Concurrent Hearing and Genetic Screening among Newborns in Ningbo, China

Objective. To detect the carrier rates of deafness gene variants in populations in Ningbo and analyze the risk of hereditary hearing loss through concurrent hearing and genetic screening tests. Methods. Two thousand one hundred and seventy-four newborns were enrolled from November 2018 to August 2019. All subjects underwent hearing screening and newborn deafness genetic screening with 15 variants in 4 genes, and the positive sites were simultaneously verified by sequencing. Results. The total carrier rate of genetic variants in Ningbo reached 4.32%, when GJB2 c.235delC was the variant with the highest prevalence (2.12%), approximately accounting for 48.9% of the total carrier frequency. The carrier frequency of SLC26A4 c.919-2A>G was 0.87%, while the most common variant in mitochondrial DNA (mtDNA) MT-RNR1 gene was m.1555A>G, and its carrier frequency was 0.184%. In the OAE testing, 92 newborns passing hearing screening were tested positively for variants in 4 genes, and 2 of 42 newborns who failed in the first hearing test were found to mutate in 4 genes. Conclusion. Herein, the results concerning the carrier rates for deafness gene mutations of Ningbo population are reported. Our study is beneficial to the insight into the deafness genomic epidemiology for deafness genes in Ningbo population and provides the reference for healthcare in Ningbo.

CHD7 regulates otic lineage differentiation and deafness gene expression in human inner ear organoids

Mutations in the chromatin remodeling enzyme CHD7 cause CHARGE syndrome, which affects multiple organs including the inner ear. We investigated how CHD7 mutations affect otic development in human inner ear organoids. We found loss of CHD7 or its chromatin remodeling activity leads to complete absence of hair cells and supporting cells, which can be explained by dysregulation of key otic development-associated genes in mutant otic progenitors. Further analysis of the mutant otic progenitors suggested that CHD7 can regulate otic genes through a chromatin remodeling-independent mechanism. Results from transcriptome profiling of hair cells revealed disruption of deafness gene expression as a potential underlying mechanism of CHARGE-associated sensorineural hearing loss. Notably, co-differentiating CHD7 knockout and wild-type cells in chimeric organoids partially rescued mutant phenotypes by restoring otherwise severely dysregulated otic genes. Taken together, our results suggest that CHD7 plays a critical role in regulating human otic lineage differentiation and deafness gene expression.

Genetic Heterogeneity in GJB2, COL4A3, ATP6V1B1 and EDNRB Variants Detected Among Hearing Impaired Families in Morocco

Deafness has a very variable disease. It may occur as a result of external auditory canal involvement or a deficiency in the sound conduction mechanism (transmission deafness) or impairment of the cochlear, cochlear nerve or central auditory perception. Genetics is the most common cause, as approximately 70% of hearing disorders are of hereditary origin. 1/3 of hereditary deafness is syndromic (associated with other symptoms) and 2/3 are non-syndromic (isolated deafness). At this date, 173 loci of deafness gene have been reported in the literature (69 DFNA, 94 DFNB, 6 X-linked DFN, 2 DFNM, 1 DFNY and 1 AUNA1). For syndromic deafness, approximately 400 syndromes associated with hearing disorders are already described. Thus, the determination of causal mutations is a valuable aid for accurate and early diagnosis. This makes it possible to better guide the management since forms of deafness respond better to the cochlear implant than others. The correct diagnosis also gives an idea of ​​the evolutionary profile of deafness and whether it is a syndromic deafness requiring special surveillance. In this study, we have examined the genetic causes of sensorineural hearing loss in Moroccan patients through whole exome sequencing (WES) to identify candidate genes for six severely deaf Moroccan families. The results revealed four genetic variants in the genes GJB2, COL4A3, ATP6V1B1 and EDNRB, which are therefore common causes of syndromic and non-syndromic deafness.

