Meeting Abstract

34.4  Friday, Jan. 4  Robustness of gastrulation to biomechanical variation among embryos of Xenopus laevis VON DASSOW, M.**; DAVIDSON, L.A.; Univ. of Pittsburgh; Univ. of Pittsburgh mvondass@yahoo.com

Embryo mechanical properties are important in morphogenesis because tissue movements are a function of both the forces exerted by cells and the mechanical properties of the tissues on which those forces act. To determine how robust gastrulation is to variation in tissue stiffness, we have adapted pipette aspiration to make non-destructive measurement of the stiffness of Xenopus laevis gastrula stage embryos. This method allows estimation of embryo-to-embryo variability in stiffness by making repeated measurements on individual embryos and observing their subsequent development. Natural embryo-to-embryo variation in stiffness places a lower bound on how robust morphogenesis is to stiffness. Furthermore, if stage-to-stage differences in stiffness are a significant factor in guiding morphogenesis, they must be consistent from embryo-to-embryo. We measure the displacement of a small portion of the embryo surface into a 125 �m diameter channel as we drop the pressure within the channel. The apparent stiffness is nearly linear for displacements of 1/4 to 1/2 of the channel radius. Over long time scales (45 minutes), substantial contractions and relaxations of the aspirated tissue are common and last several minutes. Preliminary measurements of the changes in stiffness of the dorsal quadrant during gastrulation suggest that embryo stiffness increases by a factor of 9 (median) between stages 10 and 12. An increase in stiffness is apparent in all embryos examined so far, although the magnitude varies greatly, from 1.7 to 74 fold. Contractions and relaxations of the tissue may contribute to this variation. All embryos completed blastopore closure. Our preliminary results suggest that the embryo-to-embryo differences in stiffness are smaller than the stage-to-stage differences in stiffness.