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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.
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