Methodology Report

ENU Mutagenesis Screen to Establish Motor Phenotypes in Wild-Type Mice and Modifiers of a Pre-Existing Motor Phenotype in Tau Mutant Mice

Table 1

Phenotyping protocol for ENU/K3 mice. Four phenotypes are being scored, limb clasping, tremor, and gait abnormalities (cardinal features defining Parkinsonism) and body weight.

(1) Limb clasping
Procedure: → Lift the mice by the tail just so much above the grid, that they try to reach it with their front paws. Keep the mice in this position for at least 30 seconds. Should the phenotype not be obvious, touch hind limbs? This will ensure that clasping becomes obvious

StageDefinition
0No clasping (wild-type phenotype)
1Short and transient clasping only after stimulation (grabbing of grid or touching of hind limbs)
2Persistent hind limb clasping after stimulation (grabbing of grid or touching of hind limbs)
3Spontaneous hind limb clasping without major stimulation (when lifted for a few seconds by the tail)
4Spontaneous clasping of hind- and fore limbs
5Clasping of hind- or fore limbs persists for more than 5 sec after mice have been placed back into the home cage

(2) Tremor
Procedure: → Observe mice in home cage

StageDefinition
0No tremor (wild-type)
1Intermitted mild tremor
2Continuous mild tremor
3Continuous intensive tremor

(3) Gait anomalies
Procedure: → Place mice on metal surface in the sterile hood. Ensure that surface between cages is clean. Observe gait and posture

StageDefinition
0Normal gait, normal posture (wild-type)
1Intermittendly shaking gait, normal posture
2Shaking gait, spreading of hind limbs, flattening of the rear body part
3Continuously shaking gait, spreading of hind limbs, postural instability, dragging of rear body

(4) Body weight
Procedure: → Weigh mouse on the same balance in the same container. Record two digits after the comma

Schedule
Procedure: → First analysis at 4 weeks of age, with follow-ups every week until x weeks of age