Systematic Review of Hearing Loss Genes in the African American Population

First report of an Ivorian family with nonsyndromic hearing loss caused by GJB2 compound heterozygous variants

The primary etiology of congenital hearing loss is attributed to genetic factors, with GJB2 identified as a pivotal gene across diverse ethnic groups. Additionally, nonsyndromic hearing loss is predominantly inherited in an autosomal recessive manner. We used Sanger sequencing to analyze GJB2 in 17 deaf children from 13 unrelated Ivory Coast families. One family had two children born with severe congenital deafness and exhibited pathogenic compound heterozygous variants. These variants included a nonsense substitution (c.132G > A or p.Trp44Ter) and a newly discovered duplication of 7 base pairs (c.205_211dupTTCCCCA or p.Ser72ProfsTer32). Segregation testing confirmed these variants, marking the first identification of GJB2 in an Ivorian family with congenital hearing loss.

Next-generation sequencing for genetic testing of hearing loss populations

BACKGROUND AND AIMS

Hearing loss is a common sensorineural disease with genetic heterogeneity. More than 140 genes are known to cause hereditary hearing loss. We aim to uncover the etiologies of hearing loss and provide patients with reasonable reproductive choices.

MATERIALS AND METHODS

Total 825 participants were recruited, including 74 individuals, 47 couples, and 219 families, to identify the molecular etiologies of hearing loss using next-generation sequencing (NGS). Novel mutations were verified with a minigene splicing assay and the construction of three-dimensional protein models.

RESULTS

A positive molecular diagnosis was obtained for 244 patients, a rate of 63.05 %. Total 470 mutations were identified in 18 causative genes in positive patients. The most common genes mutated were GJB2 and SLC26A4. 47 novel mutations were identified. Further analysis predicted that two splicing mutations would cause abnormal mRNA splicing and three missense mutations would affect the protein structure. The results of prenatal diagnosis showed that the genotypes of 15 fetuses were the same as the probands.

CONCLUSION

Our findings expand the mutation spectrum of hearing loss and highlight the importance of genetic diagnosis and prenatal diagnosis to allow accurate and personalized guidance for those at high risk of deafness.

Comprehensive Gene Panel Testing for Hearing Loss in Children: Understanding Factors Influencing Diagnostic Yield

OBJECTIVE

To evaluate factors influencing the diagnostic yield of comprehensive gene panel testing (CGPT) for hearing loss (HL) in children and to understand the characteristics of undiagnosed probands.

STUDY DESIGN

This was a retrospective cohort study of 474 probands with childhood-onset HL who underwent CGPT between 2016 and 2020 at a single center. Main outcomes and measures included the association between clinical variables and diagnostic yield and the genetic and clinical characteristics of undiagnosed probands.

RESULTS

The overall diagnostic yield was 44% (209/474) with causative variants involving 41 genes. While the diagnostic yield was high in the probands with congenital, bilateral, and severe HL, it was low in those with unilateral, noncongenital, or mild HL; cochlear nerve deficiency; preterm birth; neonatal intensive care unit admittance; certain ancestry; and developmental delay. Follow-up studies on 49 probands with initially inconclusive CGPT results changed the diagnostic status to likely positive or negative outcomes in 39 of them (80%). Reflex to exome sequencing on 128 undiagnosed probands by CGPT revealed diagnostic findings in 8 individuals, 5 of whom had developmental delays. The remaining 255 probands were undiagnosed, with 173 (173/255) having only a single variant in the gene(s) associated with autosomal recessive HL and 28% (48/173) having a matched phenotype.

CONCLUSION

CGPT efficiently identifies the genetic etiologies of HL in children. CGPT-undiagnosed probands may benefit from follow-up studies or expanded testing.

Exome Sequencing Expands the Genetic Diagnostic Spectrum for Pediatric Hearing Loss

OBJECTIVES

Genetic testing is the standard-of-care for diagnostic evaluation of bilateral, symmetric, sensorineural hearing loss (HL). We sought to determine the efficacy of a comprehensive genetic testing method, exome sequencing (ES), in a heterogeneous pediatric patient population with bilateral symmetric, bilateral asymmetric, and unilateral HL.

METHODS

Trio-based ES was performed for pediatric patients with confirmed HL including those with symmetric, asymmetric, and unilateral HL.

RESULTS

ES was completed for 218 probands. A genetic cause was identified for 31.2% of probands (n = 68). The diagnostic rate was 40.7% for bilateral HL, 23.1% for asymmetric HL, and 18.3% for unilateral HL, with syndromic diagnoses made in 20.8%, 33.3%, and 54.5% of cases in each group, respectively. Secondary or incidental findings were identified in 10 families (5.52%).

CONCLUSION

ES is an effective method for genetic diagnosis for HL including phenotypically diverse patients and allows the identification of secondary findings, discovery of deafness-causing genes, and the potential for efficient data re-analysis.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:2417-2424, 2023.

