Teratogenic Drug Topiramate Upregulates TGFβ1 and SOX9 Expression in Primary Palatal Mesenchyme Cells

Topiramate is a commonly prescribed anti-epileptic drug with over 8 million prescriptions dispensed annually. Topiramate use during pregnancy has been linked to significantly increased risk of babies born with orofacial clefts (OFCs). However, the exact molecular mechanism of topiramate teratogenicity is unknown. We used an unbiased antibody array analysis to test the effect of topiramate on human embryonic palatal mesenchyme (HEPM) cells. This analysis identified 40 differentially expressed proteins, showing strong connectivity to known OFC genes. However, among known OFC genes, only TGF{beta}1 was significantly upregulated in the antibody array analysis. Next, we validated that topiramate could increase expression of TGF{beta}1 and of downstream target phospho-SMAD2 in primary mouse embryonic palatal mesenchyme (MEPM) cells. Furthermore, we showed that topiramate treatment of primary MEPM cells increased expression of SOX9. SOX9 overexpression in chondrocytes is known to cause cleft palate in mouse. We propose that topiramate mediates upregulation of TGF{beta}1 signaling through activation of {gamma}-aminobutyric acid (GABA) receptors in the palate. TGF{beta}1 and SOX9 play critical roles in orofacial morphogenesis, and their abnormal overexpression may underlie the teratogenic effects of topiramate.