The Forkhead Transcription Factor FOXP2 Is Required for Regulation of p21WAF1/CIP1 in 143B Osteosarcoma Cell Growth Arrest.

Duncan M Gascoyne,Hayley Spearman,Linden Lyne,Alison H Banham,Simon E Fisher,Peter I Croucher,Marta Perez-Alcantara,Les Coulton,Rathi Puliyadi,Jean-Marc Vanacker

doi:10.1371/journal.pone.0128513

Abstract

Mutations of the forkhead transcription factor FOXP2 gene have been implicated in inherited speech-and-language disorders, and specific Foxp2 expression patterns in neuronal populations and neuronal phenotypes arising from Foxp2 disruption have been described. However, molecular functions of FOXP2 are not completely understood. Here we report a requirement for FOXP2 in growth arrest of the osteosarcoma cell line 143B. We observed endogenous expression of this transcription factor both transiently in normally developing murine osteoblasts and constitutively in human SAOS-2 osteosarcoma cells blocked in early osteoblast development. Critically, we demonstrate that in 143B osteosarcoma cells with minimal endogenous expression, FOXP2 induced by growth arrest is required for up-regulation of p21WAF1/CIP1. Upon growth factor withdrawal, FOXP2 induction occurs rapidly and precedes p21WAF1/CIP1 activation. Additionally, FOXP2 expression could be induced by MAPK pathway inhibition in growth-arrested 143B cells, but not in traditional cell line models of osteoblast differentiation (MG-63, C2C12, MC3T3-E1). Our data are consistent with a model in which transient upregulation of Foxp2 in pre-osteoblast mesenchymal cells regulates a p21-dependent growth arrest checkpoint, which may have implications for normal mesenchymal and osteosarcoma biology.

Highlights

The FOXP2 forkhead transcription factor was identified in 2001 from independent studies mapping mutations associated with human inherited speech-and-language disorder and using homology screening to identify novel forkhead proteins in the mouse lung.[1, 2] FOXP2 shares characteristics with other members of the FOXP subfamily, including a C-terminal winged helix forkhead DNA binding domain and is proposed to function predominantly as a PLOS ONE | DOI:10.1371/journal.pone.0128513 June 2, 2015FOXP2 Function in Mesenchymal Growth Arrest
The osteoblast transcription factor RUNX2 is expressed in myeloma[30] and we hypothesised that FOXP2 might play a role in normal bone biology
We have shown that FOXP2 is expressed in developing osteoblasts and have demonstrated that FOXP2 can promote growth arrest and likely control differentiation by regulating expression of the critical cell-cycle inhibitor p21WAF1/CIP1

Summary

Introduction

The FOXP2 forkhead transcription factor was identified in 2001 from independent studies mapping mutations associated with human inherited speech-and-language disorder and using homology screening to identify novel forkhead proteins in the mouse lung.[1, 2] FOXP2 shares characteristics with other members of the FOXP subfamily, including a C-terminal winged helix forkhead DNA binding domain and is proposed to function predominantly as a PLOS ONE | DOI:10.1371/journal.pone.0128513 June 2, 2015FOXP2 Function in Mesenchymal Growth Arrest.

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