Dystrophin Orchestrates the Epigenetic Profile of Muscle Cells Via miRNAs

Mammalian musculature is a very robust and dynamic tissue that goes through many rounds of degeneration and regeneration in an individual’s lifetime. There is a biological program that maintains muscle progenitor cells that, when activated, give rise to intermediate myoblast progeny that consequently differentiate into mature muscle cells. Recent works have provided a picture of the role that microRNAs (miRNAs) play in maintaining aspects of this program. Intriguingly, a subset of these miRNAs is de-regulated in muscular dystrophies (MDs), a group of fatal inherited neuromuscular disorders that are often associated with deficiencies in the Dystrophin (Dys) complex. Apparently, transcriptional expression of many of the muscle specific genes and miRNAs is dependent on chromatin state regulated by the Dys–Syn–nNOS pathway. This puts Dystrophin at the epicenter of a highly regulated program of muscle gene expression in which miRNAs help to coordinate networking between multiple phases of muscle maintenance, degeneration, and regeneration. Therefore, understanding the role of miRNAs in physiology of normal and diseased muscle tissue could be useful for future applications in improving the MD therapies and could open new clinical perspectives

New Dystrophin/Dystroglycan interactors control neuron behavior in Drosophila eye

<p>Abstract</p> <p>Background</p> <p>The Dystrophin Glycoprotein Complex (DGC) is a large multi-component complex that is well known for its function in muscle tissue. When the main components of the DGC, Dystrophin (Dys) and Dystroglycan (Dg) are affected cognitive impairment and mental retardation in addition to muscle degeneration can occur. Previously we performed an array of genetic screens using a <it>Drosophila </it>model for muscular dystrophy in order to find novel DGC interactors aiming to elucidate the signaling role(s) in which the complex is involved. Since the function of the DGC in the brain and nervous system has not been fully defined, we have here continued to analyze the DGC modifiers' function in the developing <it>Drosophila </it>brain and eye.</p> <p>Results</p> <p>Given that disruption of <it>Dys </it>and <it>Dg </it>leads to improper photoreceptor axon projections into the lamina and eye neuron elongation defects during development, we have determined the function of previously screened components and their genetic interaction with the DGC in this tissue. Our study first found that mutations in <it>chif, CG34400, Nrk</it>, <it>Lis1, capt </it>and <it>Cam </it>cause improper axon path-finding and loss of <it>SP2353, Grh, Nrk, capt, CG34400, vimar, Lis1 </it>and <it>Cam </it>cause shortened rhabdomere lengths. We determined that <it>Nrk</it>, <it>mbl</it>, <it>capt </it>and <it>Cam </it>genetically interact with <it>Dys </it>and/or <it>Dg </it>in these processes. It is notable that most of the neuronal DGC interacting components encountered are involved in regulation of actin dynamics.</p> <p>Conclusions</p> <p>Our data indicate possible DGC involvement in the process of cytoskeletal remodeling in neurons. The identification of new components that interact with the DGC not only helps to dissect the mechanism of axon guidance and eye neuron differentiation but also provides a great opportunity for understanding the signaling mechanisms by which the cell surface receptor Dg communicates via Dys with the actin cytoskeleton.</p

Paraffin-Embedded and Frozen Sections of Drosophila Adult Muscles

The molecular characterization of muscular dystrophies and myopathies in humans has revealed the complexity of muscle disease and genetic analysis of muscle specification, formation and function in model systems has provided valuable insight into muscle physiology. Therefore, identifying and characterizing molecular mechanisms that underlie muscle damage is critical. The structure of adult Drosophila multi-fiber muscles resemble vertebrate striated muscles 1 and the genetic tractability of Drosophila has made it a great system to analyze dystrophic muscle morphology and characterize the processes affecting muscular function in ageing adult flies 2. Here we present the histological technique for preparing paraffin-embedded and frozen sections of Drosophila thoracic muscles. These preparations allow for the tissue to be stained with classical histological stains and labeled with protein detecting dyes, and specifically cryosections are ideal for immunohistochemical detection of proteins in intact muscles. This allows for analysis of muscle tissue structure, identification of morphological defects, and detection of the expression pattern for muscle/neuron-specific proteins in Drosophila adult muscles. These techniques can also be slightly modified for sectioning of other body parts

