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Newborn screening for common genetic variants associated with permanent hearing loss: Implementation in Ontario and review of the first 3 years.

PURPOSE: Early hearing detection and intervention (EHDI) programs using audiometric screening techniques alone have a limited ability to detect noncongenital childhood permanent hearing loss (PHL). In 2019, Ontario launched universal newborn screening (NBS) for PHL risk factors, including congenital cytomegalovirus and 22 common variants in GJB2 and SLC26A4. Here, we describe our experience in screening for genetic risk factors. METHODS: Ontario newborns who participated in universal newborn hearing screening (UNHS) were offered risk factor screening using dried blood spots (DBS) collected for conventional newborn screening. The screening was conducted using a custom MassArray assay, and positive results were confirmed by Sanger sequencing or polymerase chain reaction. Diagnostic audiological assessments were performed for all screen-positive infants. RESULTS: Of the 412,424 infants screened, 93 had 2 variants in GJB2 or SLC26A4. Of these, 72 had confirmed PHL, 20 had normal hearing, and 1 declined follow-up. Thirteen infants with PHL (1 in 31,724; 11.8% of screen positives) were not identified through audiometric testing as they passed (3) or missed (10) the screening. Importantly, among infants who ultimately received cochlear implants, the detection of genetic etiology through NBS led to an accelerated time to diagnosis, assessment, and intervention. CONCLUSION: Genetic screening has strengthened UNHS and care for infants with or at risk of PHL in Ontario. This study is a step toward the broader inclusion of genomic testing in NBS.

Humans

Validating the splicing effect of rare variants in the SLC26A4 gene using minigene assay.

BACKGROUND: The SLC26A4 gene is the second most common cause of hereditary hearing loss in human. The aim of this study was to utilize the minigene assay in order to identify pathogenic variants of SLC26A4 associated with enlarged vestibular aqueduct (EVA) and hearing loss (HL) in two patients. METHODS: The patients were subjected to multiplex PCR amplification and next-generation sequencing of common deafness genes (including GJB2, SLC26A4, and MT-RNR1), then bioinformatics analysis was performed on the sequencing data to identify candidate pathogenic variants. Minigene experiments were conducted to determine the potential impact of the variants on splicing. RESULTS: Genetic testing revealed that the first patient carried compound heterozygous variants c.[1149 + 1G > A]; [919-2 A > G] in the SLC26A4 gene, while the second patient carried compound heterozygous variants c.[2089 + 3 A > T]; [919-2 A > G] in the same gene. Minigene experiments demonstrated that both c.1149 + 1G > A and c.2089 + 3 A > T affected mRNA splicing. According to the ACMG guidelines and the recommendations of the ClinGen Hearing Loss Expert Panel for ACMG variant interpretation, these variants were classified as "likely pathogenic". CONCLUSIONS: This study identified the molecular etiology of hearing loss in two patients with EVA and elucidated the impact of rare variants on splicing, thus contributing to the mutational spectrum of pathogenic variants in the SLC26A4 gene.

Humans

National genomic projects in Asia and Africa: a review.

National genome projects (NGPs) are increasingly shaping precision medicine by improving representation of population-specific genetic diversity. This review compiles findings from NGPs across Asia and Africa, regions that remain underrepresented in global genomic databases despite their extensive demographic and genetic diversity. A total of 53 studies from 24 countries were identified to understand (1) the genomic approach utilized, (2) novel findings that have emerged, and (3) strategies for improving research in these regions. The NGPs implement population-based variome databases (20 NGPs), linear reference genome assemblies (8 NGPs), and graph-based pangenome assemblies (1 NGP). Novel variants ranged between 0.28% (China) and 19.6% (Iran), whereas rare variants accounted for up to 88.9% of the detected variants in the Chinese population. Each NGP documents its country's evolutionary and migration history, which impacts disease frequency and pharmacogenomic variants. Clinically, NGPs revealed strong population stratification in disease-associated and pharmacogenomic variants. For example, the GJB2 rs72474224 hearing-loss variant ranged from 13% in Vietnam and 12% in Hong Kong to 0.0894% in Turkey, while the VKORC1 rs9923231 pharmacogenomic variant reached 89.2% in Taiwan but was 20%-25% in European-related Russian subpopulations. These findings demonstrate that clinically relevant allele frequencies, pathogenicity assessments, and drug-response markers differ substantially across ancestries. This review highlights ongoing efforts and strategies to enhance the representativeness of genomic data through NGPs in Asia and Africa. We also suggest future directions for national projects, including integrating family-based studies, multi-omic data, and standardized pipelines to accelerate discovery and support the equitable implementation of precision medicine.

Humans