Patterning of the Branchial Arches in a 5-Mo-Old <i>dre</i> Mutant

<div><p>(A and B) The strict organization of the brachial arch into primary (p) and secondary (s) lamellae in a wild-type situation (100× magnification). Higher magnification shows stacks of single chondrocytes in the primary lamellae.</p><p>(C and D) Sectioning of a <i>dre</i> mutant shows disturbed patterning, resulting in the absence of secondary lamellae and the presence of foci of chondrocyte-like cells in the primary lamellae (arrowsHE, hematoxylin and eosin stain; wt, wild-type.</p><p>(E and F) Alcian Blue staining reveals the presence of differentiated chondrocytes in the wild-type (wt) primary lamellae, but not in the <i>dre</i> mutant, indicating that the differentiation of these chondrocytes is affected (200×).</p><p>(G and H) Branchial arches of <i>uki</i> and <i>lep</i> mutants appear to be wild-type (wt).</p>