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Fig. 4. Transverse paraffin sections of stage 36 control
and mutant embryos following whole-mount in situ
analyses for expression of either XMLC2 or XcTnI
mRNA. Sections were stained for expression of
XcTnI, but similar results were observed in sections
stained for XMLC2. Dorsal is at the top. (A) En control
injected embryo. At this stage, the heart is
looped and has partitioned atria and ventricular
chambers (Nieuwkoop and Faber, 1956). Note the
relatively large size of myocardial tissue in
comparison to XcTnI mRNA-positive tissue in the
mutant sections shown in B and C. (B) Embryo
injected with both EnHDX2.3 and EnHDX2.5
showing the unfused phenotype. Two distinct heart
tubes can be seen forming, despite the fact that the
primordia have not contacted each other. (C) Embryo
injected with both EnHDX2.3 and EnHDX2.5.
Whole mount in situ analysis of this embryo revealed a small asymmetrically located heart on one side, with no visible staining for XcTnI on
the other. This external phenotype was confirmed by sectioning. Note that there is no morphological evidence of a heart tube on the side which
lacks expression of XcTnI. Note general lack of development on this side of the embryo. M, midgut; N, notochord; O, otic vesicle and R,
rhombencephalon. |
