Mutation analysis of the myocyte enhancer factor 2A gene (MEF2A) in patients with left ventricular hypertrophy/hypertrophic cardiomyopathy

Myocyte Enhancer Factor 2A Plays a Central Role in the Regulatory Networks of Cellular Physiopathology

Cell regulatory networks are the determinants of cellular homeostasis. Any alteration to these networks results in the disturbance of cellular homeostasis and induces cells towards different fates. Myocyte enhancer factor 2A (MEF2A) is one of four members of the MEF2 family of transcription factors (MEF2A-D). MEF2A is highly expressed in all tissues and is involved in many cell regulatory networks including growth, differentiation, survival and death. It is also necessary for heart development, myogenesis, neuronal development and differentiation. In addition, many other important functions of MEF2A have been reported. Recent studies have shown that MEF2A can regulate different, and sometimes even mutually exclusive cellular events. How MEF2A regulates opposing cellular life processes is an interesting topic and worthy of further exploration. Here, we reviewed almost all MEF2A research papers published in English and summarized them into three main sections: 1) the association of genetic variants in MEF2A with cardiovascular disease, 2) the physiopathological functions of MEF2A, and 3) the regulation of MEF2A activity and its regulatory targets. In summary, multiple regulatory patterns for MEF2A activity and a variety of co-factors cause its transcriptional activity to switch to different target genes, thereby regulating opposing cell life processes. The association of MEF2A with numerous signaling molecules establishes a central role for MEF2A in the regulatory network of cellular physiopathology.

Shenfu Injection attenuates rat myocardial hypertrophy by up-regulating miR-19a-3p expression

Shenfu Injection (SFI) is a classical Chinese medicine used to treat heart failure. Our previous study demonstrated that miRNAs underwent changes in rats with myocardial hypertrophy induced by abdominal aortic constriction. Interestingly, there was a significant change in miR-19a-3p, whose target gene is known to be associated with MEF2 signaling. However, whether and how SFI regulates miR-19a-3p in the treatment of myocardial hypertrophy has not been investigated. The purpose of the present study was to investigate the regulatory effect of SFI on miR-19a-3p in MEF2 signaling in the rat hypertrophic myocardium. We found that the miR-19a-3p expression level was significantly decreased in the hypertrophic myocardium, and MEF2A was the target gene of miR-19a-3p. The protein expressions of MEF2A, β-MHC, BNP and TRPC1 were significantly increased in hypertrophic cardiomyocytes. MiR-19a-3p was up-regulated after SFI treatment, and the protein expressions of these genes were significantly decreased. In addition, miR-19a-3p over-expression in hypertrophic cardiomyocytes could decrease MEF2A mRNA and protein expressions, and anti-miR-19a-3p showed the opposite result. Our study provided substantial evidence that miR-19a-3p played a functional role in MEF2 signaling in myocardial hypertrophy. SFI attenuated cardiomyocyte hypertrophy probably through up-regulating or maintaining the miR-19a-3p levels and regulating the MEF2 signaling pathway.

Effects of new polymorphisms in the bovine myocyte enhancer factor 2D (MEF2D) gene on the expression rates of the longissimus dorsi muscle

Myocyte enhancer factor 2D (MEF2D), a product of the MEF2D gene, belongs to the myocyte enhancer factor 2 (MEF2) protein family which is involved in vertebrate skeletal muscle development and differentiation during myogenesis. The aim of the present study was to search for polymorphisms in the bovine MEF2D gene and to analyze their effect on MEF2D mRNA and on protein expression levels in the longissimus dorsi muscle of Polish Holstein–Friesian cattle. Overall, three novel variations, namely, insertion/deletion g.−818_−814AGCCG and g.−211C<A transversion in the promoter region as well as g.7C<T transition in the 5′untranslated region (5′UTR), were identified by DNA sequencing. A total, 375 unrelated bulls belonging to six different cattle breeds were genotyped, and three combined genotypes (Ins-C-C/Ins-C-C, Del-A-T/Del-A-T and Ins-C-C/Del-A-T) were determined. The frequency of the combined genotype Ins-C-C/Ins-C-C and Del-A-T/Del-A-T was varied between the breeds and the average frequency was 0.521 and 0.037, respectively. Expression analysis showed that the MEF2D variants were highly correlated with MEF2D mRNA and protein levels in the longissimus dorsi muscle of Polish Holstein–Friesian bulls carrying the three different combined genotypes. The highest MEF2D mRNA and protein levels were estimated in the muscle of bulls with the Ins-C-C/Ins-C-C homozygous genotype as compared to the Del-A-T/Del-A-T homozygotes (P < 0.01) and Ins-C-C/Del-A-T heterozygotes (P < 0.05). A preliminary association study showed no significant differences in the carcass quality traits between bulls with various MEF2D combined genotypes in the investigated population of Polish Holstein–Friesian cattle.

Promoter variant-dependent mRNA expression of the MEF2A in longissimus dorsi muscle in cattle

The myocyte enhancer factor 2A (MEF2A) gene encodes a member of the myocyte enhancer factor 2 (MEF2) protein family that is involved in vertebrate skeletal, cardiac, and smooth muscle development and differentiation during myogenesis. According to recent studies, MEF2 genes might be major regulators of postnatal skeletal muscle growth; thus, they are considered to be important, novel candidates for muscle development and body growth in farm animals. The aim of the present study was to search for polymorphisms in the bovine MEF2A gene and analyze their effect on the MEF2A mRNA expression level in the longissimus dorsi muscle of Polish Holstein-Fresian cattle. In total, 4094 bp of the whole coding sequence and the promoter region of MEF2A were re-sequenced in 30 animals, resulting in the detection of 6 novel variants as well as one previously reported SNP. Three linked mutations in the promoter region (-780T/G, g.-768T/G, and g.-222A/G) and only two genotypes were identified in two Polish breeds (TTA/TTA and TTA/GGG). Three SNPs in the coding region [g.1599G/A (421aa), g.1626G/A (429aa), and g.1641G/A (434aa)] appeared to be silent substitutions and segregated as two intragene haplotypes: GGG and AAA. Expression analysis showed that the mutations in the promoter region are highly associated with the MEF2A mRNA level in the longissimus dorsi muscle of bulls carrying two different genotypes. The higher MEF2A mRNA level was estimated in the muscle of bulls carrying the TTA/TTA (p<0.01) genotype as compared with those with TTA/GGG. The results obtained suggest that the nucleotide sequence mutation in MEF2A might be useful marker for body growth traits in cattle.