错义突变和功能丧失突变对家族性和散发性梅尼埃病遗传结构的不同影响

《MedComm》：Different Contribution of Missense and Loss-of-Function Variants to the Genetic Structure of Familial and Sporadic Meniere Disease

　　该研究通过全外显子测序比较了散发性（SMD）和家族性（FMD）Meniere病患者的罕见变异负担，发现两者在基因表达和变异分布上存在差异，但部分基因如ADGRV1、MYO7A等存在重叠，提示遗传异质性。功能验证显示NIN、CCDC88C、ANKRD24等新基因与听力损失相关。分隔符：

　　
Meniere disease (MD) is a chronic inner ear disorder characterized by episodic vertigo, fluctuating sensorineural hearing loss (SNHL), tinnitus, and aural fullness. This study aimed to investigate whether the genetic burden in sporadic MD (SMD) overlaps with familial MD (FMD), potentially revealing hidden inheritance patterns in sporadic cases. A total of 287 SMD patients and 93 FMD patients were analyzed through exome sequencing and gene burden analysis (GBA). Key findings include:

**Genetic Burden Differences Between SMD and FMD**
1. **Missense Variants**: FMD patients exhibited significantly higher accumulation of missense variants (median 226.5 vs. 194 in SMD; p=2.42×10??3) and genes linked to auditory/vestibular phenotypes (median 226.5 vs. 194; p=2.42×10??3). Variants in genes involved in hair cell stereocilia and tectorial membrane proteins were also more abundant in FMD (median 122 vs. 103 in SMD; p=1.47×10?32).
2. **Loss-of-Function (LoF) Variants**: While LoF variants were more frequent in FMD overall, this difference was not significant in genes expressed in the stria vascularis.

**Shared and Distinct Candidate Genes**
- **Shared Genes**: 28.1% of SMD-enriched genes overlapped with FMD-enriched genes, including ADGRV1, MEGF8, MYO7A, and PRKDC. These genes are associated with hair cell stereocilia organization, ion channel function, and cell adhesion.
- **Distinct SMD Genes**: 31 genes with inner ear annotations were enriched in SMD, including ZNF469 and PCDH15. These genes are linked to hair cell development and mechanotransduction.
- **Distinct FMD Genes**: 51 FMD-enriched genes, such as NOTCH1 and ANKRD24, showed higher variant burden. Notably, 11 genes in the OTOscope v9 panel for hearing loss diagnosis were identified in FMD.

**Functional Validation and Expression Insights**
- **KO Mouse Models**: Validation using knockout mice revealed that NIN, CCDC88C, and ANKRD24 caused hearing loss, aligning with clinical phenotypes. NIN KO mice exhibited hearing deficits across frequencies, while CCDC88C and ANKRD24 specifically affected high-frequency hearing.
- **Gene Expression**: Single-cell RNA-seq data showed NIN expressed broadly in hair cells and neurons, CCDC88C enriched in hair cells and vestibular cells, and ANKRD24 localized to stereocilia rootlets. These patterns support their roles in auditory and vestibular dysfunction.

**Pathogenic Implications**
- **Missense Variants**: Overload in genes regulating stria vascularis (e.g., FLNB, COL11A2) and hair cell stereocilia (e.g., MYO7A, ADGRV1) suggests multiallelic recessive inheritance.
- **LoF Variants**: Lower enrichment in stria vascularis genes in SMD implies distinct mechanisms compared to FMD.

**Limitations and Future Directions**
- **Exome Limitations**: The study focused on exonic variants, potentially missing regulatory or non-coding regions.
- **Unfiltered Genes**: genes like MYO15A and USH2A, excluded due toFLAGS status, may still contribute.
- **Autoimmune Factors**: Immune-related genes (e.g., BTNL8) were enriched but require further functional studies.

**Conclusion**
SMD and FMD exhibit divergent genetic architectures. SMD shows higher enrichment in stria vascularis and hair cell genes with missense variants, while FMD accumulates LoF variants in shared pathways. Overlapping genes like ADGRV1 and MYO7A suggest a common mechanism involving stereocilia stability and ion channel function. This study highlights the complexity of MD genetics and the need for comprehensive functional analyses to identify causative variants.

The research utilized exome sequencing and GBA to compare rare variant burdens between SMD and FMD cohorts. Key steps included:
1. **Data Collection**: 454 MD patients (287 SMD, 93 FMD) from Spain were analyzed.
2. **GBA Analysis**: Enriched genes were prioritized by expression in the inner ear, HPO/MGI annotations, and variant impact.
3. **Functional Validation**: ABR data from 96 NIN KO, 146 CCDC88C KO, and 6 ANKRD24 KO mice confirmed auditory deficits.

**Ethical Compliance**: Ethical approval (MS/2014/02) and informed consent were obtained. Data were anonymized for publication.

This study advances the understanding of MD genetics, identifying novel candidate genes and highlighting the importance of distinguishing between sporadic and familial forms for diagnostic strategies. Future work should integrate whole-genome data and explore immune-mediated pathways to uncover comprehensive pathogenic mechanisms.