High impact information on her5

• Our results provide the first model for vertebrate endoderm patterning where an early regulatory step at gastrulation, mediated by her5 controls cell contribution jointly to the anterior- and posteriormost mesendodermal regions [1].
• We report that the zebrafish hairy/enhancer of split [E(spl)]-related gene her5 plays a critical role in this process [1].
• In this process, her5 acts as an active transcriptional repressor [1].
• Ectopic misexpressions of wild-type and mutant forms of her5 reveal that her5 functions primarily within the endodermal/endmost mesendodermal germ layer to inhibit cell participation to the endmost-fated mesendoderm [1].
• To follow the dynamics of MH maintenance in vivo, we used artificial chromosome transgenesis in zebrafish to construct lines where egfp transcription is driven by the complete set of regulatory elements of her5, the first known gene expressed in the MH area [2].

Anatomical context of her5

• Our results suggest that by regulating the expression of her5, the Bmp2b/Chordin gradient directs the anteroposterior patterning of endoderm in zebrafish embryos [3].

Other interactions of her5

• In particular, increased levels of Bmp signalling in chordino gastrulae are associated with a markedly reduced her5 expression domain, that may be abolished by injecting bmp2b mRNA [3].
• When both loci are deleted, the expression of pax2.1, en2, and her5 is lost in the ventral portion of the MHB beginning at the 8-somite stage [4].
• Alterations of dorsoventral Bmp signalling do not perturb the induction of endodermal precursors, as shown by normal amounts of cells expressing cas and sox17 in swirl and chordino gastrulae, but affect dramatically the expression pattern of her5, a regulator of endoderm anteroposterior patterning in zebrafish [3].
• In contrast, onset of wnt1, fgf8 and her5 expression occurs normally in the null mutants, but is eliminated later on [5].

References