Figure 4.

Patterns of spindle assembly in centriole duplication mutants. Spindle assembly phenotypes caused by different types of centriole assembly defects are depicted. The cellular composition of sperm (blue) and eggs (pink) that give rise to a particular spindle assembly pattern are shown at the top. Sperm centrioles are shown in green while centrioles generated in the embryo are shown in orange. Gametes drawn in lighter colors indicate the absence of a centriole assembly factor in either the maternal or paternal germ line. Brackets indicate sister cells in four-cell embryos. Wild-type embryos inherit a centriole pair from sperm that is duplicated faithfully during each cell cycle, giving rise to only bipolar spindles with centriole pairs at the poles. In a maternal block to duplication the sperm centriole pair is not duplicated in the embryo yielding a bipolar spindle with single centriole at each pole during the first cell cycle and monopolar spindles thereafter (bi/mono/mono pattern). In a paternal block, sperm donate a single centriole that is duplicated in the embryo yielding a monopolar spindle with a centriole pair at its pole during the first cell cycle, followed by bipolar spindles during subsequent cell cycles (mono/bi/bi pattern). In embryos exhibiting a maternal block to centriole maturation, the sperm centrioles duplicate normally but the daughters are unable to produce their own offspring. This results in the appearance of monopolar spindles during the third cell cycle (bi/bi/mixed mono pattern).