双边身体计划在整个动物王国中占主导地位。随着中线形态发生在原肠胚形成时开始,羊膜胚胎的双侧性变得可识别,将一个胚胎区域分成左右两侧。不久之后,左右不对称也开始。虽然已经广泛研究了在左右分隔后表达的一系列侧向性基因,中线形态发生之前和期间的侧向模式仍不清楚。这里,通过高时空分辨率的生物物理量化,应用于小鸡模型系统,我们表明,大规模的双边反向旋转细胞流动,被称为“波兰运动”,在早期原肠胚形成中显示左右不对称性。这种细胞运动在原始条纹形成之前就开始了,这是最早的中线结构,比侧向性基因的表达更早。细胞流速和涡度揭示了左右不对称性的位置和时间。双侧细胞流在开始时表现出左侧不对称,而是向右翼统治过渡。减少原始条纹形成的有丝分裂停滞导致双侧流动模式的变化,但右翼的统治地位依然存在。我们的数据表明,在节点处的侧向信号的不对称调节导致左右图案之前,羊膜胃中的左右不对称性变得可以检测到。更广泛地说,我们的结果表明,在胚胎发育过程中,物理过程在影响左右向侧性方面发挥了意想不到但显著的作用.
■双边主义者由双边对称的身体计划定义。脊椎动物表现出外部双侧对称性,但在其内部器官中表现出左右(LR)不对称性。在羊膜胚胎中,LR对称性破缺的开始还没有很好的理解。这里,我们研究了雏鸡胚胎中LR对称性的破坏,因为它容易获得并且与人类发育相似。我们量化细胞流动的新生物物理方法推断,LR对称性破坏发生在LR遗传模式程序变得可检测之前。我们的工作表明,定量的生物物理参数可以帮助解开LR对称性破坏的开始,表明物理机制参与了这个关键的生物模式过程。
A bilateral body plan is predominant throughout the animal kingdom. Bilaterality of amniote embryos becomes recognizable as midline morphogenesis begins at gastrulation, bisecting an embryonic field into the left and right sides, and left-right asymmetry patterning follows. While a series of laterality genes expressed after the left-right compartmentalization has been extensively studied, the laterality patterning prior to and at the initiation of midline morphogenesis has remained unclear. Here, through a biophysical quantification in a high spatial and temporal resolution, applied to a chick model system, we show that a large-scale bilateral counter-rotating cellular flow, termed as \'polonaise movements\', display left-right asymmetries in early gastrulation. This cell movement starts prior to the formation of the primitive streak, which is the earliest midline structure, and earlier than expression of laterality genes. The cellular flow speed and vorticity unravel the location and timing of the left-right asymmetries. The bilateral flows displayed a Right dominance after six hours since the start of cell movements. Mitotic arrest that diminishes primitive streak formation resulted in changes in the bilateral flow pattern, but the Right dominance persisted. Our data indicate that the left-right asymmetry in amniote gastrula becomes detectable prior to the point when the asymmetric regulation of the laterality signals at the node leads to the left-right patterning. More broadly, our results suggest that physical processes can play an unexpected but significant role in influencing left-right laterality during embryonic development.
UNASSIGNED: Bilaterians are defined by a bilaterally symmetrical body plan. Vertebrates exhibit external bilateral symmetry but display left-right (LR) asymmetry in their internal organs. In amniote embryos, the initiation of LR symmetry breaking is not well understood. Here, we study LR symmetry breaking in the chick embryo due to its easy accessibility and similarity to human development. Our biophysical approaches to quantify cellular flows inferred that LR symmetry breaking occurs prior to the formation of Hensen\'s node, a LR organizer, which serves as a signaling center for LR patterning programs. Our work demonstrates that quantitative biophysical parameters can help unravel the initiation of LR symmetry breaking, suggesting involvement of physical mechanisms in this critical biological patterning process.