OBJECTIVE: To study the effects of Down syndrome cellular adhesion molecule (DSCAM) on differentiation of rat marrow mesenchymal stem cells (MSCs) into neurons in vitro. METHODS: MSCs from Sprague-Dawley rats were induced into neurons by baicalin. The expression of DSCAM before and after induction was evaluated by immunocytochemical staining and Western blot assay. After knockdown of DSCAM by siRNA transfection, the differentiation rate of neurons derived from MSCs was measured. RESULTS: Before induction, the expression of DSCAM was not detectable in MSCs. After bFGF preinduction for 24 hrs, DSCAM was slightly expressed in MSCs (1.71±0.67%). The DSCAM expression increased 6 hrs after baicalin induction (15.79±4.24%), reached a peak at 3 days (53.16±5.94%) and then decreased gradually. The DSCAM expression 6 days after baicalin induction (28.99±6.72%) was significantly lower than that at 3 days (P<0.01). However, after DSCAM-siRNA transfection, the DSCAM expression in MSCs was significantly reduced. MSCs did not express neuron-specific β-III-tubulin before induction. After baicalin induction for 6 hrs, 3 days and 6 days, the expression of β-III-tubulin was 1.40±0.79%, 41.59±3.17% and 59.11±4.76% respectively. But the β-III-tubulin expression significantly decreased 3 and 6 days after DSCAM-siRNA transfection (28.57±2.91% and 43.90±12.31% respectively). CONCLUSIONS: DSCAM may play an important role in MSCs differentiation into neural cells.［Chin J Contemp Pediatr, 2009, 11 (6):486-489］