Actin-driven chromosomal motility leads to symmetry breaking in mammalian meiotic oocytes.
Movement of meiosis I (MI) chromosomes from the oocyte centre to a subcortical location is the first step in the establishment of cortical polarity. This is required for two consecutive rounds of asymmetric meiotic cell divisions, which generate a mature egg and two polar bodies. Here we use live-cell imaging and genetic and pharmacological manipulations to determine the force-generating mechanism underlying this chromosome movement. Chromosomes were observed to move toward the cortex in a pulsatile manner along a meandering path. This movement is not propelled by myosin-II-driven cortical flow but is associated with a cloud of dynamic actin filaments trailing behind the chromosomes/spindle. Formation of these filaments depends on the actin nucleation activity of Fmn2, a formin-family protein that concentrates around chromosomes through its amino-terminal region. Symmetry breaking of the actin cloud relative to chromosomes, and net chromosome translocation toward the cortex require actin turnover.
Li
Hongbin
H
Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA.
Guo
Fengli
F
Rubinstein
Boris
B
Li
Rong
R
D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D016764:Cell Polarity; D002478:Cells, Cultured; D033481:Chromosomes, Mammalian / Q000378:metabolism*; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D007700:Kinetics; D008540:Meiosis; D051379:Mice; D008815:Mice, Inbred Strains; D018715:Microscopy, Video; D009865:Oocytes / Q000378:metabolism* / Q000648:ultrastructure
D000199:Actins; D005456:Fluorescent Dyes; D007211:Indoles; C007293:DAPI