Mitochondrial Methionyl-tRNA Formyltransferase (MTFMT) Mouse Model to elucidate Mitochondrial Translation initiation Defect and Disease Mechanisms in Leigh Syndrome

Project Summary Mutations in genes that constitute the mitochondrial translational machinery cause various mitochondrial disorders. These disorders lead to a wide range of clinical manifestations, including but not limited to Leigh syndrome, (LS) mitochondrial encephalopathy, and myopathy. LS is a severe mitochondrial disorder caused by mitochondrial and nuclear DNA mutations. Biallelic mutations in MTFMT (OMIM 611766), a nuclear gene that encodes mitochondrial methionyl-tRNA formyltransferase, lead to combined oxidative phosphorylation (OXPHOS) deficiency and LS. MTFMT catalyzes the synthesis of N-formylmethionine-tRNAMet (fMet- tRNAMet or tRNAfMet), a crucial step in mitochondrial translation initiation and protein synthesis. Despite the established role of MTFMT mutations in LS, the precise mechanisms by which these mutations disrupt mitochondrial translation and cause LS remain unclear. The most common MTFMT mutation is c.626C>T, which generates a splicing suppressor resulting in exon 4 skipping and protein truncation (p. R181SfsX5). The lack of appropriate animal models has been a significant barrier in understanding the disease's pathogenesis. To bridge this knowledge gap, we have developed a novel transgenic mouse model, replacing murine exon 4 with either wild-type (WT) or mutant human exon 4 harboring the c.626C>T mutation. Preliminary data show that this model mimics exon 4 skipping, Mtfmt protein reduction, and decreased OXPHOS subunit levels, closely replicating the human molecular phenotype. This proposal seeks to utilize this innovative model to investigate the molecular and biochemical pathways disrupted by the MTFMT mutation. We aim to achieve the following: (1) Characterize the neurological and behavioral phenotypes of the Mtfmt murine model, focusing on motor function, anxiety-like behaviors, and disease progression, and (2) Define the molecular and biochemical mechanisms underlying mitochondrial dysfunction, with emphasis on mitochondrial translation fidelity, neuronal dysfunction, and gene expression. Our study will provide a novel platform for understanding LS pathogenesis and for developing potential therapies.