Development Growth & Differentiation最新文献

During early embryonic development, cells undergo rapid cleavage divisions accompanied by morphological changes driven by mechanical cues. However, the spatiotemporal mechanics of regulative embryonic cells remains poorly understood. Here, we use atomic force microscopy (AFM) to map single-cell stiffness of Xenopus laevis embryos, a model of regulative development, from early cleavage (stage 6) to the onset of gastrulation (stage 11). To ensure stable AFM mapping, vitelline membrane–removed embryos were immobilized in custom grooved agarose wells and gently held using a dulled glass pipette. AFM observations revealed marked mechanical heterogeneity within the animal hemisphere: stiffness in apical cytoplasmic regions—which are defined as the central apical surface excluding cell–cell boundaries—varied among cells, regardless of size, indicating intrinsic variability. Cell–cell boundaries consistently showed high stiffness, as commonly observed in epithelial monolayers in vitro. In contrast, in the vegetal hemisphere during gastrulation, cell–cell boundaries exhibited relatively low stiffness compared with the cytoplasmic regions. Additionally, microscale stiff inclusions were detected in the apical vegetal cytoplasm, with sizes comparable to those of yolk platelets. These findings demonstrate the capability of AFM to probe the microscale mechanical architecture of developing regulative embryos and to uncover regional mechanical asymmetries between the animal and vegetal hemispheres. Such asymmetries may contribute to key morphogenetic processes during early vertebrate development.

The GLI3 gene, a pivotal component of the hedgehog (HH) signaling pathway, plays a fundamental role in the development and patterning of various body structures, including the brain and limbs. Mutations in the GLI3 gene, particularly in the C-terminal domain, are implicated in congenital anomalies such as Greig cephalopolysyndactyly syndrome and Pallister–Hall syndrome. Recent studies have also suggested an archaic human-type mutation in the C-terminal end, which altered downstream gene regulations and anatomical structures in mice. However, the biological effects of the disruption in the Gli3 C-terminal end have not been studied well. Here we report novel Gli3 mutant mice with nonsense mutations in the C-terminal end using CRISPR/Cas12a-mediated genome editing. Analysis of the genotype–phenotype correlations has revealed that the C-terminal end of Gli3 is critical for functional protein synthesis; therefore, the disruption of this region causes severe abnormalities in brain and digit formation. These results provide insight into the mechanisms by which GLI3 mutants can cause adverse consequences during human development or result in diverse phenotypes during evolution.

The avian pallium is comprised of several nuclear regions (four main areas) and differs significantly from the mammalian telencephalon, which is a six-layered structure. Although it is known that cells with identical features at the gene expression level can exist in different regions, it remains unclear whether cells with identical features arise from the same region. In this study, we examined the cell lineages produced from each region by employing the recently developed integration-coupled gene expression On (iOn) switch and performing whole-brain imaging by light-sheet fluorescence microscopy (LSFM). We found that cells born in each area migrate across regions and, therefore, cells with identical characteristics are not always generated from the same progenitor regions. Furthermore, an examination of cell migration patterns in the dorsal ventricular ridge revealed that, as in mammals, cells preferably migrate along radial fibers in the early stages of migration, but radial fibers are not required for later migration. These results support the developmental convergence models recently proposed to describe cell lineage.

Although the differentiation of cardiac progenitors during embryogenesis has been characterized in detail in the ascidian Ciona robusta, heart development after metamorphosis remains unclear. The sub-terminal regions at both ends of the Ciona heart harbor pacemaker cells, as well as undifferentiated cells located within the growth zone. We performed an RNA-Seq analysis to identify transcription factors predominantly expressed in the sub-terminal regions of the Ciona heart. Among the 17 transcription factors predominantly expressed in one or both of the sub-terminal regions, Hox3 showed the strongest expression in both. Since the role of Hox3 during Ciona heart development remained unknown, we investigated the spatial expression and function of Hox3. In situ hybridization revealed the expression of Hox3 in undifferentiated cells within the growth zone at both ends of the heart tube. The TALEN-mediated disruption of Hox3 in cardiac progenitors resulted in irregularly swollen or shortened heart tubes. These results suggest that Hox3 plays a crucial role in heart tube formation by regulating the activity of growth zone cells. Similar Hox3 expression in the terminal regions of ascidian and vertebrate hearts suggests the partial conservation of cardiac patterning and pacemaker localization.

The simple, triploblastic, epithelial body structure of the Patiria pectinifera starfish larva contains one mesenchyme cell type distributed across the blastocoel. In this study, we elucidated the role of a novel astacin metalloproteinase, PpMC5, tethered to the membrane of mesenchyme cells. PpMC5 knockdown by injection of morpholino oligo (MO) into the oocyte inhibited normal growth throughout the bipinnaria stage and caused a dwarfed phenotype consisting of reduced cell number and size, developmental delay, and cell debris in the blastocoel. When transforming growth factor β, P. pectinifera-specific TGFb gene (PpTGFb) preincubated with dissociated PpMC5 control larval cells was injected into the blastocoel of PpMC5 morphants, their dwarfism was significantly rescued. PpTGFb-MO oocyte injection alone only decreased the cell number. Transmission electron microscopy revealed thickening of the basal lamina, oncosis, and apoptosis in PpMC5 morphants. Overall, these results suggest that PpMC5 activates PpTGFb, participates in basal lamina remodeling, regulates epithelial cell proliferation and survival, and promotes larval development. Thus, PpMC5 modulates both cellular and developmental processes.

