Multiple pkd and piezo gene family members are required for atrioventricular valve formation

Abstract

Cardiac valves ensure unidirectional blood flow through the heart, and altering their function can result in heart failure. Flow sensing via wall shear stress and wall stretching through the action of mechanosensors can modulate cardiac valve formation. However, the identity and precise role of the key mechanosensors and their effectors remain mostly unknown. Here, we genetically dissect the role of Pkd1a and other mechanosensors in atrioventricular (AV) valve formation in zebrafish and identify a role for several pkd and piezo gene family members in this process. We show that Pkd1a, together with Pkd2, Pkd1l1, and Piezo2a, promotes AV valve elongation and cardiac morphogenesis. Mechanistically, Pkd1a, Pkd2, and Pkd1l1 all repress the expression of klf2a and klf2b, transcription factor genes implicated in AV valve development. Furthermore, we find that the calcium-dependent protein kinase Camk2g is required downstream of Pkd function to repress klf2a expression. Altogether, these data identify, and dissect the role of, several mechanosensors required for AV valve formation, thereby broadening our understanding of cardiac valvulogenesis.

egr3 is a mechanosensitive transcription factor gene required for cardiac valve morphogenesis

“…Not all VICs in nr4a2b OE hearts were dTomato + , indicating that Nr4a2b may also act in a cell nonautonomous fashion in this process. As previously reported for klf2a overexpression in the AV canal, using an nfatc:Gal4 line ( 15 ), we found that nr4a2b has an inhibitory effect on valve formation in egr3 +/− larvae (fig. S5, D and E), suggesting that nr4a2b expression needs to be tightly regulated during valvulogenesis.…”

“…During early development, the valveless embryonic heart achieves unidirectional blood flow in part because of localized contraction waves and a simple vascular network ( 43 ) whose capacitance provides pressure storage and diminishes cardiac efforts ( 44 ). By 72 hpf, the AV EdCs have folded into a functional prevalvular structure capable of reducing retrograde blood flow and therefore supporting cardiac output ( 10 , 14 , 15 ). egr3 mutants, of both alleles, are indistinguishable from their wild-type siblings until 72 hpf when they start to exhibit noticeable pericardial edema ( Fig.…”

“…During heart development, the specialized endothelial cells lining the cardiac wall, known as endocardial cells (EdCs), invade the adjacent extracellular matrix (ECM) in the atrioventricular (AV) canal and outflow tract (OFT) in response to oscillatory shear stress (9)(10)(11). These migrating EdCs acquire mesenchymal characteristics, differentiate into valve interstitial cells (VICs), and proliferate to give rise to the valve leaflets (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), which are essential for cardiac function as they guarantee unidirectional blood flow.…”

Specific CaMKIIs mediate convergent extension cell movements in early zebrafish development

“…Camk2b1 crispants have also been generated and phenocopy camk2b1 morphants (Figures S1 and S2). MO‐based approaches remain valuable since stable CaMKII mutants can be compensated for by CaMKII paralogs 22,31 …”

“…MO-based approaches remain valuable since stable CaMKII mutants can be compensated for by CaMKII paralogs. 22,31 MOs also remain advantageous for early developmental studies as they can target both maternal and zygotic transcripts. Only two of the eight CaMKII ORFs, camk2b1 and camk2g1, showed morphant phenotypes consistent with roles in CE.…”