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.
Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA.
Hongbin
H
Li
Fengli
F
Guo
Boris
B
Rubinstein
Rong
R
Li
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