Effects of N-Acetylcysteine on the reproductive performance, oxidative stress and RNA sequencing of Nubian goats.

N-acetylcysteine (NAC) has been found to enhance the protective ability of cells to counter balance oxidative stress and inflammation. To investigate the effects of dietary NAC supplementation on the reproductive performance of goats, the reproductive performance and endometrial transcriptome of goats fed with diets with NAC (NAC group) and without NAC supplementation (control group) were compared. Results showed that the goats fed with 0.03% and 0.05% NAC had similar litter size, birth weight, nitric oxide (NO), sex hormones and amino acids levels compared with the goats of the control group. However, feeding with 0.07% NAC supplementation from day 0 to day 30 of gestation remarkably increased the litter size of goats. The goats of the 0.07% NAC group presented increased levels of NO relative to the control group, but their sex hormones and amino acids showed no differences. Comparative transcriptome analysis identified 207 differentially expressed genes (DEGs) in the endometrium between the control and the 0.07% NAC groups. These DEGs included 146 upregulated genes and 61 downregulated genes in the 0.07% NAC group. They were primarily involved in the cellular response to toxic substances, oxidoreductase activity, immune receptor activity, signalling receptor binding, cytokine-cytokine receptor interactions, PI3K-Akt signalling pathway and PPAR signalling pathway. In conclusion, results showed that dietary 0.07% NAC supplementation exerted a beneficial effect on the survival of goat embryos at the early pregnancy stage. Such positive outcome might be due to the increased NO production and affected expression of genes involved in the anti-inflammation pathways of the endometrium.

Identification of HMGA2 inhibitors by AlphaScreen-based ultra-high-throughput screening assays.

The mammalian high mobility group protein AT-hook 2 (HMGA2) is a multi-functional DNA-binding protein that plays important roles in tumorigenesis and adipogenesis. Previous results showed that HMGA2 is a potential therapeutic target of anticancer and anti-obesity drugs by inhibiting its DNA-binding activities. Here we report the development of a miniaturized, automated AlphaScreen ultra-high-throughput screening assay to identify inhibitors targeting HMGA2-DNA interactions. After screening the LOPAC1280 compound library, we identified several compounds that strongly inhibit HMGA2-DNA interactions including suramin, a century-old, negatively charged antiparasitic drug. Our results show that the inhibition is likely through suramin binding to the "AT-hook" DNA-binding motifs and therefore preventing HMGA2 from binding to the minor groove of AT-rich DNA sequences. Since HMGA1 proteins also carry multiple "AT-hook" DNA-binding motifs, suramin is expected to inhibit HMGA1-DNA interactions as well. Biochemical and biophysical studies show that charge-charge interactions and hydrogen bonding between the suramin sulfonated groups and Arg/Lys residues play critical roles in the binding of suramin to the "AT-hook" DNA-binding motifs. Furthermore, our results suggest that HMGA2 may be one of suramin's cellular targets.

Detection of preQ0 deazaguanine modifications in bacteriophage CAjan DNA using Nanopore sequencing reveals same hypermodification at two distinct DNA motifs.

In the constant evolutionary battle against mobile genetic elements (MGEs), bacteria have developed several defense mechanisms, some of which target the incoming, foreign nucleic acids e.g. restriction-modification (R-M) or CRISPR-Cas systems. Some of these MGEs, including bacteriophages, have in turn evolved different strategies to evade these hurdles. It was recently shown that the siphophage CAjan and 180 other viruses use 7-deazaguanine modifications in their DNA to evade bacterial R-M systems. Among others, phage CAjan genome contains a gene coding for a DNA-modifying homolog of a tRNA-deazapurine modification enzyme, together with four 7-cyano-7-deazaguanine synthesis genes. Using the CRISPR-Cas9 genome editing tool combined with the Nanopore Sequencing (ONT) we showed that the 7-deazaguanine modification in the CAjan genome is dependent on phage-encoded genes. The modification is also site-specific and is found mainly in two separate DNA sequence contexts: GA and GGC. Homology modeling of the modifying enzyme DpdA provides insight into its probable DNA binding surface and general mode of DNA recognition.

