Elsevier

Developmental Biology

Volume 395, Issue 1, 1 November 2014, Pages 154-166
Developmental Biology

FGFR-ERK signaling is an essential component of tissue separation

https://doi.org/10.1016/j.ydbio.2014.08.010Get rights and content
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Highlights

  • FGFR-ERK signaling is important for tissue separation between Hydra bud and parent.

  • Transient ERK activation (dpERK) at the bud base is essential for bud detachment.

  • Ectopic Kringelchen FGFR induces autotomy of the body column.

  • Dominant–negative FGFR causes failure to perform the final steps of detachment.

  • Failing detachment correlates with a distorted ectodermal actin cytoskeleton.

Abstract

Formation of a constriction and tissue separation between parent and young polyp is a hallmark of the Hydra budding process and controlled by fibroblast growth factor receptor (FGFR) signaling. Appearance of a cluster of cells positive for double phosphorylated ERK (dpERK) at the late separation site indicated that the RAS/MEK/ERK pathway might be a downstream target of the Hydra Kringelchen FGFR. In fact, inhibition of ERK phosphorylation by the MEK inhibitor U0126 reversibly delayed bud detachment and prevented formation of the dpERK-positive cell cluster indicating de novo-phosphorylation of ERK at the late bud base. In functional studies, a dominant-negative Kringelchen FGFR prevented bud detachment as well as appearance of the dpERK-positive cell cluster. Ectopic expression of full length Kringelchen, on the other hand, induced a localized rearrangement of the actin cytoskeleton at sites of constriction, localized ERK-phosphorylation and autotomy of the body column. Our data suggest a model in which (i) the Hydra FGFR targets, via an unknown pathway, the actin cytoskeleton to induce a constriction and (ii) FGFR activates MEK/ERK signaling at the late separation site to allow tissue separation.

Keywords

Receptor tyrosine kinase
Autotomy
Actin cytoskeleton
Dominant-negative FGFR

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