Journal of Medical Genetics最新文献

Biallelic pathogenic variants in C2orf69 cause a fatal autosomal recessive multisystem disorder characterized by recurrent autoinflammation, hypomyelination, progressive neurodegeneration, microcephaly, failure to thrive, liver dysfunction, respiratory chain defects and accumulation of glycogen in skeletal muscle. No missense variants in C2orf69 have been reported to date.We report a 6-year-old boy with microcephaly, global developmental delays, lower limb spasticity with hyperreflexia, epilepsy, abnormal brain MRI, failure to thrive, recurrent fevers and transaminitis. Whole-exome sequencing identified a homozygous missense c.320 C>G, p.(Pro107Arg) variant of uncertain significance (VUS) in C2orf69 Skeletal muscle biopsy showed active and chronic muscle fibre degeneration with deposits of periodic acid-Schiff-positive material in affected tissues, consistent with abnormal glycogen storage. Mitochondrial respiratory assays were normal in muscle tissue. Primary patient fibroblasts showed normal levels of mRNA expression but significantly reduced levels of endogenous C2ORF69 protein and GBE1 by Western blot. We report a patient with a homozygous missense variant in C2orf69, causing loss of function. Depletion of endogenous GBE1 in affected cells can be considered a biomarker for this disorder and assist in the interpretation of VUS in C2orf69 This expands the clinical and genetic spectrum of C2orf69-related disorder.

In 1997, the Journal of Medical Genetics published our paper on the spectrum of clinical features associated with interstitial chromosome 22q11 deletions. This copy number variation is associated with an extraordinary range of clinical features, which led initially to its association with several diagnostic labels. Since 1997 work on clinical and basic science aspects of the syndrome and the genes reduced to hemizygosity have provided a wealth of information pertaining to both best practice care and underlying biology. It is recognised that 22q11.2 deletion syndrome is an excellent model for probing mechanisms underlying psychiatric disease, cardiovascular development and much more.

Background: Li-Fraumeni syndrome (LFS) predisposes individuals to a wide range of cancers from childhood onwards, underscoring the crucial need for accurate interpretation of germline TP53 variants for optimal clinical management of patients and families. Several unclassified variants, particularly those potentially affecting splicing, require specialised testing. One such example is the NM_000546.6:c.1101-2A>C (rs587781664) variant, located at the splice acceptor site of the last intron of TP53, identified in a female patient with breast cancer diagnosed in her 20s.

Methods: To interpret this variant, which has been classified as a variant of uncertain significance (VUS), we developed specific assays including a p53 functional assay, RT-QMPSF, Splice and Expression Analyses by exon Ligation and High-Throughput Sequencing and long RT-droplet digital PCR.

Results: We demonstrated a loss of p53 transcriptional activity, and a half reduction in TP53 mRNA expression. Additionally, we detected the use of a novel alternative last exon downstream of exon 11, which we have named exon 12. This transcript, typically detectable at low levels in most individuals, was found to be more highly expressed in the c.1101-2A>C carrier, predominantly transcribed from the mutant allele due to the disruption of the splice acceptor site in intron 10.

Conclusion: By combining these approaches, we successfully reclassified this intronic VUS as 'pathogenic', enabling appropriate genetic counselling for the patient and her family. Additionally, we identified a novel TP53 alternative transcript that is expressed in both physiological and pathological contexts, with heightened expression in the patient with LFS. This discovery provides a basis for further investigation into the role of TP53 isoforms in LFS oncogenesis.

Background: Increasing evidence indicates a robust correlation between epilepsy and variants of the Kv7.2 (KCNQ2) channel, which is critically involved in directing M-currents and regulating neuronal excitability within the nervous system. With the advancement of next-generation sequencing, the identification of KCNQ2 variants has surged. Nonetheless, their functional impacts are still being determined, introducing uncertainty into the diagnostic process for affected families and potentially hindering their ability to participate in targeted precision medicine trials. This study aims to elucidate the pathogenicity of these novel variants and explore potential therapeutic interventions.