Binding of anticancer drug adriamycin to parallel G-quadruplex DNA [d-(TTAGGGT)]4 comprising human telomeric DNA leads to thermal stabilization: A multiple spectroscopy study.

Adriamycin is known to exert its anti cancer action by inhibiting DNA duplication, RNA transcription and topoisomerase-II enzyme action. Recent findings of its binding to G-quadruplex DNA resulting in telomere dysfunction indicated multiple strategies of its action. The interaction of anticancer drug adriamycin with parallel stranded inter molecular G-quadruplex DNA [d-(TTAGGGT)]4 comprising human telomeric DNA sequence TTAGGG was investigated by absorption, fluorescence, circular dichroism and nuclear magnetic resonance spectroscopy to understand mode of their interaction. The adriamycin binds as monomer to G-quadruplex DNA with affinity (Kb1 = 9.8x105 M-1 and Kb2 = 6.7x105 M-1 ) higher than that reported for daunomycin, at two independent sites, mainly in terminal stacking and groove binding modes. The bound complex formed as a result of specific interactions induces thermal stabilization of DNA by 12.5-28.1°C, which is likely to hinder telomere association with telomerase enzyme and contribute significantly to adriamycin-induced apoptosis in cancer cell lines. The findings have therapeutic potential towards drug designing by way of altering substituent groups on anthracyclines to enhance efficacy using additional mechanism of targeting pathway of telomere maintenance by disrupting telomerase association with telomeres.

Epigenomic promoter alterations predict for benefit from immune checkpoint inhibition in metastatic gastric cancer.

BACKGROUND: Utilization of alternative transcription start sites through alterations in epigenetic promoter regions causes reduced expression of immunogenic N-terminal peptides, which may facilitate immune evasion in early gastric cancer. We hypothesized that tumors with high alternate promoter utilization would be resistant to immune checkpoint inhibition in metastatic gastric cancer. PATIENTS AND METHODS: Two cohorts of patients with metastatic gastric cancer treated with immunotherapy were analyzed. The first cohort (N = 24) included patients treated with either nivolumab or pembrolizumab. Alternate promoter utilization was measured using the NanoString® (NanoString Technologies, Seattle, WA, USA) platform on archival tissue samples. The second cohort was a phase II clinical trial of patients uniformly treated with pembrolizumab (N = 37). Fresh tumor biopsies were obtained, and transcriptomic analysis was carried out on RNAseq data. Alternate promoter utilization was correlated to T-cell cytolytic activity, objective response rate and survival. RESULTS: In the first cohort 8 of 24 (33%) tumors were identified to have high alternate promoter utilization (APhigh), and this was used to define the APhigh tertile of the second cohort (13 APhigh of 37). APhigh tumors exhibited decreased markers of T-cell cytolytic activity and lower response rates (8% versus 42%, P = 0.03). Median progression-free survival was lower in the APhigh group (55 versus 180 days, P = 0.0076). In multivariate analysis, alternative promoter utilization was an independent predictor of immunotherapy survival [hazard ratio 0.29, 95% confidence interval 0.099-0.85, P = 0.024). Analyzing tumoral evolution through paired pre-treatment and post-treatment biopsies, we observed consistent shifts in alternative promoter utilization rate associated with clinical response. CONCLUSION: A substantial proportion of metastatic gastric cancers utilize alternate promoters as a mechanism of immune evasion, and these tumors may be resistant to anti-PD1 immune checkpoint inhibition. Alternate promoter utilization is thus a potential mechanism of resistance to immune checkpoint inhibition, and a novel predictive biomarker for immunotherapy. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT#02589496.

Shiga Toxin as a Potential Trigger of CFHR1 Deletion-Associated Thrombotic Microangiopathy.

Thrombotic microangiopathy (TMA) may result from a variety of clinical conditions, including thrombotic thrombocytopenic purpura, Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome and complement-mediated hemolytic uremic syndrome. Thrombocytopenic purpura is diagnosed when ADAMTS13 is <10%, while a diagnosis of Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome is made with the evidence of infection by Shiga toxin-producing Escherichia coli. Diagnosis of complement-mediated hemolytic uremic syndrome is not dependent on a specific laboratory test and is a diagnosis of exclusion. TMA is a rare disease and finding individuals that have more than 1 concurrent etiology leading to TMA is even more rare. Here we describe the presentation and management of an individual with CFHR1 deletion-associated TMA also found to have a positive stool Shiga toxin. We discuss the significance of Shiga toxin in serving as a trigger for development of TMA in an individual predisposed to development of TMA due to presence of a homozygous deletion in CFHR1.

