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PubMed2025

Self-organization of mouse embryonic stem cells into reproducible pre-gastrulation embryo models via CRISPRa programming.

Embryonic stem cells (ESCs) can self-organize into structures with spatial and molecular similarities to natural embryos. During development, embryonic and extraembryonic cells differentiate through activation of endogenous regulatory elements while co-developing via cell-cell interactions. However, engineering regulatory elements to self-organize ESCs into embryo models remains underexplored. Here, we demonstrate that CRISPR activation (CRISPRa) of two regulatory elements near Gata6 and Cdx2 generates embryonic patterns resembling pre-gastrulation mouse embryos. Live single-cell imaging revealed that self-patterning occurs through orchestrated collective movement driven by cell-intrinsic fate induction. In 3D, CRISPRa-programmed embryo models (CPEMs) exhibit morphological and transcriptomic similarity to pre-gastrulation mouse embryos. CPEMs allow versatile perturbations, including dual Cdx2-Elf5 activation to enhance trophoblast differentiation and lineage-specific activation of laminin and matrix metalloproteinases, uncovering their roles in basement membrane remodeling and embryo model morphology. Our findings demonstrate that minimal intrinsic epigenome editing can self-organize ESCs into programmable pre-gastrulation embryo models with robust lineage-specific perturbation capabilities.

Animals↗

PubMed2001

Common developmental genetic mechanisms for patterning invertebrate and vertebrate brains.

Recent genetic studies on embryonic brain development in the fly Drosophila melanogaster together with investigations on early morphogenesis and patterning in the embryonic brain of the mouse revealed developmental mechanisms that are strikingly similar in insects and mammals. The homeotic (Hox) genes are expressed in a virtually colinear anteroposterior pattern in the developing posterior brain of insects and mammals, where they are required for the specification of segmental neuronal identity. The otd/Otx cephalic gap genes are expressed in the anterior brain of insects and mammals and are of central importance for its formation because in both phyla loss of otd/Otx2 causes the loss of the entire rostral brain. Specific Pax genes are involved in numerous aspects of brain development in both phyla. These developmental genetic findings reveal a striking evolutionary conservation of cephalic gap gene, homeotic gene, and Pax gene action in embryonic brain development that extends beyond gene structure to encompass patterned expression and function. This comparative evidence indicates that the genetic programs which direct embryonic brain development are remarkably conserved and lends further support to the hypothesis that a common molecular bauplan underlies brain development in invertebrates and vertebrates. In consequence, it seems increasingly likely that both modern brain types share their evolutionary origin in a common ancestral bilaterian brain which was established before the protostome-deuterostome divergence over 600 million years ago.

Animals↗

PubMed2006

Use of a ROSA26:GFP transgenic line for long-term Xenopus fate-mapping studies.

Widespread and persistent marker expression is a prerequisite for many transgenic applications, including chimeric transplantation studies. Although existing transgenic tools for the clawed frog, Xenopus laevis, offer a number of promoters that drive widespread expression during embryonic stages, obtaining transgene expression through metamorphosis and into differentiated adult tissues has been difficult to achieve with this species. Here we report the application of the murine ROSA26 promoter in Xenopus. GFP is expressed in every transgenic tissue and cell type examined at post-metamorphic stages. Furthermore, transgenic ROSA26:GFP frogs develop normally, with no apparent differences in growth or morphology relative to wild-type frogs. ROSA26 transgenes may be used as a reliable marker for embryonic fate-mapping of adult structures in Xenopus laevis. Utility of this transgenic line is illustrated by its use in a chimeric grafting study that demonstrates the derivation of the adult bony jaw from embryonic cranial neural crest.

Animals↗

PubMed1983

The glycosidic antigen recognised by a novel monoclonal antibody, 75.12, is developmentally regulated on mouse embryonal carcinoma cells.

Monoclonal antibody 75.12 raised against the human ovarian teratocarcinoma cell line PA1 detects a 'Y' or iso-leb glycosidic structure. Using the 75.12 antibody we have established that the Y antigen is expressed on some but not all mouse embryonal carcinoma (EC) lines. The Y or 75.12 antigen-positive EC cell lines F9 and PCC4 cease to express the antigen after differentiation induced with retinoic acid and this decreased expression parallels the morphological differentiation of the EC cells. These results support not only the idea that carbohydrate structures present on embryonic cells undergo marked alteration during differentiation, but also that established mouse EC cells may differ in their differentiation states.

Animals↗

PubMed1983

The development of interependymal pores in the rhombencephalic posterior tela in late embryonic, larval and metamorphosing stages of Rana pipiens.

