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A
B
Wt
Tg
*
58
Wt
*
Stage 60
57
*
*
56
Tg
T 3 (days)
- 3
0369 2
Heat shock
Stage 61
T 3 addition
Figure 10.4 Transgenic expression of PRMT1 accelerates metamorphosis. (A) Over-
expression of PRMT1 accelerates natural metamorphosis. A wild type (Wt) and trans-
genic (Tg) tadpole overexpression PRMT1 under a heat shock-inducible promoter
control developed to stages 60 and 61 (note the pointier head of the transgenic animal,
arrow), respectively, after 6 days of heat shock treatment starting at stage 58, the onset
of metamorphic climax. (B) PRMT1 overexpression also leads to faster development dur-
ing T3-induced metamorphosis. Wt and Tg animals were heat-shocked daily starting at
stage 56. Three days after the first heat-shock treatment, all the animals were treated
with T3 and continued to be subjected to heat shock treatment daily. The average
developmental stages for the Wt and Tg animals at indicated time points were plotted.
* p
values
0.05 when compared to the Wt animals. See Matsuda et al. (2009) for more
<
details.
their unique metamorphic changes at specific developmental stages. For
example, in Xenopus , the hindlimb bud begins to grow around stage 48 and
the most dramatic morphological differentiation takes place around stages
53-58 ( Fig. 10.5 ). Subsequently, the hindlimb undergoes mostly growth
with little morphological changes ( Fig. 10.5 )( Nieuwkoop & Faber, 1956 ).
On the other hand, tail metamorphosis, that is, total resorption, is one of
the last changes to occur. Although some changes in the tail, such as fin resorp-
tion, take place earlier, the reduction in tail length does not occur until around
stage 62 and its completion marks the end of metamorphosis ( Fig. 10.5 )
( Dodd & Dodd, 1976 ). Finally, the intestine begins its remodeling around
stage 58 when its connective tissue and muscle layers increase in thickness
( Ishizuya-Oka & Shimozawa, 1987; McAvoy & Dixon, 1977; Shi &
Ishizuya-Oka, 1996 ). This is followed by the degeneration of the larval epi-
thelium through programmed cell death (apoptosis) around stages 60-62 and
the formation of the adult epithelium toward the end of metamorphosis
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