Deafness-Dystonia-Optic Neuronopathy (DDON) syndrome is a rare X-linked inherited disease characterized by progressive deafness, dystonia, ataxia, visual problems, and memory deficit, which is caused by mutations in the gene DDP1/TIMM8A. The encoded protein, Tim8a, is a mitochondrial protein. In the present study, we found a novel mutation in the DDP1 gene (NM_004085.3, c.82C>T, p.Q28X) and generated a mouse model carrying a similar mutation of Tim 8a, p.I23fs49X. The mutant mice show less weight gain, hearing impairment, and cognitive deficit. Electron microscopic analysis indicates abnormal mitochondrial structure in several brain areas. Further study of the detailed molecular mechanism of the mitochondria dysfunction caused by mutant Tim8a is ongoing. (By Dr. Pingping Song, https://jmg.bmj.com/content/early/2020/08/19/jmedgenet-2020-106925 )