Xotx genes in the developing brain of Xenopus laevis

Abstract

The vertebrate Otx gene family is related to otd, a gene contributing to head development in Drosophila. We previously reported on the expression of Xotx2 gene, homologous to the murine Otx2 gene, during early Xenopus development. In the present paper we report an extensive analysis of the expression pattern of Xotx2 during later stages of development and also the cloning and developmental expression of two additional Otx Xenopus genes, Xotx1 and Xotx4. These latter two genes bear a good degree of homology to murine Otx1, higher for Xotx1 than for Xotx4. Both these genes are expressed in the forebrain and midbrain regions and their developmental patterns of expression are very similar, although not perfectly superimposable. Spatial and temporal expression patterns of the three Xotx genes suggest that they may be involved in the early subdivision of the rostral brain, providing antero-posterior positional information within the most anterior districts of the neuraxis. The three Xotx genes are expressed in all the developing sense organs of the head, eyes, olfactory system and otic vesicles. By in situ hybridization the earliest detectable expression is found in anterior mesendoderm for Xotx2, and in presumptive anterior neuroectoderm for Xotx1 and Xotx4. In addition, we examined whether Xotx1 is expressed in exogastrulae, finding that Xotx1 expression can be activated in the apparent absence of vertical signals of neural induction.

Characterizing gene expression during lens formation in Xenopus laevis: Evaluating the model for embryonic lens induction

“…CAK has been shown to play a role in the activation of cdks as well as in the function of TFIIH and RNA polymerase II. Retroviral transduction of antisense Mat1 constructs into fetal human lens (Pannese et al, 1995;Kablar et al, 1996;Hirsch and Harris, 1997;Penzel et al, 1997;Zygar et al, 1998;Schaefer et al, 1999;Kenyon et al, 1999;Hollemann and Pieler, 1999;Zhou et al, 2000;Ishibashi and Yasuda, 2001;Pommereit et al, 2001).…”

“…The two genes known to have the earliest zygotic expression in the presumptive lens ectoderm are Xotx2 and Xlens1, which are first expressed around stage 13 ( Fig. 4; Kablar et al, 1996;Penzel et al, 1997;Kenyon et al, 1999; note that maternal Xotx2 mRNA is also present in the ectoderm at much earlier stages; Pannese et al, 1995, Zygar et al, 1998. Their expression could be triggered by the early phase of induction; however, both competence and the early phase of induction are initiated before this time at approximately stage 11 (i.e., there are no genes like examples II or III shown in Fig.…”

Tbx3 represses bmp4 expression and, with Pax6, is required and sufficient for retina formation

“…Otx2 blocks the repression of tbx3 by Noggin in ectodermal explants, and is coexpressed with Noggin and Tbx3 in the dorsal blastopore lip and early anterior neural plate suggesting that tbx3 might be regulated by Otx2 in these regions ( Fig. S1; Pannese et al, 1995;Kablar et al, 1996;Zuber et al, 2003). However, otx2 expression does not overlap that of tbx3 during eye field specification or determination .…”

Isolation and characterization of a novel gene, xMADML, involved in Xenopus laevis eye development

“…The expression patterns of six different transcription factors Xotx2, xSix3, Sox2, Sox3, Pax6, XLmaf, and lens ␥6-crystallin in xMADML-MO containing eyes were compared with the expression patterns in the contralateral, uninjected eyes, to control, uninjected embryos, and to published expression patterns ( Fig. 8; Pannese et al, 1995;Kablar et al, 1996;Penzel et al, 1997;Mizuseki et al, 1998;Zygar et al, 1998;Schaefer et al, 1999;Zhou et al, 2000;Ishibashi and Yasuda, 2001;Carl et al, 2002). The expression patterns of Xotx2, XL-maf, and ␥6-crystallin were all maintained in the morpholino-injected eyes, although the expression levels were lower compared with the uninjected side (Fig.…”

“…Among several transcription factors shown to participate in vertebrate eye development are the following: Pax-6, a transcription factor sufficient to cause ectopic eye formation in Drosophila and Xenopus (Halder et al, 1995;Altmann et al, 1997;Chow et al, 1999;Ashery-Padan et al, 2000;Zuber et al, 2003); XL-maf and XMafB, transcription factors able to activate the expression of lens crystallins in Xenopus (Ishibashi and Yasuda, 2001); Prox1 and xSix3, homeodomain transcription factors necessary for proper lens cell development in Xenopus, Drosophila, fish, and mouse (Oliver et al, 1993(Oliver et al, , 1996Tomarev et al, 1996Tomarev et al, , 1998Schaefer et al, 1999;Zhou et al, 2000;Carl et al, 2002;Zuber et al, 2003); Sox2 and Sox3, transcription factors containing an HMG domain, which are important in the regulation of crystallin expression and fiber cell differentiation in Xenopus, mouse, and chick (Kamachi et al, 1995(Kamachi et al, , 1998Uwanogho et al, 1995;Penzel et al, 1997;Schaefer et al, 1999;Kondoh et al, 2004); and Xotx2, a homeobox gene important in patterning the anterior central nervous system (CNS) and placodal structures in Xenopus (Pannese et al, 1995;Kablar et al, 1996;Schaefer et al, 1999). Many of these transcription factors have been shown to interact in a complex network of genes; however, the full complement of genes necessary for embryonic eye development, including hundreds of potential downstream targets, has not been identified.…”