Apoptosis of cochlear hair cells is a key step towards age-related hearing loss. Although numerous genes have been implicated in the genetic causes of late-onset, progressive hearing loss, few show direct links to the proapoptotic process. By genome-wide linkage analysis and whole exome sequencing, we identified a heterozygous p.L183V variant in THOC1 as the probable cause of the late-onset, progressive, non-syndromic hearing loss in a large family with autosomal dominant inheritance. Thoc1, a member of the conserved multisubunit THO/TREX ribonucleoprotein complex, is highly expressed in mouse and zebrafish hair cells. The thoc1 knockout (thoc1 mutant) zebrafish generated by gRNA-Cas9 system lacks the C-startle response, indicative of the hearing dysfunction. Both Thoc1 mutant and knockdown zebrafish have greatly reduced hair cell numbers, while the latter can be rescued by embryonic microinjection of human wild-type THOC1 mRNA but to significantly lesser degree by the c.547C>G mutant mRNA. The Thoc1 deficiency resulted in marked apoptosis in zebrafish hair cells. Consistently, transcriptome sequencing of the mutants showed significantly increased gene expression in the p53-associated signaling pathway. Depletion of p53 or applying the p53 inhibitor Pifithrin-α significantly rescued the hair cell loss in the Thoc1 knockdown zebrafish. Our results suggested that THOC1 deficiency lead to late-onset, progressive hearing loss through p53-mediated hair cell apoptosis. This is to our knowledge the first human disease associated with THOC1 mutations and may shed light on the molecular mechanism underlying the age-related hearing loss. We identified a variant in THOC1 as the probable cause of the hearing loss in a large family with autosomal dominant inheritance. In addition, we showed THOC1 was expressed in mouse and zebrafish hair cells. Furthermore, we revealed that thoc1 deficiency caused the reduction of hair cell numbers in zebrafish and the hypomorphic Thoc1 induced hair cell apoptosis. These defects could be attenuated by the inhibition of p53.

Background: Nonsyndromic hearing loss is clinically and genetically heterogeneous. In this study, we characterized the clinical features of 12 Chinese Han deaf families in which mutations in common deafness genes GJB2 , SLC26A4, and MT‐RNR1 were excluded. Methods: Targeted next‐generation sequencing of 147 known deafness genes was performed in probands of 10 families, while whole‐exome sequencing was applied in those of the rest two. Results: Pathogenic mutations in a total of 11 rare deafness genes, OTOF , CDH23 , PCDH15 , PDZD7 , ADGRV1 , KARS , OTOG , GRXCR2 , MYO6 , GRHL2 , and POU3F4 , were identified in all 12 probands, with 16 mutations being novel. Intrafamilial cosegregation of the mutations and the deafness phenotype were confirmed by Sanger sequencing. Conclusion: Our results expanded the mutation spectrum and genotype‒phenotype correlation of nonsyndromic hearing loss in Chinese Hans and also emphasized the importance of combining both next‐generation sequencing and detailed auditory evaluation to achieve a more accurate diagnosis for nonsyndromic hearing loss.

Nonsyndromic hearing loss has been shown to have high genetic heterogeneity. In this report, we aimed to disclose the genetic causes of the subjects from the ten Chinese deaf families who did not have pathogenic common genes/mutation. Next-generation sequencing (NGS) of 142 known deafness genes was performed in the probands of ten families followed by cosegregation analysis of all family members. We identified novel pathogenic variants in six families including p.D1806E/p.R1588W, p.R964W/p.R1588W, and p.G17C/p.G1449D in CDH23; p.T584M/p.D1939N in LOXHD1; p.P1225L in MYO7A; and p.K612X in EYA4. Sanger sequencing confirmed that these mutations segregated with the hearing loss of each family. In four families, no pathogenic variants were identified. Our study provided better understanding of the mutation spectrum of hearing loss in the Chinese population.

Although the transcriptional alterations inside the facial nucleus after facial nerve injury have been well studied, the gene expression changes in the facial nerve trunk after injury are still unknown. In this study, we established an adult rat model of facial nerve crush injury by compressing the right lateral extracranial nerve trunk. Transcriptome sequencing, differential gene expression analysis, and cluster analysis of the injured facial nerve trunk were performed, and 39 intersecting genes with significant variance in expression were identified. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the 39 intersecting genes revealed that these genes are mostly involved in leukocyte cell-cell adhesion and phagocytosis and have essential roles in regulating nerve repair. Quantitative real-time polymerase chain reaction assays were used to validate the expression of pivotal genes. Finally, nine pivotal genes that contribute to facial nerve recovery were identified, including Arhgap30, Akr1b8, C5ar1, Csf2ra, Dock2, Hcls1, Inpp5d, Sla, and Spi1. Primary Schwann cells were isolated from the sciatic nerve of neonatal rats. After knocking down Akr1b8 in Schwann cells with an Akr1b8-specific small interfering RNA plasmid, expression levels of monocyte chemoattractant protein-1 and interleukin-6 were decreased, while cell proliferation and migration were not obviously altered. These findings suggest that Akr1b8 likely regulates the interaction between Schwann cells and macrophages through regulation of cytokine expression to promote facial nerve regeneration. This study is the first to reveal a transcriptome change in the facial nerve trunk after facial nerve injury, thereby revealing the potential mechanism underlying repair of facial nerve injury. This study was approved by the Animal Ethics Committee of Nantong University, China in 2018 (approval No. S20180923-007).