Mitochondrial Physiology Network 10.9: 107 (2005) - download pdf

Mitochondrial biogenesis in rat embryo during placentation process.

Maria P Alcolea, B Colom, I Lladó, M Gianotti, FJ García Palmer

Grup de Metabolisme Energètic i Nutrició, Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Dept. Biologia Fonamental i Ciències de la Salut, Universitat de les Illes Balears (UIB), Palma de Mallorca (07122), Spain. - vdbsbcp4@uib.es

    Mitochondrial biogenesis is a complex event that requires the coordinated regulation of both mitochondrial and nuclear genome by several transcriptional activators and coactivators [1]. Although important advances in this field have been achieved, the molecular pathways are not well known. In this sense, the mitochondria of rat embryo during placentation are a suitable model to further understand the mitochondrial proliferation-differentiation process, due to the important oxidative metabolism activation that takes place at this stage of development [2]. Thus, the gene expression of some proteins involved in mitochondrial replication, transcription and function, such as mitochondrial single strand DNA binding protein (mtSSB) [3], mitochondrial transcription factor A (TFAM) [4] and cytochrome c oxidase subunit I (COXI) respectively, have been investigated in rat embryo throughout gestational days 11, 12 and 13. We have shown that during the period studied there was a reduction in mtSSB mRNA levels accompanied by a great decrease in cellular mitochondrial DNA content (mtDNA). In addition to that, an important rise in the ratio between TFAM and mtDNA, and also in COXI relative gene expression was observed on gestational day 13. All these results together suggest that during the placentation period the rat embryo mitochondria reduce their proliferation and enter a differentiation stage by increasing their transcriptional activity probably through the physiological TFAM function as a mitochondrial transcription factor. To sum up, the present study supports the fact that embryo development is a physiological condition where mitochondrial biogenesis is well illustrated. Therefore, the current model could be of great interest for further understanding many unknown aspects of mitochondriogenesis, which should help understand the pathophysiology of mitochondrial diseases.

     Supported by projects BFIS2000-0988-C06-06, BFIS2000-0988-C06-05 and PI021339 of the Spanish government.

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4. Gaspari M, Falkenberg M, Larsson NG, Gustafsson CM (2004) The mitochondrial RNA polymerase contributes critically to promoter specificity in mammalian cells. Embo J. 23: 4606-4614.