Development Growth & Differentiation最新文献

The neural tube, the embryonic precursor to the vertebrate central nervous system, comprises distinct progenitor and neuronal domains, each with specific proliferation programs. In this study, we identified TMEM196, a novel transmembrane protein that plays a crucial role in regulating cell proliferation in the floor plate in chick embryos. TMEM196 is expressed in the floor plate, and its overexpression leads to reduced cell proliferation without affecting the pattern formation of the neural tube. We also established the floor plate differentiation protocol of the mouse embryonic stem cells, and analyzed the function of TMEM196 with this system. Mutating the Tmem196 gene does not alter cell division and overall differentiation remains unchanged within the neural cells. However, TMEM196 inhibits Wnt signaling, and Tmem196 mutant cells exhibit aberrant paraxial mesoderm differentiation, suggesting that TMEM196 selects the floor plate cell fate at the binary decision of the neuromesodermal cells. These findings highlight TMEM196 as a key regulator of both cell proliferation and floor plate determination, contributing to proper regionalization during embryogenesis.

Recent molecular phylogenetic studies have raised two questions about the evolutionary history of the calcified exoskeleton of mollusks. The first question concerns the homology of the two types of skeleton: whether spicules and shell plates share an evolutionary origin. The second question is the homology of the shell plates between chitons and other mollusks, including gastropods and bivalves. To gain insight into these questions, we examined the early development of shell plates and spicules in chitons. We identified several developmental genes that are involved in both shell plates and spicules, suggesting that spicules and shell plates share a common evolutionary origin. We also found that subpopulations of the dorsal shell field (the ridge and the plate field) have specific gene expression profiles. The differential gene expression of the ridge and plate field is not identical to the profiles of the zones of the gastropod shell field. This observation may suggest an independent evolutionary origin of the shell plates in chitons and gastropods.

Sonic Hedgehog (Shh), encoding an extracellular signaling molecule, is vital for heart development. Shh null mutants show congenital heart disease due to left–right asymmetry defects stemming from functional anomaly in the midline structure in mice. Shh signaling is also known to affect cardiomyocyte differentiation, endocardium development, and heart morphogenesis, particularly in second heart field (SHF) cardiac progenitor cells that contribute to the right ventricle, outflow tract, and parts of the atrium. Despite extensive studies, our understanding remains incomplete. Notably, Shh signaling is suggested to promote cardiac differentiation, while paradoxically preventing premature differentiation of SHF progenitors. In this study, we elucidate the role of Shh signaling in the earliest phase of cardiac differentiation. Our meta-analysis of single-cell RNA sequencing suggests that cardiogenic nascent mesoderm cells expressing the bHLH transcription factor Mesp1 interact with axial mesoderm via Hh signaling. Activation of Hh signaling using a Smoothened agonist delayed or suppressed the differentiation of primitive streak cells expressing T-box transcription factor T to Mesp1⁺ nascent mesoderm cells both in vitro and ex vivo. Conversely, inhibition of Hh signaling by cyclopamine facilitated cardiac differentiation. The reduction of Eomes, an inducer of Mesp1, by Hh signaling appears to be the underlying mechanism of this phenomenon. Our data suggest that SHH secreted from axial mesoderm inhibits premature differentiation of T⁺ cells to Mesp1⁺ nascent mesoderm cells, thereby regulating the pace of cardiac differentiation. These findings enhance our comprehension of Shh signaling in cardiac development, underscoring its crucial role in early cardiac differentiation.

Despite the significant literature about morphological features of limb skeletons involved in tetrapod limb evolution, some questions about carpal and tarsal elements remain. In anurans, the ecomorphological and biomechanical approaches studied long hind limbs (to jump) and forelimbs (to land) and emphasized the role of the long bones in locomotion but disregarded what happens with the nodular elements of the carpus and tarsus. Here, we present a comparative study of nodular elements of the carpus and tarsus in anurans based on whole-mount specimens stained with Alcian Blue (cartilage) and Alizarin Red S (bone and calcified cartilage). The sample comprises 113 species belonging to 33 anuran families and postmetamorphic series in selected species. Further, we analyze the histology of the carpus and tarsus in individuals of nine species. In most anurans, the carpal and tarsal elements are cartilaginous in adult stages. The cartilaginous matrix may present different degrees of calcification. Few taxa present truly ossified carpals and tarsals with marrow cavity, blood cells, and hematopoietic cells. Interpretation of the interspecific variation in the carpus and tarsus skeletons on the most recent anuran phylogeny suggests that the delayed ossification of carpals and tarsals has evolved in derived lineages (e.g. Pelobatoidea and Neobatrachia).

Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression, in conjunction with cyclins. The cyclin-CDK system is highly conserved among eukaryotes, and CDK1 is considered essential for progression through the M phase. However, the extent to which cell cycle progression depends on CDK1 varies between cell types. Therefore, a range of cell types must be analyzed to comprehensively elucidate the role of CDK1. Cdk1-knockout mice exhibit lethality at an early developmental stage, specifically before the differentiation of various cell types. The aim of the present study was to characterize the effects of CDK1 deficiency in amphibian newts. Cdk1 was disrupted by injecting fertilized newt eggs with CRISPR/Cas9, and the resulting effects on embryonic development and cell proliferation were then evaluated. In both wild-type and Cdk1-crispant newt embryos, CDK1 protein was either stored in the egg until late embryogenesis or potentially derived from maternal mRNA, which may also be stored during this period. The embryos survived to the hatching stage, during which the cells responsible for forming the basic organs differentiated. To further characterize the long-term effects of Cdk1 knockout, parabiosis experiments were conducted using wild-type embryos and Cdk1 crispants. The results suggested that an endocycle occurred in the crispant larvae, as evidenced by increases in the size of several types of cells. It is anticipated that studies using newts will provide further insights into the role of Cdk1 in regulating the cell cycle.

