Caveolin 3 gene and mitochondrial tRNA methionin gene in Duchenne muscular dystrophy

Background: It was recently reported that Duchene muscular dystrophy(DMD) patients and mdx mice have elevated levels of caveolin-3 expression in their skeletal muscles. However, it remains unknown whether this increased caveolin-3 levels contribute to the pathogenesis of DMD. Also mitochondrial DNA mutation in the tRNA methionin (tRNA Met) gene has been shown to be associated with muscle weakness, severe exercise intolerance, lactic acidosis and growth retardation. Since DMD is X-linked maternally inherited disease, mitochondrial mutation in tRNA (Met) gene can be suspected to be the cause for the inefficient splicing of dystrophin gene during its expression and can be implicated as the cause of dystrophin inactive protein. Aim of the Work: The aim of the present study is to investigate whether mutations in caveolin gene leads to its increased expression and/or mutation in the tRNA (Met) gene can be associated with DMD pathogenesis. Patients and Methods: Expression of caveolin mRNA by RT-PCR and mutations in caveolin gene and tRNA (Met) gene were measured in 28 patients presented with DMD symptoms using the single strand conformation polymorphism assay (SSCP). Results: Results gave further proof to decreased expression of inducible nitric oxide synthase (iNOS) mRNA, which leads to increased expression in caveolin3 mRNA in lymphocytes of DMD patients compared to controls. However using SSCP, there was no evidence for tRNA (Met) gene mutation among DMD patients and only one patient presented a mutation in the caveolin gene compared to controls. Conclusion: There is an inverse relation between iNOS and Caveolin 3 in lymphocytes of DMD patients compared to controls. However, Caveolin 3 gene mutation is excluded as the main cause of increased caveolin gene expression. Also, there was no evidence for tRNA (Met) gene mutation among DMD patients.Keywords: mRNA, duchene muscular dystrophy (DMD), inducible nitric oxide synthase (iNOS) mRNA, mitochondrial DNA

Characterization of DNA Sequences Required for the CcrAB-Mediated Integration of Staphylococcal Cassette Chromosome mec, a Staphylococcus aureus Genomic Island

The mobile element staphylococcal cassette chromosome mec (SCCmec), which carries mecA, the gene responsible for methicillin resistance in staphylococci, inserts into the chromosome at a specific site, attB, mediated by serine recombinases, CcrAB and CcrC, encoded on the element. This study sought to determine the sequence specificity for CcrB DNA binding in vitro and for CcrAB-mediated SCCmec insertion in vivo. CcrB DNA binding, as assessed in vitro by electrophoretic mobility shift assay (EMSA), revealed that a 14-bp sequence (CGTATCATAAGTAA; the terminal sequence of the orfX gene) was the minimal requirement for binding, containing an invariant sequence (TATCATAA) found in all chromosomal (attB) and SCCmec (attS) integration sites. The sequences flanking the minimal attB and attS binding sites required for insertion in vivo were next determined. A plasmid containing only 37 bp of attS and flanking sequences was required for integration into the attB site at 92% efficiency. In contrast, at least 200 bp of sequence within orfX, 5′ to the attB core, and 120 bp of specific sequence 3′ to the orfX stop site and attB core were required for the highest insertion frequency. Finally, an attS-containing plasmid was inserted into wild-type Staphylococcus aureus strains without integrated SCCmec (methicillin susceptible) at various frequencies which were determined both by sequences flanking the att site and by the presence of more than one att site on either the chromosome or the integration plasmid. This sequence specificity may play a role in the epidemiology of SCCmec acquisition