Differential regulation of cranial and cardiac neural crest by serum response factor and its cofactors.

Colin J Dinsmore,Philippe Soriano

doi:10.7554/elife.75106

Abstract

Serum response factor (SRF) is an essential transcription factor that influences many cellular processes including cell proliferation, migration, and differentiation. SRF directly regulates and is required for immediate early gene (IEG) and actin cytoskeleton-related gene expression. SRF coordinates these competing transcription programs through discrete sets of cofactors, the ternary complex factors (TCFs) and myocardin-related transcription factors (MRTFs). The relative contribution of these two programs to in vivo SRF activity and mutant phenotypes is not fully understood. To study how SRF utilizes its cofactors during development, we generated a knock-in SrfaI allele in mice harboring point mutations that disrupt SRF-MRTF-DNA complex formation but leave SRF-TCF activity unaffected. Homozygous SrfaI/aI mutants die at E10.5 with notable cardiovascular phenotypes, and neural crest conditional mutants succumb at birth to defects of the cardiac outflow tract but display none of the craniofacial phenotypes associated with complete loss of SRF in that lineage. Our studies further support an important role for MRTF mediating SRF function in cardiac neural crest and suggest new mechanisms by which SRF regulates transcription during development.

Highlights

Multicellular development requires the precise management of cellular behaviors including proliferation, migration, and differentiation
Serum Response Factor (SRF) is necessary for the expression of immediate early genes (IEGs) in cells stimulated with serum or growth factors, as well as many genes related to the actin cytoskeleton, contractility, and muscle differentiation. 45 SRF binds a conserved DNA regulatory sequence known as a CArG box, a motif found at many cytoskeletal and growth-factor inducible gene promoters
In order to test the requirement for SRF-Myocardin Related Transcription Factors (MRTFs) interactions genetically, we introduced four knock-in point mutations to the I helix of the SRF DNA-binding domain previously shown to disrupt SRF-MRTF-DNA ternary complex formation while leaving SRF-TCF201 DNA complex formation unaffected (Figure 2 Supplement 1A-C) (Hipp et al, 2019; 202 Zaromytidou et al, 2006)

Summary

Introduction

Multicellular development requires the precise management of cellular behaviors including proliferation, migration, and differentiation. The ternary complex factors (TCFs) are E26 transformation-specific (ETS) family proteins activated by extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation (Mylona et al, 2016) Once activated, they bind DNA and promote cellular proliferation by transcribing IEGs in coordination with SRF (Esnault et al, 2017; Gualdrini et al, 2016). Opposing SRF-TCF activity are the Myocardin Related Transcription Factors (MRTFs) These cofactors rely on SRF to bind DNA, promote cytoskeletal gene expression, and are important in muscle differentiation (Posern & Treisman, 2006). Polymerization of G-actin into F-actin liberates MRTFs to translocate to the nucleus and bind SRF (Miralles et al, 2003) This can be promoted by multiple signaling pathways, including phosphoinositide 3-kinase (PI3K), that stimulate guanine nucleotide exchange factors to activate F-actin-promoting Rho-family GTPases (Brachmann et al, 2005; Hanna & El-Sibai, 2013; Jimenez et al, 2000; Vasudevan & Soriano, 2014).

Methods

Results

Conclusion