Polarized epithelial morphogenesis is an essential process in animal development. While this process is mostly attributed to directional cell intercalation, it can also be induced by other mechanisms. Using live-imaging analysis and a three-dimensional vertex model, we identified ‘cell sliding,’ a novel mechanism driving epithelial morphogenesis, in which cells directionally change their position relative to their subjacent (posterior) neighbors by sliding in one direction. In Drosophila embryonic hindgut, an initial left-right (LR) asymmetry of the cell shape (cell chirality in three dimensions), which occurs intrinsically before tissue deformation, is converted through LR asymmetric cell sliding into a directional axial twisting of the epithelial tube. In a Drosophila inversion mutant showing inverted cell chirality and hindgut rotation, cell sliding occurs in the opposite direction to that in wild-type. Unlike directional cell intercalation, cell sliding does not require junctional remodeling. Cell sliding may also be involved in other cases of LR-polarized epithelial morphogenesis.

We present the experimental observation of pulsed squeezed light from a degenerate optical parametric amplifier pumped by a second harmonic of a continuous-wave mode-locked $\mathrm{Nd}:{\mathrm{YVO}}_4$ laser. With a single pass through a 10 mm long periodically poled ${\mathrm{KTiOPO}}_4$ crystal, the classical parametric gain of 11 is observed. The measured noise reduction in the quiet quadrature is 3.2 dB below the shot-noise level.

How left–right (LR) asymmetric forms in the animal body is a fundamental problem in Developmental Biology. Although the mechanisms for LR asymmetry are well studied in some species, they are still poorly understood in invertebrates. We previously showed that the intrinsic LR asymmetry of cells (designated as cell chirality) drives LR asymmetric development in the Drosophila embryonic hindgut, although the machinery of the cell chirality formation remains elusive. Here, we found that the Drosophila homologue of the Id gene, extra macrochaetae (emc), is required for the normal LR asymmetric morphogenesis of this organ. Id proteins, including Emc, are known to interact with and inhibit E‐box‐binding proteins (E proteins), such as Drosophila Daughterless (Da). We found that the suppression of da by wild‐type emc was essential for cell chirality formation and for normal LR asymmetric development of the embryonic hindgut. Myosin ID (MyoID), which encodes the Drosophila Myosin ID protein, is known to regulate cell chirality. We further showed that Emc‐Da regulates cell chirality formation, in which Emc functions upstream of or parallel to MyoID. Abnormal Id‐E protein regulation is involved in various human diseases. Our results suggest that defects in cell shape may contribute to the pathogenesis of such diseases.

The chirality of tissues and organs is essential for their proper function and development. Tissue-level chirality derives from the chirality of individual cells that comprise the tissue, and cellular chirality is considered to emerge through the organization of chiral molecules within the cell. However, the principle of how molecular chirality leads to cellular chirality remains unresolved. To address this fundamental question, we experimentally studied the chiral behaviors of isolated epithelial cells derived from a carcinoma line and developed a theoretical understanding of how their behaviors arise from molecular-level chirality. We first found that the nucleus undergoes clockwise rotation, accompanied by robust cytoplasmic circulation in the same direction. During the rotation, actin and Myosin IIA assemble into the stress fibers with a vortex-like chiral orientation at the ventral side of the cell periphery, concurrently forming a concentric pattern at the dorsal side. Further analysis revealed that the intracellular rotation is driven by the concentric actomyosin filaments located dorsally, not by the ventral vortex-like chiral stress fibers. To elucidate how these concentric actomyosin filaments induce chiral rotation, we analyzed a theoretical model developed based on the theory of active chiral fluid. This model demonstrated that the observed cell-scale unidirectional rotation is driven by the molecular-scale chirality of actomyosin filaments even in the absence of cell-scale chiral orientational order. Our study thus provides novel mechanistic insights into how the molecular chirality is organized into the cellular chirality, representing an important step toward understanding left–right symmetry breaking in tissues and organs.

Chirality is a fundamental feature in biology, from the molecular to the organismal level. An animal has chirality in the left–right asymmetric structure and function of its body. In general, chirality occurring at the molecular and organ/organism scales has been studied separately. However, recently, chirality was found at the cellular level in various species. This “cell chirality” can serve as a link between molecular chirality and that of an organ or animal. Cell chirality is observed in the structure, motility, and cytoplasmic dynamics of cells and the mechanisms of cell chirality formation are beginning to be understood. In all cases studied so far, proteins that interact chirally with F-actin, such as formin and myosin I, play essential roles in cell chirality formation or the switching of a cell’s enantiomorphic state. Thus, the chirality of F-actin may represent the ultimate origin of cell chirality. Links between cell chirality and left–right body asymmetry are also starting to be revealed in various animal species. In this review, the mechanisms of cell chirality formation and its roles in left–right asymmetric development are discussed, with a focus on the fruit fly Drosophila, in which many of the pioneering studies were conducted.

Division of labor is a prominent feature of social insect societies, where different castes engage in different specialized tasks. As brain differences are associated with behavioral differences, brain anatomy may be linked to caste polymorphism. Here, we show that termite brain morphology changes markedly with caste differentiation and age in the termite, Reticulitermes speratus. Brain morphology was shown to be associated with reproductive division of labor, with reproductive individuals (alates and neotenic reproductives) having larger brains than nonreproductives (workers and soldiers). Micro‐computed tomography (CT) imaging and dissection observations showed that the king's brain morphology changed markedly with shrinkage of the optic lobes during their long life in the dark. Behavioral experiments showed that mature primary kings lose visual function as a result of optic lobe shrinkage. These results suggested that termites restructure their nervous systems to perform necessary tasks as they undergo caste differentiation, and that they also show flexible changes in brain morphology even after the final molt. This study showed that brain morphology in social insects is linked to caste and aging, and that the evolution of the division of labor is underpinned by the development of diverse neural systems for specialized tasks.