SPD-3 is required for spindle alignment in C. elegans embryos and localizes to mitochondria

During the development of multicellular organisms, cellular diversity is usually achieved through asymmetric cell divisions that produce two daughter cells having different developmental potentials. Prior to an asymmetric cell division, cellular components segregate to opposite ends of the cell defining an axis of polarity. The mitotic spindle rotationally aligns along this axis of polarity, thereby ensuring that the cleavage plane is positioned such that segregated components end up in individual daughter cells. Here we report our characterization of a novel gene required for spindle alignment in C. elegans. During the first mitosis in spd-3(oj35) embryos the spindle failed to align along the anterior/posterior axis leading to abnormal cleavage configurations. spd-3(oj35) embryos had additional defects reminiscent of dynein/dynactin loss-of-function possibly caused by the mislocalization of dynactin. Surprisingly, we found that SPD-3::GFP localized to mitochondria. Consistent with this localization, spd-3(oj35) worms exhibited a slow growth phenotype, and elevated ATP levels, similar to phenotypes described in other mitochondrial mutants in C. elegans. To our knowledge, SPD-3 is the first example of a link between mitochondria and spindle alignment in C. elegans.

Key Words: mitochondria, smg-1, spd-3, spindle alignment, spindle orientation

Online ISS 1091-6490
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