Fig. 2

Zebrafish heart development and role of PRC1/PRC2 in heart development. a Heart development in zebrafish begins shortly after fertilization. During gastrulation, cardiac progenitor cells migrate towards the midline and localize in the anterior lateral plate mesoderm (ALPM). By 15 h post-fertilization (hpf), cardiac progenitor cells are established, and by 19 hpf, they migrate and fuse at the midline to form a cardiac disc. By 24 hpf, this disc transitions into a heart tube, which begins beating and initiates circulation throughout the body. At 36 hpf, the heart undergoes leftward bending, forming an "S" shape that defines the future atria and ventricle. Chamber formation and alignment occur during the hatching period (48–72 hpf), when the heart begins to pump blood irregularly. After 48hpf, valve formation at the AV canal, IFT, OFT, and BA development occurs to ensure blood flow from the heart to the gills. b PRC2 is involved in regulating the early stages of heart development, while PRC1 contributes to the the formation and specification of the chambered heart from the looped heart structure. c In embryos lacking PRC1 and PRC2, the heart fails to undergo proper looping, resulting in a string-like appearance. PRC1 is essential for cardiac sarcomere assembly, the maintenance of cardiac contraction, and the formation of the atrioventricular canal (AVC) and valve structures between the atria and ventricle. In PRC1-deficient embryos, AVC and valve development are disrupted, along with impairments in the cardiac conduction system (CCS). V, ventricle; A, atria; BA, bulbous arteriosus; AVC, atrioventricular canal; OFT, outflow tract; IFT, inflow tract