Abstract: Objective · To explore the main mutation types and pathogenicity of the coding region of keratin 9 gene (KRT9) in Chinese Han population, and to provide reference information for the classification and prediction of clinical diagnosis of the disease with epidermolytic palmoplantar keratoderma (EPPK). Methods · 834 subjects were recruited 278 families that were not affectedEPPK in the Chinese Han population. The mutations in the coding region of KRT9 gene were detectedusing the next-generation sequencing (NGS)-based gene panel combined with Sanger sequencing. The pathogenicity analysis of variants was performedusing SIFT and Polyphen-2 prediction software. Results · A total of twelve KRT9 gene mutations were detected in the Chinese Han population based on 834 individuals 278 families. Among the twelve different mutations, six synonymous mutations and six missense mutations were identified, respectively. The assessment of pathogenicity of KRT9 gene variants was analyzedbioinformatics tools, such as SIFT and Polyphen-2 prediction, conservative analysis, and database query. Furthermore, these missense mutations were classified as benign or possibly benign variants. Conclusion · In this study, six missense mutations in the coding region of KRT9 gene exon were detected in the Chinese Han population. According to the American Society of Medical Genetics and Genomics (ACMG) variant classification guide, all the six variants were benign or possibly benign. However, previous reports have found that a KRT9 c.1216T>C (p.C406R) mutation was pathogenic in a pedigree with EPPK, which were inconsistent with our findings, and the pathogenicity of this mutation still has to be verifiedfurther functional experiments.

Key words: KRT9 gene, epidermolytic palmoplantar keratoderma (EPPK), gene mutation, variant classification