title: Early stages of induction of anterior head ectodermal properties in Xenopus embryos are mediated by transcriptional cofactor ldb1.
abstract: BACKGROUND
  Specific molecules involved in early inductive signaling from anterior neural tissue to the placodal ectoderm to establish a lens-forming bias, as well as their regulatory factors, remain largely unknown. In this study, we sought to identify and characterize these molecules.
  
  
  RESULTS
  Using an expression cloning strategy to isolate genes with lens-inducing activity, we identified the transcriptional cofactor ldb1. This, together with evidence for its nuclear dependence, suggests its role as a regulatory factor, not a direct signaling molecule. We propose that ldb1 mediates induction of early lens genes in our functional assay by transcriptional activation of lens-inducing signals. Gain-of-function assays demonstrate that the inductive activity of the anterior neural plate on head ectodermal structures can be augmented by ldb1. Loss-of-function assays show that knockdown of ldb1 leads to decreased expression of early lens and retinal markers and subsequently to defects in eye development.
  
  
  CONCLUSIONS
  The functional cloning, expression pattern, overexpression, and knockdown data show that an ldb1-regulated mechanism acts as an early signal for Xenopus lens induction.
authors.affiliation: Shepherd University, Department of Biology, Shepherdstown, West Virginia.
authors.forename: Carol Zygar
authors.initials: CZ
authors.lastname: Plautz
authors.forename: Brett E
authors.initials: BE
authors.lastname: Zirkle
authors.forename: Malia J
authors.initials: MJ
authors.lastname: Deshotel
authors.forename: Robert M
authors.initials: RM
authors.lastname: Grainger
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D004475:Ectoderm / Q000166:cytology / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007903:Lens Capsule, Crystalline / Q000166:cytology / Q000196:embryology*; D009432:Neural Crest / Q000166:cytology / Q000196:embryology; D038081:Organogenesis / Q000502:physiology*; D012160:Retina / Q000166:cytology / Q000196:embryology; D029867:Xenopus Proteins / Q000096:biosynthesis* / Q000235:genetics; D014982:Xenopus laevis
chemical_list: D004268:DNA-Binding Proteins; C486314:XLdb1 protein, Xenopus; D029867:Xenopus Proteins
keywords: Induction; Xenopus; expression cloning; ldb1; lens; placodes