The nucleotide sequence, structure, and preliminary studies on the transcriptional regulation of the bovine alpha skeletal actin gene

Generation of an efficient artificial promoter of bovine skeletal muscle α-actin gene (ACTA1) through addition of cis-acting element

The promoter of skeletal muscle α-actin gene (ACTA1) is highly muscle specific. The core of the bovine ACTA1 promoter extends from +29 to -233, about 262 base pairs (bp), which is sufficient to activate transcription in bovine muscle satellite cells. In this study, analysis by PCR site-specific mutagenesis showed that the cis-acting element SRE (serum response element binding factor) was processed as a transcriptional activator. In order to enhance the bovine ACTA1 promoter's activity, we used a strategy to modify it. We cloned a fragment containing three SREs from the promoter of ACTA1, and then one or two clones were linked upstream of the core promoter (262 bp) of ACTA1. One and two clones increased the activity of the ACTA1 promoter 3-fold and 10-fold, respectively, and maintained muscle tissue specificity. The modified promoter with two clones could increase the level of ACTA1 mRNA and protein 4-fold and 1.1-fold, respectively. Immunofluorescence results showed that green fluorescence of ACTA1 increased. Additionally, the number of total muscle microfilaments increased. These genetically engineered promoters might be useful for regulating gene expression in muscle cells and improving muscle mass in livestock.

The Early-Onset Myocardial Infarction Associated PHACTR1 Gene Regulates Skeletal and Cardiac Alpha-Actin Gene Expression

The phosphatase and actin regulator 1 (PHACTR1) locus is a very commonly identified hit in genome-wide association studies investigating coronary artery disease and myocardial infarction (MI). However, the function of PHACTR1 in the heart is still unknown. We characterized the mechanisms regulating Phactr1 expression in the heart, used adenoviral gene delivery to investigate the effects of Phactr1 on cardiac function, and analyzed the relationship between MI associated PHACTR1 allele and cardiac function in human subjects. Phactr1 mRNA and protein levels were markedly reduced (60%, P<0.01 and 90%, P<0.001, respectively) at 1 day after MI in rats. When the direct myocardial effects of Phactr1 were studied, the skeletal α-actin to cardiac α-actin isoform ratio was significantly higher (1.5-fold, P<0.05) at 3 days but 40% lower (P<0.05) at 2 weeks after adenovirus-mediated Phactr1 gene delivery into the anterior wall of the left ventricle. Similarly, the skeletal α-actin to cardiac α-actin ratio was lower at 2 weeks in infarcted hearts overexpressing Phactr1. In cultured neonatal cardiac myocytes, adenovirus-mediated Phactr1 overexpression for 48 hours markedly increased the skeletal α-actin to cardiac α-actin ratio, this being associated with an enhanced DNA binding activity of serum response factor. Phactr1 overexpression exerted no major effects on the expression of other cardiac genes or LV structure and function in normal and infarcted hearts during 2 weeks’ follow-up period. In human subjects, MI associated PHACTR1 allele was not associated significantly with cardiac function (n = 1550). Phactr1 seems to regulate the skeletal to cardiac α-actin isoform ratio.

DNA damage, RAD9 and fertility/infertility of Echinococcus granulosus hydatid cysts

Hydatidosis, caused by the larval stage of the platyhelminth parasite Echinococcus granulosus, affects human and animal health. Hydatid fertile cysts are formed in intermediate hosts (human and herbivores) producing protoscoleces, the infective form to canines, at their germinal layers. Infertile cysts are also formed, but they are unable to produce protoscoleces. The molecular mechanisms involved in hydatid cysts fertility/infertility are unknown. Nevertheless, previous work from our laboratory has suggested that apoptosis is involved in hydatid cyst infertility and death. On the other hand, fertile hydatid cysts can resist oxidative damage due to reactive oxygen and nitrogen species. On these foundations, we have postulated that when oxidative damage of DNA in the germinal layers exceeds the capability of DNA repair mechanisms, apoptosis is triggered and hydatid cysts infertility occurs. We describe a much higher percentage of nuclei with oxidative DNA damage in dead protoscoleces and in the germinal layer of infertile cysts than in fertile cysts, suggesting that DNA repair mechanisms are active in fertile cysts. rad9, a conserved gene, plays a key role in cell cycle checkpoint modulation and DNA repair. We found that RAD9 of E. granulosus (EgRAD9) is expressed at the mRNA and protein levels. As it was found in other eukaryotes, EgRAD9 is hyperphosphorylated in response to DNA damage. Our results suggest that molecules involved in DNA repair in the germinal layer of fertile hydatid cysts and in protoscoleces, such as EgRAD9, may allow preserving the fertility of hydatid cysts in the presence of ROS and RNS.

