were less likely to result in a molecular diagnosis with a diagnostic yield of 16 %. Additional factors linked to higher yields included female gender, the presence of minor dysmorphic features - particularly involving the face, extremities, ears, eyes, and hair - and a syndromic phenotype. Additional CNV calling in a subset of 438 patients which consented to reanalysis of sequencing data added 1.5 % to diagnostic yield.

The UNC13A gene encodes a presynaptic protein that is crucial for setting the strength and dynamics of information transfer between neurons. Here we describe a neurodevelopmental syndrome caused by germline coding or splice-site variants in UNC13A. The syndrome presents with variable degrees of developmental delay and intellectual disability, seizures of different types, tremor and dyskinetic movements and, in some cases, death in early childhood. Using assays with expression of UNC13A variants in mouse hippocampal neurons and in Caenorhabditis elegans, we identify three mechanisms of pathogenicity, including reduction in synaptic strength caused by reduced UNC13A protein expression, increased neurotransmission caused by UNC13A gain-of-function and impaired regulation of neurotransmission by second messenger signalling. Based on a strong genotype-phenotype-functional correlation, we classify three UNC13A syndrome subtypes (types A-C). We conclude that the precise regulation of neurotransmitter release by UNC13A is critical for human nervous system function.

Nuclear Speckle Splicing Regulator Protein 1 (NSRP1) is a splice factor found in nuclear speckles, which are small membrane-free organelles implicated in epigenetic regulation, chromatin organization, DNA repair, and RNA modification. Bi-allelic loss-of-function variants in NSRP1 have recently been identified in patients suffering from a severe neurodevelopmental disorder, presenting with neurodevelopmental delay, epilepsy, microcephaly, hypotonia, and spastic cerebral palsy. Described patients acquired neither independent walking nor speech and often showed anomalies on cerebral MRI. Here we describe the case of a 14-year-old girl with motor and language delay as well as intellectual disability, who presents an ataxic gait but walks without assistance and speaks in short sentences. Whole-genome sequencing revealed the compound heterozygous NSRP1 variants c.114 + 2T > G and c.1595T > A (p.Val532Glu). Functional validation using HEK293T cells transfected with either wild-type or mutated GFP-tagged Nsrp1 suggests that the Val532Glu variant interferes with the function of the nuclear localization signal, and leads to mislocalization of NSRP1 in the cytosol, thus confirming the pathogenicity of the observed variant. This case helps to expand the phenotypic and genetic spectrum associated with pathogenic NSRP1 variants and indicates that this diagnosis should also be suspected in patients with milder phenotypes.

Myhre syndrome (MS, MIM 139210) is a rare multisystemic disorder caused by recurrent pathogenic missense variants in SMAD4. The clinical features have been mainly documented in childhood and comprise variable neurocognitive development, recognizable craniofacial features, a short stature with a pseudo-muscular build, hearing loss, thickened skin, joint limitations, diverse cardiovascular and airway manifestations, and increased fibrosis often following trauma or surgery. In contrast, adults with MS are underreported obscuring potential clinical variability. Here, we describe 24 adults with MS, including 17 diagnosed after the age of 18 years old, and we review the literature on adults with MS. Overall, our cohort shows a milder phenotype as well as lower mortality rates compared to what has been published in literature. Individuals with a codon 500 variant in SMAD4 present with a more pronounced neurodevelopmental and systemic phenotype. However, in contrast to the literature, we observe cardiovascular abnormalities in individuals with the p.(Arg496Cys) variant. In addition, we describe scoliosis as a new manifestation and we report fertility in two additional males with the p.(Arg496Cys). In conclusion, our study contributes novel insights into the clinical variability of MS and underscores the importance of variant-specific considerations, and we provide recommendations for the management of MS in adulthood.

Cystinuria is suspected antenatally by a hyperechogenic fetal colonic content. We report the first prenatal case of autosomal dominant SLC7A9-related cystinuria associated with isolated hyperechogenic kidneys as the only prenatal sonographic sign.

The Hec1a-IFNB-Luc reporter cell line allows the detection of all 10 flaviviruses tested, including the 4 dengue virus serotypes. Its use for serodiagnostic purposes, measuring neutralizing antibody activity in sera, and the assessment of the antiviral activities of small-molecule compounds was confirmed, and it was found to be comparable to clinically applied assays.

Although transmitted mainly through direct (sexual) contact, mpox virus (MPXV) can be detected in ambient air. We explored the use of air sampling for diagnosis or (genomic) surveillance of mpox in a sexual health clinic. For six out of six patients who were infected with MPXV, all four of our ambient air PCR tests were positive. For 14 uninfected patients, PCR was positive in three ambient air samples, albeit with higher cycle threshold (Ct) values. Genomic sequencing of samples from two positive patients showed matching sequences between air and clinical samples.

HADDTS (Hypotonia, Ataxia, Developmental-Delay and Tooth-enamel defects) is a newly emerging syndrome caused by CTBP1 mutations. Only five reports (13 cases) are available; three contained muscle-biopsy results but none presented illustrated histomyopathology. We report a patient in whom whole-exome sequencing revealed a heterozygous de novo CTBP1 missense mutation (c.1024 C>T; p.(Arg342Trp)). Progressive muscular weakness and myopathic electromyography suggested a myopathological substrate; muscle-biopsy revealed dystrophic features with endomysial-fibrosis, fiber-size variability, necrotic/degenerative vacuolar myopathy, sarcoplasmic/myofibrillar- and striation-alterations, and enzyme histochemical and structural mitochondrial alterations/defects including vacuolar mitochondriopathy. Our report expands the number of cases in this extremely rare condition and provides illustrated myopathology, muscle-MRI, and electron-microscopy. These are crucial for elucidating the nature and extent of the underlying myopathological-correlates and to characterize the myopatholgical phenotype spectrum in this genetic neurodevelopmental condition.