Multi-Center in-Depth Screening of Neonatal Deafness Genes: Zhejiang, China

PurposeThe conventional genetic screening for deafness involves 9–20 variants from four genes. This study expands screening to analyze the mutation types and frequency of hereditary deafness genes in Zhejiang, China, and explore the significance of in-depth deafness genetic screening in newborns.MethodsThis was a multi-centre study conducted in 5,120 newborns from 12 major hospitals in the East-West (including mountains and islands) of Zhejiang Province. Concurrent hearing and genetic screening was performed. For genetic testing, 159 variants of 22 genes were screened, including CDH23, COL11A1, DFNA5, DFNB59, DSPP, GJB2, GJB3, KCNJ10, MT-RNR1, MT-TL1, MT-TS1, MYO15A, MYO7A, OTOF, PCDH15, SLC26A4, SOX10, TCOF1, TMC1, USH1G, WFS1, and WHRN using next-generation sequencing. Newborns who failed to have genetic mutations or hearing screening were diagnosed audiologically at the age of 6 months.ResultsA total of 4,893 newborns (95.57%) have passed the initial hearing screening, and 7 (0.14%) have failed in repeated screening. Of these, 446 (8.71%) newborns carried at least one genetic deafness-associated variant. High-risk pathogenic variants were found in 11 newborns (0.21%) (nine homozygotes and two compound heterozygotes), and eight of these infants have passed the hearing screening. The frequency of mutations in GJB2, GJB3, SLC26A4, 12SrRNA, and TMC1 was 5.43%, 0.59%, 1.91%, 0.98%, and 0.02%, respectively. The positive rate of in-depth screening was significantly increased when compared with 20 variants in four genes of traditional testing, wherein GJB2 was increased by 97.2%, SLC26A4 by 21% and MT-RNR1 by 150%. The most common mutation variants were GJB2c.235delC and SLC26A4c.919-2A > G, followed by GJB2c.299_300delAT. Homoplasmic mutation in MT-RNR1 was the most common, including m.1555A > G, m.961T > C, m.1095T > C. All these infants have passed routine hearing screening. The positive rate of MT-RNR1 mutation was significantly higher in newborns with high-risk factors of maternal pregnancy.ConclusionThe positive rate of deafness gene mutations in the Zhejiang region is higher than that of the database, mainly in GJB2c.235delC, SLC26A4 c.919-2A > G, and m.1555A > G variants. The expanded genetic screening in the detection rate of diseasecausing variants was significantly improved. It is helpful in identifying high-risk children for follow-up intervention.

A nonsense TMEM43 variant leads to disruption of connexin-linked function and autosomal dominant auditory neuropathy spectrum disorder

Genes that are primarily expressed in cochlear glia-like supporting cells (GLSs) have not been clearly associated with progressive deafness. Herein, we present a deafness locus mapped to chromosome 3p25.1 and an auditory neuropathy spectrum disorder (ANSD) gene, TMEM43, mainly expressed in GLSs. We identify p.(Arg372Ter) of TMEM43 by linkage analysis and exome sequencing in two large Asian families segregating ANSD, which is characterized by inability to discriminate speech despite preserved sensitivity to sound. The knock-in mouse with the p.(Arg372Ter) variant recapitulates a progressive hearing loss with histological abnormalities in GLSs. Mechanistically, TMEM43 interacts with the Connexin26 and Connexin30 gap junction channels, disrupting the passive conductance current in GLSs in a dominant-negative fashion when the p.(Arg372Ter) variant is introduced. Based on these mechanistic insights, cochlear implant was performed on three subjects, and speech discrimination was successfully restored. Our study highlights a pathological role of cochlear GLSs by identifying a deafness gene and its causal relationship with ANSD.

Concurrent Hearing and Genetic Screening of 18 001 Neonates with Hearing Diagnose in Nantong, China

Objectives: Concurrent hearing and genetic screening of newborns is expected to play an important role in the early detection and diagnosis of congenital deafness, which triggers an intervention, as well as in predicting late-onset and progressive hearing loss and identifying individuals who are at risk of drug-induced hearing loss (HL).Methods: A Deafness Gene Variant Detection Array Kit covering fifteen variants in four genes was used to screen for deafness genes in 18001 infants.Results: A total of 108 neonates did not pass the second hearing screening. In addition, 912 (5.07%) screened positive for deafness-associated variants, including 78 (0.43%) genetically referred and 834 (4.63%) genetic deafness-associated variant carriers. Of the 912 screened positive cases, 880 passed the hearing screening, and 32 failed. A total of 62 (0.34%) cases carried the mtDNA 12S rRNA variants. A total of 108 cases did not pass the hearing screening and underwent a hearing diagnostic examination. An expanded DNA test identified 17 patients who possessed deafness gene mutations, increasing the detection rate to 5.16%.Conclusion: Early detection, diagnosis, and interventions are necessary for newborns who are susceptible to deafness. A good strategy is to use a small panel to quickly screen all subjects and then apply an extended panel to study the cause of deafness in affected patients.

A biallelic variant in CLRN2 causes non-syndromic hearing loss in humans

Deafness, the most frequent sensory deficit in humans, is extremely heterogeneous with hundreds of genes involved. Clinical and genetic analyses of an extended consanguineous family with pre-lingual, moderate-to-profound autosomal recessive sensorineural hearing loss, allowed us to identify CLRN2, encoding a tetraspan protein, as a new deafness gene. Homozygosity mapping followed by exome sequencing identified a 14.96 Mb locus on chromosome 4p15.32p15.1 containing a likely pathogenic missense variant in CLRN2 (c.494C > A, NM_001079827.2) segregating with the disease. Using in vitro RNA splicing analysis, we show that the CLRN2 c.494C > A variant leads to two events: (1) the substitution of a highly conserved threonine (uncharged amino acid) to lysine (charged amino acid) at position 165, p.(Thr165Lys), and (2) aberrant splicing, with the retention of intron 2 resulting in a stop codon after 26 additional amino acids, p.(Gly146Lysfs*26). Expression studies and phenotyping of newly produced zebrafish and mouse models deficient for clarin 2 further confirm that clarin 2, expressed in the inner ear hair cells, is essential for normal organization and maintenance of the auditory hair bundles, and for hearing function. Together, our findings identify CLRN2 as a new deafness gene, which will impact future diagnosis and treatment for deaf patients.