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Fig. 2. Expression of Xlens1 mRNA during development. (A-D) are anterior views of the head and (E-F) are lateral views. (A) Xlens1 is first detected at stage 13 in a narrow field across the anterior midline (arrow), separating the anterior neural plate (np) from ventral head epidermis (he). (B) At stage 15 Xlens1 expression has spread laterally to the anterior- lateral margins of the neural plate (np), reaching the limits of the trigeminal placode anlagen (arrow). (C) At stage 18 the midline expression of Xlens1 is depleted (arrow), and the lateral patches adjacent to the anterior neural tube (nt) are prominent. (D) At stage 22 Xlens1 expression is confined to the ectoderm overlying the optic vesicle. (E) At stage 28, Xlens1 expression is confined to the ectoderm overlying the optic cup. (F) At stage 34, only the lens vesicle expresses Xlens1. (G) Sagittal section through the midline band at stage 15. Xlens1- expressing cells are in the superficial (s) and deep (d) layers of the ectoderm, just anterior to the anterior rim (arrowhead) of the neural plate (np). Anterior, right; dorsal top. (H) Sagittal section through the midline at stage 18. Xlens1 expression is mostly depleted from the midline cells of the anterior ectodermal placode (ap), which will become the adenohypophyseal and olfactory placodes. A few Xlens1-expressing cells are still detected (white arrowhead) just anterior to the most rostral edge (black arrowhead) of the neural tube (nt). (I) Sagittal section through the lateral patch of Xlens1 expression in the same stage 18 embryo as in H. Xlens1 expression is mostly depleted from the placode (ap) anterior to the neural tube (nt), but is at high levels in both the superficial and deep (sensorial) layers of the ectoderm overlying the lateral aspects of the neural tube. Arrowhead delineates between the neural tube and the placode. (J) Transverse section through the optic vesicle (ov) at stage 22 embryo. Xlens1 expression is confined to the ectoderm overlying the vesicle. There is a sharp depletion of Xlens1 expression at dorsal and ventral points (arrowheads) where mesoderm intervenes between the optic vesicle and surface ectoderm. di, diencephalon. Dorsal, up; lateral, right. (K) Higher magnification of J, demonstrating that only the deep (d, sensorial) layer of cells in the PLE express Xlens1. Some cells (arrowheads) appear to have downregulated Xlens1 expression. s, superficial layer. (L) Transverse section of a stage 31/32 lens vesicle. Xlens1 is expressed only in the anterior epithelial cells of the lens (ae), adjacent to the surface ectoderm. The inner layer of the surface ectoderm (cornea) covering the lens vesicle also appears to express this gene (arrowhead). r, retina. (M) Transverse section of a stage 34 lens vesicle depicting both β-crystallin (blue) and Xlens1 (brown) expression. The lens fiber cells (lf) express β-crystallin, but do not express Xlens1. Magnification, 70(G-I), 75(J), 170(K), 250(L,μ). |
