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.