
前腸中胚葉の前腸内胚葉と前腸中胚葉の分離は、Nodal-Lefty制御ループと染色体リモデリングによって調節される。


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During gastrulation, the mesendoderm is firstly specified by morphogens such as Nodal, and then segregates into endoderm and mesoderm in a Nodal concentration-dependent manner. However, the mechanism underlying the segregation and crosstalk of different sub-groups within the meso- and endoderm lineages remains unclear. Here, taking zebrafish prechordal plate (PP) and anterior endoderm (Endo) as research model, using single-cell multi-omics and live imaging analyses, we show that anterior Endo progenitors originate directly from PP progenitors. A single-cell transcriptomic trajectory analysis of wild-type, ndr1 knockdown and lft1 knockout Nodal explants confirms the diversification of anterior Endo fate from PP progenitors. Gene Ontology (GO) enrichment analysis indentifies that the change of chromatin organization potentiates the segregation of endodermal cell fate from PP progenitors. Single-cell ATAC & RNA sequencing further reveals that two transcriptional regulators, gsc and ripply1 , exhibit varied activation patterns in PP and Endo lineages at both the chromatin and RNA expression levels. We further demonstrate that Ripply1 functions coordinately with Gsc to repress endodermal cell fate by directly binding to the cis -elements of sox32 and sox17 . Modulating the expression levels of these regulators tilts the cell fate decision between the PP and Endo lineages.

### Competing Interest Statement

The authors have declared no competing interest.

Ripply1 and Gsc collectively suppress anterior endoderm differentiation from prechordal plate progenitors

単一細胞レベルでのゼブラフィッシュ前腸中胚葉の分離の解剖

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C. elegansの生殖腺形成では、3つのWntタンパク質(CWN-1、CWN-2、EGL-20)がLIN-17/Frizzledレセプターと協調して、生殖腺前駆細胞(SGP)の極性を制御することで、鏡像対称的な組織形成を実現している。


Organogenesis requires the proper production of diverse cell types and their positioning/migration. However, the coordination of these processes during development remains poorly understood. The gonad in C. elegans exhibits a mirror-symmetric structure guided by the migration of distal tip cells (DTCs), which result from asymmetric divisions of somatic gonadal precursors (SGPs; Z1 and Z4). We found that the polarity of Z1 and Z4, which possess mirror-symmetric orientation, is controlled by the redundant functions of the LIN-17/Frizzled receptor and three Wnt proteins (CWN-1, CWN-2, and EGL-20) with distinct functions. In lin-17 mutants, CWN-2 promotes normal polarity in both Z1 and Z4, while CWN-1 promotes reverse and normal polarity in Z1 and Z4, respectively. In contrast, EGL-20 inhibits the polarization of both Z1 and Z4. In lin-17 ; egl-20 cwn-2 triple mutants with a polarity reversal of Z1, DTCs from Z1 frequently miss-migrate to the posterior side. Our further analysis demonstrates that the mis-positioning of DTCs in the gonad due to the polarity reversal of Z1 leads to mis-migration. Similar mis-migration was also observed in cki-1(RNAi) animals producing ectopic DTCs. These results highlight the role of Wnt signaling in coordinating the production and migration of DTCs to establish a mirror-symmetric organ.

### Competing Interest Statement

The authors have declared no competing interest.

Distinct functions of three Wnt proteins control mirror-symmetric organogenesis in the C. elegans gonad

c-elegansの生殖腺形成における3つのwntタンパク質の独自の機能による鏡像対称性の制御


C. elegansの生殖腺形成における3つのWntタンパク質の独自の機能による鏡像対称性の制御



外側視床下部は大脳皮質オリゴデンドロサイト前駆細胞を生成しない。むしろ、内側視床下部と大脳皮質由来の細胞が大脳皮質オリゴデンドロサイト前駆細胞の主な起源である。


The emergence of myelinating oligodendrocytes represents a pivotal developmental milestone in vertebrates, given their capacity to ensheath axons and facilitate the swift conduction of action potentials. It is widely accepted that cortical oligodendrocyte progenitor cells (OPCs) arise from medial ganglionic eminence (MGE), lateral/caudal ganglionic eminence (LGE/CGE) and cortical radial glial cells (RGCs). Here, we used two different fate mapping strategies to challenge the established notion that the LGE generates cortical OPCs. Furthermore, we used a Cre/loxP-dependent exclusion strategy to reveal that the LGE/CGE-derived OPCs are minimal. Additionally, we showed that specifically eliminating MGE-derived OPCs leads to a significant reduction of cortical OPCs. Together, our findings indicate that the contribution of OPCs from LGE/CGE is minimal, contrary to previous beliefs. These findings provide a new view of the developmental origins of cortical OPCs and a valuable foundation for future research on both normal development and oligodendrocyte-related disease.

