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A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging

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RAG2 gene knockout in mice causes fatigue.

Paul T Golumbek¹, Richard M Keeling, Anne M Connolly

¹Department of Neurology, Washington University School of Medicine, St Louis, MO 63110, USA. golumbekp@wustl.edu

|June 8, 2007

Summary

Mice lacking T-cells and B-cells showed increased fatigue and slower body weight gain, indicating a hypoactive immune system impacts neuromuscular function. This model may offer insights into human fatigue conditions.

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Area of Science:

Immunology
Neuroscience
Physiology

Background:

The interplay between the immune and neuromuscular systems is not well understood.
Immune deficiency can potentially affect muscle function and overall physical capacity.

Purpose of the Study:

To investigate the impact of a compromised immune system on neuromuscular strength and fatigue.
To utilize RAG2(-/-) mice, which lack T-cells and B-cells, as a model to study immune-neuromuscular interactions.

Main Methods:

Comparison of neuromuscular performance (strength and fatigue) between RAG2(-/-) mice and immune-intact controls.
Assessment of parameters including inverted hang-time (HT), voluntary wheel-running (VWR) performance, and forelimb grip strength (FGS).
Histopathological analysis of medial rectus femoris muscle and measurement of serum creatine kinase (CK) levels.

Main Results:

RAG2(-/-) mice exhibited significant fatigue, evidenced by shorter hang-times and reduced VWR distance and duration.
While body weight gain was slower, forelimb grip strength and VWR speed remained proportionally normal.
Muscle histopathology revealed no alterations in fiber type proportions, type 2b fiber diameter, or central nuclei percentage. Serum CK levels were unchanged.

Conclusions:

A hypoactive immune system, as seen in RAG2(-/-) mice, directly influences body weight regulation and induces fatigue.
The precise central or peripheral mechanisms underlying these effects remain to be elucidated.
This mouse model provides a valuable tool for understanding fatigue in human conditions characterized by immune suppression or absence.