Histological analyses of mutant Ikbkap and control embryos.

<p>(<b>A–F</b>) H&E-stained transverse sections through the head of E9.5 WT (<b>A</b> and <b>D</b>), E10.5 Ikbkap^3loxP/3loxP (<b>B</b> and <b>E</b>) and E10.5 WT (<b>C</b> and <b>F</b>). A, B, D and E are shown in the same magnification for comparison. Note that the telencephalic vesicle (tv) of the mutant embryo (E) is poorly developed compared to D and F. Note also that the lamina terminalis (lt) is absent in the mutant (<b>B</b>), and that there is no evidence of formation of the optic vesicle (arrowhead). In contrast, the 4^th ventricle (4v) is well formed and comparable to the control embryo in A. tg = trigeminal ganglion. (<b>G</b> and <b>H</b>) H&E-stained transverse sections at the level of the otic vesicle of E9.5 WT (<b>G</b>) and E10.5 Ikbkap^3loxP/3loxP (<b>H</b>) embryos. Note that in the E10.5 mutant the otic vesicle (ot) has separated from the overlying surface ectoderm, a landmark of normal development of E9.5 stage (G). Note that although the dorsal aorta (arrow) and cardinal vein (white arrowhead) are visible in the mutant in H they are hypoplastic compared to the embryo in G. (<b>I–N</b>) H&E-stained transverse sections through the heart (rostral to caudal) of E9.5 WT (<b>I</b>, <b>K</b> and <b>M</b>) and E10.5 Ikbkap^3loxP/3loxP embryos (<b>J</b>, <b>L</b> and <b>N</b>). Note the abnormal relative position of the outflow tract (oft) in the mutant heart (<b>L</b>) compared to a normal embryo (<b>K</b>). The myocardium and also the level of trabeculation of the ventricle in the mutant (<b>J</b> and <b>L</b>) appear comparable to an E9.5 control embryo (<b>I</b> and <b>K</b>). v = ventricle, a = atrium, Li = liver. Note that development of a WT E10.5 heart has proceeded significantly (<b>O</b>) with extensive trabeculation, separation of left and right ventricles, and formation of the endocardial cushion (ec).