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Science Advances Mar 2024Mechanisms specifying amniotic ectoderm and surface ectoderm are unresolved in humans due to their close similarities in expression patterns and signal requirements....
Mechanisms specifying amniotic ectoderm and surface ectoderm are unresolved in humans due to their close similarities in expression patterns and signal requirements. This lack of knowledge hinders the development of protocols to accurately model human embryogenesis. Here, we developed a human pluripotent stem cell model to investigate the divergence between amniotic and surface ectoderms. In the established culture system, cells differentiated into functional amnioblast-like cells. Single-cell RNA sequencing analyses of amnioblast differentiation revealed an intermediate cell state with enhanced surface ectoderm gene expression. Furthermore, when the differentiation started at the confluent condition, cells retained the expression profile of surface ectoderm. Collectively, we propose that human amniotic ectoderm and surface ectoderm are specified along a common nonneural ectoderm trajectory based on cell density. Our culture system also generated extraembryonic mesoderm-like cells from the primed pluripotent state. Together, this study provides an integrative understanding of the human nonneural ectoderm development and a model for embryonic and extraembryonic human development around gastrulation.
Topics: Humans; Ectoderm; Cell Differentiation; Mesoderm; Pluripotent Stem Cells
PubMed: 38427729
DOI: 10.1126/sciadv.adh7748 -
The International Journal of... 2014Cranial placodes are transient ectodermal structures contributing to the paired sensory organs and ganglia of the vertebrate head. Placode progenitors are initially... (Review)
Review
Cranial placodes are transient ectodermal structures contributing to the paired sensory organs and ganglia of the vertebrate head. Placode progenitors are initially spread and intermixed within a continuous embryonic territory surrounding the anterior neural plate, the so-called pan-placodal region, which progressively breaks into distinct and compact placodal structures. The mechanisms driving the formation of these discrete placodes from the initial scattered distribution of their progenitors are poorly understood, and the implication of cell fate changes, local sorting out or massive cell movements is still a matter of debate. Here, we discuss different models that could account for placode assembly and review recent studies unraveling novel cellular and molecular aspects of this key event in the construction of the vertebrate head.
Topics: Animals; Clonal Evolution; Ectoderm; Gene Expression Regulation, Developmental; Head; Humans; Nerve Tissue Proteins; Nervous System
PubMed: 24860990
DOI: 10.1387/ijdb.130351mb -
Journal of Anatomy Jan 2013The vertebrate oral region represents a key interface between outer and inner environments, and its structural and functional design is among the limiting factors for... (Review)
Review
The vertebrate oral region represents a key interface between outer and inner environments, and its structural and functional design is among the limiting factors for survival of its owners. Both formation of the respective oral opening (primary mouth) and establishment of the food-processing apparatus (secondary mouth) require interplay between several embryonic tissues and complex embryonic rearrangements. Although many aspects of the secondary mouth formation, including development of the jaws, teeth or taste buds, are known in considerable detail, general knowledge about primary mouth formation is regrettably low. In this paper, primary mouth formation is reviewed from a comparative point of view in order to reveal its underestimated morphogenetic diversity among, and also within, particular vertebrate clades. In general, three main developmental modes were identified. The most common is characterized by primary mouth formation via a deeply invaginated ectodermal stomodeum and subsequent rupture of the bilaminar oral membrane. However, in salamander, lungfish and also in some frog species, the mouth develops alternatively via stomodeal collar formation contributed both by the ecto- and endoderm. In ray-finned fishes, on the other hand, the mouth forms via an ectoderm wedge and later horizontal detachment of the initially compressed oral epithelia with probably a mixed germ-layer derivation. A very intriguing situation can be seen in agnathan fishes: whereas lampreys develop their primary mouth in a manner similar to the most common gnathostome pattern, hagfishes seem to undergo a unique oropharyngeal morphogenesis when compared with other vertebrates. In discussing the early formative embryonic correlates of primary mouth formation likely to be responsible for evolutionary-developmental modifications of this area, we stress an essential role of four factors: first, positioning and amount of yolk tissue; closely related to, second, endoderm formation during gastrulation, which initiates the process and constrains possible evolutionary changes within this area; third, incipient structure of the stomodeal primordium at the anterior neural plate border, where the ectoderm component of the prospective primary mouth is formed; and fourth, the prime role of Pitx genes for establishment and later morphogenesis of oral region both in vertebrates and non-vertebrate chordates.
