Animal models continue to be important tools for understanding disease mechanisms and for preclinical testing of potential therapeutics. Although the mouse is currently the most widely used species to model neurobiological disorders, we recognize that other model systems may also provide important insights.
Relative to the mouse, the rat has a larger brain and exhibits a more complex behavioural repertoire but still retains many tractable characteristics that make it amenable for laboratory research. Recent developments in genomic-editing technologies have facilitated the ability to manipulate the rat genome, thus spurring interest in the rat as a model for genetically linked disorders.
As such, our funder SFARI is working with the Medical College of Wisconsin (MCW) to generate and distribute CRISPR/Cas9 rat models of autism. Models will be maintained in the outbred Long-Evans background strain, as this is often the strain of choice for cognitive, behavioural and systems neuroscience studies. The intent is for these models to be available to any qualified researcher, with minimal cost and restrictions.
Fmr1
Syngap x 2
Cdkl5
Grin2A
CHAMP1
New Nlgn3
In production/validation:
Fmr1 cON/y; Syngap1 cON/-
Nlgn3 cON/y
CAG-Cre/ERT
Fmr1_FLOX
Nlgn3_FLOX
Syngap_FLOX
As an initial effort to characterize these lines, these models are being behaviorally phenotyped at SIDB and the Center for Development and Repair in Bangalore. Rat models are phenotyped according to a rigorous pipeline that assesses behaviours relevant to autism spectrum disorder, such as social and motor skills, and learning and sensory processing. Different cohorts of rats are run through different subsets of tasks to overcome potential order effects on behaviours and to limit the number of tasks each animal is put through.
Resulting data will be available pre-publication via downloadable behavioral datasheets (see links to available datasheets above). The SIDB behavioral pipeline includes the following tasks:
In addition, prior to pipeline phenotyping, some rats are characterized using the following experimental set-ups/methods:
Eco-ethological housing system that permits rats to express a wide-range of innate behaviors that can be recorded and analyzed without disturbing animals.
The following schematic of the Habitat is an experimental set up devised by Peter Kind and colleagues at SIDB to study rat social, cognitive and motor behaviors in the lab. These complex behaviors include rat social hierarchies, fear and isolation, communication, play, memory, motor coordination, reaction to novelty and circadian rhythms.
Automated, machine-learning-based method developed by Sandeep Robert Datta and colleagues to characterize behavior in rodents (mice and rats) (Wiltschko AB et al, 2015). More information about this tool can be found here.
Between the SIDB Edinburgh and Bangalore sites, we have 15 - 20 different rat models, all monogenic forms of autism spectrum disorder, typically the high-confidence genes on the SFARI Gene list.
Earlier in 2021, we successfully generated our first conditional-on (c-on) using Crispr technology and the Flex system. To date, we have generated both the c-on models for Fmr1 and Syngap. We have also generated a tamoxifen inducible CAGG-Cre rat line to induce constitutive gene re-expression at selected ages. These animals will allow us to discern whether particular monogenic forms of ASD have critical periods for gene re-expression.