Lucy Feng

Bio: Lucy Feng is an academic researcher from UCL Institute of Child Health. The author has contributed to research in topics: Muscular dystrophy & Duchenne muscular dystrophy. The author has an hindex of 38, co-authored 85 publications receiving 5628 citations. Previous affiliations of Lucy Feng include Great Ormond Street Hospital & Robert Jones and Agnes Hunt Orthopaedic Hospital.

Local restoration of dystrophin expression with the morpholino oligomer AVI-4658 in Duchenne muscular dystrophy: a single-blind, placebo-controlled, dose-escalation, proof-of-concept study

Abstract: Summary Background Mutations that disrupt the open reading frame and prevent full translation of DMD , the gene that encodes dystrophin, underlie the fatal X-linked disease Duchenne muscular dystrophy. Oligonucleotides targeted to splicing elements (splice switching oligonucleotides) in DMD pre-mRNA can lead to exon skipping, restoration of the open reading frame, and the production of functional dystrophin in vitro and in vivo, which could benefit patients with this disorder. Methods We did a single-blind, placebo-controlled, dose-escalation study in patients with DMD recruited nationally, to assess the safety and biochemical efficacy of an intramuscular morpholino splice-switching oligonucleotide (AVI-4658) that skips exon 51 in dystrophin mRNA. Seven patients with Duchenne muscular dystrophy with deletions in the open reading frame of DMD that are responsive to exon 51 skipping were selected on the basis of the preservation of their extensor digitorum brevis (EDB) muscle seen on MRI and the response of cultured fibroblasts from a skin biopsy to AVI-4658. AVI-4658 was injected into the EDB muscle; the contralateral muscle received saline. Muscles were biopsied between 3 and 4 weeks after injection. The primary endpoint was the safety of AVI-4658 and the secondary endpoint was its biochemical efficacy. This trial is registered, number NCT00159250. Findings Two patients received 0·09 mg AVI-4658 in 900 μL (0·9%) saline and five patients received 0·9 mg AVI-4658 in 900 μL saline. No adverse events related to AVI-4658 administration were reported. Intramuscular injection of the higher-dose of AVI-4658 resulted in increased dystrophin expression in all treated EDB muscles, although the results of the immunostaining of EDB-treated muscle for dystrophin were not uniform. In the areas of the immunostained sections that were adjacent to the needle track through which AVI-4658 was given, 44–79% of myofibres had increased expression of dystrophin. In randomly chosen sections of treated EDB muscles, the mean intensity of dystrophin staining ranged from 22% to 32% of the mean intensity of dystrophin in healthy control muscles (mean 26·4%), and the mean intensity was 17% (range 11–21%) greater than the intensity in the contralateral saline-treated muscle (one-sample paired t test p=0·002). In the dystrophin-positive fibres, the intensity of dystrophin staining was up to 42% of that in healthy muscle. We showed expression of dystrophin at the expected molecular weight in the AVI-4658-treated muscle by immunoblot. Interpretation Intramuscular AVI-4658 was safe and induced the expression of dystrophin locally within treated muscles. This proof-of-concept study has led to an ongoing systemic clinical trial of AVI-4658 in patients with DMD. Funding UK Department of Health.

Mutations in the human LARGE gene cause MDC1D, a novel form of congenital muscular dystrophy with severe mental retardation and abnormal glycosylation of α-dystroglycan

