Furthermore, ID3 has been demonstrated to be a downstream target of the TGFβ/BMP7 signaling pathway, which has been known to play a significant role in various cellular processes such as migration, apoptosis, and proliferation alongside the processes of angiogenesis using two pathways: ALK5-SMAD2/3 pathway and ALK1-SMAD1/5/8 pathway, important processes/pathways involved in PAH and HHT [11–14]. Here, SMAD1 is linked to pulmonary arterial hypertension.