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Fig. 4. Ectopic expression of ephrin-B ligands leads to
aberrant intersomitic vein projections. One blastomere of 2-
cell stage embryos was injected with either 250 pg of ephrin-
B2 (A-D) or with 500 pg of ephrin-B3 RNA (E,F). RNA
encoding nucbgal was coinjected as a lineage tracer.
Embryos were fixed at stage 36, stained for nucbgal and
hybridized with Msr. (A,B) Control (A) and injected side (B)
of an embryo expressing ephrin-B2 ectopically. The posterior
cardinal vein appears dilated and the intersomitic veins
(arrowhead) have failed to grow dorsally. (C,D) Close-up
view of control (C) and ephrin-B2 injected (D) trunk regions.
Frequently, intersomitic veins are found projecting either
abnormally into adjacent somites (arrow) or displaying
reduced growth (arrowhead). (E,F) Trunk region of control
(E) and injected (F) side of an embryo expressing ephrin-B3
ectopically. Intersomitic veins are disorganized, penetrate
aberrantly into the neighboring somites (arrow), and
occasionally form loop-like structures (arrowhead). Scale
bars: 400 mm (A,B); 200 mm (C-F). |
