Joachim Gerhold, a postdoc in the lab of Prof. Hans Spelbrink received an EMBO-fellowship

Gerhold, Joachim

Joachim Gerhold, a postdoc in the lab of Prof. Hans Spelbrink (Dept. Paediatrics, IGMD, Mitochondrial DNA maintenance group; NCMLS, Energy & Redox Metabolism) received a 2 year long-term EMBO-fellowship to conduct his project " Protein islands in a membrane sea: do mitochondrial lipid-microdomains play a role in mtDNA maintenance, organization and dynamics?". 

The vast majority of eukaryotic cells is dependent on functional mitochondria. To ensure their function, mitochondria are dependent on their own small genome, the mtDNA, encoding essential components of the respiratory chain and ATP synthase. MtDNA has both permanently and temporary associated proteins in poorly defined structures called nucleoids, which are essential for mtDNA maintenance. Nucleoids have been implied to be membrane associated but the nature of this association is poorly understood. We have shown very recently that some mtDNA replication proteins are present in localized structures at the inner mitochondrial membrane even in the absence of mtDNA. In cells with mtDNA, only a subset of the mtDNA-nucleoids contain these proteins suggesting that mtDNA replication occurs at particular membrane domains. Recently it was also shown that mitochondrial outer membrane lipid-microdomains are crucial in organizing proteins involved in mitochondrial dynamics and apoptosis. 

Defective mtDNA maintenance has been associated directly with diseases like progressive external ophthalmoplegia, various ataxias and mitochondrial depletion syndrome, but for many patients precise molecular diagnosis is still lacking. Although being a vital cellular process, to date relatively little is known about mtDNA maintenance. Through analyses of different preparations of nucleoids, the proposed project has the potential to identify new mtDNA maintenance proteins allowing their further characterization and pinpointing potential disease genes. At a more fundamental level, very little is known to date concerning the reported association of nucleoid complexes with the inner-mitochondrial membrane. The elucidation of aspects of this association will contribute significantly to our knowledge of thein situorganization and dynamics of nucleoids and the dynamics of mtDNA replication. Finally, the proposed project aims to test whether a specific type of lipid-microdomain occurs in the inner mitochondrial membrane and is involved in organization, maintenance and dynamics of mtDNA. The project will contribute significantly to an emerging field of mitochondrial biology with important implications for many mitochondrial processes and diseases.

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