Methods: Whole-cell patch-clamp recordings, western blotting, and immunofluorescent staining were performed to elucidate the functional consequences of the identified variants. Moreover, coimmunoprecipitation techniques were conducted to explore protein interactions, thus facilitating a deeper understanding of the underlying pathogenetic mechanisms contributing to the disease. Ultimately, the effects of pharmacological interventions were evaluated in vitro using the patch-clamp technique.

Results: Herein, we identified 12 novel KCNQ2 variants, further expanding the mutational spectrum of KCNQ2. Our investigation revealed that one gain-of-function variant (p.L102V (c.304C>G)) and three loss-of-function variants (p.H328Q (c.984C>G), p.A336V (c.1007C>T) and p.D563Efs*22 (c.1688_1689insACTT)) had different impacts on the binding of calmodulin and phosphati-dylinositol-4,5-bisphosphate, potentially altering their localisation and protein stability. Furthermore, the application of ML213, unlike Retigabine and ICA-069673, led to a significant increase in the current of p.H328Q.

Conclusion: This study expanded the mutational spectrum of KCNQ2 and analysed the genetic and functional consequences, as well as the pharmacological rescue, of four de novo KCNQ2 variants. These findings offer valuable insights into the precise medicine of KCNQ2-related epilepsy.

Background: Tuberous sclerosis complex (TSC) is a genetic disease characterised by the growth of benign tumours. The Tuberous sclerosis Associated Neuropsychiatric Disorders (TAND) Checklist is used to identify patient-reported neurocognitive deficits. Patients may, however, under-recognise mild cognitive impairment. We aimed to determine the frequency of abnormal scores on three objective tests of cognitive function in people with and without diagnosed intellectual disability and examine associations between scores on these tests with self-reported TAND Checklist symptoms.

Methods: We conducted a cross-sectional study where people with TSC (PwTSC; n=46) completed the TAND Checklist and three cognitive tests: Symbol Digit Modalities Test (SDMT), Montreal Cognitive Assessment test and Trail Making Test-Parts A and B. We examined associations between cognitive test scores and the TAND Checklist using Pearson's correlations (95% CI). Receiver operating characteristics (ROC) curves were plotted to determine the screening accuracy of each measure in identifying physician-diagnosed neurocognitive disorders.

Results: There were minimal correlations between the cognitive test scores and the TAND Checklist. More than 20% of PwTSC reported no cognitive issues on the TAND Checklist but had abnormal performance on at least one cognitive test. The ROC curves demonstrated similar results, with areas under the curve of 0.93 (95% CI 0.79 to 1.00) for the SDMT but only 0.70 (95% CI 0.45 to 0.95) for the TAND Checklist.

Conclusion: Objective tests of cognitive function are useful in identifying unrecognised neurocognitive deficits in PwTSC. Deficits likely have multifactorial origins, including undiagnosed intellectual disability and the impact of chronic epilepsy.

Introduction: Genotype-phenotype correlations in PURA-related neurodevelopmental disorders (PURA-NDDs) remain unclear. This systematic review aimed to clarify these correlations.

Methods: Searches of PubMed and Embase were conducted on 8 August 2024 to identify studies that had investigated genetically diagnosed PURA-NDDs (5q31.3 deletion syndrome and PURA syndrome). All types and languages of studies were included. Study quality was assessed using a 20-item criterion checklist. Genetic and clinical data were extracted from each article and genotype-phenotype correlations were explored.

Results: Our analysis included 46 studies encompassing 230 patients with PURA-NDDs (5q31.3 deletion syndrome 18 (8%) and PURA syndrome 212 (92%)). Patients with 5q31.3 deletion syndrome exhibited more congenital defects (50% vs 12%, p<0.0001), respiratory difficulties (94% vs 63%, p=0.013) and walking disability (94% vs 55%, p=0.0026) than patients with PURA syndrome. In PURA syndrome, protein-truncating (nonsense or frameshift) variants were associated with more speech deficits (93% vs 80%, p=0.014) than non-protein-truncating (missense or in-frame) variants. PURA variant location had no effect on congenital defect occurrence or neurodevelopmental outcome. Overall, respiratory difficulties, walking disability and speech deficits were more commonly observed in the following order: 5q31.3 deletion (94%, 94% and 100%, respectively), multiple PUR-repeat deletions (68%, 60% and 95%, respectively), single PUR-repeat deletion or alteration (61%, 53% and 85%, respectively), and deletion or alteration located outside PUR repeats (38%, 33% and 43%, respectively).