From September 16 to 19, 2024, an international symposium to celebrate the centennial of the discovery of the gastrula organizer by Hans Spemann and Hilde Mangold, was held at the University of Freiburg, Germany, where they studied embryology. There were 41 plenary lectures, 11 short talks, and 182 poster presentations, with more than 300 participants from 23 countries. The symposium covered research topics broadly related to developmental, cell, genome, and evolutionary biology, mainly focused on early animal development. In addition to in vivo studies on topics such as gastrulation, embryonic patterning, cell polarity, and morphogenesis, recent studies using gastruloids and organoids, which recapitulate embryogenesis and organogenesis in in vitro cell culture, were also presented at this symposium, entitled Self-Organization in Biology. Most of the reported studies used vertebrate models such as mice, frogs, and zebrafish; however, evolutionary studies involving invertebrate and plant models were also presented. Presentations employing traditional methods such as cell transplantation and phenotype screening, and state-of-the-art technologies such as single-cell omics, high-resolution imaging, and computational analysis showed that experimental embryology has a long history, to which studies of the organizer have contributed significantly. Here we discuss memorable aspects of the symposium in the hope that this report will encourage young scientists to actively participate in face-to-face international conferences.

5′Hox genes regulate pattern formation along the axes of the limb. Previously, we showed that Hoxa13/Hoxd13 double-mutant newts lacked all digits of the forelimbs during development and regeneration, showing that newt Hox13 is necessary for digit formation in development and regeneration. In addition, we found another unique phenotype. Some of the Hox13 crispant newts showed hindlimb defects, in which whole or almost whole hindlimbs were lost, suggesting a novel function of Hox13 in limb development. Using germline mutants, we showed that mutation in Hox13 led to hindlimb defects. The limb buds of Hox13 crispants formed, however, did not show outgrowth. Expression of Fgf10 and Tbx4, which are involved in limb outgrowth, decreased in the hindlimb buds of Hox13 crispants. In addition, hindlimb defects were observed in both Fgf10 and Tbx4 crispant newts. Finally, Fgf10 and Tbx4 interacted with Hox13 genetically. Our results revealed a novel function of Hox13 in regulating the outgrowth of the newt hindlimb bud through interaction with Fgf10 and Tbx4.

Transcription factors collaborate with epigenetic regulatory factors to orchestrate cardiac differentiation for heart development, but the underlying mechanism is not fully understood. Here, we report that GATA-6 induces cardiac differentiation but peroxisome proliferator-activated receptor α (PPARα) reverses GATA-6-induced cardiac differentiation, possibly because GATA-6/PPARα recruits the polycomb protein complex containing EZH2/Ring1b/BMI1 to the promoter of the cardiac-specific α-myosin heavy chain (α-MHC) gene and suppresses α-MHC expression, which ultimately inhibits cardiac differentiation. Furthermore, Ring1b ubiquitylates PPARα and GATA-6. By overexpression and knockout of EZH2/BMI1, it was demonstrated that the polycomb protein complex inhibits cardiac differentiation induced by GATA-6 and PPARα. Together, our results demonstrate that the polycomb protein complex interacts with GATA-6/PPARα to inhibit cardiac differentiation, a finding that could facilitate the development of new therapies for congenital heart disease.

In the embryonic neuroepithelium (NE), neural progenitor cells undergo cell cycle-dependent interkinetic nuclear migration (IKNM) along the apicobasal axis. Extensive IKNM supports increasing cell production rates per unit apical surface, as typically observed in the mammalian telencephalic NE. Apical nucleokinesis during the G2 phase is an essential premitotic event, but its occurrence has not yet been quantitatively analyzed at a large 3D-scale with sufficient spatiotemporal resolution. Here, we comprehensively analyzed apically migrating nuclei/somata in reference to their surroundings from embryonic day (E)11 to E13 in the mouse telencephalon. The velocity of apical nucleokinesis decreased, with more frequent nuclear pausing occurring at E12 and E13, whereas the nuclear density in the middle NE zone (20–40-μm deep) increased. This result, together with the results of Shh-mediated overproliferation experiments in which the nuclear density was increased in vivo at E11, suggests that apical nucleokinesis is physically influenced by the surrounding nuclei. Mean square displacement analysis for nuclei being passed by the apically migrating nuclei via horizontal sectioning in toto-recorded movies revealed that the “tissue fluidity” or physical permissiveness of the NE to apical nucleokinesis gradually decreased (E11 > E12 > E13). To further investigate the spatial relationship between preexisting mitoses and subsequent premitotic apical nucleokinesis, the horizontal distribution of mitoses was cumulatively (~3 hr) analyzed under in toto monitoring. The four-dimensional cumulative apical mitoses presented a “random”, not “clustered” or “regular”, distribution pattern throughout the period examined. These methodologies provide a basis for future comparative studies of interspecies differences.