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Fig. 2. Rx expression, phenotypes and regulation.
(A-C) Expression pattern of Xrx1 in
Xenopus embryos. (A) Anterior view of an
early neurula stage embryo showing expression
of Xrx1 in a single field. (B) Anterior view
of a tadpole showing Xrx1 expression in the
pineal gland (PG), ventral hypothalamus (VH),
and two developing retinas (R). The cement
gland (CG) does not express Xrx1. (C) A lateral
view of a tadpole showing Xrx1 expression in
the retina (R) and pineal gland (PG). Notice the
lack of expression in the lens. (D) Effects of
elimination of Rx function in mouse embryos.
Comparison of the Rx-/- mouse embryo (right)
with Rx+/- sibling demonstrates that Rx function
is required for eye formation. (E,F) Elimination
of Xrx1 function by Rx specific morpholino
(RxMO) in Xenopus embryos results in the
absence of eye formation. (E) Uninjected side
of embryo showing normal eye development,
while the eye is completely missing on the
opposite, RxMO injected side (F). (G,H) Mutations
in the human RX (RAX) gene cause anophthalmia.
(G) Absence of ocular tissue in a
patient with a mutation in RX gene. (H) CT scan
of the same patient showing anophthalmic
orbit (red arrow) and other orbit (red arrowhead).
(I,J) Overexpression of Xrx1 RNA in
Xenopus embryos results in overproliferation
of the cells of the retina and anterior neural
tube. (I) A cross section through a Xenopus
embryo injected on the right side with Xrx1
RNA showing a duplication of the anterior
neural tube and overproliferation of retinal cells.
(J) Both the retinal pigment epithelium (RPE)
and the neuroretina (NR) show overproliferation
in this eye from an embryo injected with Xrx1
RNA. As a result, the RPE and the neuroretina
show additional folding of the cell layers. (K,L).
Regulatory elements of the Xrx1 direct GFP
expression into the developing retina of Xenopus
embryos. (K) Lateral view of a Xenopus
embryo under transmitted light. (L) The same embryo viewed under fluorescence optics shows GFP expression in the developing retina. Images (A-C)
and (I,J) are modified from Mathers et al., (1997), and images (K,L) are from Zhang et al., (2003). (D-H) are our unpublished data. CG, cement gland; NR,
neuroretina; NT, neural tube; PG, pineal gland; R, retina; RPE, retinal pigment epithelium; SNT, secondary neural tube; VH, ventral hypothalamus. |
