Expression of Dlx5 in whole-mount mouse embryos during gastrulation and neurulation stages. In all panels except G, I, and M, anterior (rostral) faces toward the left. A, Lateral bright-field view of a late-streak stage egg cylinder (6.75 dpc), showing expression in a lateral band just below the embryonic/extraembryonic junction. The gray lines mark the boundary between the embryonic and extraembryonic halves of the egg cylinder. B, High-power view of an embryo similar to that in A, showing the rostrocaudal gradient ofDlx5 expression, with the highest level at the rostral end (arrowhead). C, Early neural plate stage embryo (7.25 dpc), with expression in a broad circumferential band that is widest rostrally and curls dorsally at the base of the emerging allantois. D, Late neural plate stage (7.5 dpc), showing more intense rostral expression, with the band of expression fainter and narrower caudally. E, Early head-fold stage (7.75 dpc), showing expression at the lateral edges of the neural plate (arrowhead). F, Lateral dark-field view at the late head-fold stage (8.0 dpc), showing expression in a thin lateral stripe rostrally that is barely detectable caudally (arrowhead). G, Frontal bright-field view of an embryo similar to that shown inF. Expression is strongest at the anterior margin of the neural plate and diminishes caudolaterally (arrowhead).H, Lateral view of a two-somite embryo (8.25 dpc), with strong expression detectable only in the ventral ectoderm beneath the head folds and with weak expression in the otic placode (arrowhead). I, Frontal view of the embryo shown in H. Note that rostral expression is weaker in the midline (arrowhead). J, Dorsal view of a four-somite embryo, showing expression at the lateral edges of the neural groove before neural tube closure (arrowheads). K, Higher-power view of the posterior neuropore of the embryo shown in J. Note that weak expression can be detected after neural tube closure (arrowhead). L, Lateral view of a six-somite embryo, showing expression in the ventral cephalic epithelium underneath the head folds and in the developing otic vesicles. M, Frontal view of an eight-somite embryo, showing bilateral expression in the ventral cephalic epithelium before anterior neuropore closure, but not at the midline (arrowhead). N, High-power lateral view of the embryo shown in M, showing staining in the ventral cephalic epithelium that continues faintly at the boundary of the anterior neuropore (arrowhead). Also shown is staining in the otic vesicle and in the newly forming mesenchyme of the first branchial arch. O, Lateral view of a 10-somite embryo (8.5 dpc), showing prominent expression in the ventral cephalic epithelium, the first branchial arch, the otic vesicles, and the tail bud. P, Higher-power view of an embryo similar in stage to that in O, showing staining in the tail bud and in the lateral edges of the posterior neuropore (arrowheads). Al, Allantois;AN, anterior neuropore; AVE, anterior visceral endoderm; BA, first branchial arch;C, caudal; HF, head folds;Ht, heart; Nd, node; NT, neural tube; OV, otic vesicle; PN, posterior neuropore; PS, primitive streak;R, rostral; RE, rostral ectoderm;Tb, tail bud; VCE, ventral cephalic epithelium; VYS, visceral yolk sac. Scale bars, 200 μm.