Developmental forced gait assessment. We determined P21 was the youngest age at which reliable gait data could be collected from C57BL/6J mice (P18 for FVB mice). Previous research suggested that gait may mature in the mouse by P24; however this was based solely on duration of swing and stance phases in Swiss mice without controlling for gait speed1. Thus we developed a longitudinal approach to assess gait at a constant speed at multiple ages spanning P21 – P30 and again in adulthood to determine stability of phenotypes. Gait data will be collected using the DigiGait Imaging System (Mouse Specifics, Inc), an advanced system with ventral plane imaging technology that generates digital paw prints from the animal as it runs on a motorized treadmill2. Dynamic gait signals are then quantified to describe posture and kinematics. Weight and body size measurements will be collected as covariates at each testing age.
See Akula … Maloney. Brain and Behavior, 2020 (PMID: 32333523) and Rahn …Maloney JNDD 2021 (PMID: 33743598).
1. Clarke KA, Still J. (2001). Development and consistency of gait in the mouse. Physiology & Behavior. 73(1):159–164. Available from: http://www.sciencedirect.com/science/article/pii/S0031938401004449
2. Hampton TG, Stasko MR, Kale A, Amende I, Costa ACS. (2004). Gait dynamics in trisomic mice: quantitative neurological traits of Down syndrome. Physiology & Behavior. 82(2–3):381–389. Available from: http://www.sciencedirect.com/science/article/pii/S0031938404001283
The purpose of this data collection is to assess ultrasonic vocalization (USV) difference between the experimental and control littermates on postnatal days 6, 8, 10 and 12 (alternative P5, 7, 9, 11) and to assess the physical characteristics and somatosensory responses of the mice during development to determine any developmental delays. To evaluate gross development, the mice are weighed and evaluated for physical milestones of development including pinna detachment by P5/6 and eye opening by P14.
While human language cannot be explored in mice, vocal communication behavior is conserved across taxa (Ehret, 1980). Mouse pups produce isolation calls as a way to attract the dam for maternal care (Haack et al., 1983), thus it is one of the earliest forms of social communication we can examine in mice. This behavior also has a developmental trajectory, beginning just after birth, peaking during first week postnatal and disappearing around P14, making it useful for examining delay in early social circuits. See Maloney et al. Autism Research 2018 (PMID: 28842941) and Chen et al. Neuron 2021 (PMID: 34614421) for example publication
This battery of motor and reflex assessments was derived from Feather-Schussler & Ferguson, J Vis Exp. 2016; (117): 53569 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5226120/). The tasks were selected to provide a comprehensive assessment of motor development that is sensitive enough to detect motor development delay. The ages at each assessment were based on the age at which mice develop the motor function being assessed. See Chen et al. Neuron 2021 (PMID: 34614421) for example publication.
Suggested phenotyping order:
Age Development Assessments in Chronological Order
P5 Weight, Pinnae detachment, USV**
P6 Surface righting reflex, Grasping reflex
P7 Weight, USV**
P8 Ambulatory Assessment, Hindlimb foot angle
P9 Weight, USV**
P10 Weight, Negative Geotaxis, Forelimb Suspension test, Grip Strength
P11 Weight, USV**
P12 Weight, Hindlimb Suspension Test, Grip Strength
P13 —
P14 Weight, Surface righting reflex, grasping reflex, grip strength
**See Maternal Isolation Pup USV Recording for protocol