Of all Y-chromosomal genes, the sex-determining region Y (SRY) gene is the most studied.189 SRY is a DNA-binding transcription factor regulating gene expression at the early initiation of testes development, but SRY also functions outside the reproductive system.190 As such, SRY directly binds the promoter of BMPR2 to upregulate BMPR2 expression in PAH fibroblasts.191 As females lack SRY, this BMPR2 transcriptional regulation does not occur. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.