The structure of the roof of the fourth cerebral ventricle has been studied by scanning and transmission electron microscopy in Rana pipiens from the late embryonic stages, through the larval stages to metamorphosis. Stage 20 and 21 post-hatching embryos have a rhombencephalic roof consisting of undifferentiated embryonic cells. From embryonic stage 22-25 there is progressive differentiation into choroid plexus and posterior tela ependymal cells. Between 1 and 3 interependymal pores occur in the posterior tela and there is a small incipient subarachnoid space dorsal to the posterior tela. During the larval stages, total pore number increases with larval length in a curvilinear manner, with the steepest increase occurring in the latter part of the larval stages. By metamorphosis, total pore number (50-100) approaches that found previously in the adult amphibian. The diameter of individual pores ranges from 1 to 200 microns. Small pores are more numerous than large pores at all stages and both small and large pores become more numerous as development proceeds. Large pores may form by the fusion of two or more smaller pores. It is concluded that pore formation is a gradual process with its onset in the late embryonic stage and concurrent with the onset of choroid plexus and subarachnoid space development. It is suggested that the onset of CSF secretion and circulation may take place shortly after hatching.

Animals↗

PubMed1987

Fourth ventricular floor in human embryos: scanning electron microscopic observations.

The ultrastructural surface features of the normal fourth ventricular floor of seven human embryos ranging from Carnegie stage 14 to stage 19 (crown-rump length: 7.6-16.2 mm) were examined by using scanning electron microscopy (SEM). Low-power SEM views showed the median sulcus, sulcus limitans, and neuromeres, transient structures characteristic of the earlier embryonic period. High-power SEM observation revealed supraependymal cells (SE cells) and supraependymal fibers (SE fibers) which exhibited a characteristic localization, as well as generalized surface-membrane modifications such as microvilli and cilia. SE cells could be classified into two major groups. The type 1 SE cells seem to possess neuronal functions, as deduced from morphological similarities to their counterparts in adults and the specialized distribution closely related to neuromeres. The type 2 SE cell morphologically resembled the phagocytic SE cell described in related literature. SE fibers ran a course either rostrocaudally in the median sulcus or mediolaterally on the neuromeres, most frequently near the interneuromeric cleft; they made contact with type 1 SE cells and ependymal surface modifications and then penetrated the ependymal layer.

Cerebral Ventricles↗

PubMed1992

Incorporation of fluorescently labeled contractile proteins into freshly isolated living adult cardiac myocytes.

When fluorescently labeled contractile proteins are injected into embryonic muscle cells, they become incorporated into the cells' myofibrils. In order to determine if this exchange of proteins is unique to the embryonic stage of development, we isolated adult cardiac myocytes and microinjected them with fluorescently labeled actin, myosin light chains, alpha-actinin, and vinculin. Each of these proteins was incorporated into the adult cardiomyocytes and was colocalized with the cells' native proteins, despite the fact that the labeled proteins were prepared from noncardiac tissues. Within 10 min of injection, alpha-actinin was incorporated into Z-bands surrounding the site of injection. Similarly, 30 sec after injection, actin was incorporated into the entire I-bands at the site of injection. Following a 3-h incubation, increased actin fluorescence was noted at the intercalated disc. Vinculin exchange was seen in the intercalated discs, as well as in the Z-bands throughout the cells. Myosin light chains required 4-6 h after injection to become incorporated into the A-bands of the adult muscle. Nonspecific proteins, such as fluorescent BSA, showed no association with the myofibrils or the former intercalated discs. When adult cells were maintained in culture for 10 days, they retain the ability to incorporate these contractile proteins into their myofibrils. T-tubules and the sarcoplasmic reticulum could be detected in periodic arrays in the freshly isolated cells using the membrane dye WW781 and DiOC6[3], respectively. In conclusion, the myofibrils in adult, as in embryonic, muscle cells are dynamic structures, permitting isoform transitions without dismantling of the myofibrils.

Actinin↗

PubMed1980

Clonal analysis of the avian neural crest: migration and maturation of mixed neural crest clones injected into host chicken embryos.

