Publication Date

2017-05-05

Availability

Embargoed

Embargo Period

2018-05-05

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Human Genetics and Genomics (Medicine)

Date of Defense

2017-04-17

First Committee Member

Carlos T. Moraes

Second Committee Member

Stephan Züchner

Third Committee Member

Juan Young

Fourth Committee Member

John N. Barrett

Abstract

The Mitochondrial Methionyl-tRNA Formyltransferase (Mtfmt) is a nuclear gene encoding for a protein with exclusive function in mitochondria. During initiation of mitochondrial protein synthesis, the MTFMT enzyme N-formylates the first methionine that appears to be required for the synthesis of the 13 polypeptides encoded by the mitochondrial DNA. In humans, mutations in the MTFMT gene are associated with Leigh syndrome. Studies in fibroblasts from patients sharing the most frequent disease allele (c.626 C>T in exon 4), showed mitochondrial protein synthesis. Biochemical studies into the mutation suggest that protein synthesis depend upon residual levels of the mutated MTFMT protein. My dissertation work, aims to contribute to solve a fundamental but controversial question related to the absolute requirements of N-formylation in mammals and to gain insights on the disruption mechanism of MTFMT in Leigh syndrome. I generated conditional knockout (KO) mouse models in muscle and in the Central Nervous System. Unexpectedly, a novel and unique mutation in the 3’ loxP site of the conditional Mtfmt allele prevented the deletion of the gene in vivo. Ex vivo, I was able to delete the gene in dermal fibroblasts, producing a complete MTFMT KO cell model. I demonstrated that MTFMT activity is required to transfer the N-formyl group onto the mitochondrial Met-tRNAMet; N-formylation is not an absolute requirement for mitochondrial protein synthesis in mammals but has important roles in the efficiency of synthesis of certain mitochondrial protein subunits; and absence of N-formylation affects both the assembly of individual complexes I and IV and the respirasome.

Keywords

MTFMT; N-formylation; mitochondrial protein synthesis; Leigh syndrome; respirasome; OXPHOS complexes I and IV

Available for download on Saturday, May 05, 2018

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