Specifically, knockdown of TSPAN5 in iPSC-derived neurons to 5% of its baseline significantly decreased 5-HT concentrations in the culture media (Fig. 1e, f), with associated downregulation of the expression of DDC, TPH1, TPH2, MAOA, MAOB (Fig. 1g), consistent with our previous report that used a neuroblastoma cell line, SK-N-BE(2) [1]. Here, TPH2 is linked to neuroblastoma.