Body Patterning: The processes occurring in early development that direct morphogenesis. They specify the body plan ensuring that cells will proceed to differentiate, grow, and diversify in size and shape at the correct relative positions. Included are axial patterning, segmentation, compartment specification, limb position, organ boundary patterning, blood vessel patterning, etc.Sepia: A genus of cuttlefish in the family Sepiidae. They live in tropical, subtropical and temperate waters in most oceans.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Drosophila: A genus of small, two-winged flies containing approximately 900 described species. These organisms are the most extensively studied of all genera from the standpoint of genetics and cytology.Drosophila Proteins: Proteins that originate from insect species belonging to the genus DROSOPHILA. The proteins from the most intensely studied species of Drosophila, DROSOPHILA MELANOGASTER, are the subject of much interest in the area of MORPHOGENESIS and development.Homeodomain Proteins: Proteins encoded by homeobox genes (GENES, HOMEOBOX) that exhibit structural similarity to certain prokaryotic and eukaryotic DNA-binding proteins. Homeodomain proteins are involved in the control of gene expression during morphogenesis and development (GENE EXPRESSION REGULATION, DEVELOPMENTAL).Embryo, Nonmammalian: The developmental entity of a fertilized egg (ZYGOTE) in animal species other than MAMMALS. For chickens, use CHICK EMBRYO.Hedgehog Proteins: A family of intercellular signaling proteins that play and important role in regulating the development of many TISSUES and organs. Their name derives from the observation of a hedgehog-like appearance in DROSOPHILA embryos with genetic mutations that block their action.Morphogenesis: The development of anatomical structures to create the form of a single- or multi-cell organism. Morphogenesis provides form changes of a part, parts, or the whole organism.In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Zebrafish: An exotic species of the family CYPRINIDAE, originally from Asia, that has been introduced in North America. They are used in embryological studies and to study the effects of certain chemicals on development.Zebrafish Proteins: Proteins obtained from the ZEBRAFISH. Many of the proteins in this species have been the subject of studies involving basic embryological development (EMBRYOLOGY).Mesoderm: The middle germ layer of an embryo derived from three paired mesenchymal aggregates along the neural tube.Ectoderm: The outer of the three germ layers of an embryo.Bone Morphogenetic Proteins: Bone-growth regulatory factors that are members of the transforming growth factor-beta superfamily of proteins. They are synthesized as large precursor molecules which are cleaved by proteolytic enzymes. The active form can consist of a dimer of two identical proteins or a heterodimer of two related bone morphogenetic proteins.Embryonic Induction: The complex processes of initiating CELL DIFFERENTIATION in the embryo. The precise regulation by cell interactions leads to diversity of cell types and specific pattern of organization (EMBRYOGENESIS).Extremities: The farthest or outermost projections of the body, such as the HAND and FOOT.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Rhombencephalon: The posterior of the three primitive cerebral vesicles of an embryonic brain. It consists of myelencephalon, metencephalon, and isthmus rhombencephali from which develop the major BRAIN STEM components, such as MEDULLA OBLONGATA from the myelencephalon, CEREBELLUM and PONS from the metencephalon, with the expanded cavity forming the FOURTH VENTRICLE.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Genes, Homeobox: Genes that encode highly conserved TRANSCRIPTION FACTORS that control positional identity of cells (BODY PATTERNING) and MORPHOGENESIS throughout development. Their sequences contain a 180 nucleotide sequence designated the homeobox, so called because mutations of these genes often results in homeotic transformations, in which one body structure replaces another. The proteins encoded by homeobox genes are called HOMEODOMAIN PROTEINS.Xenopus Proteins: Proteins obtained from various species of Xenopus. Included here are proteins from the African clawed frog (XENOPUS LAEVIS). Many of these proteins have been the subject of scientific investigations in the area of MORPHOGENESIS and development.Fibroblast Growth Factor 8: A fibroblast growth factor that preferentially activates FIBROBLAST GROWTH FACTOR RECEPTOR 4. It was initially identified as an androgen-induced growth factor and plays a role in regulating growth of human BREAST NEOPLASMS and PROSTATIC NEOPLASMS.Gastrula: The developmental stage that follows BLASTULA or BLASTOCYST. It is characterized by the morphogenetic cell movements including invagination, ingression, and involution. Gastrulation begins with the formation of the PRIMITIVE STREAK, and ends with the formation of three GERM LAYERS, the body plan of the mature organism.WingSomites: Paired, segmented masses of MESENCHYME located on either side of the developing spinal cord (neural tube). Somites derive from PARAXIAL MESODERM and continue to increase in number during ORGANOGENESIS. Somites give rise to SKELETON (sclerotome); MUSCLES (myotome); and DERMIS (dermatome).Limb Buds: Distinct regions of mesenchymal outgrowth at both flanks of an embryo during the SOMITE period. Limb buds, covered by ECTODERM, give rise to forelimb, hindlimb, and eventual functional limb structures. Limb bud cultures are used to study CELL DIFFERENTIATION; ORGANOGENESIS; and MORPHOGENESIS.Wnt Proteins: Wnt proteins are a large family of secreted glycoproteins that play essential roles in