BMPR2 affects valve development via ECM-receptor interaction in zebrafish.

Abnormal cardiac valve development may lead to functional impairment in adulthood. BMPR2, a highly conserved receptor of the BMP family, exists in two subtypes (bmpr2a and bmpr2b) in zebrafish. However, the roles of bmpr2a and bmpr2b in valve development remain unclear. In this study, we generated three bmpr2a/b mutant zebrafish strains, namely, bmpr2a- and bmpr2b-knockout zebrafish (bmpr2a (-/-) and bmpr2b (-/-) , respectively) using CRISPR/Cas9 and bmpr2a and bmpr2b double-knockout zebrafish (bmpr2a (-/-) ;bmpr2b (-/-) ) according to bmpr2a (-/-) and bmpr2b (-/-) hybridization. Using cardiac function assessment (M-mode), we characterized the cardiac developmental phenotypes of the three zebrafish mutant strains. Transcriptomic profiling (RNA-seq) was combined with whole-mount in situ hybridization (WISH) and qRT-PCR to validate gene-expression changes. The results indicated that bmpr2a (-/-) , bmpr2b (-/-) , and bmpr2a (-/-) ;bmpr2b (-/-) mutant zebrafish strains exhibited valve developmental defects at 52 hours post-fertilization (hpf), followed by cardiac contractile dysfunction. RNA-seq revealed upregulation of cardiac markers (myl9a, myl9b, tnnc1a, cmlc1, myl7, and nppa) and valve-related genes (fn1b, has2, and nfatc1), along with the downregulation of klf2a, as validated by WISH and qRT-PCR. Pathway analysis identified the ECM-receptor interaction as a key regulatory axis of bmpr2a/b-mediated valve development. In this study, we demonstrate that bmpr2a and bmpr2b cooperatively regulate cardiac contractile function and valve development in zebrafish, providing insights into BMPR2-mediated cardiovascular morphogenesis in humans.