scholarly journals Requirement of a Myocardin-Related Transcription Factor for Development of Mammary Myoepithelial Cells

2006 ◽  
Vol 26 (15) ◽  
pp. 5797-5808 ◽  
Author(s):  
Shijie Li ◽  
Shurong Chang ◽  
Xiaoxia Qi ◽  
James A. Richardson ◽  
Eric N. Olson
Keyword(s):  
Transcription Factor ◽  
Smooth Muscle ◽  
Myoepithelial Cell ◽  
Serum Response Factor ◽  
Cell Lineage ◽  
Myoepithelial Cells ◽  
Embryonic Cell ◽  
Loss Of Function ◽  
Muscle Gene Expression ◽  
Related Transcription Factor

ABSTRACT The mammary gland consists of a branched ductal system comprised of milk-producing epithelial cells that form ductile tubules surrounded by a myoepithelial cell layer that provides contractility required for milk ejection. Myoepithelial cells bear a striking resemblance to smooth muscle cells, but they are derived from a different embryonic cell lineage, and little is known of the mechanisms that control their differentiation. Members of the myocardin family of transcriptional coactivators cooperate with serum response factor to activate smooth muscle gene expression. We show that female mice homozygous for a loss-of-function mutation of the myocardin-related transcription factor A (MRTF-A) gene are unable to effectively nurse their offspring due to a failure in maintenance of the differentiated state of mammary myoepithelial cells during lactation, resulting in apoptosis of this cell population, a consequent inability to release milk, and premature involution. The phenotype of MRTF-A mutant mice reveals a specific and essential role for MRTF-A in mammary myoepithelial cell differentiation and points to commonalities in the transcriptional mechanisms that control differentiation of smooth muscle and myoepithelial cells.

scholarly journals Enhancement of mDia2 activity by Rho-kinase-dependent phosphorylation of the diaphanous autoregulatory domain

2011 ◽  
Vol 439 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Dean P. Staus ◽  
Joan M. Taylor ◽  
Christopher P. Mack
Keyword(s):  
Smooth Muscle ◽  
Actin Polymerization ◽  
Serum Response Factor ◽  
Rho Kinase ◽  
Specific Gene ◽  
Related Transcription Factor ◽  
Inhibitory Domain ◽  
Serum Response ◽  
Acidic Region ◽  
Basic Region

It is clear that RhoA activates the DRF (diaphanous-related formin) mDia2 by disrupting the molecular interaction between the DAD (diaphanous autoregulatory domain) and the DID (diaphanous inhibitory domain). Previous studies indicate that a basic motif within the DAD contributes to mDia2 auto-inhibition, and results shown in the present study suggest these residues bind a conserved acidic region within the DID. Furthermore, we demonstrate that mDia2 is phosphorylated by ROCK (Rho-kinase) at two conserved residues (Thr1061 and Ser1070) just C-terminal to the DAD basic region. Phosphomimetic mutations to these residues in the context of the full-length molecule enhanced mDia2 activity as measured by increased actin polymerization, SRF (serum response factor)-dependent smooth muscle-specific gene transcription, and nuclear localization of myocardin-related transcription factor B. Biochemical and functional data indicate that the T1061E/S1070E mutation significantly inhibited the ability of DAD to interact with DID and enhanced mDia2 activation by RhoA. Taken together, the results of the present study indicate that ROCK-dependent phosphorylation of the mDia2 DAD is an important determinant of mDia2 activity and that this signalling mechanism affects actin polymerization and smooth muscle cell-specific gene expression.

scholarly journals MRTFA augments megakaryocyte maturation by enhancing the SRF regulatory axis

2018 ◽  
Vol 2 (20) ◽  
pp. 2691-2703 ◽  
Author(s):  
Nur-Taz Rahman ◽  
Vincent P. Schulz ◽  
Lin Wang ◽  
Patrick G. Gallagher ◽  
Oleg Denisenko ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Target Genes ◽  
Serum Response Factor ◽  
Sequencing Data ◽  
Binding Motifs ◽  
Ets Proteins ◽  
Human Cd34 ◽  
Genomic Association ◽  
Hel Cells ◽  
Related Transcription Factor

Abstract Serum response factor (SRF) is a ubiquitously expressed transcription factor that binds DNA at CArG (CC[A/T]6GG) domains in association with myocardin-family proteins (eg, myocardin-related transcription factor A [MRTFA]) or the ternary complex factor family of E26 transformation-specific (ETS) proteins. In primary hematopoietic cells, knockout of either SRF or MRTFA decreases megakaryocyte (Mk) maturation causing thrombocytopenia. The human erythroleukemia (HEL) cell line mimics the effects of MRTFA on Mk maturation, and MRTFA overexpression (MRTFAOE) in HEL cells enhances megakaryopoiesis. To identify the mechanisms underlying these effects, we performed integrated analyses of anti-SRF chromatin immunoprecipitation (ChIP) and RNA-sequencing data from noninduced and phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA])–induced HEL cells, with and without MRTFAOE. We found that 11% of genes were upregulated with TPA induction, which was enhanced by MRTFAOE, resulting in an upregulation of 25% of genes. MRTFAOE increased binding of SRF to genomic sites and enhanced TPA-induced expression of SRF target genes. The TPA-induced genes are predicted to be regulated by SRF and ETS factors, whereas those upregulated by TPA plus MRTFAOE lack ETS binding motifs, and MRTFAOE skews SRF binding to genomic regions with CArG sites in regions relatively lacking in ETS binding motifs. Finally, ChIP–polymerase chain reaction using HEL cells and primary human CD34+ cell–derived subpopulations confirms that both SRF and MRTFA have increased binding during megakaryopoiesis at upregulated target genes (eg, CORO1A). We show for the first time that MRTFA increases both the genomic association and activity of SRF and upregulates genes that enhance primary human megakaryopoiesis.

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