Dietary genistein supplementation for breeders and their offspring improves the growth performance and immune function of broilers.

Genistein (GEN) is mainly extracted from soy plants and has potential functions as an antioxidant and in promoting immune function and growth. This study evaluated the effects of feeding breeders and their offspring dietary GEN on the immune function and growth performance of broiler chicks. Breeders were assigned to a control diet or GEN diet (control diet +400 mg/kg GEN), and their offspring were fed a control diet or GEN diet (control diet +40 mg/kg GEN). GEN treatment increased the body weight gain, tibial length, tibial width and slaughter performance of broilers and decreased the feed conversion ratio. The treatment also affected skeletal muscle myosin assembly and growth and increased growth hormone levels and IGF-I and IGFBP1 expression. Following GEN treatment, antigen processing and presentation, macrophage activation, B lymphocyte, NK cell and helper T cell proliferation, and CD4+ T lymphocyte differentiation all increased significantly. Increases were also observed in IgM and IgG concentrations, antibody titers, and antioxidant capacity. In addition, GEN treatment activated the Toll-like receptor signaling pathway and MAPK cascade signaling pathway. In summary, dietary GEN supplementation for breeders and their offspring can improve the growth performance and immune function of broiler chicks.

16S Ribosomal RNA Gene Sequencing to Evaluate the Effects of 6 Commonly Prescribed Antibiotics.

INTRODUCTION: The rapid antibiotic sensitivity test (RAST) is a novel in-office culture and sensitivity system for endodontic infections. The purpose of this research was to validate the RAST system as a viable, in-office alternative to antibiotic sensitivity testing using turbidity to determine antibiotic sensitivities of endodontic infections. METHODS: Aspirates were taken from the root canals of 9 necrotic human teeth at the initiation of root canal therapy. These samples were cultured in the RAST medium, and antibiotic sensitivity to 6 antibiotics was tested. Further analysis was performed using 16S ribosomal RNA (rRNA) gene sequencing. RESULTS: Thirty-one bacterial phyla were identified as well as 2 phyla of the kingdom Archaea. Augmentin (Dr. Reddy's Laboratories Ltd, Hyderabad, India) and ampicillin performed identically at 24 hours, inhibiting turbidity in 100% of the samples. At 48 hours in anaerobic conditions, Augmentin outperformed ampicillin by 13%. Ciprofloxacin was the least efficacious antibiotic. At 48 hours, only 22% of anaerobic ciprofloxacin cultures affectively inhibited bacterial growth. CONCLUSIONS: The RAST medium is a viable in-office alternative to antibiotic susceptibility testing in an off-site laboratory. It is able to support the growth of a wide variety of microorganisms in both aerobic and anaerobic environments, and, in combination with 16S rRNA gene sequencing, it led to the identification of a new archaebacterial phylum, Crenarchaeota, as part of the endodontic infection microbiome.

Hydrogen peroxide activated quinone methide precursors with enhanced DNA cross-linking capability and cytotoxicity towards cancer cells.

Quinone methide (QM) formation induced by endogenously generated H2O2 is attractive for biological and biomedical applications. To overcome current limitations due to low biological activity of H2O2-activated QM precursors, we are introducing herein several new arylboronates with electron donating substituents at different positions of benzene ring and/or different neutral leaving groups. The reaction rate of the arylboronate esters with H2O2 and subsequent bisquinone methides formation and DNA cross-linking was accelerated with the application of Br as a leaving group instead of acetoxy groups. Additionally, a donating group placed meta to the nascent exo-methylene group of the quinone methide greatly improves H2O2-induced DNA interstrand cross-link formation as well as enhances the cellular activity. Multiple donating groups decrease the stability and DNA cross-linking capability, which lead to low cellular activity. A cell-based screen demonstrated that compounds 2a and 5a with a OMe or OH group dramatically inhibited the growth of various tissue-derived cancer cells while normal cells were less affected. Induction of H2AX phosphorylation by these compounds in CLL lymphocytes provide evidence for a correlation between cell death and DNA damage. The compounds presented herein showed potent anticancer activities and selectivity, which represent a novel scaffold for anticancer drug development.

