Variants in Genes Associated with Hearing Loss in Children: Prevalence in a Large Canadian Cohort.

OBJECTIVE: The objective of this study was to assess the prevalence of genetic variants associated with hearing loss in a large cohort of children in Canada using high throughput next generation sequencing (NGS). METHODS: A total of 485 children with hearing loss underwent NGS testing with an 80 gene panel of syndromic and non-syndromic variants known to be associated with hearing loss. Genetic variants were classified as pathogenic, likely pathogenic, likely benign, benign, or variants of uncertain significance (VUS), according to the American College of Medical Genetics and Genomics guidelines. RESULTS: Across the 80 genes tested, 923 variants, predominantly in 28 genes, were identified in 324 children. Pathogenic variants occurred in 19/80 (23.8%) of the hearing loss related genes tested and confirmed the etiology of hearing loss in 73/485 (15.1%) of children. GJB2 was the most prevalent gene, affecting 28/73 (38.4%) children with confirmed genetic hearing loss in our cohort. Most identified variants (748/923, 81.0%, in 76/80 genes) were of uncertain significance. CONCLUSION: Genetic testing using NGS identified the etiology in approximately 15% of childhood hearing loss in a Canadian cohort which is lower than what is typically reported. GJB2 was the most common genetic cause of hearing loss. VUS are commonly identified, presenting clinical challenges for counseling. LEVEL OF EVIDENCE: Level 4 Laryngoscope, 2024.

Regionally defined proteomic profiles of human cerebral tissue and organoids reveal conserved molecular modules of neurodevelopment.

Cerebral organoids have emerged as robust models for neurodevelopmental and pathological processes, as well as a powerful discovery platform for less-characterized neurobiological programs. Toward this prospect, we leverage mass-spectrometry-based proteomics to molecularly profile precursor and neuronal compartments of both human-derived organoids and mid-gestation fetal brain tissue to define overlapping programs. Our analysis includes recovery of precursor-enriched transcriptional regulatory proteins not found to be differentially expressed in previous transcriptomic datasets. To highlight the discovery potential of this resource, we show that RUVBL2 is preferentially expressed in the SOX2-positive compartment of organoids and that chemical inactivation leads to precursor cell displacement and apoptosis. To explore clinicopathological correlates of this cytoarchitectural disruption, we interrogate clinical datasets and identify rare de novo genetic variants involving RUVBL2 in patients with neurodevelopmental impairments. Together, our findings demonstrate how cell-type-specific profiling of organoids can help nominate previously unappreciated genes in neurodevelopment and disease.

Diagnostic outcomes for molecular genetic testing in children with suspected Ehlers-Danlos syndrome.

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders characterized by hyperextensible skin, hypermobile joints, easy bruisability, and fragility of the connective tissues. The diagnosis is based on clinical assessment and phenotype-guided genetic testing. Most EDS subtypes can be confirmed by genetic testing except for hypermobile EDS. This study explored the utility of applying the 2017 EDS classification criteria and molecular genetic testing in establishing an EDS diagnosis in children. In this retrospective study, we reviewed 72 patients referred to a tertiary care center for evaluation of EDS who underwent one or more forms of genetic testing. Eighteen patients (18/72, 25%) met the clinical criteria for one of the EDS subtypes and of these, 15 (15/18, 83%) were confirmed molecularly. Fifty-four patients (54/72, 75%) had features that overlapped EDS and other syndromes associated with joint hypermobility but did not fully meet clinical criteria. Twelve of them (12/54, 22%) were later shown to have a positive molecular genetic diagnosis of EDS. Different molecular genetic tests were performed on the cohort of 72 patients (EDS panel, n = 44; microarray, n = 25; whole exome sequencing [WES], n = 9; single gene sequencing, n = 3; familial variant testing, n = 10; other genetic panels n = 3). EDS panel was completed in 44 patients (61%), and a molecular diagnosis was confirmed in nine of the patients who satisfied criteria for one of the EDS subtypes (9/12, 75%) and in nine of the patients who did not fully meet criteria (9/32, 28%). We observed a correlation between generalized joint hypermobility, poor healing, easy bruising, atrophic scars, skin hyperextensibility, and developmental dysplasia of the hip with a positive molecular result. This study provides guidance for the use of molecular genetic testing in combination with the 2017 clinical diagnostic criteria in children presenting with EDS characteristics.

Diagnostic yield of genome sequencing for prenatal diagnosis of fetal structural anomalies.

