Fig. 5. rnt-1 is necessary for seam cell proliferation, not fate determination. Lineage traces are shown up to mid L3. The L1 asymmetric division is omitted for simplicity. Seam cells are indicated by circles, hyp7 nuclei by squares, and glial and neuronal cells by diamonds. Broken lines indicate incomplete lineages. The data shown are lineage traces for single animals. Five animals were lineaged and found to give similar results. (A) Wild-type hermaphrodite V1-V6 and T lineages. (B) rnt-1(ok351) hermaphrodite lineage trace of V1-V6 and T divisions. V2 and V3 divisions display a similar pattern in the lineage trace shown; the anterior branch divides normally, but there is a failure of the L2 asymmetric division in the posterior branch, leading to a reduction in hypodermal nuclei. V4 and V6 display a different defect; this time the L2 proliferative division fails, causing a reduction in seam and hypodermal nuclei. V5 divisions are normal in this lineage trace, leading to the correct formation of the post-deirid neuroblast. Normal post-deirids appeared to be present in all rnt-1 animals analysed (data not shown). V1 displays a similar defect to V2 and V3 in the posterior branch, a failure of the L2 asymmetric division, but there is an additional defect in the anterior branch. Both daughter nuclei from the L2 `asymmetric' division appear to fuse with the hypodermal syncytium, rather than the posterior daughter undergoing the proliferative fate. In the T lineage, the anterior branch is normal, but there is a division failure in the posterior branch, yielding just one seam cell, rather than a seam cell plus a glial cell. (C) Wild-type male V1-V4, V5, V6 and T lineages. A description of these divisions is given in the legend to Fig. 3. (D) rnt-1(ok351); him-8(e1489) male seam cell lineage trace. In V1 the L2 proliferative division occurs normally but there are no further divisions. Both daughters resemble seam cells. In V2, the posterior daughter of the L2 proliferative division does not divide further in L2 or L3 (it remains as a seam cell), while the anterior daughter undergoes one further asymmetric division in L2 to produce a hypodermal daughter and a seam daughter that fails to divide further in L3. In V3, the L2 proliferative division occurs normally and the anterior branch undergoes the normal asymmetric divisions in L2 and L3, while the posterior branch undergoes one asymmetric division in L2, after which the posterior seam daughter fails to divide further. In V4, the L2 proliferative division occurs normally and the anterior branch displays a similar division pattern to the anterior branch of V2, while the posterior branch undergoes the normal L2 and L3 asymmetric divisions. In V5, the anterior branch is normal but the posterior branch fails after the first L3 proliferative division, with both daughters failing to divide. In V6, L2 divisions are normal but there are failures in L3 divisions. The wild-type male V6 lineage normally undergoes two rounds of division in early L3, whereas in this rnt-1 male, only one round of division occurs in each branch. In the T lineage, the anterior branch was normal but there was, unusually, an extra proliferative division in the posterior branch during L2.