Metal-mediated Epigenetic Regulation of Gene Expression.

Epigenetics is the study of heritable changes in gene expression that occur without alterations in the DNA sequence. Several studies have shown that environmental chemicals can alter epigenetic modifications, including histone modifications and DNA methylation. Environmental chemicals may show toxic effects via epigenetic mechanism-regulated changes in gene expression. Previously, we reported that zinc treatment rapidly decreased Lys(4)-trimethylated and Lys(9)-acetylated histone H3 in the metallothionein (MT) promoter, and also decreased total histone H3. The chromatin structure in the MT promoter may be locally disrupted by zinc-induced nucleosome removal. We also showed that chromium (VI) inhibited MT gene transcription by modifying the transcription potential of the co-activator p300. MT is a small cysteine-rich protein that is active in zinc homeostasis, cadmium detoxification, and protection against reactive oxygen species. Epigenetic changes might influence the cytoprotective function of the MT gene. In this review, I briefly summarize the results of previous studies and discuss the mechanisms and toxicological significance of metal-mediated epigenetic modifications.

Cumulative Impact of Polychlorinated Biphenyl and Large Chromosomal Duplications on DNA Methylation, Chromatin, and Expression of Autism Candidate Genes.

Rare variants enriched for functions in chromatin regulation and neuronal synapses have been linked to autism. How chromatin and DNA methylation interact with environmental exposures at synaptic genes in autism etiologies is currently unclear. Using whole-genome bisulfite sequencing in brain tissue and a neuronal cell culture model carrying a 15q11.2-q13.3 maternal duplication, we find that significant global DNA hypomethylation is enriched over autism candidate genes and affects gene expression. The cumulative effect of multiple chromosomal duplications and exposure to the pervasive persistent organic pollutant PCB 95 altered methylation of more than 1,000 genes. Hypomethylated genes were enriched for H2A.Z, increased maternal UBE3A in Dup15q corresponded to reduced levels of RING1B, and bivalently modified H2A.Z was altered by PCB 95 and duplication. These results demonstrate the compounding effects of genetic and environmental insults on the neuronal methylome that converge upon dysregulation of chromatin and synaptic genes.

Transition State Structure of RNA Depurination by Saporin L3.

Saporin L3 from the leaves of the common soapwort is a catalyst for hydrolytic depurination of adenine from RNA. Saporin L3 is a type 1 ribosome inactivating protein (RIP) composed only of a catalytic domain. Other RIPs have been used in immunotoxin cancer therapy, but off-target effects have limited their development. In the current study, we use transition state theory to understand the chemical mechanism and transition state structure of saporin L3. In favorable cases, transition state structures guide the design of transition state analogues as inhibitors. Kinetic isotope effects (KIEs) were determined for an A14C mutant of saporin L3. To permit KIE measurements, small stem-loop RNAs that contain an AGGG tetraloop structure were enzymatically synthesized with the single adenylate bearing specific isotopic substitutions. KIEs were measured and corrected for forward commitment to obtain intrinsic values. A model of the transition state structure for depurination of stem-loop RNA (5'-GGGAGGGCCC-3') by saporin L3 was determined by matching KIE values predicted via quantum chemical calculations to a family of intrinsic KIEs. This model indicates saporin L3 displays a late transition state with the N-ribosidic bond to the adenine nearly cleaved, and the attacking water nucleophile weakly bonded to the ribosyl anomeric carbon. The transition state retains partial ribocation character, a feature common to most N-ribosyl transferases. However, the transition state geometry for saporin L3 is distinct from ricin A-chain, the only other RIP whose transition state is known.