OBJECTIVE: Genome sequencing (GS >30x) is beginning to be adopted as a comprehensive genome-wide test for the diagnosis of rare disease in the post-natal setting. Recent studies demonstrated the utility of exome sequencing (ES) in prenatal diagnosis, we investigate the potential benefits for GS to act as a comprehensive prenatal test for diagnosis of fetal abnormalities. METHODS: We performed GS on a prospective cohort of 37 singleton fetuses with ultrasound-identified structural abnormalities undergoing invasive prenatal testing. GS was performed in parallel with standard diagnostic testing, and the prioritized variants were classified according to ACMG guidelines and reviewed by a panel of board-certified laboratory and clinical geneticists. RESULTS: Diagnostic sequence variants were identified in 5 fetuses (14%), with pathogenic variants found in NIPBL, FOXF1, RERE, AMMECR1, and FLT4. A further 7 fetuses (19%) had variants of uncertain significance (VUS) that may explain the phenotypes. Importantly, GS also identified all pathogenic variants reported by clinical microarray (2 CNVs, 5%). CONCLUSION: Prenatal GS offered diagnoses (sequence variants and CNVs) in 19% of fetuses with structural anomalies. GS has the potential of replacing multiple consecutive tests, including microarray, gene panels, and WES, to provide the most comprehensive analysis in a timely manner necessary for prenatal diagnosis.

Whole exome sequencing uncovered highly penetrant recessive mutations for a spectrum of rare genetic pediatric diseases in Bangladesh.

Collectively, rare genetic diseases affect a significant number of individuals worldwide. In this study, we have conducted whole-exome sequencing (WES) and identified underlying pathogenic or likely pathogenic variants in five children with rare genetic diseases. We present evidence for disease-causing autosomal recessive variants in a range of disease-associated genes such as DHH-associated 46,XY gonadal dysgenesis (GD) or 46,XY sex reversal 7, GNPTAB-associated mucolipidosis II alpha/beta (ML II), BBS1-associated Bardet-Biedl Syndrome (BBS), SURF1-associated Leigh Syndrome (LS) and AP4B1-associated spastic paraplegia-47 (SPG47) in unrelated affected members from Bangladesh. Our analysis pipeline detected three homozygous mutations, including a novel c. 863 G > C (p.Pro288Arg) variant in DHH, and two compound heterozygous variants, including two novel variants: c.2972dupT (p.Met991Ilefs*) in GNPTAB and c.229 G > C (p.Gly77Arg) in SURF1. All mutations were validated by Sanger sequencing. Collectively, this study adds to the genetic heterogeneity of rare genetic diseases and is the first report elucidating the genetic profile of (consanguineous and nonconsanguineous) rare genetic diseases in the Bangladesh population.

Chitayat-Hall and Schaaf-Yang syndromes:a common aetiology: expanding the phenotype of MAGEL2-related disorders.

BACKGROUND: Chitayat-Hall syndrome, initially described in 1990, is a rare condition characterised by distal arthrogryposis, intellectual disability, dysmorphic features and hypopituitarism, in particular growth hormone deficiency. The genetic aetiology has not been identified. METHODS AND RESULTS: We identified three unrelated families with a total of six affected patients with the clinical manifestations of Chitayat-Hall syndrome. Through whole exome or whole genome sequencing, pathogenic variants in the MAGEL2 gene were identified in all affected patients. All disease-causing sequence variants detected are predicted to result in a truncated protein, including one complex variant that comprised a deletion and inversion. CONCLUSIONS: Chitayat-Hall syndrome is caused by pathogenic variants in MAGEL2 and shares a common aetiology with the recently described Schaaf-Yang syndrome. The phenotype of MAGEL2-related disorders is expanded to include growth hormone deficiency as an important and treatable complication.

Mosaic microdeletion of 17p11.2-p12 and duplication of 17q22-q24 in a girl with Smith-Magenis phenotype and peripheral neuropathy.

We report on a girl with a de novo mosaic derivative chromosome 17 involving a 7.4 Mb deletion of chromosome region 17p11.2 to 17p12 and a duplication of a 12.35 Mb region at 17q22 to 17q24. She was ascertained because of developmental delay, peripheral neuropathy, brachydactyly and minor anomalies. The derivative chromosome was present in approximately 12% of lymphocytes based on FISH studies, and was detected by array comparative genomic hybridization. To our knowledge, this is the third case of mosaicism involving deletion of the 17p11.2 region and the lowest level of mosaicism reported in a patient with Smith-Magenis syndrome (SMS).