The Transcription Factor MEF2 Is a Novel Regulator of Gsta Gene Class in Mouse MA-10 Leydig Cells

Abstract

Testosterone is essential for spermatogenesis and the development of male sexual characteristics. However, steroidogenesis produces a significant amount of reactive oxygen species (ROS), which can disrupt testosterone production. The myocyte enhancer factor 2 (MEF2) is an important regulator of organogenesis and cell differentiation in various tissues. In the testis, MEF2 is present in Sertoli and Leydig cells throughout fetal and adult life. MEF2-deficient MA-10 Leydig cells exhibit a significant decrease in steroidogenesis concomitant with a reduction in glutathione S-transferase (GST) activity and in the expression of the 4 Gsta members (GST) that encode ROS inactivating enzymes. Here, we report a novel role for MEF2 in ROS detoxification by directly regulating Gsta expression in Leydig cells. Endogenous Gsta1-4 mRNA levels were decreased in MEF2-deficient MA-10 Leydig cells. Conversely, overexpression of MEF2 increased endogenous Gsta1 levels. MEF2 recruitment to the proximal Gsta1 promoter and direct binding on the -506-bp MEF2 element were confirmed by chromatin immunoprecipitation and DNA precipitation assays. In MA-10 Leydig cells, MEF2 activates the Gsta1 promoter and cooperates with Ca(2+)/calmodulin-dependent kinases I to further enhance Gsta1 promoter activity. These effects were lost when the -506-bp MEF2 element was mutated or when a MEF2-Engrailed dominant negative protein was used. Similar results were obtained on the Gsta2, Gsta3, and Gsta4 promoters, suggesting a global role for MEF2 factors in the regulation of all 4 Gsta genes. Altogether, our results identify a novel role for MEF2 in the expression of genes involved in ROS detoxification, a process essential for adequate testosterone production in Leydig cells.

Transcription Factors in the Regulation of Leydig Cell Gene Expression and Function

“…Consistent with this, microarray analysis of MEF2A/2D-depleted MA-10 Leydig cells identified several differently regulated genes known to be involved in fertility, gonad morphology, and steroidogenesis ( 97 ). To date, direct gene targets for MEF2 factors in Leydig cells include Nur77 ( 52 ), Gsta1-4 ( 53 ), Star (involving a MEF2/GATA4 cooperation) ( 47 ), and Akr1c14 (through a cooperation with COUP-TFII) ( 27 ). The complete network of genes regulated by MEF2 factors in Leydig cells as well as MEF2 interacting partners remain to be fully elucidated.…”

MEF2 signaling and human diseases

“…In MA-10 Leydig cells, steroid hormone biosynthesis and steroidogenic gene expression are regulated by luteinizing hormone (LH), which activates Ca 2+ signaling pathways and MEF2 transcription factors [ 53 ]. Another study showed that MEF2 itself can bind and activate Gsta1 promoter as well as cooperate with Ca 2+ /calmodulin-CamKI to further enhance the initiation of Gsta1 transcription in Sertoli and Leydig cells [ 54 ].…”

Ca2+/Calmodulin-Dependent Protein Kinase II and Androgen Signaling Pathways Modulate MEF2 Activity in Testosterone-Induced Cardiac Myocyte Hypertrophy

“…Recent evidence suggested that testosterone links MEF2C to AR-regulated transcription ( Bagchi et al, 2011 ), and, notably, AR-binding regions were reported to be enriched in MEF2-binding sequences, and MEF2C-dependent genes were also identified as targets for AR signaling, which suggests a functional interaction of these two transcription factors in skeletal muscle ( Wyce et al, 2010 ). Furthermore, testosterone was shown to stimulate cardiac myocyte differentiation from mouse embryonic stem cells and P19 embryonic carcinoma cells through AR-regulated transcription involving ARE regions of MEF2C-regulated genes, which led to an increase in histone acetylation in the DNA ( Di-Luoffo et al, 2015 ), and the MADS domains of MEF2 were reported to potentially generate regulatory protein–protein interactions for MEF2C and AR ( Black and Olson, 1998 ). Thus, the differential expression of testosterone-regulated genes entails the integration of transcriptional modulators ( Verrijdt et al, 2003 ; McEwan, 2004 ; Heemers and Tindall, 2007 ).…”