### Competing Interest Statement

The authors have declared no competing interest.

The Lateral/Caudal Ganglionic Eminence Makes a Limited Contribution to Cortical Oligodendrocytes

発生期の大脳皮質オリゴデンドロサイト前駆細胞は外側視床下部から生成されない


AGS タンパク質のGoLocoモチーフの進化的変化が、海ウニ胚における微小細胞の形成を促進する。


The evolutionary introduction of asymmetric cell division (ACD) into the developmental program facilitates the formation of a new cell type, contributing to developmental diversity and, eventually, to species diversification. The micromere of the sea urchin embryo may serve as one of those examples: An ACD at the 16-cell stage forms micromeres unique to echinoids among echinoderms. We previously reported that a polarity factor, Activator of G-protein Signaling (AGS), plays a crucial role in micromere formation. However, AGS and its associated ACD factors are present in all echinoderms and across most metazoans, leaving a question of what evolutionary modification of AGS protein or its surrounding molecular environment contributed to the evolutionary acquisition of micromeres only in echinoids. In this study, we learned that the GoLoco motifs at the AGS C-terminus play critical roles in regulating micromere formation in sea urchin embryos. Further, other echinoderms’ AGS or chimeric AGS that contain the C-terminus of AGS orthologs from various organisms showed varied localization and function in micromere formation. In contrast, the sea star or the pencil urchin orthologs of other ACD factors were consistently localized at the vegetal cortex in the sea urchin embryo, suggesting that AGS may be a unique variable factor that facilitates ACD diversity among echinoderms. Consistently, sea urchin AGS appears to facilitate micromere-like cell formation and accelerate the enrichment timing of the germline factor Vasa during early embryogenesis of the pencil urchin, an ancestral type of sea urchin. Based on these observations, we propose that the molecular evolution of a single polarity factor facilitates ACD diversity while preserving the core ACD machinery among echinoderms and beyond during evolution.

Highlights 

### Competing Interest Statement

The authors have declared no competing interest.

The evolutionary modifications of a GoLoco motif in the AGS protein facilitate micromere formation in the sea urchin embryo

海ウニ胚における-ags-タンパク質のgolocoモチーフの進化的変化が微小細胞の形成を促進する


海ウニ胚における AGS タンパク質のGoLocoモチーフの進化的変化が微小細胞の形成を促進する



PRC2は初期発生過程における遺伝子発現の安定化に重要な役割を果たす。PRC2の阻害は内胚葉分化の効率を高めるが、同時に非系統的な遺伝子発現を引き起こす。


The genetic circuitry that encodes the developmental programme of mammals is regulated by transcription factors and chromatin modifiers. During early gestation, the three embryonic germ layers are established in a process termed gastrulation. The impact of deleterious mutations in chromatin modifiers such as the polycomb proteins manifests during gastrulation, leading to early developmental failure and lethality in mouse models. Embryonic stem cells have provided key insights into the molecular function of polycomb proteins, but it is impossible to fully appreciate the role of these epigenetic factors in development, or how development is perturbed due to their deficiency, in the steady-state. To address this, we have employed a tractable embryonic stem cell differentiation system to model primitive streak formation and early gastrulation. Using this approach, we find that loss of the repressive polycomb mark H3K27me3 is delayed relative to transcriptional activation, indicating a subordinate rather than instructive role in gene repression. Despite this, chemical inhibition of polycomb enhanced endodermal differentiation efficiency, but did so at the cost of lineage fidelity. These findings highlight the importance of the polycomb system in stabilising the developmental transcriptional response and, in so doing, in shoring up cellular specification.

### Competing Interest Statement

The authors have declared no competing interest.