Autosomal dominant and recessive mutations in COL12A1 cause the Ehlers-Danlos/myopathy overlap syndrome. Here, we describe a boy with fetal hypokinesia, severe neonatal weakness, striking hyperlaxity, high arched palate, retrognathia, club feet, and pectus excavatum. His motor development was initially delayed but muscle strength improved with time while hyperlaxity remained very severe causing recurrent joint dislocations. Using trio exome sequencing and a copy number variation (CNV) analysis tool, we identified an in-frame de novo heterozygous deletion of the exons 45 to 54 in the COL12A1 gene. Collagen XII immunostaining on cultured skin fibroblasts demonstrated intracellular retention of collagen XII, supporting the pathogenicity of the deletion. The phenotype of our patient is slightly more severe than other cases with dominantly acting mutations, notably with the presence of fetal hypokinesia. This case highlights the importance of CNVs analysis in the COL12A1 gene in patients with a phenotype suggesting Ehlers-Danlos/myopathy overlap syndrome.

Nemaline myopathy (NM) is a muscle disorder with broad clinical and genetic heterogeneity. The clinical presentation of affected individuals ranges from severe perinatal muscle weakness to milder childhood-onset forms, and the disease course and prognosis depends on the gene and mutation type. To date, 14 causative genes have been identified, and ACTA1 accounts for more than half of the severe NM cases. ACTA1 encodes α-actin, one of the principal components of the contractile units in skeletal muscle. We established a homogenous cohort of ten unreported families with severe NM, and we provide clinical, genetic, histological, and ultrastructural data. The patients manifested antenatal or neonatal muscle weakness requiring permanent respiratory assistance, and most deceased within the first months of life. DNA sequencing identified known or novel ACTA1 mutations in all. Morphological analyses of the muscle biopsy specimens showed characteristic features of NM histopathology including cytoplasmic and intranuclear rods, cytoplasmic bodies, and major myofibrillar disorganization. We also detected structural anomalies of the perinuclear space, emphasizing a physiological contribution of skeletal muscle α-actin to nuclear shape. In-depth investigations of the nuclei confirmed an abnormal localization of lamin A/C, Nesprin-1, and Nesprin-2, forming the main constituents of the nuclear lamina and the LINC complex and ensuring nuclear envelope integrity. To validate the relevance of our findings, we examined muscle samples from three previously reported ACTA1 cases, and we identified the same set of structural aberrations. Moreover, we measured an increased expression of cardiac α-actin in the muscle samples from the patients with longer lifespan, indicating a potential compensatory effect. Overall, this study expands the genetic and morphological spectrum of severe ACTA1 -related nemaline myopathy, improves molecular diagnosis, highlights the enlargement of the perinuclear space as an ultrastructural hallmark, and indicates a potential genotype/phenotype correlation.

The magnitude of the 2022 multi-country monkeypox virus (MPXV) outbreak has surpassed any preceding outbreak. It is unclear whether asymptomatic or otherwise undiagnosed infections are fuelling this epidemic. In this study, we aimed to assess whether undiagnosed infections occurred among men attending a Belgian sexual health clinic in May 2022. We retrospectively screened 224 samples collected for gonorrhea and chlamydia testing using an MPXV PCR assay and identified MPXV-DNA-positive samples from four men. At the time of sampling, one man had a painful rash, and three men had reported no symptoms. Upon clinical examination 21–37 days later, these three men were free of clinical signs, and they reported not having experienced any symptoms. Serology confirmed MPXV exposure in all three men, and MPXV was cultured from two cases. These findings show that certain cases of monkeypox remain undiagnosed and suggest that testing and quarantining of individuals reporting symptoms may not suffice to contain the outbreak.

Chikungunya virus (CHIKV) is an emerging arthropod-borne virus that has spread globally during the last two decades. The virus is mainly transmitted by Aedes aegypti and Aedes albopictus mosquitos and is thus capable of replicating in both human and mosquito cells. CHIKV has a broad tropism in vivo, capable of replicating in various tissues and cell types but largely excluding blood cells. This was reflected in vitro by a broad array of adherent cell lines supporting CHIKV infection. One marked exception to this general rule is the resistance of the lung cancer-derived A549 cell line to CHIKV infection. We verified that A549 cells were restrictive to infection by multiple alphaviruses while being completely permissive to flavivirus infection. The adaptive growth of a primary CHIKV strain through multiple passages allowed the emergence of a CHIKV strain that productively infected A549 cells while causing overt cytopathic effects and without a fitness cost for replication in otherwise CHIKV-susceptible cells. Whole genome sequencing of polyclonal and monoclonal preparations of the adapted virus showed that a limited number of mutations consistently emerged in both structural (2 mutations in E2) and non-structural proteins (1 mutation in nsP1 and 1 mutation in nsP2). The introduction of the adaptive mutations, individually or in combinations, into a wild-type molecular clone of CHIKV allowed us to determine the relative contributions of the mutations to the new phenotype. We found that the mutations in the E2 envelope protein and non-structural proteins contributed significantly to the acquired phenotype. The nsP mutations were introduced in a split-genome trans-replicase assay to monitor their effect on viral genome replication efficiency. Interestingly, neither mutation supported increased viral genomic replication in either Vero or A549 cells.

We report the levels of neutralising antibodies against Wuhan, Delta and Omicron variants in unimmunized infected (group 1), immunised and boosted (group 2) and infected immunised and boosted (group 3) adult individuals. Our observations support the rapid administration of a booster vaccine dose to prevent infection and disease caused by Omicron.