Receptor tyrosine kinases modulate distinct transcriptional programs by differential usage of intracellular pathways.

Harish N Vasudevan,Philippe Soriano,Fenglei He,Pierre Mazot

doi:10.7554/elife.07186

Harish N Vasudevan, Philippe Soriano + Show 2 more

Open Access

https://doi.org/10.7554/elife.07186

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Journal: eLife	Publication Date: May 7, 2015
Citations: 48	License type: CC BY 4.0

Affiliation: Icahn School of Medicine at Mount Sinai

Abstract

Receptor tyrosine kinases (RTKs) signal through shared intracellular pathways yet mediate distinct outcomes across many cell types. To investigate the mechanisms underlying RTK specificity in craniofacial development, we performed RNA-seq to delineate the transcriptional response to platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) signaling in mouse embryonic palatal mesenchyme cells. While the early gene expression profile induced by both growth factors is qualitatively similar, the late response is divergent. Comparing the effect of MEK (Mitogen/Extracellular signal-regulated kinase) and PI3K (phosphoinositide-3-kinase) inhibition, we find the FGF response is MEK dependent, while the PDGF response is PI3K dependent. Furthermore, FGF promotes proliferation but PDGF favors differentiation. Finally, we demonstrate overlapping domains of PDGF-PI3K signaling and osteoblast differentiation in the palate and increased osteogenesis in FGF mutants, indicating this differentiation circuit is conserved in vivo. Our results identify distinct responses to PDGF and FGF and provide insight into the mechanisms encoding RTK specificity.

Highlights

Receptor tyrosine kinases (RTKs) signal through a shared set of intracellular pathways, including extracellular signal-related kinase (ERK) and phosphatidylinositol 3-kinase (PI3K), yet the in vivo functions directed by different RTKs can be quite distinct, raising the question of how specific cellular responses are elicited (Lemmon and Schlessinger, 2010)
We first plotted the expression of all genes with FPKM values >1 at both 1 hr (Figures 1B and 4 hr (Figure 1B’); only a small number of genes are differentially regulated between the 1-hr platelet-derived growth factor (PDGF) and 1-hr fibroblast growth factor (FGF) samples (Cuffdiff q < 0.1, Supplementary File 2; Trapnell et al, 2010), the difference in the response to these two growth factors is much greater at 4 hr
Our studies show that PDGF and FGF signaling in mouse embryonic palatal mesenchyme (MEPM) regulate different gene expression programs and phenotypic outputs, with PDGF mainly promoting cell differentiation through PI3K and FGF favoring cell proliferation through ERK

Summary

Introduction

Receptor tyrosine kinases (RTKs) signal through a shared set of intracellular pathways, including extracellular signal-related kinase (ERK) and phosphatidylinositol 3-kinase (PI3K), yet the in vivo functions directed by different RTKs can be quite distinct, raising the question of how specific cellular responses are elicited (Lemmon and Schlessinger, 2010). Distinct responses may be encoded by modulation of individual pathways downstream of receptor activation, with each pathway regulating a specific outcome. Many cellular responses may require integration from multiple input pathways, and signal specificity could arise from this unique combination of pathways. Analysis of mice harboring point mutations to disrupt binding of specific effector proteins to RTKs suggests both these models may apply in vivo; platelet-derived growth factor (PDGF) Receptor α (Pdgfra) mutants display effectorspecific phenotypes in line with the former model (Klinghoffer et al, 2002), but PDGF Receptor β (Pdgfrb) mediated outcomes require combined output across multiple pathways, consistent with the latter model (Tallquist et al, 2003).

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