The C-terminal tail is not involved in BMP-induced Smad signaling, however, in patients suffering from primary pulmonary hypertension (PPH), the C-terminal tail of BMPR-II was found to be truncated, suggesting a unique role for BMPR-II in Smad-independent signaling [27, 28]. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.