Sequence Specificity of BAL 31 Nuclease for ssDNA Revealed by Synthetic Oligomer Substrates Containing Homopolymeric Guanine Tracts

Background: The extracellular nuclease from Alteromonas espejiana, BAL 31 catalyzes the degradation of single-stranded and linear duplex DNA to 59-mononucleotides, cleaves negatively supercoiled DNA to the linear duplex form, and cleaves duplex DNA in response to the presence of apurinic sites. Principal Findings: In this work we demonstrate that BAL 31 activity is affected by the presence of guanine in singlestranded DNA oligomers. Specifically, nuclease activity is shown to be affected by guanine’s presence in minimal homopolymeric tracts in the middle of short oligomer substrates and also by its presence at the 39 end of ten and twenty base oligomers. GNC rich regions in dsDNA are known to cause a decrease in the enzyme’s nuclease activity which has been attributed to the increased thermal stability of these regions, thus making it more difficult to unwind the strands required for enzyme access. Our results indicate that an additional phenomenon could be wholly or partly responsible for the loss of activity in these GNC rich regions. Thus the presence of a guanine tract per se impairs the enzyme’s functionality, possibly due to the tract’s bulky nature and preventing efficient progression through the active site. Conclusions: This study has revealed that the general purpose BAL 31 nuclease commonly used in molecular genetics exhibits a hithertofore non-characterized degree of substrate specificity with respect to single-stranded DNA (ssDNA

Changes in Dry State Hemoglobin over Time Do Not Increase the Potential for Oxidative DNA Damage in Dried Blood

BACKGROUND: Hemoglobin (Hb) is the iron-containing oxygen transport protein present in the red blood cells of vertebrates. Ancient DNA and forensic scientists are particularly interested in Hb reactions in the dry state because both regularly encounter aged, dried bloodstains. The DNA in such stains may be oxidatively damaged and, in theory, may be deteriorated by the presence of Hb. To understand the nature of the oxidative systems potentially available to degrade DNA in the presence of dried Hb, we need to determine what molecular species Hb forms over time. These species will determine what type of iron (i.e. Fe(2+)/Fe(3+)/Fe(4+)) is available to participate in further chemical reactions. The availability of "free" iron will affect the ability of the system to undergo Fenton-type reactions which generate the highly reactive hydroxyl radical (OH*). The OH* can directly damage DNA. METHODOLOGY/PRINCIPAL FINDINGS: Oxygenated Hb (oxyHb) converts over time to oxidized Hb (metHb), but this happens more quickly in the dry state than in the hydrated state, as shown by monitoring stabilized oxyHb. In addition, dry state oxyHb converts into at least one other unknown species other than metHb. Although "free" iron was detectable as both Fe(2+) and Fe(3+) in dry and hydrated oxyHb and metHb, the amount of ions detected did not increase over time. There was no evidence that Hb becomes more prone to generating OH* as it ages in either the hydrated or dry states. CONCLUSIONS: The Hb molecule in the dried state undergoes oxidative changes and releases reactive Fe(II) cations. These changes, however, do not appear to increase the ability of Hb to act as a more aggressive Fenton reagent over time. Nevertheless, the presence of Hb in the vicinity of DNA in dried bloodstains creates the opportunity for OH*-induced oxidative damage to the deoxyribose sugar and the DNA nucleobases

