Ectopic expression and knockdown of a zebrafish sox21 reveal its role as a transcriptional repressor in early development

Argenton, F., Giudici, S., Deflorian, G., Cimbro, S., Cotelli, F., and Beltrame, M.
Mechanisms of Development   121(2): 131-142 (Journal)
Registered Authors
Argenton, Francesco, Beltrame, Monica, Cotelli, Franco, Deflorian, Gianluca
HMG-box, Sox, Zebrafish, Dorso-ventral patterning, Axis splitting, Maternal transcript, Morpholino
MeSH Terms
  • Animals
  • Animals, Genetically Modified
  • Base Sequence
  • Body Patterning/genetics
  • Body Patterning/physiology
  • DNA-Binding Proteins/genetics*
  • DNA-Binding Proteins/physiology
  • Female
  • Gastrula
  • Gene Expression
  • Gene Targeting
  • High Mobility Group Proteins/genetics*
  • High Mobility Group Proteins/physiology
  • Oligodeoxyribonucleotides, Antisense/genetics
  • Oligodeoxyribonucleotides, Antisense/pharmacology
  • Repressor Proteins/genetics
  • Repressor Proteins/physiology
  • SOXB2 Transcription Factors
  • Zebrafish/embryology*
  • Zebrafish/genetics*
  • Zebrafish/physiology
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/physiology
15037315 Full text @ Mech. Dev.
Sox proteins are DNA-binding proteins belonging to the HMG box superfamily and they play key roles in animal embryonic development. Zebrafish Sox21a is part of group B Sox proteins and its chicken and mouse orthologs have been described as transcriptional repressor and activator, respectively, in two different target gene contexts. Zebrafish sox21a is present as a maternal transcript in the oocyte and is mainly expressed at the developing midbrain–hindbrain boundary from the onset of neurulation. In order to understand its role in vivo, we ectopically expressed sox21a by microinjection. Ectopic expression of full length sox21a leads to dorsalization of the embryos. A subset of the dorsalized embryos shows a partial axis splitting, and hence an ectopic neural tube, as an additional phenotype. At gastrulation, injected embryos show expansion of the expression domains of organizer-specific genes, such as chordin and goosecoid. Molecular markers used in somitogenesis highlight that sox21a-injected embryos have shortened AP axis, undulating axial structures, enlarged or even radialized paraxial territory. The developmental abnormalities caused by ectopic expression of sox21a are suggestive of defects in convergence–extension morphogenetic movements. Antisense morpholino oligonucleotides, designed to functionally knockdown sox21a, cause ventralization of the embryos. Moreover, gain-of-function experiments with chimeric constructs, where Sox21a DNA-binding domain is fused to a transcriptional activator (VP16) or repressor (EnR) domain, suggests that zebrafish Sox21a acts as a repressor in dorso-ventral patterning.
Genes / Markers
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Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes