TPH1 and juvenile idiopathic arthritis: However, our DEA highlighted other transcription factors that may play a role in shaping the transcriptomic landscape of Tph cells, such as BHLHE40. A putative central role for this basic helix-loop-helix transcription factor in oligo JIA SF Tph was supported by the simultaneous upregulation of BHLHE40-AS1 and ID2 in these cells, both of which might act as regulators of BHLHE40.