BMPR2 and pulmonary arterial hypertension: The genetic impact on PAH development suggest a protective role for specific genes expressed from the Y-chromosome.25 The Y-chromosomal expressed SRY transcription factor upregulates BMPR2 expression in PAH fibroblasts.191 As discussed above, TGFβ signalling can influence X-chromosomal inactivation in females, further enhancing TGFβ signalling disbalance in PAH.