Quail neural crest cells were grown in vitro at clonal density for 7 to 10 days. Mixed neural crest colonies and clones (containing both pigmented and unpigmented cells) were implanted into the trunk region of 2 1/2-day-old host chicken embryos by a previously described injection technique (Bronner and Cohen '79). Here we describe the migratory behavior and subsequent phenotypic expression of the injected cells. Unpigmented cells and pigmented cells both migrated along the ventral neural crest pathway; there were, however, some differences in migratory behavior between the two cell types. After 3 days in vivo, unpigmented quail neural crest cells contributed to the sympathetic ganglion, adrenal medulla, and/or aortic plexus in the host. Many of the unpigmented cells became catecholamine-containing neuroblasts. Unpigmented cells were never observed in the gonads or the gut, but localized only in regions normally populated by trunk neural crest precursors to neurons and supportive cells. Melanocytes derived from the same precursor, however, were often found in the gonads or gut, in addition to normal neural crest locations in the trunk. These results demonstrate that quail neural crest cells grown in tissue culture for 7 days or more retain the ability to migrate and contribute to normal neural crest structures when placed in the embryonic environment. Under the conditions described, a single neural crest cell gave rise to daughter cells expressing the melanotic phenotype (detected in tissue culture) and adrenergic phenotypes (detected after injection in vivo). This demonstrates that at least some single cells of the premigratory crest in the trunk region are pluripotent.

Adrenergic Fibers↗

PubMed1984

A developmental gradient of dendritic loss in the avian cochlear nucleus occurring independently of primary afferents.

Cochlear nerve axons and their target neurons in nucleus magnocellularis (NM) of the chicken undergo extensive parallel structural transformations during development. Between embryonic days 12 and 17 (E12-E17), each immature highly branched axon condenses into a mature calyxlike ending applied to a single NM neuron. Simultaneously, NM neurons are transformed from multipolar cells with many long dendrites into spherical unipolar neurons with only an axon. We tested the hypothesis that cochlear nerve input is necessary for the transformation of NM cells by surgically destroying one otocyst on E3, thereby preventing formation of the nerve. Nucleus magnocellularis neurons from embryos at E11-E12, E13-14, and E17-18 were stained by horseradish peroxidase injected into their axons or by a Golgi-Hortega method. In camera lucida drawings, the number of dendrites on each cell was counted and the cell's position along the posterior-to-anterior and lateral-to-medial axes of the nucleus quantified. At E11-12, neurons throughout NM on both the deafferented and normally innervated sides of the brain have about ten dendrites. At E13-14, there is a steep spatial gradient in dendritic number bilaterally; cells at anteromedial positions have about two dendrites, while cells in posterolateral positions have an average of nine dendrites. By E17-18, only 14% of the neurons on either side have a dendrite, and these cells are evenly distributed throughout the nucleus. We conclude that cochlear nerve axons are not required for normal spatio-temporal gradients of dendritic loss, even though the absence of these axons causes severe atrophic changes in NM.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗

PubMed1988

The development of the corpus callosum in cats: a light- and electron-microscopic study.

Changes in the size and shape of the corpus callosum (CC)--and in number, size, and structure of callosal axons--between embryonic day 38 (E38) and postnatal day 150 (P150) were studied by light and electron microscope in 25 kittens. The development of the CC was divided into three phases: 1. Embryonic development (E38, 53, 58): At E38, only part of the body of the CC was formed. At E53 and E58, the CC was still very short, but its different parts (genu, body, and splenium) had formed. The cross-sectional callosal area (CCA) was 5.4 mm2 at E53 and 5.6 mm2 at E58. The CC contained 46.3 and 56.4 million axons at E53 and E58 respectively. Mean axon diameters were 0.26 micron at E53 and 0.27 micron at E58. 2. Early postnatal development (P4, 9, 15, 18, 21, 26): The CC at P4 was much longer than at E58 and still slightly elongated during this phase; CCA reached 8.55 mm2 at P4 and 8.88 mm2 at P26. There was a substantial axonal loss (66.8 million at P4 and 52.6 million at P26). From P15 onward, premyelinated and myelinated axons were seen. Mean axon diameter increased from 0.30 micron at P4 to 0.33 micron at P26. 3. Late postnatal development (P39, 57, 92, 107, 150). The CC grew dramatically in both length and thickness, the latter especially in the genu. CCA was 10.1 mm2 at P39 and 15.3 mm2 at P150. The number of axons still decreased (46.5 million at P39 and 31.9 million at P150). The growth of the CCA paralleled the increase of myelinated axons (0.5% at P26 and 29.6% at P150 and in the mean axon diameters (0.34 micron at P39 and 0.42 micron at P150). A number of axonal ultrastructural peculiarities (electron-dense bodies, large vacuoles, lamellated bodies, etc., including those mentioned below) were noticed; their frequency at different ages was estimated as the percent of total axons. Interestingly, accumulations of vesicles inside axons increased from 4.1% at E53 to 8.9% at P26, dropped to 0.2% at P39, and remained below 1% thereafter. Swollen mitochondria increased from 0.2% at E53 to 0.9% at P26 and dropped to 0.06% (on the average) from P39 onward. Accumulations of vesicles and swollen mitochondria increased during the phase of rapid axonal elimination; thus, they may indicate axonal retraction and/or degeneration. Microglia-gitter cells and astrocytes showing signs of phagocytosis were found during the embryonic and early postnatal development and may be involved in axon elimination.

