Otitis media susceptibility and shifts in the head and neck microbiome due to

BACKGROUND: Otitis media (OM) susceptibility has significant heritability, however the role of rare variants in OM is mostly unknown. Our goal is to identify novel rare variants that confer OM susceptibility. METHODS: We performed exome and Sanger sequencing of >1,000 DNA samples from 551 multi-ethnic families with OM and unrelated individuals, RNA-sequencing, and microbiome sequencing and analyses of swabs from the outer ear, middle ear, nasopharynx and oral cavity. We also examined protein localization and gene expression in infected and healthy middle ear tissues. RESULTS: A large, intermarried pedigree that includes 81 OM-affected and 53 unaffected individuals co-segregates two known rare A2ML1 variants, a common FUT2 variant and a rare, novel pathogenic variant c.1682A>G (p.Glu561Gly) within SPINK5 (LOD=4.09). Carriage of the SPINK5 missense variant resulted in increased relative abundance of Microbacteriaceae in the middle ear, along with occurrence of Microbacteriaceae in the outer ear and oral cavity but not the nasopharynx. Eight additional novel SPINK5 variants were identified in twelve families and individuals with OM. A role for SPINK5 in OM susceptibility is further supported by lower RNA counts in variant carriers, strong SPINK5 localization in outer ear skin, faint localization to middle ear mucosa and eardrum, and increased SPINK5 expression in human cholesteatoma. CONCLUSION: SPINK5 variants confer susceptibility to non-syndromic OM. These variants potentially contribute to middle ear pathology through breakdown of mucosal and epithelial barriers, immunodeficiency such as poor vaccination response, alteration of head and neck microbiota, and facilitation of entry of opportunistic pathogens into the middle ear.