title: Ectopic expression and knockdown of a zebrafish sox21 reveal its role as a transcriptional repressor in early development.
abstract: 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.
authors.affiliation: Dipartimento di Biologia, Universita' di Padova, Padua, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Argenton
authors.forename: Simona
authors.initials: S
authors.lastname: Giudici
authors.forename: Gianluca
authors.initials: G
authors.lastname: Deflorian
authors.forename: Simona
authors.initials: S
authors.lastname: Cimbro
authors.forename: Franco
authors.initials: F
authors.lastname: Cotelli
authors.forename: Monica
authors.initials: M
authors.lastname: Beltrame
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D005260:Female; D005775:Gastrula; D015870:Gene Expression; D018390:Gene Targeting; D006609:High Mobility Group Proteins / Q000235:genetics* / Q000502:physiology; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D055749:SOXB2 Transcription Factors; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics* / Q000502:physiology; D029961:Zebrafish Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D012097:Repressor Proteins; D055749:SOXB2 Transcription Factors; D029961:Zebrafish Proteins; C119840:sox21a protein, zebrafish