The fragile X premutation is a tandem CGG trinucleotide repeat expansion on the FMR1 gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse with CGG trinucleotide repeat lengths between 70 and 350 has been developed and used to model the histopathology and cognitive deficits reported in carriers of the fragile X premutation. Previous studies have shown that CGG KI mice show progressive deficits in processing spatial and temporal information. To characterize the motor deficits associated with the fragile X premutation, male and female CGG KI mice ranging from 2 to 16 months of age with trinucleotide repeats ranging from 72 to 240 CGG in length were tested for their ability to perform a skilled ladder rung walking test. The results demonstrate that both male and female CGG KI mice showed a greater number of foot slips as a function of increased CGG repeat length, independent of the age of the animal or general activity level.

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Behavioural Brain Research
Erasmus MC: University Medical Center Rotterdam

Hunsaker, M., von Leden, R., Ta, B., Goodrich-Hunsaker, N., Arque, G., Kim, K., … Berman, R. (2011). Motor deficits on a ladder rung task in male and female adolescent and adult CGG knock-in mice. Behavioural Brain Research, 222(1), 117–121. doi:10.1016/j.bbr.2011.03.039