English: Forced Swimming Test (FST). Sequence 1). General overview of the swimming test device. Sequence 2) Wild-type FST training session. Five month-old wild-type mice are actively swimming at the second week of FST. Sequence 3) Sepn1−/− FST training session. Five month-old Sepn1−/− are actively swimming at the second week of FST exercise, similarly to wild-types. Sequence 4) Sepn1−/− FST week 10. While 6 month-old wild-types are still actively swimming after 10 weeks, Sepn1−/− mice of the same age showed a marked reduction of motility, accompanied by a global rigidity. Sequence 5) Sepn1−/− Immediately post-FST, week 10. Once taken out of the water, 6 month-old Sepn1−/− mice, which have been practicing FST for 10 weeks, remained stiff with a global body and limbs rigidity. This rigidity lasted for several minutes, before the mice recovered their mobility, a behavior that was not observed in wild-types. Sequence 6) Spontaneous activity of wild-type mice after 10 weeks FST. Six month-old wild-type mice that have been subjected to FST for 10 weeks are shown for comparison with Sequence 7) Sepn1−/− spontaneous activity post 10 weeks FST. Although 6 month-old Sepn1−/− mice subjected to FST for 10 weeks showed normal mobility, they displayed a clear deformation of the back. Sequence 8) Comparison between Sepn1−/− and wild-type, post 14 weeks FST. 14 month-old mutant or wild-type mice practicing FST for 14 weeks. The mutant mouse can easily be distinguished, because of the severe kyphosis. Note that despite the deformation of the back, the SelN-deficient mouse remained active.