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

The Biochemical Reactions Of Dry State Dna

The biochemistry of dry state DNA is of interest to the fields of forensics, ancient DNA, and DNA storage. The exact chemical nature of the degradation of the DNA molecule in the dry state has not been studied prior. If determined what chemical changes the DNA molecule undergoes, to what degree and in what time frame then protocols can be implemented to bypass the impact of this damage or to repair it when necessary. It is suspected that similar reactions occur to the dry state DNA molecule as does to the hydrated molecule. It cannot be assumed, however that these types of chemical processes occur to the same extent and at the same rates. In general the generic process of hydrolysis encompasses two important reactions, that of deamination and of base loss from the 2’-deoxyribose backbone. Base loss is believed to ultimately lead to chain scission. It is also suspect that reactive oxygen species (ROS) have an important role in the chemistry associated with DNA. Species such as hydroxyl radicals (OH•) and singlet oxygen (1O2) can lead to strand scissions and chemically modified bases. Throughout this project various techniques were used to determine damage to DNA and its molecular constituents under conditions leading to hydrolytic and oxidative damage. Novel techniques used in this study include ionpairing chromatography and denaturing HPLC (DHPLC) to measure glycosidic bond cleavage and strand breaks. The extent to which the macromolecule haemoglobin (Hb) can lead to oxidative damage of DNA in dried blood stains by acting as a Fenton chemistry catalyst was evaluated. Additionally the enzymatic activity of the extracellular nuclease from Alteromonas espejiana, BAL 31 was studied as it pertains to the degradation of single-stranded short homopolymeric oligonucleotides. This study serves as the basis for future, more in depth experimentation into the more specific nature of dry state DNA biochemistry. It was found that to a large extent the same degradation reactions (base hydrolysis, base modifications, and strand breaks) do occur in the dry state as in the hydrated state when heat and UV radiation are used as energy sources. Reaction rates indicate that base hydrolysis and deamination occur much more slowly, yet have the same energies of activation in both states. Single strand breaks of dry state duplex DNA occur with a half life of 24 ± 2 days and appears to occur in a mechanistic manner which could be of interest when attempting to repair such damage. In addition, base loss alone does not correlate with the extent of single strand breaks detected. Thermodynamic data can lead to the conclusion that DNA degradation in both dry and hydrated states is not a spontaneous process. It is also concluded that though the Hb molecule undergoes oxidative changes over time, these changes do not impact its ability to become a more aggressive Fenton reagent. However, the presence of Hb in the vicinity of DNA does create the opportunity for OH•induced damage to the deoxyribose sugar, and most likely the DNA bases themselves. This study also reveals that the general purpose BAL 31 nuclease commonly used in molecular genetics exhibits a hithertofore non-characterized degree of substrate specificity with respect to single-stranded DNA oligomers. Specifically, BAL 31 nuclease activity was found to be affected by the presence of guanine in ssDNA oligomers

Hydrolysis Of Dna And Its Molecular Components In The Dry State

The biochemistry of dry state DNA is of interest to the field of forensic biology. The precise chemical nature of the hydrolytic degradation products of the DNA molecule in the dry state has not been previously investigated in detail. In this study we found that the mechanistic chemistry of DNA hydrolysis appears to be the same for the hydrated and dry states. The thermodynamic parameters are also similar in both states and the activation energies for base hydrolysis are indistinguishable. The principal difference between the two states is the rate at which hydrolytic degradation occurs. The duplex configuration of dry state DNA offers much more protection for the molecule than is offered in single strand and nucleotide species. Single strand breaks of dry state duplex DNA occur with a half life of 24 ± 2 days at 65 °C and appear to occur in a mechanistic manner. © 2009 Elsevier Ireland Ltd. All rights reserved

All data comprise an average of three samples.

<p>(A) Spectra of hydrated Hb at various time periods where it is evident that the oxyHb is oxidizing to primarily metHb. (B) Concentration of oxyHb (▪), metHb (•), and hemichromes (▴) from hydrated Hb incubated over a 2200 hour time period in ambient conditions. (C) Spectra of dry Hb at various time periods where it is evident that the oxyHb is oxidizing to not only metHb, but what is suspected to be hemichromes. (D) Concentrations of oxyHb (▪), metHb (•), and hemichromes (▴) from dry Hb incubated over a 2200 hour time period in ambient conditions.</p

Hydrolysis of homodecameric oligomers.

<p>C₁₀, A₁₀, T₁₀, and G₁₀ were incubated at 37°C with 1 U, 0.5 U, and 0 U of BAL 31. The relative hydrolysis efficacy of each homopolymeric oligomer is indicated by the percentage recovery of their constituent 5′dNMPs over time (3–72 h). Incubation at 30°C gave similar results.</p