[Research Articles] In Vivo-Directed Evolution of a New Adeno-Associated Virus for Therapeutic Outer Retinal Gene Delivery from the Vitreous

Sci Transl Med 12 June 2013:
Vol. 5, Issue 189, p. 189ra76
Sci. Transl. Med. DOI: 10.1126/scitranslmed.3005708 BLINDNESS Deniz Dalkara1,*, Leah C. Byrne1,*, Ryan R. Klimczak2, Meike Visel2, Lu Yin3, William H. Merigan3, John G. Flannery1,2,† and David V. Schaffer1,2,4,†

1Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720–1462, USA.

2Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720–1462, USA.

3Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA.

4Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720–1462, USA. ?†Corresponding author. E-mail: schaffer{at}berkeley.edu (D.V.S.); flannery{at}berkeley.edu (J.G.F.) ?* These authors contributed equally to this work.

Inherited retinal degenerative diseases are a clinically promising focus of adeno-associated virus (AAV)–mediated gene therapy. These diseases arise from pathogenic mutations in mRNA transcripts expressed in the eye’s photoreceptor cells or retinal pigment epithelium (RPE), leading to cell death and structural deterioration. Because current gene delivery methods require an injurious subretinal injection to reach the photoreceptors or RPE and transduce just a fraction of the retina, they are suitable only for the treatment of rare degenerative diseases in which retinal structures remain intact. To address the need for broadly applicable gene delivery approaches, we implemented in vivo–directed evolution to engineer AAV variants that deliver the gene cargo to the outer retina after injection into the eye’s easily accessible vitreous humor. This approach has general implications for situations in which dense tissue penetration poses a barrier for gene delivery. A resulting AAV variant mediated widespread delivery to the outer retina and rescued the disease phenotypes of X-linked retinoschisis and Leber’s congenital amaurosis in corresponding mouse models. Furthermore, it enabled transduction of primate photoreceptors from the vitreous, expanding its therapeutic promise.

Copyright © 2013, American Association for the Advancement of ScienceCitation: D. Dalkara, L. C. Byrne, R. R. Klimczak, M. Visel, L. Yin, W. H. Merigan, J. G. Flannery, D. V. Schaffer, In Vivo–Directed Evolution of a New Adeno-Associated Virus for Therapeutic Outer Retinal Gene Delivery from the Vitreous. Sci. Transl. Med. 5, 189ra76 (2013).

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Catalysts' outer coordination spheres take their place in the spotlight

Wendy Shaw wrote a comprehensive review article on outer coordination spheres.

(Phys.org) —Once dismissed as shrubbery, experimental and computational research shows the outer coordination sphere greatly influences a catalyst's effectiveness, according to Dr. Wendy Shaw at Pacific Northwest National Laboratory in her invited review article. The outer coordination sphere is the complex structure that wraps around the catalyst's central active site and controls the activity, selectivity and specificity of the catalyst. Shaw's Catalysis Reviews article focuses on bottom-up design research. In this approach, aspects of the outer coordination sphere are added as needed.

"The advantage is that you can add just the features you need to get the effects you want," said Shaw.

In her article, Shaw explores studies of a minimal outer coordination sphere based on amino acids. She goes beyond these simple arrangements to examine structured peptide use. These more complex structures allow scientists to add specific positioning of an amino acid near the active site to change the molecular properties at the metal, controlling the catalyst's behavior. She also examines the newer area of enzyme mimics. She notes several exciting studies are using computers to design enzymes from scratch that catalyze reactions that aren't found in nature.

Looking back at the 61-page review, with 226 references, she notes that many of the catalysts fall into two categories: those that function but have undefined outer coordination spheres and those that do not work but have rigorously defined spheres. Few, such as a PNNL rhodium-based catalyst, perform the task at hand and have defined structures. For her, the takeaway message is the large influence that changes far from the active site can exert over the reactivity of the catalyst, and the power of integrating computational chemistry and experimentation to create functional and structurally characterized catalysts.

More information: Shaw WJ. 2012. The Outer-Coordination Sphere: Incorporating Amino Acids and Peptides as Ligands for Homogeneous Catalysts to Mimic Enzyme Function. Catalysis Reviews 54(4):489-550. DOI: 10.1080/01614940.2012.679453

Provided by Pacific Northwest National Laboratory

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