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Fig. 7. BRO-1- and RNT-1-induced seam cell hyperplasia. (A) Bar chart
showing seam cell number in him-5(e1490) SCM::GFP L4 hermaphrodites
(strain AW60; n=24) (effectively WT), and animals with the same
reporter carrying an integrated rnt-1::GFP transgene
(msIs114, labelled as Is[RNT-1], strain AW189;
n=55), an integrated rnt-1::GFP transgene in a
bro-1(tm1183) mutant background (strain AW191; n=23), and
those with a bro-1(tm1183) mutation alone (strain AW186;
n=37). The dotted line represents WT seam cell number (16 per side).
As strains containing the integrated rnt-1::GFP transgene in a
bro-1 mutant background tend to die around the L4-adult transition it
was necessary to keep strain AW191 viable using an extrachromosomal rescuing
bro-1::RFP array. Seam cell number was then counted in animals that
had lost the array. (B) Bar chart showing seam cell number in
SCM::GFP him-5(e1490) L4 hermaphrodites (n=24; effectively
WT), and animals with the same reporter carrying an integrated
bro-1::GFP transgene, msIs344 (labelled as
Is[BRO-1], strain AW188; n=57), an integrated
bro-1::GFP transgene in a rnt-1(tm388) mutant background
(strain AW185; n=41), and those with a rnt-1 (tm388)
mutation alone (strain AW187; n=53). (C) Expression level of
bro-1 mRNA in WT and msIs344[bro-1::GFP] strains, measured
using semi-quantitative RT-PCR. The doublet seen for bro-1
corresponds to the full length bro-1 transcript and a shorter
alternatively spliced form. (D,E) Lineage analysis of
BRO-1-induced seam cell hyperplasia. V lineage traces are shown up to mid L3,
omitting the L1 asymmetric division. (D) WT hermaphrodite. (E) Hermaphrodite
overexpressing bro-1 (by carrying an integrated bro-1::GFP
array, msIs344, strain YK149). Extra divisions were observed in V1.p
and V2.p. In V1.p, the division of the anterior seam daughter of the
symmetrical division at the beginning of L2 is itself symmetrical, giving rise
to an anterior daughter that retains seam (stem-cell) characteristics rather
than adopting the hypodermal fate. This extra seam cell then divides
asymmetrically along with the other seam cells in L3 (circled with a dashed
line). In the posterior branch there is an extra proliferative (symmetrical)
division at the beginning of L3, giving rise to two seam daughters capable of
further (asymmetric) division (circled with a dashed line). In V2.p, the
division of the anterior V2-derived seam cell is transformed into a
symmetrical division, giving rise to an anterior daughter that retains seam
(stem-cell) characteristics (circled with a dashed line), and quickly divides
further. Overall, three extra seam cells have been produced by these lineage
alterations during L2 and early L3.
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helix; black box, ß sheet) are shown on the top of the
alignment (Tahirov et al.,
2001