Draft genome sequence of Inquilinus limosus strain MP06, a multidrug-resistant clinical isolate

The bacterium, Inquilinus limosus, with its remarkable antimicrobial multiresistant profile, has increasingly been isolated in cystic fibrosis patients. We report draft genome sequence of a strain MP06, which is of considerable interest in elucidating the associated mechanisms of antibiotic resistance in this bacterium and for an insight about its persistence in airways of these patients.

Sequence-dependent thymine dimer formation and photoreversal rates in double-stranded DNA.

The kinetics of thymine-thymine cyclobutane pyrimidine dimer (TT-CPD) formation was studied at 23 thymine-thymine base steps in two 247-base pair DNA sequences irradiated at 254 nm. Damage was assayed site-specifically and simultaneously on both the forward and reverse strands by detecting emission from distinguishable fluorescent labels at the 5'-termini of fragments cleaved at CPD sites by T4 pyrimidine dimer glycosylase and separated by gel electrophoresis. The total DNA strand length of nearly 1000 bases made it possible to monitor damage at all 9 tetrads of the type XTTY, where X and Y are non-thymine bases. TT-CPD yields for different tetrads were found to vary by as much as an order of magnitude, but similar yields were observed at all instances of a given tetrad. Kinetic analysis of CPD formation at 23 distinct sites reveals that both the formation and reversal photoreactions depend sensitively on the identity of the nearest-neighbour bases on the 5' and the 3' side of a photoreactive TT base step. The lowest formation and reversal rates occur when two purine bases flank a TT step, while the highest formation and reversal rates are observed for tetrads with at least one flanking C. Overall, the results show that the probabilities of CPD formation and photoreversal depend principally on interactions with nearest-neighbour bases.

The interaction of cisplatin with a human telomeric DNA sequence containing seventeen tandem repeats.

The anti-tumour drug, cisplatin, preferentially forms adducts at G-rich DNA sequences. Telomeres are found at the ends of chromosomes and, in humans, contain the repeated DNA sequence (GGGTTA)(n) that is expected to be targeted by cisplatin. Using a plasmid clone with 17 tandem telomeric repeats, (GGGTTA)(17), the DNA sequence specificity of cisplatin was investigated utilising the linear amplification procedure that pin-pointed the precise sites of cisplatin adduct formation. This procedure used a fluorescently labelled primer and capillary electrophoresis with laser-induced fluorescence detection to determine the DNA sequence specificity of cisplatin. This technique provided a very accurate analysis of cisplatin-DNA adduct formation in a long telomeric repeat DNA sequence. The DNA sequence specificity of cisplatin in a long telomeric tandem repeat has not been previously reported. The results indicated that the 3'-end of the G-rich strand of the telomeric repeat was preferentially damaged by cisplatin and this suggests that the telomeric DNA repeat has an unusual conformation.

The DNA sequence specificity of bleomycin cleavage in telomeric sequences in human cells.

Bleomycin is an antibiotic drug that is widely used in cancer chemotherapy. Telomeres are located at the ends of chromosomes and comprise the tandemly repeated DNA sequence (GGGTTA)( n ) in humans. Since bleomycin cleaves DNA at 5'-GT dinucleotide sequences, telomeres are expected to be a major target for bleomycin cleavage. In this work, we determined the DNA sequence specificity of bleomycin cleavage in telomeric sequences in human cells. This was accomplished using a linear amplification procedure, a fluorescently labelled oligonucleotide primer and capillary gel electrophoresis with laser-induced fluorescence detection. This represents the first occasion that the DNA sequence specificity of bleomycin cleavage in telomeric DNA sequences in human cells has been reported. The bleomycin DNA sequence selectivity was mainly at 5'-GT dinucleotides, with lesser amounts at 5'-GG dinucleotides. The cellular bleomycin telomeric DNA damage was also compared with bleomycin telomeric damage in purified human genomic DNA and was found to be very similar. The implications of these results for the understanding of bleomycin's mechanism of action in human cells are discussed.

The thermodynamics of translesion DNA synthesis past major adducts of enantiomeric analogues of antitumor cisplatin.

