Details

Autor(en) / Beteiligte

• Arkhipova, Valeriya
• Wendik, Björn
• Devos, Nathalie
• Ek, Olivier
• Peers, Bernard
• Meyer, Dirk

Titel

Characterization and regulation of the hb9/mnx1 beta-cell progenitor specific enhancer in zebrafish

Ist Teil von

• Developmental biology, 2012-05, Vol.365 (1), p.290-302

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2012

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Differentiation of insulin producing beta-cells is a genetically well defined process that involves functions of various conserved transcription factors. Still, the transcriptional mechanisms underlying specification and determination of beta-cell fate are poorly defined. Here we provide the description of a beta-cell progenitor specific enhancer as a model to study initial steps of beta-cell differentiation. We show that evolutionary non-conserved upstream sequences of the zebrafish hb9 gene are required and sufficient for regulating expression in beta-cells prior to the onset of insulin expression. This enhancer contains binding sites for paired-box transcription factors and two E-boxes that in EMSA studies show interaction with Pax6b and NeuroD, respectively. We show that Pax6b is a potent activator of endodermal hb9 expression and that this activation depends on the beta-cell enhancer. Using genetic approaches we show that pax6b is crucial for maintenance but not induction of pancreatic hb9 transcription. As loss of Pax6b or Hb9 independently results in the loss of insulin expression, the data reveal a novel cross-talk between the two essential regulators of early beta-cell differentiation. While we find that the known pancreatic E-box binding proteins NeuroD and Ngn3 are not required for hb9 expression we also show that removal of both E-boxes selectively eliminates pancreatic specific reporter expression. The data provide evidence for an Ngn3 independent pathway of beta-cell specification that requires function of currently not specified E-box binding factors. ► Beta-cell progenitor enhancer localizes to non-conserved hb9 promoter sequences. ► E-boxes are required for hb9 induction. ► Induction is independent of Ngn3 and NeuroD. ► Pax6b activates enhancer. ► Pax6b is required for hb9 maintenance.