FIG.7.

Disruption of microtubule organization and distribution of β-COP-positive vesicles in Lis1- or Ndel1-null MEFs. Aberrant microtubule organization and abnormal distribution of β-COP-positive vesicles in Lis1 or Ndel1-null MEFs generated by CRE-mediated recombination. Cotransfected plasmids for rescue were shown on the top. (A and B) The loss of LIS1 causes a redistribution and an enrichment of microtubules near the nucleus (A), whereas loss of NDEL1 results in amorphous microtubules (B). Perinuclear accumulation of microtubules in Lis1-null MEFs was only rescued by GFP-LIS1 expression (see panel A). GFP-NDEL1 expression also rescued the amorphous microtubule organization in Ndel1-null MEFs, but GFP-LIS1 and GFP-NDE1 were less effective (see panel B). To address dynein regulation by LIS1 and NDEL1, we examined the distribution of β-COP-positive vesicles, which display juxtanuclear localization in a dynein-dependent fashion. (C and D) The predominant juxtanuclear staining pattern was disrupted in Lis1-null MEFs (C) and in Ndel1-null MEFs (D), resulting in a homogeneous distribution accompanied by punctuate accumulation. Loss of this Golgi pattern by Lis1 inactivation was only rescued by exogenous expression of GFP-LIS1 (see panel C). In contrast, loss of the Golgi pattern by Ndel1 inactivation was efficiently rescued by exogenous expression of GFP-LIS1, GFP-NDEL1, and GFP-NDE1 (see panel D).