Anteroposterior patterning of the zebrafish ear through Fgf- and Hh-dependent regulation of hmx3a expression.

Anteroposterior patterning of the zebrafish ear through Fgf- and Hh-dependent regulation of hmx3a expression.

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In the zebrafish, Fgf and Hh signalling assign anterior and posterior identity, respectively, to the poles of the developing ear.Mis-expression of fgf3 PHOSPHATIDYL CHOLINE or inhibition of Hh signalling results in double-anterior ears, including ectopic expression of hmx3a.To understand how this double-anterior pattern is established, we characterised transcriptional responses in Fgf gain-of-signalling or Hh loss-of-signalling backgrounds.

Mis-expression of fgf3 resulted in rapid expansion of anterior otic markers, refining over time to give the duplicated pattern.Response to Hh inhibition was very different: initial anteroposterior asymmetry was retained, with de novo duplicate expression domains appearing later.We show that Hmx3a is required for normal anterior otic patterning, and that otic patterning defects in hmx3a-/- mutants are a close phenocopy to those seen in fgf3-/- mutants.

However, neither loss nor gain of hmx3a function was sufficient to generate GRUNDIG GSBS16312X American-Style Fridge Freezer - Stainless Steel full ear duplications.Using our data to infer a transcriptional regulatory network required for acquisition of otic anterior identity, we can recapitulate both the wild-type and the double-anterior pattern in a mathematical model.