Non-Syndromic Hearing Loss in a Romanian Population: Carrier Status and Frequent Variants in the GJB2 Gene

The genetic causes of autosomal recessive nonsyndromic hearing loss (ARNSHL) are heterogeneous and highly ethnic-specific. We describe GJB2 (connexin 26) variants and carrier frequencies as part of our study and summarize previously reported ones for the Romanian population. In total, 284 unrelated children with bilateral congenital NSHL were enrolled between 2009 and 2018 in northwestern Romania. A tiered diagnostic approach was used: all subjects were tested for c.35delG, c.71G>A and deletions in GJB6 (connexin 30) using PCR-based methods. Furthermore, 124 cases undiagnosed at this stage were analyzed by multiplex-ligation-dependent probe amplifications (MLPA), probe mix P163, and sequencing of GJB2 exon 2. Targeted allele-specific PCR/restriction fragment length polymorphism (RFLP) established definite ethio-pathogenical diagnosis for 72/284 (25.35%) of the cohort. Out of the 124 further analyzed, in 12 cases (9.67%), we found compound heterozygous point mutations in GJB2. We identified one case of deletion of exon 1 of the WFS1 (wolframin) gene. Carrier status evaluation used Illumina Infinium Global Screening Array (GSA) genotyping: the HINT cohort-416 individuals in northwest Romania, and the FUSE cohort-472 individuals in southwest Romania. GSA variants yielded a cumulated risk allele presence of 0.0284. A tiered diagnostic approach may be efficient in diagnosing ARNSHL. The summarized contributions to Romanian descriptive epidemiology of ARNSHL shows that pathogenic variants in the GJB2 gene are frequent among NSHL cases and have high carrier rates, especially for c.35delG and c.71G>A. These findings may serve in health strategy development.

Genetic testing for pediatric hearing loss: no time to waste

Since the discovery of the first human deafness gene a quarter of a century ago, our approach to clinical evaluation of children with hearing loss has changed dramatically. What was once a low-yield scattershot approach has changed to a clearly definable pathway involving genetic testing, imaging, and congenital cytomegalovirus testing. There still however is a great deal of work to be done to expand the correct use of this testing, particularly genetic testing.

Assessment of Hearing Screening Combined With Limited and Expanded Genetic Screening for Newborns in Nantong, China

IMPORTANCE

Early identification and intervention for newborns with hearing loss (HL) may lead to improved physiological and social-emotional outcomes. The current newborn hearing screening is generally beneficial but improvements can be made.

OBJECTIVE

To assess feasibility and evaluate utility of a modified genetic and hearing screening program for newborn infants.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study used a 4-stage genetic and hearing screening program at 6 local hospitals in Nantong city, China. Participants were newborn infants born between January 2016 and June 2020 from the Han population. Statistical analysis was performed from April 1 to May 1, 2021.

EXPOSURES

Limited genetic screening for 15 variants in 4 common HL-associated genes and newborn hearing screening (NHS) were offered concurrently to all newborns. Hearing rescreening and/or diagnostic tests were provided for infants with evidence of HL on NHS or genetic variants on screening. Expanded genetic tests for a broader range of genes were targeted to infants with HL with negative results of limited genetic tests.

MAIN OUTCOMES AND MEASURES

The detection capability for infants with hearing impairment who passed conventional hearing screening, as well as infants with normal hearing at risk of late-onset HL due to genetic susceptibility.

RESULTS

Among a total of 35 930 infants, 32 512 infants completed the follow-up and were included for analysis. Among the infants included in the analysis, all were from the Han population in China and 52.3% (16 988) were male. The modified genetic and hearing screening program revealed 142 cases of HL and 1299 cases of genetic variation. The limited genetic screening helped identify 31 infants who passed newborn hearing screening, reducing time for diagnosis and intervention; 425 infants with normal hearing with pathogenic SLC26A4 variation and 92 infants with MT-RNR1 variation were at risk for enlarged vestibular aqueduct and aminoglycoside-induced ototoxicity respectively, indicating early aversive or preventive management.

CONCLUSIONS AND RELEVANCE

This study found that performing modified genetic and hearing screening in newborns was feasible and provides evidence that the program could identify additional subgroups of infants who need early intervention. These findings suggest an advantage for universal adoption of such a practice.

Systematic Review of Pathogenic GJB2 Variants in the Latino Population

OBJECTIVES

Define the extent to which GJB2-related hearing loss is responsible for non-syndromic hearing loss (NSHL) in the Latino population.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed. PubMed and MEDLINE were accessed from 1966 to 2019 using permutations of the MeSH terms: "Hearing Loss," "Hearing Impairment," "Deafness," "Latin American," "Latino," "GJB2," and "Genetic." Additionally, countries designated as Latino by the US Office of Management and Bureau were cross-referenced as key terms against the aforementioned search criteria. Exclusion criteria included non-English publications, a non-Latino study population, and literature not investigating GJB2. An allele frequency analysis of pathogenic GJB2 variants in the Latino population was performed and stratified by country of origin and reported ethnicity.

RESULTS

One hundred twenty two unique studies were identified of which 64 met our inclusion criteria. Forty three studies were included in the GJB2 systematic review. A total of 38 pathogenic GJB2 variants were identified across 20 countries in the Latino population. The prevalence of pathogenic GJB2 variants varied by country; however, were generally uncommon with the exception of c.35delG (p.Gly12Valfs*) which displayed an allele frequency of 3.1% in the combined Latino population; ranging from 21% in Colombia to 0% in Guatemala.

CONCLUSION

Variation in the prevalence of pathogenic GJB2 variants by country likely reflect the heterogeneous nature of ethnic ancestral contributions to the Latino population. Additional research utilizing next generation sequencing might aid in the development of assays for high throughput diagnosis of inherited hearing loss in the multitude of ethnic sub-groups that comprise this and other traditionally marginalized populations.