Biology subjects

McNamara, J. O.

Publications and source records attributed to McNamara, J. O..

3 recordsLinked to original sources

bioRxiv2025

Circuit-specific gene editing for precision modulation of neuronal activity with CRISPR-rabies virus

CRISPR gene editing has revolutionized our ability to study and manipulate specific genes, enabling novel insights into gene function and potential therapies for brain disorders. Recent advances in cell-type-specific regulatory elements and viral delivery systems have made precise in vivo gene editing possible. However, neurons with similar molecular profiles can belong to different circuits, complicating efforts to manipulate circuit function and behavior. To address this, we developed CRISPR-rabies virus (CRV), which leverages the trans-synaptic spread of rabies virus to enable gene editing within anatomically defined neural circuits. By pairing CRV with cell type-specific Cas9 expression, we achieved targeted gene modifications in specific circuits. We demonstrate that CRV can modulate sodium and potassium channel expression in parvalbumin interneurons, thereby effectively regulating synaptic transmission of pyramidal neurons in the CA3 region of the hippocampus. Its compatibility with 3'-capture single-cell RNA-seq allows simultaneous circuit perturbation and molecular profiling. In summary, CRV allows precise circuit-level gene modulation, providing a platform for studying gene function in neural circuits and developing novel gene therapies for brain disorders.

neuroscience↗

bioRxiv2022

Rapid Phenotypic Detection of Carbapenem-Resistant E. coli with Fluorogenic Culture Media

Faster, and simpler methods that determine the susceptibility of bacterial pathogens to antibiotics are needed to enable more effective treatment of bacterial infections and reduce the overuse of antibiotics. Here, we demonstrate a simple method for rapidly detecting bacteria and simultaneously determining their antibiotic susceptibility status. We demonstrate the method with E. coli, a high-impact pathogen, and meropenem, a member of the carbapenem class of antibiotics which is usually reserved for multi-drug resistant infections. Inclusion of a fluorogenic oligonucleotide substrate for endonuclease I, a well-conserved nuclease of the Enterobacteriaceae family, in a tryptic soy agar-based media enabled fluorescence-based detection of E. coli growth within 9 hours. Plating established carbapenem-resistant and -susceptible E. coli strains on this media with and without inclusion of meropenem, followed by fluorescent imaging yielded a clear phenotypic measure of the antibiotic susceptibility status of the strains in 9 hours. In addition to its simplicity and fast turnaround time, advantages of this approach include its ability to provide a measure of the bacterial load of the tested samples, and its easy integration into current microbiology laboratory workflows.

microbiology↗

bioRxiv2022

Reaction Conditions Promoting the Specific Detection of SARS-CoV-2 NendoU Enzymatic Activity

Methods that enable rapid detection of SARS-CoV-2 provide valuable tools for detecting and controlling Covid-19 outbreaks and also facilitate more effective treatment of infected individuals. The predominant approaches developed use PCR to detect viral nucleic acids or immunoassays to detect viral proteins. Each approach has distinct advantages and disadvantages, but alternatives that do not share the same limitations could enable substantial improvements in outbreak detection and management. For instance, methods that have comparable sensitivity to PCR, but that are not prone to the false-positive results that stem from the tendency of PCR to detect molecular degradation products could improve accurate identification of infected individuals. An alternative approach with potential to achieve this entails harnessing the unique enzymatic properties of SARS-CoV-2 enzymes to generate SARS-Cov-2-specific signals that indicate the presence of the virus. This route benefits from the high sensitivity provided by enzymatic signal amplification and also the fact that signal is generated only by intact viral enzymes, not degradation products. Here, we demonstrate enzymatic reaction conditions that enable the preferential detection of NendoU of SARS-CoV-2, versus several of its orthologues, with a fluorogenic oligonucleotide substrate. These compositions provide a possible technical foundation for a novel approach for detecting SARS-CoV-2 that has distinct advantages from current approaches.

microbiology↗