McNally Lab Movies

Movies 1-14 show female meiosis occurring in utero in living, anesthetized C. elegans. These movies were published in Yang, McNally and McNally. 2003. MEI-1/katanin is required for translocation of the meiosis I spindle to the oocyte cortex in

C. elegans. Developmental Biology.

As shown in the diagram above, meiotic maturation initiates with germinal vesicle breakdown in the most proximal oocyte in the gonad. The oocyte is then squeezed into the spermatheca (where fertilization occurs) then out of the spermatheca into the uterus. Most of meiosis I and meiosis II occur after exit from the spermatheca.

movie1.mov Movie 1: GFP-tubulin in wild-type C. elegans. Before germinal vesicle breakdown (GVBD), GFP-tubulin is excluded from the germinal vesicle. During GVBD, GFP-tubulin invades the nucleus. The meiosis I spindle forms as the oocyte is squeezed into the spermatheca. Translocation of the spindle to the cortex occurs while the oocyte is in the spermatheca. Shortening and rotation of both meiosis I and meiosis II spindles are shown after exit from the spermatheca.

movie2.mov Movie 2: GFP-tubulin in wild-type C. elegans. The meiosis I spindle translocates to the cortex after exit of the oocyte/embryo from the spermatheca. The site of cortical translocation is indicated by the yellow arrow. The cortex of the oocyte/embryo has been highlighted for clarity. This sequence stops before shortening and rotation of the meiosis I spindle.

movie3.mov Movie 3: GFP-tubulin in wild-type C. elegans. Translocation of the meiosis I spindle to the cortex is followed by sequential shortening and rotation of first the meiosis I spindle, then the meiosis II spindle. Sliding of the meiosis I spindle along the cortex before shortening and rotation is clearly shown.

movie4.mov Movie 4: GFP-histone in wild-type C. elegans. Before germinal vesicle breakdown (GVBD), bivalent chromosomes are scattered and motile within the nucleus. After GVBD, chromosomes move closer together and become less motile, presumably due to capture by microtubules. Rotation and anaphase chromosome segregation are clearly visible for the meiosis I spindle. Rotation of the meiosis II spindle is obscured by the angle of the spindle but anaphase II is clearly visible. At the end of this sequence, the female pronucleus forms. The male pronucleus which forms next to the female pronucleus in this sequence, more typically forms at the opposite end of the embryo.

movie5.mov Movie 5: GFP-histone in tubulin (RNAi) C. elegans. In the oocyte indicated by the arrow, meiotic chromosomes never translocate to the cortex. This oocyte was depleted of microtubules by tubulin RNAi. Note that the number of chromosomes increases during the sequence indicating that the spindle checkpoint has not been activated.

movie6.mov Movie 6: GFP-histone in latrunculin A-treated C. elegans. Cytokinesis fails in oocyte/embryos depleted of F-actin by latrunculin A treatment as indicated by the collapse of chromosomes after anaphase I and assembly of a meiosis II spindle with 12 rather than 6 sister chromatid pairs. Two female pronclei (one small and one large) form at the end of this sequence. Spindle translocation, rotation and anaphase are normal in latrunculin-treated worms. In this sequence, both MI and MII spindles rotate from an orientation perpendicular to the plane of focus.

movie7.mov Movie 7: GFP-tubulin in latrunculin A-treated C. elegans. Spindle assembly, translocation and rotation occur normally after depletion of F actin with latrunculin A. In this sequence, rotation of the meiosis I spindle is clearly evident. The meiosis II spindle (which has 12 rather than 6 sister chromatid pairs, evident as dark holes) rotates from an orientation perpendicular to the plane of focus.

movie8.mov Movie 8: DIC imaging of meiotic cytoplasmic streaming in wild-type C. elegans. In the oocyte/embryo which enters and exits the spermatheca at the beginning of this sequence, circular cytoplasmic streaming initiates after exit from the spermatheca. Reversals in direction of streaming are clearly visible. Streaming stops shortly before pronuclei form at the end of this sequence.

movie9.mov Movie 9: Cytoplasmic streaming drives meiotic chromosomes into the cortex in MEI-1 depleted embryos. GFP-histone images were overlaid on DIC time-lapse images of a mei-1 mutant embryo in utero. Chromosomes remain associated with the cortex while streaming is directed toward that position on the cortex. Chromosomes move away from the cortex when cytoplasmic streaming changes direction. Note the multiple pronuclei formed at the end of the sequence due to the absence of MEI-1.

movie10.mov Movie 10: GFP-tubulin in a mei-1(RNAi) embryo filmed in utero. A disorganized mass of microtubules forms and wanders around the embryo. An organized spindle never forms, movement to the cortex is delayed and unstable and the diameter and intensity of the microtubule mass does not change over time.

movie11.mov Movie 11: GFP-histone in a mei-1 mutant embryo depleted of FZY-1/CDC20 by RNAi. In the absence of cytoplasmic streaming [due to fzy-1(RNAi)], MEI-1 depleted spindles do not translocate to the cortex and instead drift slowly in the cytoplasm.

movie12.mov Movie 12: GFP-tubulin in a fzy-1(RNAi) embryo filmed in utero. This meiotic spindle is arrested at metaphase I due to depletion of the CDC20 ortholog FZY-1. The spindle translocates to the cortex but does not shorten and does not rotate. Exit of the oocyte/embryo from the spermatheca occurs at the beginning of this sequence.

movie13.mov Movie 13: Spinning disk confocal microscopy of GFP-tubulin in a mei-1(RNAi) worm. Neither parallel nor anti-parallel bundles of microtubules ever form during meiotic spindle assembly in an oocyte/embryo depleted of MEI-1. Only the early stages of meiosis are shown in this sequence.

movie14.mov Movie 14: GFP-histone in a mei-1(RNAi) worm. Anaphase chromosome segregation never occurs in MEI-1 depleted meiotic spindles. Note the wandering movements of the chromosomes toward and away from the cortex and the formation of multiple pronuclei at the end of the sequence. This sequence begins just after germinal vesicle breakdown and follows the oocyte/embryo into and out of the spermatheca.