Assembly of cytoskeletal proteins into cleavage furrows of tissue culture cells

We review results obtained after fluorescent actin and myosin II probes wer e microinjected into interphase and prophase PtK2 and LLC-PK tissue culture cells to follow the changing distribution of these cytoskeletal proteins i n the live cells during division. The fluorescent probes first begin to ass emble into the future furrow region during mid-anaphase before any sign of initial contractions. The total concentrations of F-actin and myosin in the cleavage furrow begin to decrease a few minutes after the onset of furrow contraction. The cell's shape and the position of its mitotic spindle affec t the deposition of cytoskeletal proteins in the forming cleavage furrow. I n cells with two spindles, contractile proteins were recruited not only to the cortex bordering the former metaphase plates but also to the cortex mid way between each pair of adjacent non-daughter poles or centrosomes. The fu rrowing between adjacent poles seen in these cultured cells are similar to the furrows observed by Rappaport [(1961) J Exp Zool 148:81-89] when echino derm eggs were manipulated into a torus shape so that the poles of two mito tic spindles were adjacent to one another. These observations on injected t issue culture cells suggest that vertebrate cells share common mechanisms f or the establishment of the cleavage furrow with echinoderm cells. Microsc. Res. Tech. 49:190-201, 2000. (C) 2000 Wiley-Liss, Inc.