Role of actin polymerization during early s‐looping of the vertebrate embryonic heart

Abstract

During vertebrate development, the embryonic heart undergoes sequential morphogenesis to transition from c‐looping to s‐looping morphology. C‐looping begins at stage 10 (36 hrs.) and finishes by stage 12 (48 hrs.) when the heart tube gets its characteristic c‐shaped bend. Early s‐looping begins shortly thereafter and finishes by stage 16 (56 hrs.), when the primitive atrium moves superior to the primitive ventricle. Previous studies indicated that actin polymerization is essential for cell‐shape changes generating the characteristic bend of c‐looping. Here we extend the study to investigate the role of actin polymerization and orientation in driving the next phase of heart morphogenesis, the early s‐looping stage. Whole 48‐hr chicken embryos are isolated and cultured in varying concentrations of Cytochalasin D, an actin polymerization inhibitor, until the end of early s‐looping. Treated cultures are fixed, stained with Phalloidin‐Alexa 488 and wheat germ agglutinin— Alexa 594, and imaged using confocal microscopy. We will present results from these inhibitor studies detailing the three‐dimensional intracellular arrangement of actin and how this promote changes in overall heart morphology during early s‐looping. Research supported by NIH‐AREA 1F32HL079764.