Figure 1.

lin-5 mutants are defective in mitosis, but continue DNA replication. A and B, Early L2 stage wild-type animal (A) and lin-5(e1348) mutant (B) fixed and stained with the DNA dye PI. Anterior is to the left, ventral is down. In the lin-5 mutant, the ventral cord P cells are undivided and polyploid, whereas in the wild-type animal, the corresponding cells have divided multiple times. The P cells and daughter cells are indicated for P₂–P₁₀. Between the P cells are neuronal nuclei that do not divide postembryonically and have 2n DNA contents. C and D, Wild-type animal (C) and lin-5(e1348) mutant (D) stained after labeling with BrdU from 6–14 h of development. DNA synthesis appeared normal in lin-5 mutants, but was not followed by cell division. Incorporation of BrdU can be detected in all P cells and several other postembryonic blast cells. E–G, Single embryos: wild-type embryo (E), lin-5(ev571ts) embryo developed at the nonpermissive temperature (F), and lin-5(RNAi) embryo (G) stained with PI to illustrate the early embryonic arrest with polyploid nuclei in the absence of maternal lin-5 function. Bars, 10 μm.