Abstract: The congenital muscular dystrophies (CMD) are a heterogeneous group of autosomal recessive disorders. A new pathomechanism has recently been identified in a group of these disorders in which known or putative glycosyltransferases are defective. Common to all these conditions is the hypoglycosylation of alpha-dystroglycan. Fukuyama CMD, muscle-eye-brain disease and Walker-Warburg syndrome, each associated with eye abnormalities and neuronal migration defects, result from mutations in fukutin, POMGnT1 and POMT1, respectively, while mutations in the fukutin-related protein (FKRP) gene cause congenital muscular dystrophy 1C, typically lacking brain involvement. Another putative glycosyltransferase, Large, is mutated in the myodystrophy mouse. The human homologue of this gene is therefore a strong candidate for involvement in novel forms of muscular dystrophy. We studied 36 patients with muscular dystrophy and either mental retardation, structural brain changes or abnormal alpha-dystroglycan immunolabelling, unlinked to any reported CMD loci. Linkage analysis in seven informative families excluded involvement of LARGE but sequencing of this gene in the remaining 29 families identified one patient with a G1525A (Glu509Lys) missense mutation and a 1 bp insertion, 1999insT. This 17-year-old girl presented with congenital muscular dystrophy, profound mental retardation, white matter changes and subtle structural abnormalities on brain MRI. Her skeletal muscle biopsy showed reduced immunolabelling of alpha-dystroglycan. Immunoblotting with an antibody to a glycosylated epitope demonstrated a reduced molecular weight form of alpha-dystroglycan that retained some laminin binding activity. This is the first description of mutations in the human LARGE gene and we propose to name this new disorder MDC1D.

Refining genotype phenotype correlations in muscular dystrophies with defective glycosylation of dystroglycan.

Abstract: Muscular dystrophies with reduced glycosylation of alpha-dystroglycan (alpha-DG), commonly referred to as dystroglycanopathies, are a heterogeneous group of autosomal recessive conditions which include a wide spectrum of clinical severity. Reported phenotypes range from severe congenital onset Walker-Warburg syndrome (WWS) with severe structural brain and eye involvement, to relatively mild adult onset limb girdle muscular dystrophy (LGMD). Specific clinical syndromes were originally described in association with mutations in any one of six demonstrated or putative glycosyltransferases. Work performed on patients with mutations in the FKRP gene has identified that the spectrum of phenotypes due to mutations in this gene is much wider than originally assumed. To further define the mutation frequency and phenotypes associated with mutations in the other five genes, we studied a large cohort of patients with evidence of a dystroglycanopathy. Exclusion of mutations in FKRP was a prerequisite for participation in this study. Ninety-two probands were screened for mutations in POMT1, POMT2, POMGnT1, fukutin and LARGE. Homozygous and compound heterozygous mutations were detected in a total of 31 probands (34 individuals from 31 families); 37 different mutations were identified, of which 32 were novel. Mutations in POMT2 were the most prevalent in our cohort with nine cases, followed by POMT1 with eight cases, POMGnT1 with seven cases, fukutin with six cases and LARGE with only a single case. All patients with POMT1 and POMT2 mutations had evidence of either structural or functional central nervous system involvement including four patients with mental retardation and a LGMD phenotype. In contrast mutations in fukutin and POMGnT1 were detected in four patients with LGMD and no evidence of brain involvement. The majority of patients (six out of nine) with mutations in POMT2 had a Muscle-Eye-Brain (MEB)-like condition. In addition we identified a mutation in the gene LARGE in a patient with WWS. Our data expands the clinical phenotypes associated with POMT1, POMT2, POMGnT1, fukutin and LARGE mutations. Mutations in these five glycosyltransferase genes were detected in 34% of patients indicating that, after the exclusion of FKRP, the majority of patients with a dystroglycanopathy harbour mutations in novel genes.

Mutations in GDP-mannose pyrophosphorylase b cause congenital and limb-girdle muscular dystrophies associated with hypoglycosylation of α-dystroglycan

