Handling of the cotton rat in studies for the pre-clinical evaluation of oncolytic viruses

Inducing Cre-lox Recombination in Mouse Cerebral Cortex Through In Utero Electroporation

Cell-autonomous neuronal functions of genes can be revealed by causing loss or gain of function of a gene in a small and sparse population of neurons. To do so requires generating a mosaic in which neurons with loss or gain of function of a gene are surrounded by genetically unperturbed tissue. Here, we combine the Cre-lox recombination system with in utero electroporation in order to generate mosaic brain tissue that can be used to study the cell-autonomous function of genes in neurons. DNA constructs (available through repositories), coding for a fluorescent label and Cre recombinase, are introduced into developing cortical neurons containing genes flanked with loxP sites in the brains of mouse embryos using in utero electroporation. Additionally, we describe various adaptations to the in utero electroporation method that increase survivability and reproducibility. This method also involves establishing a titer for Cre-mediated recombination in a sparse or dense population of neurons. Histological preparations of labeled brain tissue do not require (but can be adapted to) immunohistochemistry. The constructs used guarantee that fluorescently labeled neurons carry the gene for Cre recombinase. Histological preparations allow morphological analysis of neurons through confocal imaging of dendritic and axonal arbors and dendritic spines. Because loss or gain of function is achieved in sparse mosaic tissue, this method permits the study of cell-autonomous necessity and sufficiency of gene products in vivo.

Passive narcosis for anesthesia induction in cotton rats (Sigmodon hispidus)

Cotton rats (Sigmodon hispidus) are widely used as animal models for infectious disease and immunological research. They emulate many aspects of human disease pathogenesis, and the introduction of cotton rat-specific immunological reagents, cell lines and sequencing of relevant genes have all helped to increase the popularity of this disease model. However, the use of cotton rats is problematic owing to their propensity for aggressive responses when handled, which can lead to escape, increased stress to the animals, and bites to staff. When cotton rats are co-housed, which is recommended under current social housing guidelines, these risks are increased. Here, we describe a method of isoflurane anesthesia induction in the home cage that reduces the risk of animal escape, minimizes stress during induction, and provides additional safety for staff. The method uses inexpensive materials that are widely available and can be easily disinfected. Our method also eliminates the need for expensive and cumbersome machines traditionally used with anesthetic chambers, and uses a minimal amount of inhalant anesthetic, saving resources and protecting staff from inhalation of leaked gas.