EMBRYONIC AND FETAL DEVELOPMENT, and tissue maintenance. They bind to FRIZZLED RECEPTORS and act as PARACRINE PROTEIN FACTORS to initiate a variety of SIGNAL TRANSDUCTION PATHWAYS. The canonical Wnt signaling pathway stabilizes the transcriptional coactivator BETA CATENIN.Insect Proteins: Proteins found in any species of insect.Branchial Region: A region, of SOMITE development period, that contains a number of paired arches, each with a mesodermal core lined by ectoderm and endoderm on the two sides. In lower aquatic vertebrates, branchial arches develop into GILLS. In higher vertebrates, the arches forms outpouchings and develop into structures of the head and neck. Separating the arches are the branchial clefts or grooves.Wnt1 Protein: A proto-oncogene protein and member of the Wnt family of proteins. It is expressed in the caudal MIDBRAIN and is essential for proper development of the entire mid-/hindbrain region.Fibroblast Growth Factors: A family of small polypeptide growth factors that share several common features including a strong affinity for HEPARIN, and a central barrel-shaped core region of 140 amino acids that is highly homologous between family members. Although originally studied as proteins that stimulate the growth of fibroblasts this distinction is no longer a requirement for membership in the fibroblast growth factor family.Chick Embryo: The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.Nodal Protein: The founding member of the nodal signaling ligand family of proteins. Nodal protein was originally discovered in the region of the mouse embryo primitive streak referred to as HENSEN'S NODE. It is expressed asymmetrically on the left side in chordates and plays a critical role in the genesis of left-right asymmetry during vertebrate development.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Genes, Insect: The functional hereditary units of INSECTS.Endoderm: The inner of the three germ layers of an embryo.Bone Morphogenetic Protein 4: A bone morphogenetic protein that is a potent inducer of bone formation. It also functions as a regulator of MESODERM formation during EMBRYONIC DEVELOPMENT.Nervous System: The entire nerve apparatus, composed of a central part, the brain and spinal cord, and a peripheral part, the cranial and spinal nerves, autonomic ganglia, and plexuses. (Stedman, 26th ed)Organizers, Embryonic: Cells in certain regions of an embryo that self-regulate embryonic development. These organizers have been found in dorsal and ventral poles of GASTRULA embryos, including Spemann organizer in amphibians, and Hensen node in chicken and mouse. These organizer cells communicate with each other via a network of secreted signaling proteins, such as BONE MORPHOGENETIC PROTEINS and their antagonists (chordin and noggin).Head: The upper part of the human body, or the front or upper part of the body of an animal, typically separated from the rest of the body by a neck, and containing the brain, mouth, and sense organs.Trans-Activators: Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.Animals, Genetically Modified: ANIMALS whose GENOME has been altered by GENETIC ENGINEERING, or their offspring.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Embryonic Development: Morphological and physiological development of EMBRYOS.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Neural Tube: A tube of ectodermal tissue in an embryo that will give rise to the CENTRAL NERVOUS SYSTEM, including the SPINAL CORD and the BRAIN. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. For malformation of the neural tube, see NEURAL TUBE DEFECTS.Vertebrates: Animals having a vertebral column, members of the phylum Chordata, subphylum Craniata comprising mammals, birds, reptiles, amphibians, and fishes.Neural Crest: The two longitudinal ridges along the PRIMITIVE STREAK appearing near the end of GASTRULATION during development of nervous system (NEURULATION). The ridges are formed by folding of NEURAL PLATE. Between the ridges is a neural groove which deepens as the fold become elevated. When the folds meet at midline, the groove becomes a closed tube, the NEURAL TUBE.Drosophila melanogaster: A species of fruit fly much used in genetics because of the large size of its chromosomes.Notochord: A cartilaginous rod of mesodermal cells at the dorsal midline of all CHORDATE embryos. In lower vertebrates, notochord is the backbone of support. In the higher vertebrates, notochord is a transient structure, and segments of the vertebral column will develop around it. Notochord is also a source of midline signals that pattern surrounding tissues including the NEURAL TUBE development.Telencephalon: The anterior subdivision of the embryonic PROSENCEPHALON or the corresponding part of the adult prosencephalon that includes the cerebrum and associated structures.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Xenopus: An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.Organogenesis: Formation of differentiated cells and complicated tissue organization to provide specialized functions.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.T-Box Domain Proteins: Proteins containing a region of conserved sequence, about 200 amino acids long, which encodes a particular sequence specific DNA binding domain (the T-box domain). These proteins are transcription factors that control developmental pathways. The prototype of this family is the mouse Brachyury (or T) gene product.Gastrulation: A process of complicated morphogenetic cell movements that reorganizes a bilayer embryo into one with three GERM LAYERS and specific orientation (dorsal/ventral; anterior/posterior). Gastrulation describes the germ layer development of a non-mammalian BLASTULA or that of a mammalian BLASTOCYST.