Topics: Animals; Basement Membrane; Biological Evolution; Ectoderm; Gene Expression Regulation, Developmental; Mouth; Phylogeny; Vertebrates
PubMed: 22804777
DOI: 10.1111/j.1469-7580.2012.01540.x -
Developmental Biology May 2014
Topics: Animals; Biological Evolution; Body Patterning; Ectoderm; Gene Expression Regulation, Developmental; Humans; Neural Crest; Vertebrates
PubMed: 24684751
DOI: 10.1016/j.ydbio.2014.02.009 -
Developmental Biology Sep 2017John Saunders was a highly skilled embryologist who pioneered the study of limb development. His studies on chick embryos provided the fundamental framework for... (Review)
Review
John Saunders was a highly skilled embryologist who pioneered the study of limb development. His studies on chick embryos provided the fundamental framework for understanding how vertebrate limbs develop. This framework inspired generations of scientists and formed the bridge from experimental embryology to molecular mechanisms. Saunders investigated how feathers become organized into tracts in the skin of the chick wing and also identified regions of programmed cell death. He discovered that a region of thickened ectoderm that rims the chick wing bud - the apical ectodermal ridge - is required for outgrowth and the laying down of structures along the proximo-distal axis (long axis) of the wing, identified the zone of polarizing activity (ZPA; polarizing region) that controls development across the anteroposterior axis ("thumb to little finger "axis) and contributed to uncovering the importance of the ectoderm in development of structures along the dorso-ventral axis ( "back of hand to palm" axis). This review looks in depth at some of his original papers and traces how he made the crucial findings about how limbs develop, considering these findings both in the context of contemporary knowledge at the time and also in terms of their immediate impact on the field.
Topics: Animals; Body Patterning; Ectoderm; Embryology; Extremities; History, 20th Century; Wings, Animal
PubMed: 28625869
DOI: 10.1016/j.ydbio.2017.05.028 -
Genes Nov 2019During vertebrate embryogenesis, precise regulation of gene expression is crucial for proper cell fate determination. Much of what we know about vertebrate development... (Review)
Review
During vertebrate embryogenesis, precise regulation of gene expression is crucial for proper cell fate determination. Much of what we know about vertebrate development has been gleaned from experiments performed on embryos of the amphibian ; this review will focus primarily on studies of this model organism. An early critical step during vertebrate development is the formation of the three primary germ layers-ectoderm, mesoderm, and endoderm-which emerge during the process of gastrulation. While much attention has been focused on the induction of mesoderm and endoderm, it has become clear that differentiation of the ectoderm involves more than the simple absence of inductive cues; rather, it additionally requires the inhibition of mesendoderm-promoting genes. This review aims to summarize our current understanding of the various inhibitors of inappropriate gene expression in the presumptive ectoderm.
Topics: Animals; Cell Differentiation; Ectoderm; Endoderm; Gastrulation; Gene Expression Regulation, Developmental; Germ Layers; Mesoderm; Xenopus laevis
PubMed: 31698780
DOI: 10.3390/genes10110895 -
Proceedings of the National Academy of... Jul 2022The vertebrate inner ear arises from a pool of progenitors with the potential to contribute to all the sense organs and cranial ganglia in the head. Here, we explore the...
The vertebrate inner ear arises from a pool of progenitors with the potential to contribute to all the sense organs and cranial ganglia in the head. Here, we explore the molecular mechanisms that control ear specification from these precursors. Using a multiomics approach combined with loss-of-function experiments, we identify a core transcriptional circuit that imparts ear identity, along with a genome-wide characterization of noncoding elements that integrate this information. This analysis places the transcription factor Sox8 at the top of the ear determination network. Introducing Sox8 into the cranial ectoderm not only converts non-ear cells into ear progenitors but also activates the cellular programs for ear morphogenesis and neurogenesis. Thus, Sox8 has the unique ability to remodel transcriptional networks in the cranial ectoderm toward ear identity.
