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Figure 2. Expression of XlHbox 1 in Xenopus Hindlimb Buds
Transverse section through the hindlimb buds of a stage 50 (2 week)
Xenopus tadpole immunostained with antibody B. Note that the mesoderm is not stained above background, while the posterior (medial) region of the ectoderm (EC) shows strong expression. Arrow indicates
ectodermal staining. Abbreviations: HL, hindlrmb; Re, rectum; D, dorsal;
V, ventral; En, endoderm. |
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Figure 1. A gradient of XlHbox 1 protein in X. laevis Forelimb Buds
(a-f) Serial transverse sections through a stage 51 tadpole (3 week; all stages according to Nieuwkoop and Faber, 1987). Section (a) is the most
anterior and section(f) the most posterior. Note the anteroposterior gradient of stained nuclei in the mesoderm. XlHbox 1 protein was immunolocalized
with antibody B (Oliver et al., 1988) which is directed against amino acids 2-148 of the long XlHbox 1 protein and therefore detects both the long
and the short versions of this protein that have been described by Cho et al. (1988). (g-k) Serial parasagittal sections through a stage 52 (4 week)
tadpole. (g) is the most distal and (k) the most proximal. Note the mesodermal gradient of expression (best seen in panel [i]) and the stronger staining
over the posterior ectoderm. lmmunolocalizations were with antibody C (Oliver et al., 1988) which is specific for amino acids 2-73 of the long protein
and therefore does not react with the short XlHbox 1 protein (Cho et al., 1988; Oliver et al., 1988). Transcription of XlHbox 1 in embryos is driven
by two prdmoters, resulting in the production of either a short or a long protein, which differ by 82 amino acids at the amino terminus (Cho et al.,
1988). All the results reported here for limb bud mesoderm and ectoderm, both in frogs and mice, can be explained by expression of the long XlHbox
1 protein exclusively. This is because the immunostaining with antiserum C (Oliver et al., 1988) which is specific for the first 73 amino acids of the
long protein’([g-k]) is the same as that obtained with antibody B ([a-f]), which does not distinguish between the two types of protein. Similar results
were obtained by using the “nonoverlapping” antibody A (see Experimental Procedures). (I) Schematic representation of the plane and direction
of sectioning in the preceding panels in stylized limb buds. Note that at these stages Xenopus forelimb buds are contained inside a cavity called
the atrium (Nieuwkoop and Faber, 1987). Abbreviations: A, anterior; P posterior; D, dorsal; V, ventral; Di, distal; Pr, proximal. |
