Two Smad1 and Smad4 bind to the nucleus and bind to specific transcriptional promoters or repressors, which act on transcriptional regulators to inhibit cell proliferation and promote cell apoptosis.[6] Therefore, it is presumed that abnormal BMPR2, as a cell surface receptor, may disrupt the signal pathway mediated by BMPR2, leading to uncontrolled proliferation of pulmonary artery wall cells, thus causing pulmonary arterial hypertension.[7]. Here, SMAD1 is linked to pulmonary arterial hypertension.