RESUMO
<p><b>OBJECTIVE</b>To explore the regulatory effect of fragile X mental retardation protein (FMRP) on the translation of microtubule associated protein 1B (MAP1B).</p><p><b>METHODS</b>The expressions of MAP1B protein and MAP1B mRNA in the brains of 1-week and 6-week old fragile X mental retardation-1 (Fmr1) knockout (KO) mice were investigated by immunohistochemistry, Western blot, and in situ hybridization, with the age-matched wild type mice (WT) as controls.</p><p><b>RESULTS</b>The mean optical density (MOD) of MAP1B was significantly decreased in each brain region in KO6W compared with WT6W, whereas in KO1W, this decrease was only found in the hippocampus and cerebellum. MAP1B in 6-week mice was much less than that in 1-week mice of the same genotype. The results of Western blot and in situ hybridization showed that MAP1B protein and MAP1B mRNA were significantly decreased in the hippocampus of both KO1W and KO6W.</p><p><b>CONCLUSION</b>The decreased MAP1B protein and MAP1B mRNA in the Fmr1 knockout mice indicate that FMRP may positively regulate the expression of MAP1B.</p>