The Pt(II)-coordination complex [PtCl(2)(DAB)] (DAB=2,3-diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged-DNA-processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2-d(GG) intrastrand cross-link formed by the R,R and S,S enantiomers of [Pt(DAB)](2+) in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication-bypass past 1,2-d(GG) adducts of the [Pt(DAB)](2+) enantiomers. In the sequence TGGT, the 1,2-d(GG) intrastrand cross-links that were formed by the enantiomeric pairs of [Pt(DAB)](2+) inhibited DNA polymerization in a chirality-dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt-d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum-coordinated compounds on the processing of these lesions by damaged-DNA processing-enzymes.

Age-related changes in the central auditory system: comparison of D-galactose-induced aging rats and naturally aging rats.

One of the most common complaints among aging individuals is difficulty in understanding speech in a compromised listening environment, such as when background noise is present. Age-related hearing loss (presbycusis) is associated with both peripheral and central neural processing deficits, as it occurs even in those with only a mild peripheral hearing impairment. The current study was designed to investigate potential causative mechanisms of this impairment by using a rat model in which presbycusis is inducible by administration of D-galactose (D-gal). One group of these rats was injected subcutaneously with 150 mg D-gal daily for 8 weeks, while control animals received vehicle only. These groups were compared to naturally aged rats (24 months) that had received no other treatment. Central auditory function of the three groups was evaluated by measuring the auditory brainstem response (ABR) and middle latency response (MLR). A TaqMan real time PCR assay was used to quantify a 4834-bp deletion in the mitochondrial DNA (mtDNA) of the auditory cortex (AC), inferior colliculus (IC) and cochlear nucleus (CN). We assessed changes in lipid peroxidation levels and apoptosis rates, and examined pathological changes corresponding to D-gal-induced aging and natural aging. Both groups of aged rats exhibited delayed ABR latencies (III, IV, V), MLR Pa latency, and I-IV interpeak latency. Moreover, increased mtDNA 4834 bp deletion rates, lipid peroxidation levels, rates of neuronal apoptosis and neurodegenerative changes in the AC, IC and CN were similar among the D-gal induced and NA rats. However, the threshold of ABR in the D-gal group showed no significant change from the control group. These observations suggest that age-related central auditory dysfunction and its corresponding pathological changes are present in both naturally aging rats and the D-gal mimetic aging model. Oxidative stress, large-scale mtDNA 4834 bp deletion, and apoptosis are likely to be involved in the progressive weakening of the central auditory system associated with the aging process.

Isolation and characterization of enantioselective DNA aptamers for ibuprofen.

Single stranded DNA aptamers that can bind to ibuprofen, a widely used anti-inflammation drug, were selected from random DNA library of 10(15) nucleotides by FluMag-SELEX process. Five different sequences were selected and their enantioselectivity and affinity were characterized. Three out of five aptamer candidates did not show any affinity to (S)-ibuprofen, but only to racemic form of ibuprofen, suggesting that they are (R)-ibuprofen specific aptamers. Another two aptamer candidates showed affinity to both racemic form and (S)-ibuprofen, which were considered as (S)-ibuprofen specific aptamers. The affinity of five ssDNA aptamers isolated was in a range of 1.5-5.2microM. In addition, all of these five aptamers did not show any affinity to analogues of ibuprofen in its profen's group (fenoprofen, flubiprofen, and naproxen) and the antibiotics of oxytetracycline, another control.

Comparative analysis of antisense oligonucleotide sequences targeting exon 53 of the human DMD gene: Implications for future clinical trials.

Duchenne muscular dystrophy (DMD) is caused by the lack of functional dystrophin protein, most commonly as a result of a range of out-of-frame mutations in the DMD gene. Modulation of pre-mRNA splicing with antisense oligonucleotides (AOs) to restore the reading frame has been demonstrated in vitro and in vivo, such that truncated but functional dystrophin is expressed. AO-induced skipping of exon 51 of the DMD gene, which could treat 13% of DMD patients, has now progressed to clinical trials. We describe here the methodical, cooperative comparison, in vitro (in DMD cells) and in vivo (in a transgenic mouse expressing human dystrophin), of 24 AOs of the phosphorodiamidate morpholino oligomer (PMO) chemistry designed to target exon 53 of the DMD gene, skipping of which could be potentially applicable to 8% of patients. A number of the PMOs tested should be considered worthy of development for clinical trial.