Anuran tadpoles regenerate their tails after amputation. However, when vitamin A is administered, some anuran species such as Rana ornativentris occasionally form ectopic limbs instead of tail. Few analyses of this phenomenon at the molecular level exist. To investigate the molecular mechanisms underlying ectopic limb development, we quantified the expression of genes related to normal limb positioning and development. We observed the downregulation of a posterior hox gene prior to the appearance of ectopic limb buds in the regenerating tail. This hox expression change also preceded the upregulation of pitx1, which is expressed in the earliest hind limb bud. These results suggest that Hox genes are involved in ectopic limb induction upstream of hind limb genes.

The fate and specification of the endoderm lining the ventral foregut and outside the foregut cranial to the anterior intestinal portal of the 9–12 somite stage avian embryo were analyzed to determine whether this endoderm was specified according to its fate. The ventral foregut endoderm contributed to the ventral endoderm of the gut from the pharynx to the duodenum, and to the thyroid, respiratory organ, and liver. Pre-pharyngeal cells were distributed throughout the ventral foregut, with pre-thyroid cells lying medially in the anterior to middle part and pre-pharyngeal pouch cells lying laterally. Progenitors of posterior organs from the esophagus to the liver were found in the posteriormost quarter, with those of more posterior organs located in more posterior and medial locations. In the endoderm outside the foregut, progenitors of the liver, ventral jejunum, and extraembryonic endoderm were found, with those of more posterior organs taking more anterior locations. When cultured with somatic mesoderm, most parts of the ventral foregut endoderm showed pharynx/esophagus-like differentiation, whereas the middle part developed thyroid-like follicles. The posteriormost part exhibited stomach-like differentiation, as well as intestinal and pancreatic differentiation, which also appeared from the endoderm outside the foregut. It showed no or a rare appearance of a hepatic cord–like structure or albumin, respectively, but often developed bile duct–like Hex-expressing epithelia. However, the expression of Nkx2.1 but not of Hex, which is characteristic of the pulmonary epithelium, was not observed. These endoderms are likely to be specified in almost complete accordance with their fate, except for the respiratory organ.

Superoxide dismutases (SODs) are key regulators of reactive oxygen species (ROS) and redox balance. Although intracellular SODs have been extensively studied, growing attention has been directed toward understanding the roles of extracellular SODs in both Dictyostelium and mammalian systems. In Dictyostelium discoideum, SodC is a glycosylphosphatidylinositol (GPI)-anchored enzyme that modulates extracellular superoxide to regulate Ras, PI3K signaling, and cytoskeletal remodeling during directional cell migration. Loss of SodC leads to persistent Ras activation, impaired migration, and defective vesicle trafficking, including contractile vacuole (CV) morphogenesis and function. The mammalian EC-SOD (SOD3) localizes not only on the extracellular heparin-binding sites but also within vesicular compartments such as phagosomes, secretory vesicles, and exosomes. EC-SOD limits inflammation, preserves the extracellular matrix, modulates immune and cancer cell migration, and modulates Ras–Erk and PI3K-PKB signaling pathways. Despite evolutionary divergences, both SodC in Dictyostelium and EC-SOD in humans serve to modulate extracellular oxidative cues and maintain cellular function. The conserved and multifaceted roles of extracellular SODs in redox regulation, signaling, vesicle trafficking, and cell migration offer insights relevant to both fundamental biology and disease.

Multicellular organisms generate organizational complexity through morphogenesis, in which mechanical forces orchestrate the movements and deformations of cells and tissues, while chemical signals regulate the molecular events that generate and coordinate these forces. One common denominator that is critical both for mechanics and biochemistry is material property. Material properties define how materials deform or rearrange under applied forces, and how rapidly molecules interact or spread in space and time. Notably, at the two length scales that are highly relevant to multicellular morphogenesis—tissue and cytoplasmic—material properties undergo rigidity transitions. For example, tissue structures transition between fluid-like and solid-like states, while cytoplasm undergoes changes in the degrees of crowdedness and diffusivity. These transitions in space and time, as well as their underlying mechanisms, have emerged as a crucial area of research for the understanding of morphogenesis. However, tissue-scale and cytoplasmic transitions have thus far been studied primarily in separate settings designed specifically for each length scale, even though tissue properties typically arise from cellular and cytoplasmic processes—such as cell–cell adhesion, cell motility, membrane/cortical tension, and intracellular signaling, while cells themselves operate within tissues, responding to mechanical and chemical signals that spread across them. Here we review the mechanisms controlling rigidity transitions at both scales and propose an integrated, multi-scale perspective, in which we explore plausible feedback mechanisms that can link the two scales. By bridging this conceptual gap, we aim to forecast new biological mechanisms that control morphogenesis beyond the physical principles governing rigidity transitions in inert systems.