Tim29 is required for stem cell activity during regeneration in the flatworm Macrostomum lignano

Abstract

Domain of Unknown Function (DUF) genes are broadly conserved in metazoa but have an unknown biological function. Previously, we established transcriptional profiles of the germline and stem cells of the flatworm Macrostomum lignano (Grudniewska et al., 2016). Here, we used this information to probe the function of DUF genes in M. lignano. Recently, Kang et al. (2016) found that DUF2366 is a mitochondrial inner membrane protein that interacts with the protein import complex TIM22. DUF2366 was renamed TIM29, and shown to stabilize the TIM22 complex, but its biological role remained largely unknown. We now demonstrate that DUF2366/TIM29 is dispensable in the homeostatic condition in M. lignano, but is essential to adapt to a highly proliferative state required for regeneration. Our results show that de-DUFing the function of DUF genes might require special biological conditions, such as regeneration, and establishes M. lignano as an informative platform to study DUF genes.