Anterior specification of embryonic ectoderm: the role of the Xenopus cement gland-specific gene XAG-2.
In a search for novel developmental genes expressed in a spatially restricted pattern in dorsal ectoderm of Xenopus we have identified XAG-2, a cement gland-specific gene with a putative role in ectodermal patterning. XAG-2 encodes a secreted protein, which is expressed in the anterior region of dorsal ectoderm from late gastrula stages onwards. Activation of XAG-2 transcription is observed in response to organizer-secreted molecules including the noggin, chordin, follistatin and cerberus gene products. Overexpression of XAG-2 but not of the related cement gland marker XAG-1 induces both cement gland differentiation and expression of anterior neural marker genes in the absence of mesoderm formation. Further, we show that XAG-2 signaling depends on an intact fibroblast growth factor (FGF) signal transduction pathway and that XAG-2-induced anterior neural fate of ectodermal cells can be transformed to a more posterior character by retinoic acid. Based on these findings we propose a role for XAG-2 in the specification of dorsoanterior ectodermal fate, i.e. in the formation of cement gland and induction of forebrain fate of Xenopus.
Aberger
F
F
Institute of Genetics, University of Salzburg, Hellbrunnerstrasse 34, A-5020, Salzburg, Austria. fritz.aberger@sbg.ac.at
Weidinger
G
G
Grunz
H
H
Richter
K
K
D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning / Q000235:genetics; D046508:Culture Techniques; D004475:Ectoderm / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000502:physiology; D004627:Embryonic Induction; D005088:Exocrine Glands / Q000196:embryology*; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018021:Lithium Chloride / Q000378:metabolism; D008969:Molecular Sequence Data; D019704:Protein Disulfide-Isomerases; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D014212:Tretinoin / Q000378:metabolism; D014466:Ultraviolet Rays; D029867:Xenopus Proteins; D014982:Xenopus laevis
D011506:Proteins; C113450:XAG-1 protein, Xenopus; D029867:Xenopus Proteins; D014212:Tretinoin; D019704:Protein Disulfide-Isomerases; C113451:XAG-2 protein, Xenopus; D018021:Lithium Chloride