Abstract: Congenital muscular dystrophies with hypoglycosylation of α-dystroglycan (α-DG) are a heterogeneous group of disorders often associated with brain and eye defects in addition to muscular dystrophy. Causative variants in 14 genes thought to be involved in the glycosylation of α-DG have been identified thus far. Allelic mutations in these genes might also cause milder limb-girdle muscular dystrophy phenotypes. Using a combination of exome and Sanger sequencing in eight unrelated individuals, we present evidence that mutations in guanosine diphosphate mannose (GDP-mannose) pyrophosphorylase B (GMPPB) can result in muscular dystrophy variants with hypoglycosylated α-DG. GMPPB catalyzes the formation of GDP-mannose from GTP and mannose-1-phosphate. GDP-mannose is required for O-mannosylation of proteins, including α-DG, and it is the substrate of cytosolic mannosyltransferases. We found reduced α-DG glycosylation in the muscle biopsies of affected individuals and in available fibroblasts. Overexpression of wild-type GMPPB in fibroblasts from an affected individual partially restored glycosylation of α-DG. Whereas wild-type GMPPB localized to the cytoplasm, five of the identified missense mutations caused formation of aggregates in the cytoplasm or near membrane protrusions. Additionally, knockdown of the GMPPB ortholog in zebrafish caused structural muscle defects with decreased motility, eye abnormalities, and reduced glycosylation of α-DG. Together, these data indicate that GMPPB mutations are responsible for congenital and limb-girdle muscular dystrophies with hypoglycosylation of α-DG.

Biological Roles of Glycans

Abstract: Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

RNA therapeutics: beyond RNA interference and antisense oligonucleotides

Abstract: Here, we discuss three RNA-based therapeutic technologies exploiting various oligonucleotides that bind to RNA by base pairing in a sequence-specific manner yet have different mechanisms of action and effects. RNA interference and antisense oligonucleotides downregulate gene expression by inducing enzyme-dependent degradation of targeted mRNA. Steric-blocking oligonucleotides block the access of cellular machinery to pre-mRNA and mRNA without degrading the RNA. Through this mechanism, steric-blocking oligonucleotides can redirect alternative splicing, repair defective RNA, restore protein production or downregulate gene expression. Moreover, they can be extensively chemically modified to acquire more drug-like properties. The ability of RNA-blocking oligonucleotides to restore gene function makes them best suited for the treatment of genetic disorders. Positive results from clinical trials for the treatment of Duchenne muscular dystrophy show that this technology is close to achieving its clinical potential.

Gene therapy clinical trials worldwide to 2012 - an update

Abstract: To date, over 1800 gene therapy clinical trials have been completed, are ongoing or have been approved worldwide. Our database brings together global information on gene therapy clinical trials from official agency sources, published literature, conference presentations and posters kindly provided to us by individual investigators or trial sponsors. This review presents our analysis of clinical trials that, to the best of our knowledge, have been or are being performed worldwide. As of our June 2012 update, we have entries on 1843 trials undertaken in 31 countries. We have analysed the geographical distribution of trials, the disease indications (or other reasons) for trials, the proportions to which different vector types are used, and which genes have been transferred. Details of the analyses presented, and our searchable database are available on The Journal of Gene Medicine Gene Therapy Clinical Trials Worldwide website at: http://www.wiley.co.uk/genmed/clinical. We also provide an overview of the progress being made in clinical trials of gene therapy approaches around the world and discuss the prospects for the future.

In vivo genome editing improves muscle function in a mouse model of Duchenne muscular dystrophy.

Abstract: Duchenne muscular dystrophy (DMD) is a devastating disease affecting about 1 out of 5000 male births and caused by mutations in the dystrophin gene. Genome editing has the potential to restore expression of a modified dystrophin gene from the native locus to modulate disease progression. In this study, adeno-associated virus was used to deliver the clustered regularly interspaced short palindromic repeats (CRISPR)–Cas9 system to the mdx mouse model of DMD to remove the mutated exon 23 from the dystrophin gene. This includes local and systemic delivery to adult mice and systemic delivery to neonatal mice. Exon 23 deletion by CRISPR-Cas9 resulted in expression of the modified dystrophin gene, partial recovery of functional dystrophin protein in skeletal myofibers and cardiac muscle, improvement of muscle biochemistry, and significant enhancement of muscle force. This work establishes CRISPR-Cas9–based genome editing as a potential therapy to treat DMD.