PRC2 Promotes Canalisation During Endodermal Differentiation

マウス初期発生におけるprc2の役割-内胚葉分化の安定化


マウス初期発生におけるPRC2の役割：内胚葉分化の安定化



発生プログラムの進化には、遺伝子発現の適応的変化が重要である。異時性遺伝子発現と調節アーキテクチャーの変化が、発生の分岐に大きな役割を果たしている。


New developmental programs can evolve through adaptive changes to gene expression. The annelid Streblospio benedicti has a developmental dimorphism, which provides a unique intraspecific framework for understanding the earliest genetic changes that take place during developmental divergence. Using comparative RNAseq through ontogeny, we find that only a small proportion of genes are differentially expressed at any time, despite major differences in larval development and life-history. These genes shift expression profiles across morphs by either turning off any expression in one morph or changing the timing or amount of gene expression. We directly connect the contributions of these mechanisms to differences in developmental processes. We examine F1 offspring— using reciprocal crosses— to determine maternal mRNA inheritance and the regulatory architecture of gene expression. These results highlight the importance of both novel gene expression and heterochronic shifts in developmental evolution, as well as the trans -acting regulatory factors in initiating divergence.

### Competing Interest Statement

The authors have declared no competing interest.

The role of heterochronic gene expression and regulatory architecture in early developmental divergence

発生の初期段階における異時性遺伝子発現と調節アーキテクチャーの役割


BMP シグナリングは小脳顆粒細胞前駆細胞の集合と遷移増幅の調節に重要な役割を果たす。


The external granule layer (EGL) is a transient proliferative layer that gives rise to cerebellar granule cell neurons. Extensive EGL proliferation characterises the foliated structure of amniote cerebella, but the factors that regulate EGL formation, amplification within it, and differentiation from it, are incompletely understood. Here, we characterise bone morphogenic protein (BMP) signalling during cerebellar development in chick and human and show that while in chick BMP signalling correlates with external granule layer formation, in humans BMP signalling is maintained throughout the external granule layer after the onset of foliation. We also show via Immunohistochemical labelling of phosphorylated Smad1/5/9 the comparative spatiotemporal activity of BMP signalling in chick and human. Using in-ovo electroporation in chick, we demonstrate that BMP signalling is necessary for subpial migration of granule cell precursors and hence the formation of the external granule layer (EGL) prior to transit amplification. However, altering BMP signalling does not block the formation of mature granule neurons but significantly disrupts that pattern of morphological transitions that accompany transit amplification. Our results elucidate two key, temporally distinct roles for BMP signalling in vivo in organising first the assembly of the EGL from the rhombic lip and subsequently the tempo of granule neuron production within the EGL.

Significance statement Improper development of cerebellar granule neurons can manifest in a plethora of neurodevelopmental disorders, including but not limited to medulloblastoma and autism. Many studies have sought to understand the role of developmental signalling pathways in granule cell neurogenesis, using genetic manipulation in transgenic mice. To complement these insights, we have used comparative assessment of BMP signalling during development in chick and human embryos and in vivo manipulation of the chick to understand and segregate the spatiotemporal roles of BMP signalling, yielding important insights on evolution and in consideration of future therapeutic avenues that target BMP signalling.

### Competing Interest Statement

The authors have declared no competing interest.

BMP signalling facilitates transit amplification in the developing chick and human cerebellum

発生期の小脳における-bmp-シグナリングが遷移増幅を促進する


発生期の小脳における BMP シグナリングが遷移増幅を促進する



BMP シグナル活性化により引き起こされる羊膜分化の時間依存的な転写カスケードを明らかにした。TFAP2A が羊膜分化の進行に重要な役割を果たすことを示した。


Amniogenesis, a process critical for continuation of healthy pregnancy, is triggered in a collection of pluripotent epiblast cells as the human embryo implants. Previous studies have established that BMP signaling is a major driver of this lineage specifying process, but the downstream BMP-dependent transcriptional networks that lead to successful amniogenesis remain to be identified. This is, in part, due to the current lack of a robust and reproducible model system that enables mechanistic investigations exclusively into amniogenesis. Here, we developed an improved model of early amnion specification, using a human pluripotent stem cell-based platform in which the activation of BMP signaling is controlled and synchronous. Uniform amniogenesis is seen within 48 hours after BMP activation, and the resulting cells share transcriptomic characteristics with amnion cells of a gastrulating human embryo. Using detailed time-course transcriptomic analyses, we established a previously uncharacterized BMP-dependent amniotic transcriptional cascade, and identified markers that represent five distinct stages of amnion fate specification; the expression of selected markers was validated in early post-implantation macaque embryos. Moreover, a cohort of factors that could potentially control specific stages of amniogenesis was identified, including the transcription factor TFAP2A. Functionally, we determined that, once amniogenesis is triggered by the BMP pathway, TFAP2A controls the progression of amniogenesis. This work presents a temporally resolved transcriptomic resource for several previously uncharacterized amniogenesis states and demonstrates a critical intermediate role for TFAP2A during amnion fate specification.