Increased Body Weight Via Injecting Myogenic Expression Growth Hormone-Releasing Hormone (GHRH) Plasmid DNA into Sheep

The ectopic expression of a sheep growth hormone-releasing hormone (GHRH) from muscle tissues, using a myogenic plasmid expression vector pM-GHRH, has been shown to result in enhanced animal growth. Animal injected with pM-GHRH alone exhibited a daily weight gain rate of 0.84+/-0.02%/d (p < 0.05), while that of the control animal was only 0.73+/-0.04%/d. A more significant growth enhancement was observed in the group treated with pM-GHRH plus 0.25% bupivacaine. The animal displayed a daily weight gain rate of 0.87+/-0.03%/d (p<0.01). In addition, the group treated by pM-GHRH and bupivacaine had higher levels of growth hormone (GH) in their blood (1.18+/-0.33 ng/mL) compared with the group treated by pM-GHRH vector alone (p < 0.05). Evaluation of body composition by dissection and histochemical analysis indicated a significant increase in bulk with no organomegaly or associated pathology. PCR analysis demonstrated that there was little plasmid residue detected in the pM-GHRH treated sheep.

Molecular cloning and sequence of gilthead sea bream (Sparus aurata) alpha-skeletal actin: tissue and developmental expression

In the present study, the Sparus aurata alpha-skeletal actin was cloned from a mixed larvae complementary DNA library. The clone isolated was 1523 bp long with an open reading frame of 1134 bp coding for a 377-amino acid protein. The deduced amino acid sequence of sea bream alpha-actin is identical to Fugu alpha-actin-1. The expression of alpha-actin was initiated at the onset of segmentation. In adult fish, alpha-actin is expressed predominantly in white and red muscle.

Altered molecular response to adrenoreceptor-induced cardiac hypertrophy in Egr-1-deficient mice

Unmanipulated early growth response-1 (Egr-1)-deficient -/- mice have similar heart-to-body weight ratios but express lower amounts of atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), skeletal actin, NGF1-A binding protein (NAB)-2, Sp1, c-fos, c-jun, GATA-4, and Nkx2.5 than +/+ or +/- mice. alpha-MHC, tubulin, and NAB-1 expression was similar. Isoproterenol (Iso) and phenylephrine (PE) infusion into +/+ and -/- mice increased heart weight, ANF, beta-MHC, skeletal actin, Sp1, NAB-2, c-fos, and c-jun expression, but induction in -/- mice was lower. Only Iso + PE-treated +/+ mice showed induction of NAB-1, GATA-4, and Nkx2.5. Foci of fibrosis were found in Iso + PE-treated -/- and +/+ mice. Surprisingly, vehicle-treated -/- mice displayed fibrosis and increased Sp1, skeletal actin, Nkx2.5, and GATA-4 expression without hypertrophy. Minipump removal caused the agonist-treated hearts and gene expression to regress to control or near-control levels. Thus Egr-1 deficiency caused a blunted catecholamine-induced hypertrophy response and increased sensitivity to stress.

Multiple regions of the porcine alpha-skeletal actin gene modulate muscle-specific expression in cell culture and directly injected skeletal muscle

Transcriptional regulation of the porcine alpha-skeletal actin gene was investigated by comparative transient transfection assays in cultured mammalian cells and by direct DNA injection in skeletal muscle. Intron I sequences were necessary to direct high-level, cell-specific porcine alpha-skeletal actin expression in C2C12 myotubes, but they inhibited transcription in skeletal muscle. A 5' distal sequence (-1929 to -550), had enhancer-like activity in C2C12 myotubes and directly injected muscle, and inhibited transcription in Hela cells. In contrast, a central region (-550 to -388) enhanced basal transcription in directly injected muscle, but not in C2C12 myotubes. A distal regulatory element localized to the 3' untranslated region modulated SV40 promoter activity only in cell culture studies. These results suggest that the intragenic and 3' distal regulatory element may be differentially utilized during differentiation and maturation of skeletal muscle. All three regions decreased SV40 promoter activity in Hela cells, suggesting that they play a role in defining tissue-specific expression of porcine alpha-skeletal actin. Furthermore, different regulatory programs of alpha-skeletal actin expression appear to exist in these two experimental systems.

Structure and regulation of the porcine skeletal alpha-actin-encoding gene

The postnatal increase in skeletal alpha-actin (Sk-alpha-Act) synthesis in pigs is due, in part, to increased transcription. To characterize the factors responsible for its transcriptional regulation, we have cloned and determined the nucleotide sequence of a 5.2-kb HindIII genomic DNA fragment which contains the complete coding region of Sk-alpha-Act distributed over seven exons, plus 1.9 kb of 5' flanking region and 0.5 kb of 3' flanking sequence. The major transcription start point (tsp) of Sk-alpha-Act was determined to be 840 bp 5' to the ATG start codon by primer extension and RNase protection analysis. To demonstrate that the Sk-alpha-Act promoter was functional, L6 myoblasts, C2C12 myoblasts and HeLa cells were transfected with a construct (pPSKAFL-CAT) linking the 5' Sk-alpha-Act promoter to the chloramphenicol acetyltransferase reporter gene (cat). Cell lysates from L6 myoblasts, L6 myotubes, C2C12 myoblasts, C2C12 myotubes, and HeLa cells were analyzed for CAT activity. CAT activity was detected only in C2C12 myotubes. Thus, the porcine Sk-alpha-Act promoter is regulated in a developmental and cell-type specific manner.