Defects in blood development are coincident with the onset of circulation in IGF-2 morphant embryos. (A, B) O-dianisidine stained IGF- 2a and IGF-2b morphant embryos with reduced circulating blood at 72 hpf (heart and tail regions). Grey arrows indicate blood pooling under the heart, red arrows loss of blood circulation in the intersomitic vesicles and grey arrowheads the intermediate cell mass. (C, E) IGF-2a morphant embryos show an increase in scl and gata1 expression at the intermediate cell mass. (D, F) Knockdown of igf-2b results in an increase in the region of scl and gata1 and expression is expanded outside the intermediate cell mass. Arrowhead indicates position of intermediate cell mass and arrows indicate extent of expression along the embryo. (G, K) 22-somite stage embryos injected with control morpholino(s) showing normal scl and gata1 expression. (H-J, L-N) Expression of scl and gata1 is unaffected in IGF-2 morphant embryos before circulation commences. Frequency of embryos displaying this expression pattern: A, 20/64; B, 39/47; C, 12/43; D, 37/51; E, 19/75; F, 73/84; H, 32/32; I, 29/29; J, 35/35; L, 23/25; M, 29/31; N, 33/33. All embryos are shown in a lateral view.
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