Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder lacking highly effective disease-modifying treatment or a cure. The often-heterogenous course of ALS underlines the need for modelling the different disease aspects in multiple, distinct models to enable thorough validation of novel, putative treatments.
Amyotrophic Lateral Sclerosis (ALS) pathophysiology
ALS, also known as motor neurone disease or Lou Gehrig’s disease is a severe neurodegenerative disorder that affects the motoneurons in the brain and spinal cord. This leads to progressive and rapid muscle wasting, spasticity, and eventual paralysis. Despite the highly heterogenous clinical presentation, most ALS patients die due to respiratory failure within 2-3 years of symptom onset. ALS also exists on a continuum with frontotemporal dementia (FTD).
Although most ALS cases are sporadic, genetic data reveal that a family history of ALS is present in 5–10% of affected individuals, usually with an autosomal dominant inheritance pattern. The four genes that account for most of the familial ALS cases are C9orf72 (40%), SOD1 (20%), FUS (1–5%), and TARDBP (1–5%). In addition, virtually all ALS cases have cytoplasmic inclusions of aggregated nuclear protein TDP-43. The identification of several pathophysiological mechanisms leading to both familial and sporadic cases of ALS enables its recapitulation in in vivo models allowing preclinical testing of promising ALS-targeted therapies.
InnoSer, a leading provider of in vivo contract research services, offers several mouse models for ALS research. In combination with sensitive, standardized behavioral tests. The mouse models provide a translationally relevant platform for testing novel ALS-targeted therapies. In this article, we provide an overview of currently available ALS mouse models and their applicability, outlining our contract research services (CRO) capabilities and expertise. Although a multitude of preclinical models are available and have been developed to date (1), in this article we focus on the most commonly used research mouse ALS models.
Modelling Early-stage ALS: SOD1 mutations
SOD1 plays a crucial role in free radical scavenging and regulates the expression of genes involved in oxidative stress response. Inherited mutations in the SOD1 gene are thought to result in intracellular formation and accumulation of toxic protein aggregates. In turn, this results in increased oxidative stress which ultimately manifests as a decline in motor function.
Mice overexpressing the human protein with SOD1 mutation present significant SOD1 aggregation, oxidative stress, and motoneuron loss. Accordingly, we detect significant motor problems in transgenic SOD1 mice in motor function tests (such as grip strength test and rotarod; Figure 1) but also in spontaneous behavior (automated-home cages, PhenoTyper™; Figure 2) in comparison to their WT littermates. The behavioral deficits in these models are already detectable at young ages and show progressive development, providing a large time frame for testing targeted novel therapeutics. The SOD1G93A and SOD1G37R models are the most used transgenic SOD1 models for ALS research.
FIGURE 1. SOD1 mice show decrease in motor performance assessed by rotarod. The Rotarod is the golden standard of assessing motor performance and learning in mice. The mice are placed on a rotating rod, with increasing rotating speed. Motor performance is measured by the maximal RPM (rounds per minute) at which mice can keep up with the rotating rod. Motor learning can be assessed by training mice on the rod for several trials.
FIGURE 2. SOD1 mutant mice show progressive behavioural changes in the automatic home cages (PhenoTyper™) including a reduced frequency to climb on top of their shelter.
Modelling ALS pathophysiology: TDP-43 formation and spreading
TDP-43 proteinopathy is a pathological hallmark in almost all patients with ALS, as well as FTD and limbic-predominant age-related TDP-43 encephalopathy (LATE). Pathological accumulation of misfolded TDP-43 protein aggregates has been closely associated to the neurodegenerative phenotype observed in ALS patients.
TDP43 Transgenic Models:
TDP-43 transgenic models overexpress mutant forms of human TDP-43, leading to motoneuron degeneration and paralysis. TDP-43 mouse models used at InnoSer recapitulate the TDP-43 pathology and downstream functional impairments found in ALS and FTD (Figures 3-6).
Transgenic TDP-43 models are best suited for testing novel therapies that target the TDP-43 pathology-associated dysfunction in RNA processing and protein homeostasis. The TDP-43WT, TDP-43Q331K, and TDP-43A315T models are the most commonly used transgenic TDP-43 models for ALS research.
FIGURE 3. 4-month-old female hemizygous Prp-TDP-43-Q331K (JAX #017933) mice show reduced activity (PhenoTyper). Spontaneous behaviour relating to the motor function of mice in the automated home-cage (PhenoTyper) is tracked at high resolution and analysed by AHCODA. Highly discriminative parameters are produced, detecting changes in domains of motor function, circadian rhythm and others.
FIGURE 4. 4-month-old female hemizygous Prp-TDP-43-Q331K (JAX #017933) mice show reduced muscle function (Weights lifting test). The weight lifting test assesses muscle endurance in rodents. Mice are presented with objects of increasing weight. The readout of this test is the maximum weight that mouse can hold for 5 seconds.
FIGURE 5. 4-month-old female hemizygous Prp-TDP-43-Q331K (JAX #017933) mice show motor deficits (Rotarod). The Rotarod is the golden standard of assessing motor performance and learning in mice. Mice are placed on a rotating rod, with increasing rotating speed. Motor performance is measured by the maximal RPM (rounds per minute) at which mice are able to keep up with the rotating rod. Motor learning can be assessed by training mice on the rod for several trials.
FIGURE 6. 6-month-old female hemizygous Prp-TDP43-Q331K (JAX #017933) tested in the CatWalk™ Gait Analysis show abnormal walking patterns (Stride length). The CatWalk™ gait analysis system enables quantification of a wide range of parameters related to footprint and gait in animals. Stride length (cm) refers to the distance between successive placements of the same paw.
TDP-43 Seeding Models:
TDP-43 seeding models involve the injection of patient-derived TDP-43 aggregates into the brain of mice. Injection of brain extracts from these diseases in the brain of mice closely mimics the structural features of the TDP-43 aggregates found in patients and allows studying the spread TDP-43 aggregates as a therapeutic readout. InnoSer’s neurology study team has extensive experience with seeding-based mouse models, both with recombinant and patient-derived seeds.
Choosing the most suitable model
InnoSer’s expert neurology team is readily equipped to consult with you to determine the best model in conjunction with readout customization to meet your specific needs and goals. Consulting with our team will allow you to carry out tailored studies while collecting the most relevant data. We also advise you on the most optimal model selection, taking in your budget and study timelines.