The epsilon subunit of mitochondrial ATP synthase is required for normal spindle orientation during the Drosophila embryonic divisions

We describe the maternal effect and zygotic phenotypes of null mutations in the Drosophila gene for the epsilon subunit of mitochondrial ATP synthase, stunted (sun). Loss of zygotic sun expression leads to a dramatic delay in the growth rate of first instar larvae, and ultimately death. Embryos lacking maternally supplied sun (sun embryos) have a six-fold reduction in ATP synthase activity. Cellular analysis of sun embryos shows defects only after the nuclei have migrated to the cortex. During the cortical divisions the actin-based metaphase and cellularization furrows do not form properly, and the nuclei show abnormal spacing and division failures. The most striking abnormality is that nuclei and spindles form lines and clusters, instead of adopting a regular spacing. This is reflected in a failure to properly position neighboring non-sister centrosomes during the telophase to interphase transition of the cortical divisions. Our study is consistent with a role for Sun in mitochondrial ATP synthesis, and suggests that reduced ATP levels selectively affects molecular motors. As Sun has been identified as the ligand for the Methuselah receptor that regulates aging, Sun may function both within and outside mitochondria.

Key Words: ATP synthesis, Drosophila, Embryogenesis, epsilon subunit, spindle orientation

This article has been cited by other articles:

				M. V. Dinkelmann, H. Zhang, A. R. Skop, and J. G. White SPD-3 Is Required for Spindle Alignment in Caenorhabditis elegans Embryos and Localizes to Mitochondria Genetics, November 1, 2007; 177(3): 1609 - 1620. [Abstract] [Full Text] [PDF]

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