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FIG. 2. Temporal and spatial expression of Xstbm. (A) Quantitative
RT-PCR was performed by using 1 g of total RNA extracted
from Xenopus embryos at different stages. “U” indicates the
unfertilized eggs, and numbers indicate the developmental stages
according to Nieuwkoop and Faber (1967). Maternal transcripts
decreased gradually until the gastrula stage (stage 10), and zygotic
expression increased thereafter in the gastrula (stage 12) and
neurula (stage 15–20). (B–O) Localization of Xstbm transcripts by
whole-mount in situ hybridization. At the gastrula stage, Xstbm is
expressed in the dorsal region (B, dorsal view, stage 10; C, lateral
view, stage 12). Xstbm is expressed in the neural plate of the early neurula (D, stage 14) and late neurula (E, stage 17), and in the neural
tube thereafter in the tailbud stages (F, stage 20; G, stage 25, dorsal
view; H, stage 25, lateral view; I, stage 30, lateral view). At tailbud
stage, Xstbm is also expressed in prenephritic region (I, yellow
pointer). Sections of the gastrula (B, C) show low expression at the
dorsal lip (red pointer) and higher expression in the posterior
mesodermal–neural region (yellow pointer) above the blastoporal
lip (J, stage 10). The late gastrula shows high expression in the
prospective forebrain (K, stage 12, yellow pointer) and low expression
in the anterior mesodermal region (K, red pointer). The
superficial epithelial layer of the involuting mesodermal region
showed little or no expression at stage 10 (J, white pointer) and
stage 12 (K, white pointer). The posterior mesodermal regions of a
dorsal sandwich explant showed expression at the late neurula
stage (L, yellow pointer), but expression declined anteriorly (L, red
pointer). Transverse sections of a tailbud stage embryo in (I) showed
the expression of Xstbm increased progressively from the anterior
(M, yellow pointer) to the middle (N, yellow pointer) and posterior
notochord (O, yellow pointer). |