Conclusion: The clinical severity of PURA-NDDs appears to be associated with the deletion/alteration size including PUR repeats rather than the location of PURA variants.

Primary ciliary dyskinesia (PCD, OMIM 244400) is a rare genetic disorder that affects motile cilia and is characterised by impaired mucociliary clearance of the airway epithelium, which results in chronic upper and lower airway infections. While short-read next-generation sequencing technology has been used for the genetic testing of PCD, its effectiveness is limited in identifying variants in the HYDIN gene because of the nearly identical pseudogene HYDIN2 As we confirmed that the HYDIN2 gene was not expressed in airway cells, we obtained nasal mucosa biopsy specimens for total RNA sequencing (RNA-seq) with library enrichment using exome oligos. Among the 34 nasal samples from patients suspected of having PCD, three aberrant splicing patterns in HYDIN were identified in two samples. Variant calls from RNA-seq combined with long-read amplicon sequencing of genomic DNA detected four pathogenic variants exclusively in the HYDIN gene. Therefore, RNA-seq in combination with long-read sequencing significantly facilitates the accurate genetic diagnosis of PCD caused by HYDIN variants.

Background: Aarskog-Scott syndrome (AAS) is a rare condition with multiple congenital anomalies, caused by hemizygote variants in the FGD1 gene. Its description was based mostly on old case reports, in whom a molecular diagnosis was not always available, or on small series. The aim of this study was to better delineate the phenotype and the natural history of AAS and to provide clues for the diagnosis and the management of the patients.

Methods: Phenotypic characterisation of the largest reported AAS cohort, comprising 111 male patients with proven causative variants in FGD1, through comprehensive analyses of clinical data including congenital anomalies, growth and neurodevelopment. Review of photographs and radiographs by experts in dysmorphology and skeletal disorders.

Results: This study refines the phenotypic spectrum of AAS, with the description of new morphological and radiological features, and refines the prevalence of the features. Short stature is less frequent than previously reported and has a prenatal onset in more than half of the patients. The growth has a specific course with a catch-up during the first decade often leading to low-normal stature in adulthood. Whereas intellectual disability is rare, patients with AAS have a high prevalence of specific learning difficulties and attention hyperactivity disorder. In light of this better knowledge of AAS, we provide management recommendations.

Conclusion: A better knowledge of the natural history and phenotypic spectrum of AAS will be helpful for the clinical diagnosis and for the interpretation of FGD1 variants using a retrophenotyping strategy, which is becoming the most common way of diagnosis nowadays. Recommendations for care will improve the management of the patients.

Background: FLNA loss of function manifests across a broad spectrum of phenotypes, ranging from severe prenatal onset to asymptomatic cases. Bilateral periventricular nodular heterotopia (BPNH) consistently occurs in affected individuals. This retrospective study involving French patients with BPNH evaluates the prevalence of FLNA gene dosage anomalies and investigates genotype-phenotype correlations in a large cohort of French patients with BPNH.

Methods: A retrospective observational study was conducted on 391 individuals diagnosed with BPNH confirmed by brain MRI. Sequencing analysis using Sanger or next-generation sequencing was complemented by targeted array-comparative genomic hybridisation to identify copy number variants (CNVs).

Results: FLNA variants were identified in 40% of females and 12% of males. Among these, 87% were single nucleotide variants (SNVs), while CNVs accounted for 13%, all of which were deletions. Half of the CNVs involved a recurrent deletion spanning exons 31-48, often accompanied by a duplication of the neighbouring EMD gene. This del-dup was associated with a milder phenotype, whereas smaller de novo deletions correlated with severe outcomes. Mosaicism was also detected in three cases.

Conclusion: FLNA CNV analysis, particularly for recurrent deletions and mosaicism, is essential in the genetic evaluation of BPNH. Integrating CNV detection with SNV analysis improves diagnostic accuracy and enhances understanding of genotype-phenotype correlations.