ABSTRACT
Cardiac and skeletal muscle development and maintenance require complex interactions between DNA-binding proteins and chromatin remodeling factors. We previously reported that Smyd1, a muscle-restricted histone methyltransferase, is essential for cardiogenesis and functions with a network of cardiac regulatory proteins. Here we show that the muscle-specific transcription factor skNAC is the major binding partner for Smyd1 in the developing heart. Targeted deletion of skNAC in mice resulted in partial embryonic lethality by embryonic day 12.5, with ventricular hypoplasia and decreased cardiomyocyte proliferation that were similar but less severe than in Smyd1 mutants. Expression of Irx4, a ventricle-specific transcription factor down-regulated in hearts lacking Smyd1, also depended on the presence of skNAC. Viable skNAC(-/-) adult mice had reduced postnatal skeletal muscle growth and impaired regenerative capacity after cardiotoxin-induced injury. Satellite cells isolated from skNAC(-/-) mice had impaired survival compared with wild-type littermate satellite cells. Our results indicate that skNAC plays a critical role in ventricular cardiomyocyte expansion and regulates postnatal skeletal muscle growth and regeneration in mice.
Subject(s)
DNA-Binding Proteins/metabolism , Heart/growth & development , Molecular Chaperones/metabolism , Muscle Development/physiology , Muscle Proteins/metabolism , Muscle, Skeletal/growth & development , Regeneration/physiology , Transcription Factors/metabolism , Animals , Animals, Newborn , Body Patterning , Cell Proliferation , DNA-Binding Proteins/genetics , Embryo, Mammalian/metabolism , Embryo, Mammalian/pathology , Gene Expression Regulation, Developmental , Gene Targeting , Heart Ventricles/abnormalities , Heart Ventricles/embryology , Heart Ventricles/pathology , Mice , Muscle Development/genetics , Muscle Fibers, Skeletal/metabolism , Muscle Fibers, Skeletal/pathology , Muscle Proteins/genetics , Muscle, Skeletal/embryology , Muscle, Skeletal/pathology , Myocardium/metabolism , Myocardium/pathology , Myocytes, Cardiac/metabolism , Myocytes, Cardiac/pathology , Organ Specificity/genetics , Organogenesis/genetics , Protein Binding , Transcription Factors/geneticsABSTRACT
MicroRNAs (miRNAs) are genomically encoded small RNAs used by organisms to regulate the expression of proteins generated from messenger RNA transcripts. The in vivo requirement of specific miRNAs in mammals through targeted deletion remains unknown, and reliable prediction of mRNA targets is still problematic. Here, we show that miRNA biogenesis in the mouse heart is essential for cardiogenesis. Furthermore, targeted deletion of the muscle-specific miRNA, miR-1-2, revealed numerous functions in the heart, including regulation of cardiac morphogenesis, electrical conduction, and cell-cycle control. Analyses of miR-1 complementary sequences in mRNAs upregulated upon miR-1-2 deletion revealed an enrichment of miR-1 "seed matches" and a strong tendency for potential miR-1 binding sites to be located in physically accessible regions. These findings indicate that subtle alteration of miRNA dosage can have profound consequences in mammals and demonstrate the utility of mammalian loss-of-function models in revealing physiologic miRNA targets.