Topics: Animals; Ear, Inner; Ectoderm; Gene Expression Regulation, Developmental; SOXE Transcription Factors; Skull; Vertebrates
PubMed: 35867760
DOI: 10.1073/pnas.2118938119 -
Seminars in Cell & Developmental Biology Mar 2023Of all the cell types arising from the neural crest, ectomesenchyme is likely the most unusual. In contrast to the neuroglial cells generated by neural crest throughout... (Review)
Review
Of all the cell types arising from the neural crest, ectomesenchyme is likely the most unusual. In contrast to the neuroglial cells generated by neural crest throughout the embryo, consistent with its ectodermal origin, cranial neural crest-derived cells (CNCCs) generate many connective tissue and skeletal cell types in common with mesoderm. Whether this ectoderm-derived mesenchyme (ectomesenchyme) potential reflects a distinct developmental origin from other CNCC lineages, and/or epigenetic reprogramming of the ectoderm, remains debated. Whereas decades of lineage tracing studies have defined the potential of CNCC ectomesenchyme, these are being revisited by modern genetic techniques. Recent work is also shedding light on the extent to which intrinsic and extrinsic cues determine ectomesenchyme potential, and whether maintenance or reacquisition of CNCC multipotency influences craniofacial repair.
Topics: Neural Crest; Mesoderm; Ectoderm; Embryo, Mammalian
PubMed: 35331627
DOI: 10.1016/j.semcdb.2022.03.018 -
Journal of Applied Genetics Feb 2016Recent advances in understanding the molecular events underlying hypohidrotic ectodermal dysplasia (HED) caused by mutations of the genes encoding proteins of the tumor... (Review)
Review
Recent advances in understanding the molecular events underlying hypohidrotic ectodermal dysplasia (HED) caused by mutations of the genes encoding proteins of the tumor necrosis factor α (TNFα)-related signaling pathway have been presented. These proteins are involved in signal transduction from ectoderm to mesenchyme during development of the fetus and are indispensable for the differentiation of ectoderm-derived structures such as eccrine sweat glands, teeth, hair, skin, and/or nails. Novel data were reviewed and discussed on the structure and functions of the components of TNFα-related signaling pathway, the consequences of mutations of the genes encoding these proteins, and the prospect for further investigations, which might elucidate the origin of HED.
Topics: Ectoderm; Ectodermal Dysplasia; Humans; Inheritance Patterns; Mesoderm; Mutation; NF-kappa B; Signal Transduction; Tumor Necrosis Factor-alpha
PubMed: 26294279
DOI: 10.1007/s13353-015-0307-4 -
ELife Mar 2022The facial surface ectoderm is essential for normal development of the underlying cranial neural crest cell populations, providing signals that direct appropriate...
The facial surface ectoderm is essential for normal development of the underlying cranial neural crest cell populations, providing signals that direct appropriate growth, patterning, and morphogenesis. Despite the importance of the ectoderm as a signaling center, the molecular cues and genetic programs implemented within this tissue are understudied. Here, we show that removal of two members of the AP-2 transcription factor family, AP-2α and AP-2ß, within the early embryonic ectoderm of the mouse leads to major alterations in the craniofacial complex. Significantly, there are clefts in both the upper face and mandible, accompanied by fusion of the upper and lower jaws in the hinge region. Comparison of ATAC-seq and RNA-seq analyses between controls and mutants revealed significant changes in chromatin accessibility and gene expression centered on multiple AP-2 binding motifs associated with enhancer elements within these ectodermal lineages. In particular, loss of these AP-2 proteins affects both skin differentiation as well as multiple signaling pathways, most notably the WNT pathway. We also determined that the mutant clefting phenotypes that correlated with reduced WNT signaling could be rescued by ligand overexpression in the ectoderm. Collectively, these findings highlight a conserved ancestral function for AP-2 transcription factors in ectodermal development and signaling, and provide a framework from which to understand the gene regulatory network operating within this tissue that directs vertebrate craniofacial development.
Topics: Animals; Chromatin; Ectoderm; Gene Expression; Mice; Transcription Factor AP-2; Transcription Factors
PubMed: 35333176
DOI: 10.7554/eLife.70511