Fast-Seq: A Simple Method for Rapid and Inexpensive Validation of Packaged Single-Stranded Adeno-Associated Viral Genomes in Academic Settings.

Adeno-associated viral (AAV) vectors have shown great promise in gene delivery as evidenced by recent FDA approvals. Despite efforts to optimize manufacturing for good manufacturing practice (GMP) productions, few academic laboratories have the resources to assess vector composition. One critical component of vector quality is packaged genome fidelity. Errors in viral genome replication and packaging can result in the incorporation of faulty genomes with mutations, truncations, or rearrangements, compromising vector potency. Thus, sequence validation of packaged genome composition is an important quality control (QC), even in academic settings. We developed Fast-Seq, an end-to-end method for extraction, purification, sequencing, and data analysis of packaged single-stranded AAV (ssAAV) genomes intended for non-GMP preclinical environments. We validated Fast-Seq on ssAAV vectors with three different genome compositions (CAG-GFP, CAG-tdTomato, EF1α-FLuc), three different genome sizes (2.9, 3.6, 4.4 kb), packaged in four different capsid serotypes (AAV1, AAV2, AAV5, and AAV8), and produced using the two most common production methods (Baculovirus-Sf9 and human HEK293), from both common commercial vendors and academic core facilities supplying academic laboratories. We achieved an average genome coverage of >1,400 × and an average inverted terminal repeat coverage of >280 × , despite the many differences in composition of each ssAAV sample. When compared with other ssAAV next-generation sequencing (NGS) methods for GMP settings, Fast-Seq has several unique advantages: Tn5 transposase-based fragmentation rather than sonication, 125 × less input DNA, simpler adapter ligation, compatibility with commonly available inexpensive sequencing instruments, and free open-source data analysis code in a preassembled customizable Docker container designed for novices. Fast-Seq can be completed in 18 h, is more cost-effective than other NGS methods, and is more accurate than Sanger sequencing, which is generally only applied at 1-2 × sequencing depth. Fast-Seq is a rapid, simple, and inexpensive methodology to validate packaged ssAAV genomes in academic settings.

Directed Chemical Evolution with an Outsized Genetic Code.

The first demonstration that macromolecules could be evolved in a test tube was reported twenty-five years ago. That breakthrough meant that billions of years of chance discovery and refinement could be compressed into a few weeks, and provided a powerful tool that now dominates all aspects of protein engineering. A challenge has been to extend this scientific advance into synthetic chemical space: to enable the directed evolution of abiotic molecules. The problem has been tackled in many ways. These include expanding the natural genetic code to include unnatural amino acids, engineering polyketide and polypeptide synthases to produce novel products, and tagging combinatorial chemistry libraries with DNA. Importantly, there is still no small-molecule analog of directed protein evolution, i.e. a substantiated approach for optimizing complex (≥ 10^9 diversity) populations of synthetic small molecules over successive generations. We present a key advance towards this goal: a tool for genetically-programmed synthesis of small-molecule libraries from large chemical alphabets. The approach accommodates alphabets that are one to two orders of magnitude larger than any in Nature, and facilitates evolution within the chemical spaces they create. This is critical for small molecules, which are built up from numerous and highly varied chemical fragments. We report a proof-of-concept chemical evolution experiment utilizing an outsized genetic code, and demonstrate that fitness traits can be passed from an initial small-molecule population through to the great-grandchildren of that population. The results establish the practical feasibility of engineering synthetic small molecules through accelerated evolution.

Expedient synthesis of a modular phosphate affinity reagent.

Isolation and identification of phosphorylated macromolecules is essential for the deconvolution of most biological regulatory networks. Koike and co-workers recently reported the application of a dinuclear zinc-(pyridylmethyl)amine complex to phosphate-specific affinity purifications and gave it the shorthand name "phos-tag". This complex is valuable for studying phosphorylation because it binds selectively to phosphate dianion in the presence of acidic functional groups at physiological pH, and because the binding is largely independent of molecular context. These properties of phos-tag recommend it for applications in phosphoproteomics, metabolomics, and nucleic acid biology. The catch has been that the molecule is difficult to make and prohibitively expensive to buy. Here, we describe an efficient and inexpensive synthesis of a phos-tag derivative with a versatile alkyne handle. The alkyne handle allows for attachment of phos-tag to alkyl azides via the copper(I)-catalyzed azide-alkyne cycloaddition reaction ("click chemistry"). We characterize the phosphate binding behavior of the new phos-tag derivative in a variety of experimental assays, including its conjugation to a fluorescent reporter, to acrylamide gels, and to sepharose chromatography resin. The synthesis we report should enable a broader use of phos-tag for phosphate-related biochemistry, as both an analytical and a preparative reagent.