Figure 4 .

Effect of lin-3 overexpression on VPC induction in class 3 mutants. The bhEx31 transgenic strain carries a hs::lin-3 plasmid from C. elegans (see Materials and Methods for details). (A) The graph shows the proportion of Pn.p (1-cell stage), Pn.px (2-cell stage), and Pn.pxx (4-cell stage) bhEx31 animals at different time points of development (green and pink lines). The heat shock-induced Muv phenotype of bhEx31 is also plotted (blue line). Almost 60% of animals, when subjected to heat shock at 24 hr after L1, develop a Muv phenotype. The Muv penetrance decreases rapidly after the VPCs start to divide such that by 30 hr, when all VPCs have divided, heat shock has no effect on VPC induction (no Muv phenotype develops). Pn.p and progeny stages were determined from a total of 16 to 20 animals for each time point. For Muv penetrance analysis, each time point contained (starting from the L1+18 hr stage) 25, 63, 328, 118, 300, 214, 86, 25, and 81 animals, respectively. (B) The graph shows the Muv phenotype in mutants after the heat shock at 24 hr. The Muv frequency in bh7 animals is similar to the control (bhEx31), slightly reduced in bh14, and not present in bh20 animals. The number of animals examined in each case was 154 (control), 50 (bh7), 159 (bh14), and 112 (bh20). (C) The pattern of VPC induction in animals plotted in graph B. Although all VPCs can be induced in the control and bh7 to varying extents, only the central 3, P(5-7).p, do so in bh14, and only one (P6.p) is induced in bh20 animals. For each genotype, we examined 32 (control), 70 (bh7), 37 (bh14), and 95 (bh20) animals.