### Competing Interest Statement

The authors have declared no competing interest.

Temporally resolved early BMP-driven transcriptional cascade during human amnion specification

ヒト羊膜の初期分化過程における時間依存的な-bmp-誘導性転写カスケードの解明


ヒト羊膜の初期分化過程における時間依存的な BMP 誘導性転写カスケードの解明



シングナシデ科の特徴的な形質(頭部形状、無歯、皮膚骨格、雄の育児)の発生遺伝学的基盤を明らかにした。


Seahorses, pipefishes, and seadragons are fishes from the family Syngnathidae that have evolved extraordinary traits including male pregnancy, elongated snouts, loss of teeth, and dermal bony armor. The developmental genetic and cellular changes that led to the evolution of these traits are largely unknown. Recent syngnathid genomes revealed suggestive gene content differences and provide the opportunity for detailed genetic analyses. We created a single cell RNA sequencing atlas of Gulf pipefish embryos to understand the developmental basis of four traits: derived head shape, toothlessness, dermal armor, and male pregnancy. We completed marker gene analyses, built genetic networks, and examined spatial expression of select genes. We identified osteochondrogenic mesenchymal cells in the elongating face that express regulatory genes bmp4, sfrp1a , and prdm16 . We found no evidence for tooth primordia cells, and we observed re-deployment of osteoblast genetic networks in developing dermal armor.

Finally, we found that epidermal cells expressed nutrient processing and environmental sensing genes, potentially relevant for the brooding environment. The examined pipefish evolutionary innovations are composed of recognizable cell types, suggesting derived features originate from changes within existing gene networks. Future work addressing syngnathid gene networks across multiple stages and species is essential for understanding how their novelties evolved.

Impact Statement The production of a single cell atlas for developing syngnathid fish permits study of their unique traits.

### Competing Interest Statement

The authors have declared no competing interest.

Single Cell RNA Sequencing Provides Clues for the Developmental Genetic Basis of Syngnathidae’s Evolutionary Adaptations

単一細胞rna配列解析は-シングナシデ科の進化的適応の発生遺伝学的基盤に関するヒントを提供する


単一細胞RNA配列解析は、シングナシデ科の進化的適応の発生遺伝学的基盤に関するヒントを提供する



体軸分節化の時間的制御と空間的制御は独立したモジュールであり、自然環境下では選択圧によって結合されている。


How temporal and spatial control of developmental processes are linked remains a fundamental question. Do underlying mechanisms form a single functional unit or are these dissociable modules?

We address this question by studying the periodic process of embryonic axis segmentation, using genetic crosses of inbred medaka fish strains representing two species, Oryzias sakaizumii and latipes . Our analysis revealed correlated interspecies differences with regard to the timing of segmentation, the size of segments and of the presomitic mesoderm (PSM), from which segments are periodically formed. We then did interspecies crosses and real-time imaging quantifications, which revealed extensive phenotypic variation in ∼600 F2 embryos. Importantly, while the F2 analysis showed correlated changes of PSM and segment size, these spatial measures were not correlated to the timing of segmentation. This shows that the control of time and space of axis segmentation can, in principle, be decoupled. In line with this finding, we identified, using developmental quantitative trait loci ( dev QTL) mapping, distinct chromosomal regions linked to either the control of segmentation timing or PSM size. We were able to validate the dev QTL findings using a CRISPR/Cas9 loss-of-function approach on several candidate genes in vivo .

Combined, this study reveals that a developmental constraint mechanism underlies spatial scaling of axis segmentation, while its spatial and temporal control are dissociable modules. Our findings emphasise the need to reveal the selective constraints linking these modules in the natural environment.

### Competing Interest Statement

The authors have declared no competing interest.

Modular control of time and space during vertebrate axis segmentation

異なる脊椎動物種間における体軸分節化のタイミングと大きさの調節機構