Tissue-Specific Gain of RTK Signalling Uncovers Selective Cell Vulnerability during Embryogenesis

PLoS Genet. 2015 Sep 22;11(9):e1005533. doi: 10.1371/journal.pgen.1005533. eCollection 2015.

Abstract

The successive events that cells experience throughout development shape their intrinsic capacity to respond and integrate RTK inputs. Cellular responses to RTKs rely on different mechanisms of regulation that establish proper levels of RTK activation, define duration of RTK action, and exert quantitative/qualitative signalling outcomes. The extent to which cells are competent to deal with fluctuations in RTK signalling is incompletely understood. Here, we employ a genetic system to enhance RTK signalling in a tissue-specific manner. The chosen RTK is the hepatocyte growth factor (HGF) receptor Met, an appropriate model due to its pleiotropic requirement in distinct developmental events. Ubiquitously enhanced Met in Cre/loxP-based Rosa26(stopMet) knock-in context (Del-R26(Met)) reveals that most tissues are capable of buffering enhanced Met-RTK signalling thus avoiding perturbation of developmental programs. Nevertheless, this ubiquitous increase of Met does compromise selected programs such as myoblast migration. Using cell-type specific Cre drivers, we genetically showed that altered myoblast migration results from ectopic Met expression in limb mesenchyme rather than in migrating myoblasts themselves. qRT-PCR analyses show that ectopic Met in limbs causes molecular changes such as downregulation in the expression levels of Notum and Syndecan4, two known regulators of morphogen gradients. Molecular and functional studies revealed that ectopic Met expression in limb mesenchyme does not alter HGF expression patterns and levels, but impairs HGF bioavailability. Together, our findings show that myoblasts, in which Met is endogenously expressed, are capable of buffering increased RTK levels, and identify mesenchymal cells as a cell type vulnerable to ectopic Met-RTK signalling. These results illustrate that embryonic cells are sensitive to alterations in the spatial distribution of RTK action, yet resilient to fluctuations in signalling levels of an RTK when occurring in its endogenous domain of activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Movement / genetics
  • Embryo, Mammalian
  • Embryonic Development / genetics*
  • Gene Expression Regulation, Developmental
  • Hepatocyte Growth Factor / genetics*
  • Hepatocyte Growth Factor / metabolism
  • Mice
  • Myoblasts / metabolism*
  • Phosphorylation
  • Proto-Oncogene Proteins c-met / biosynthesis
  • Proto-Oncogene Proteins c-met / genetics*
  • Signal Transduction
  • Syndecan-4 / biosynthesis
  • Syndecan-4 / genetics

Substances

  • Sdc4 protein, mouse
  • Syndecan-4
  • Hepatocyte Growth Factor
  • HGFR protein, mouse
  • Proto-Oncogene Proteins c-met

Grant support

This work was supported by grants from INCa (Institut National du Cancer), FdF (Fondation de France), ARC (Association pour la Recherche contre le Cancer), FRM (Fondation pour la Recherche Médicale), AFM (Association Française contre les Myopathies), Fondation Bettencourt-Schueller to FM; AFM to RD. The contribution of the Region Provence Alpes Côtes d’Azur and of the Aix-Marseille Université to the IBDM animal facility, and of the France-BioImaging/PICsL infrastructure (ANR-10-INSB-04-01) for the Imaging facility, are also acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.