Aging↗

PubMed2006

Comparative anatomical study of internal brooding in three anascan bryozoans (Cheilostomata) and its taxonomic and evolutionary implications.

The anatomical structure of internal sacs for embryonic incubation was studied using SEM and light microscopy in three cheilostome bryozoans-Nematoflustra flagellata (Waters,1904), Gontarella sp., and Biflustra perfragilis MacGillivray, 1881. In all these species the brood sac is located in the distal half of the maternal (egg-producing) autozooid, being a conspicuous invagination of the body wall. It consists of the main chamber and a passage (neck) to the outside that opens independently of the introvert. There are several groups of muscles attached to the thin walls of the brood sac and possibly expanding it during oviposition and larval release. Polypide recycling begins after oviposition in Gontarella sp., and the new polypide bud is formed by the beginning of incubation. Similarly, polypides in brooding zooids degenerate in N. flagellata and, sometimes, in B. perfragilis. In the evolution of brood chambers in the Cheilostomata, such internal sacs for embryonic incubation are considered a final step, being the result of immersion of the brooding cavity into the maternal zooid and reduction of the protecting fold (ooecium). Possible reasons for this transformation are discussed, and the hypothesis of Santagata and Banta (Santagata and Banta1996) that internal brooding evolved prior to incubation in ovicells is rejected.

Animals↗

PubMed1986

Morphogenesis of isotretinoin-induced microcephaly and micrognathia studied by scanning electron microscopy.

Isotretinoin ingestion during the first trimester of human pregnancy can induce malformations of the skull, ears, face, central nervous system, eyes, palate, lungs, circulatory system, limbs, and digits. A single oral dose of isotretinoin on day 8 of gestation in hamsters induces a similar syndrome of congenital malformation. The present study concerned scanning electron microscopic (SEM) observation of embryonic and fetal hamster craniofacial structures at 4, 8, 12, 24, 48, and 72 hr after administration of an oral dose of 50 mg/kg isotretinoin or an equivalent volume of the vehicle. The variability in development among control embryos recovered 4 hr after treatment precluded objective assessment of pathologic change by SEM at very early time points. Craniofacial damage was obvious within 8-12 hr of isotretinoin treatment, and it included hypoplasia of the maxillary and mandibular processes of the first branchial arch, a rudimentary second arch, and apparent collapse of the forebrain. Equivalent fusion between the lateral nasal process and the maxillary process and between the medial nasal process and the maxillary process in treated and control embryos accounts for the very low incidence of cleft lip observed in fetuses. The terminal microstomia was not associated with excessive merging or overgrowth of the first arch components. Hypoplasia of the first arch can account for retinoid-induced macrostomia and microstomia.

Animals↗

PubMed1985

Effects of parathyroid hormone and calcitonin on carbonic anhydrase location in osteoclasts of cultured embryonic chick bone.

The ultrastructural location of carbonic anhydrase has been examined in osteoclasts of cultured embryonic chick metatarsi. In untreated cultures and in those to which parathyroid hormone (PTH) was added, the enzyme was found in close association with the plasma membrane of the ruffled border. After brief calcitonin treatment (10 min) the ruffled border disappeared and the association of carbonic anhydrase with the plasma membrane was diminished. The results indicate that the hormones employed act directly on embryonic bone to alter osteoclast structure and the intracellular location of carbonic anhydrase.

Animals↗

PubMed1994

Review: borders, patterns, and distinctive families of homeodomains.

PURPOSE: Homeotic proteins function as transcription factors in early embryogenesis of many organisms. To date, hundreds of distinctive homeoproteins have been identified, including 84 human homeodomains. However further progress in understanding functional relationships between particular homeoproteins and other embryonic regulators requires a comprehensive structural classification of these proteins. RESULTS: The most probable borders and conservative amino acid positions inside the homeodomain region have been established using a statistical analysis of variabilities of amino acid occurrences at various positions outside and inside the domain. A new format for a homeodomain sequence presentation and regular amino acid patterns which are strongly representative of distinctive homeodomain groups are proposed. Using the established patterns, 33 families of closely related homeodomains have been distinguished and classified. The total list of 297 homeodomain amino acid sequences is presented in the Appendix. CONCLUSION: The structural classification of homeodomains has been proposed. It can be useful for both the identification (or prediction) of new homeotic genes/proteins and the recognition of possible PCR-induced sequence errors. This systematics will also have an impact on understanding functional relationships among homeotic proteins and other genetic regulators of developmental processes.

