Elsevier

Neuroscience

Volume 164, Issue 3, 15 December 2009, Pages 975-985
Neuroscience

Behavioural Neuroscience
Research Paper
Pre-symptomatic detection of chronic motor deficits and genotype prediction in congenic B6.SOD1G93A ALS mouse model

https://doi.org/10.1016/j.neuroscience.2009.08.031Get rights and content

Abstract

Amyotrophic lateral sclerosis (ALS) is an incurable progressive paralytic motor neuron disease with limited therapeutic options. Since their creation by Gurney et al. (1994) [Science 264:1772–1775], transgenic superoxide dismutase-1 with glycine to alanine switch at codon 93 (SOD1G93A) mice have become the benchmark pre-clinical model for screening ALS therapies. Surprisingly, despite physiological, anatomical, ultrastructural and biochemical evidence of early motor system dysfunction, it has proven difficult to detect motor performance deficits in pre-symptomatic SOD1G93A mice. As an alternative to conventional forced motor tests, we investigated the progression of motor performance deficits in freely behaving pre-symptomatic congenic B6.SOD1G93A mice. We found that motor performance deficits began several weeks prior to the onset of overt clinical symptoms (postnatal day 45). More importantly, once motor performance deficits manifested, they persisted in parallel with disease progression. In addition, two physical measures of muscle girth revealed progressive hindlimb muscle atrophy that predicted genotype in individual pre-symptomatic mice with 80% accuracy. Together, these data suggest that muscle girth is a reliable and indirect measure of hindlimb muscle denervation and an early, objective marker for disease onset in congenic B6.SOD1G93A ALS mice. Moreover, we present regression equations based on hindlimb muscle girth for predicting genotype in future studies using B6.SOD1G93A mice. These findings support new objective criteria for clinical disease onset and provide objective measures that require little expertise. These studies demonstrate a cost-effective approach for more thorough evaluation of neuroprotective strategies that seek to disrupt disease mechanisms early in the disease process. To our knowledge, these findings are the first to report early chronic motor performance and physical deficits that are coincident with the earliest known motor dysfunction in any ALS mouse model.

Section snippets

B6.SOD1G93A transgenic mice

Experiments were performed in accordance with NIH guidelines for the use of experimental animals and approved by the University of Texas Institutional Animal Care and Use Committee. Animals were provided food and water ad libitum and housed on a 12:12 h light cycle (on at 7 am). A single male B6.Cg-Tg[SOD1-G93A]1Gur/J, hereafter referred to as B6.SOD1G93A, was purchased from The Jackson Laboratory, Bar Harbor, ME, USA (stock, 004435). These mice over-express a point mutated form of the human

Delayed tremor symptom onset in female B6.SOD1G93A mice

In B6.SOD1G93A mice, the first clinical symptoms of motor neuron disease presented as fine tremors in one or both hindlimbs when suspended by the tail (Chiu et al., 1995). Kaplan–Meier analysis revealed that tremor onset occurred significantly sooner in male (91±2 days) compared to female (100±2 days) B6.SOD1G93A mice, (P≤0.01) (Table 1). Evidence of tremor was undetected at any age in control mice. Similar to previously published results (Heiman-Patterson et al., 2005), Kaplan–Meier analysis

Discussion

The evaluation of treatment efficacy in mouse models of ALS has traditionally relied on forced exercise tasks (e.g. rotarod, paw grip endurance, treadmill, gait analysis) (Gurney et al., 1994, Kong and Xu, 1998, Weydt et al., 2003, Fischer et al., 2004, Wang et al., 2008). However, this battery of tests has proven insensitive at detecting motor deficits prior to the onset of overt clinical symptoms despite ultrastructural, histological, electrophysiological and metabolic evidence that have

Conclusion

While ∼18 different murine ALS models have contributed greatly to our current understanding of the disease mechanisms they also serve as platforms for screening candidate therapies (Turner and Talbot, 2008). An important hurdle limiting the development of neuroprotective strategies in ALS models has been the inability to detect persistent behavioral and physical changes early in the disease. This has been exacerbated by the lack of objective, non-invasive, non-technical, cost-effective and

Acknowledgments

Supported by NIH grant T32 MH065728. The authors thank Dr. Jason Shumake for his generous help. We also greatly appreciate the contributions of Sonya Sui, Samir Khatani, Anvinh Nguyen, Huma Vaid, Erin Keith, Justin Rhee, Kimi Vu, Shivam Patel, Brandon Martinez, Tameka Jones-Watlington and Gene Pershwitz.

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