MEF2 is restricted to the male gonad and regulates expression of the orphan nuclear receptor NR4A1.
Leydig cell steroidogenesis is controlled by the pituitary gonadotropin LH that activates several signaling pathways, including the Ca(2+)/calmodulin kinase I (CAMKI) pathway. In other tissues, CAMKI regulates the activity of the myocyte enhancer factor 2 (MEF2) transcription factors. MEF2 factors are essential regulators of cell differentiation and organogenesis in numerous tissues but their expression and role in the mammalian gonad had not been explored. Here we show that MEF2 factors are expressed in a sexually dimorphic pattern in the mouse gonad. MEF2 factors are present in the testis throughout development and into adulthood but absent from the ovary. In the testis, MEF2 was localized mainly in the nucleus of both somatic lineages, the supporting Sertoli cells and the steroidogenic Leydig cells. In Leydig cells, MEF2 was found to activate the expression of Nr4a1, a nuclear receptor important for hormone-induced steroidogenesis. In these cells MEF2 also cooperates with forskolin and CAMKI to enhance Nr4a1 promoter activity via two MEF2 elements (-318 and -284 bp). EMSA confirmed direct binding of MEF2 to these elements whereas chromatin immunoprecipitation revealed that MEF2 recruitment to the proximal Nr4a1 promoter was increased following hormonal stimulation. Modulation of endogenous MEF2 protein level (small interfering RNA-mediated knockdown) or MEF2 activity (MEF2-Engrailed active dominant negative) led to a significant decrease in Nr4a1 mRNA levels in Leydig cells. All together, our results identify MEF2 as a novel testis-specific transcription factor, supporting a role for this factor in male sex differentiation and function. MEF2 was also positioned upstream of NR4A1 in a regulatory cascade controlling Leydig cell gene expression.
Reproduction, Mother and Child Health (C.D., L.J.M., C.B., J.J.T., Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, Québec, Canada, G1V 4G2; and Centre de Recherche en Biologie de la Reproduction (J.J.T.), Department of Obstetrics, Gynecology, and Reproduction, Faculty of Medicine, Université Laval, Québec City, Québec, Canada, G1V 0A6.
Caroline
C
Daems
Luc J
LJ
Martin
Catherine
C
Brousseau
Jacques J
JJ
Tremblay
D000818:Animals; D001483:Base Sequence; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D016384:Consensus Sequence; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D007985:Leydig Cells / Q000378:metabolism*; D064326:MEF2 Transcription Factors / Q000378:metabolism*; D008297:Male; D051379:Mice; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000235:genetics* / Q000378:metabolism; D009928:Organ Specificity; D010053:Ovary / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats
D064326:MEF2 Transcription Factors; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; C517598:Camk1 protein, mouse