The morphogenesis of developing tissues relies on extensive cellular rearrangements in shape, position, and identity. A key process in reshaping tissues is cell intercalation-driven elongation, where epithelial cells align and intercalate along a common axis. Typically, analyses focus on how peripheral cortical forces influence cell shape changes. Less attention is given to how inhomogeneities in internal structures, particularly the nucleus, impact cell shaping. Here, we examine how pulsed contractile and extension dynamics interact with the nucleus in elongating Drosophila embryos. Our data show that tightly packed nuclei in apical layers hinder tissue remodeling/oscillatory behaviors. We identify two mechanisms for resolving internuclear tensions: nuclear deformation and dispersion. Embryos with non-deformable nuclei use nuclear dispersion to maintain near-normal extensile rates, while those with non-dispersible nuclei due to microtubule inhibition exhibit disruptions in contractile behaviors. Disrupting both mechanisms leads to severe tissue extension defects and cell extrusion. These findings highlight the critical role of nuclear shape and positioning in topological remodeling of epithelia.

中文翻译：

---

细胞核在上皮重塑过程中作为机械缓冲器。


发育中组织的形态发生依赖于形状、位置和身份方面广泛的细胞重排。重塑组织的一个关键过程是细胞嵌入驱动的伸长，其中上皮细胞沿着共同轴排列和嵌入。通常，分析的重点是外围皮质力如何影响细胞形状的变化。人们很少关注内部结构（特别是细胞核）的不均匀性如何影响细胞形状。在这里，我们研究了脉冲收缩和伸展动力学如何与伸长的果蝇胚胎中的细胞核相互作用。我们的数据表明，顶端层紧密堆积的细胞核阻碍组织重塑/振荡行为。我们确定了解决核间紧张局势的两种机制：核变形和分散。具有不可变形细胞核的胚胎利用核分散来维持接近正常的伸展率，而那些由于微管抑制而具有不可分散细胞核的胚胎表现出收缩行为的破坏。破坏这两种机制会导致严重的组织延伸缺陷和细胞挤出。这些发现强调了核形状和定位在上皮拓扑重塑中的关键作用。