Golgi clusters and vesicles mediate mitotic inheritance independently of the endoplasmic reticulum

We have examined the fate of Golgi membranes during mitotic inheritance in animal cells using four-dimensional fluorescence microscopy, serial section reconstruction of electron micrographs, and peroxidase cytochemistry to tr ack the fate of a Golgi enzyme fused to horseradish peroxidase. All three a pproaches show that partitioning of Golgi membranes is mediated by Golgi cl usters that persist throughout mitosis, together with shed vesicles that ar e often found associated with spindle microtubules. We have been unable to find evidence that Golgi membranes fuse during the later phases of mitosis with the endoplasmic reticulum (ER) as a strategy for Golgi partitioning I, Zaal, K.J., C.L. Smith, R.S. Polishchuk, N. Allan, N.B. Cole, J. Ellenberg, K. Hirschberg, J.F. Presley, T.H. Roberts, E. Siggia, et al. 1999. Cell. 9 9:589-601) and suggest that these results, in part, are the consequence of slow or abortive folding of GFP-Golgi chimeras in the ER. Furthermore, we s how that accurate partitioning is accomplished early in mitosis, by a proce ss of cytoplasmic redistribution of Golgi fragments and vesicles yielding a balance of Golgi membranes on either side of the metaphase plate before ce ll division.