Amino Acid Sequence↗

PubMed1996

Subtle differences in the mitogenic effects of recombinant human bone morphogenetic proteins -2 to -7 on DNA synthesis on primary bone-forming cells and identification of BMP-2/4 receptor.

The bone morphogenetic proteins (BMPs) are a group of related proteins capable of inducing the formation of new cartilage and bone. We report here a direct comparison of members of the BMP family in their capability to induce DNA synthesis in bone cell cultures. The promotion of DNA synthesis was determined in periosteal cells and epiphyseal and sternal chondrocytes of embryonic chick. We demonstrate that structurally homologous BMP-2 and BMP-4 exhibit the highest specific activity in the three tested cell types, whereas BMP-5, BMP-6 activity is moderately reduced in periosteal cells and highly reduced in epiphyseal and sternal chondrocytes. The specific activity of BMP-7 is the lowest in the three tested cell cultures. Receptor binding characteristics demonstrate a binding of BMP-2 with high affinity (KD = 0.45 nM) on periosteal cells, and excess of TGF-beta 1 does not displace BMP-4 binding. Chemical cross-linking with iodinated BMP-2 generates an affinity complex of 90 kDa. These findings suggest the presence of a BMP-2/BMP-4 receptor that discriminates subtle differences in function among homologous members of the BMP family.

Animals↗

PubMed1990

Genomic structure and comparison of mouse tissue-specific alkaline phosphatase genes.

A full-length human placental alkaline phosphatase (AP) cDNA was used to identify and clone related genes from mouse genomic libraries. We report the cloning, sequence, and structural comparison of the mouse embryonic and intestinal AP genes and a putative AP pseudogene. All three mouse genes are composed of 11 exons interrupted by 10 small introns (70-261 bp) with an organization analogous to that of the three human tissue-specific AP genes. Introns interrupt the coding sequences at identical positions in all three mouse and human tissue-specific AP genes. The deduced amino acid sequence of the isozymes predicts proproteins of 529, 559, and 466 amino acids for embryonic AP, intestinal AP, and pseudo-AP, respectively. A repetitive sequence inserted in exon XI of the mouse intestinal AP gene codes for a unique stretch of 41 amino acids, 20 of which are threonines. This insertion has disrupted a region recognized as being responsible for phosphatidylinositol anchorage of human placental AP to the cytoplasmic membrane. Phylogenetic analysis indicates that the three mouse AP isozymes form a distinct group separate from the human tissue-specific AP isozymes, suggesting the taxon-specific evolution of the AP genes as opposed to independent evolution of AP genes expressed in specific tissues.

Alkaline Phosphatase↗

PubMed2005

Gene regulation by histone H1: new links to DNA methylation.

Linker histones of the H1 family are among the most abundant components of chromatin. In this issue of Cell, the effect of H1 downregulation on gene expression is examined. Although a 50% reduction of histone H1 levels in embryonic stem cells affects chromatin structure globally, the expression of very few genes is altered. Intriguingly, this study reveals a new link between H1 and DNA methylation.

Animals↗

PubMed2004

Cytoskeletal actin degradation induced by lovastatin in cardiomyocytes is mediated through caspase-2.

The objective of this study was to test the hypothesis that cytoskeletal actin fragmentation is mediated through caspase-2, specifically examining the ability of a caspase-2 inhibitor to interfere with actin fragmentation, in comparison with a caspase-3 inhibitor. Cardiomyocytes were cultured from embryonic chick heart. The fine structural element of cellular F-actin was visualized by staining cardiomyocytes with NBD-phallacidin. Lovastatin induced a dramatic and concentration-dependent loss of intact F-actin. The selectivity of this effect of lovastatin was demonstrated by the absence of similar changes in F-actin when cardiomyocytes were treated with the apoptotic stimulus palmitate, the metabolism of which produces acetyl CoA, the early substrate of cholesterol synthesis, through the mevalonate pathway. FACS analysis of NBD-phallacidin-stained cells was used to quantify the amount of F-actin loss. Actin fragmentation produced by lovastatin was operative through a caspase-2 pathway, as the caspase-2 inhibitor, z-VDVAD-fmk, significantly blocked lovastatin-induced changes in F-actin, but the caspase-3 inhibitor, Ac-DEVD-CHO, did not. Interruption of the mevalonate pathway was in part responsible for lovastatin's action, as the downstream metabolite mevalonate partially reversed the effect of lovastatin on actin fragmentation. These data indicate a previously unrecognized link between cytoskeletal actin and caspase-2.

Acetyl Coenzyme A↗