Expression pattern and functional analysis of mouse Stam2 in the olfactory system

Gene trap mutant mice Stam(gt1Gaj) were investigated in order to elucidate in vivo function of Stam2 (signal transducing adaptor molecule 2) gene, which was in vitro implicated in sorting cargo marked by monoubiquitination toward degradation in the lysosomes. The expression analysis showed high Stam2 expression in the brain including the regions related to olfaction, and in the olfactory epithelium, but not in the respiratory part of nasal mucosa. To test mouse olfaction, ability to find chocolate hidden under the sawdust in the cage was examined. When food was given ad libitum before trials, mutants needed more time and failed more frequently to find the chocolate. In contrast, when the mice were fasted overnight before trial, there were no differences between mutants and wild type mice. No changes in morphology of olfactory mucosa were observed. The obtained results showed the existence of phenotype differences between mutants and wild type mice. However, different results of two approaches aimed to test olfaction, with and without food deprivation, currently do not enable to assign the particular function of Stam2 to olfaction. This emphasizes how slight modification of experimental setup in behavioural testing can cause important differences on the obtained results.