Casarosa S et al. (2005), Genetic analysis of metamorphic and premetamorp...

XB-ART-34615

Dev Dyn 2005 Jun 01;2332:646-51. doi: 10.1002/dvdy.20363.

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Genetic analysis of metamorphic and premetamorphic Xenopus ciliary marginal zone.

Casarosa S , Leone P , Cannata S , Santini F , Pinchera A , Barsacchi G , Andreazzoli M .

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A major event affecting the eye during amphibian metamorphosis is an asymmetrical growth of the ventrotemporal portion of the retina compared with its dorsonasal counterpart. This event is due to an increased proliferation of the precursors of the ventral ciliary marginal zone (CMZ). Here, we analyze the expression patterns of several key homeobox genes implicated in eye development (Xrx1, Xvax2, Xsix3, Xpax6, Xchx10, Xotx2) to understand whether they are active at the time in which the metamorphic changes of the retina occur. We also analyze their expression patterns in the ventral and dorsal CMZ and compare them with bromodeoxyuridine incorporation in the CMZ. Our results suggest that the metamorphic CMZ maintains the functional subdivisions described during embryonic development. Moreover, we find that genes involved in proliferation and cell type determination of the embryonic retina are actively transcribed in the proliferating CMZ, thus indicating a potential regulatory role for these genes in the metamorphic retina.

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Species referenced: Xenopus laevis
Genes referenced: otx2 pax6 rax six3 six6 vax2 vsx2

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Figure 1. Expression patterns of homeobox genes and double staining for bromodeoxyuridine (BrdU) incorporation and gene expression in stage 63 dorsal and ventral ciliary marginal zone (CMZ). In all dorsal CMZ panels (A,A prime ,C,C prime ,E,E prime ,G,G prime ,I,I prime ,K,K prime ), central retina is to the top-left and peripheral to the right. In all ventral CMZ panels (B,B prime ,D,D prime ,F,F prime ,H,H prime ,J,J prime ,L,L prime ), central retina is to the top-right and peripheral to the bottom-left. Expression of the genes is depicted in blue and BrdU in red. Dorsal and ventral CMZ are as indicated. A,B: Xrx1. A prime ,B prime : Double-staining BrdU and Xrx1. C,D: Xsix3. C prime ,D prime : Double-staining BrdU and Xsix3. E,F: Xotx2. E prime ,F prime : Double-staining BrdU and Xotx2. G,H: Xpax6. G prime ,H prime : Double-staining BrdU and Xpax6. I,J: Xchx10. I prime ,J prime : Double-staining BrdU and Xchx10. K,L: Xvax2. K prime ,L prime : Double-staining BrdU and Xvax2. B Prime ,D Prime ,F Prime ,H Prime ,J Prime , L Prime : In situ hybridizations on the central region of the retina. Genes are as indicated. Brackets in B prime ,D prime ,F prime ,H prime ,J prime ,L prime indicate zones I, II, and III of the CMZ. ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer.

Figure 2. Double staining for bromodeoxyuridine (BrdU) incorporation and homeobox gene expression in stage 54 dorsal and ventral ciliary marginal zone (CMZ). Orientation of panels is as in Figure 1. Expression of the genes is depicted in blue and BrdU in red. A,A prime C,C prime ,E,E prime ,G,G prime ,I,I prime ,K,K prime : Dorsal CMZ. B,B prime ,D,D prime ,F,F prime ,H,H prime ,J,J prime ,L,L prime : Ventral CMZ. A,B: Xrx1. A prime ,B prime : Double-staining BrdU (red) and Xrx1. C,D: Xsix3. C prime ,D prime : Double-staining BrdU (red) and Xsix3. E,F: Xotx2. E prime ,F prime : Double-staining BrdU (red) and Xotx2. G,H: Xpax6. G prime ,H prime : Double-staining BrdU (red) and Xpax6. I,J: Xchx10. I prime ,J prime : Double-staining BrdU (red) and Xchx10. K,L: Xvax2. K prime ,L prime : Double-staining BrdU (red) and Xvax2.