TBX3 Regulates Splicing In Vivo: A Novel Molecular Mechanism for Ulnar-Mammary Syndrome

Pavan Kumar P,Anne M Moon,Hao Hu,Chris Lehman,Sarah Franklin,Barry Moore,Mark Yandell,Uchenna Emechebe,Gregory S Barsh

doi:10.1371/journal.pgen.1004247

Abstract

TBX3 is a member of the T-box family of transcription factors with critical roles in development, oncogenesis, cell fate, and tissue homeostasis. TBX3 mutations in humans cause complex congenital malformations and Ulnar-mammary syndrome. Previous investigations into TBX3 function focused on its activity as a transcriptional repressor. We used an unbiased proteomic approach to identify TBX3 interacting proteins in vivo and discovered that TBX3 interacts with multiple mRNA splicing factors and RNA metabolic proteins. We discovered that TBX3 regulates alternative splicing in vivo and can promote or inhibit splicing depending on context and transcript. TBX3 associates with alternatively spliced mRNAs and binds RNA directly. TBX3 binds RNAs containing TBX binding motifs, and these motifs are required for regulation of splicing. Our study reveals that TBX3 mutations seen in humans with UMS disrupt its splicing regulatory function. The pleiotropic effects of TBX3 mutations in humans and mice likely result from disrupting at least two molecular functions of this protein: transcriptional regulation and pre-mRNA splicing.

Highlights

IntroductionThe crucial roles of TBX3 in development are evident in the fact that heterozygous mutations of TBX3 cause Ulnar–mammary syndrome in humans (UMS)
TBX3 belongs to the T-box family of transcription factors
TBX3 mutations in humans cause a complex of birth defects called Ulnar-mammary syndrome (UMS)

Summary

Introduction

The crucial roles of TBX3 in development are evident in the fact that heterozygous mutations of TBX3 cause Ulnar–mammary syndrome in humans (UMS). This syndrome includes limb malformations, apocrine and mammary gland hypoplasia, dental and genital abnormalities. Altered TBX3 expression is implicated in the pathogenesis of breast and other cancers by affecting cell adhesion, proliferation and senescence [1,2,3,4,5,6]. Tbx improves germ line competence of iPS cells [7] and can reprogram mature cardiomyocytes [8]. In addition to its roles in limb and mammary development, Tbx is required for formation and homeostasis of the cardiac conduction system [9,10] and plays a role in cardiac development and function in humans [11,12,13,14]

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