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.Wnt Signaling Pathway: A complex signaling pathway whose name is derived from the DROSOPHILA Wg gene, which when mutated results in the wingless phenotype, and the vertebrate INT gene, which is located near integration sites of MOUSE MAMMARY TUMOR VIRUS. The signaling pathway is initiated by the binding of WNT PROTEINS to cells surface WNT RECEPTORS which interact with the AXIN SIGNALING COMPLEX and an array of second messengers that influence the actions of BETA CATENIN.Wnt3A Protein: A Wnt protein subtype that plays a role in cell-cell signaling during EMBRYONIC DEVELOPMENT and the morphogenesis of the developing NEURAL TUBE.Wnt3 Protein: A Wnt protein subtype that plays a role in cell-cell signaling during EMBRYONIC DEVELOPMENT and the morphogenesis of the developing NEURAL TUBE. Defects in Wnt3 protein are associated with autosomal recessive tetra-AMELIA in humans.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.Wnt4 Protein: A Wnt protein that is involved in regulating multiple developmental processes such as the formation of the KIDNEY; ADRENAL GLANDS; MAMMARY GLANDS; the PITUITARY GLAND; and the female reproductive system. Defects in WNT4 are a cause of ROKITANSKY KUSTER HAUSER SYNDROME.Wnt2 Protein: A proto-oncogene protein and member of the Wnt family of proteins. It is frequently up-regulated in human GASTRIC CANCER and is a tumor marker (BIOMARKERS, TUMOR) of gastric and COLORECTAL CANCER.Receptors, Wnt: Cell-surface receptors that specifically bind to WNT PROTEINS and activate the WNT SIGNALING PATHWAY.Frizzled Receptors: A family of seven-pass transmembrane cell-surface proteins that combines with LOW DENSITY LIPROTEIN RECEPTOR-RELATED PROTEIN-5 or LOW DENSITY LIPROTEIN RECEPTOR-RELATED PROTEIN-5 to form receptors for WNT PROTEINS. Frizzled receptors often couple with HETEROTRIMERIC G PROTEINS and regulate the WNT SIGNALING PATHWAY.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.Low Density Lipoprotein Receptor-Related Protein-6: An LDL-receptor related protein that combines with cell surface FRIZZLED RECEPTORS to form WNT PROTEIN-binding receptors. The protein plays an important role in the WNT SIGNALING PATHWAY during EMBRYONIC DEVELOPMENT and in regulation of vascular cell proliferation.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).Axin Protein: A scaffolding protein that is a critical component of the axin signaling complex which binds to ADENOMATOUS POLYPOSIS COLI PROTEIN; GLYCOGEN SYNTHASE KINASE 3; and CASEIN KINASE I.TCF Transcription Factors: A family of DNA-binding proteins that are primarily expressed in T-LYMPHOCYTES. They interact with BETA CATENIN and serve as transcriptional activators and repressors in a variety of developmental processes.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.LDL-Receptor Related Proteins: A family of proteins that share sequence similarity with the low density lipoprotein receptor (RECEPTORS, LDL).Lymphoid Enhancer-Binding Factor 1: A T-cell factor that plays an essential role in EMBRYONIC DEVELOPMENT.Intercellular Signaling Peptides and Proteins: Regulatory proteins and peptides that are signaling molecules involved in the process of PARACRINE COMMUNICATION. They are generally considered factors that are expressed by one cell and are responded to by receptors on another nearby cell. They are distinguished from HORMONES in that their actions are local rather than distal.Receptor Tyrosine Kinase-like Orphan Receptors: A family of cell surface receptors that were originally identified by their structural homology to neurotropic TYROSINE KINASES and referred to as orphan receptors because the associated ligand and signaling pathways were unknown. Evidence for the functionality of these proteins has been established by experiments showing that disruption of the orphan receptor genes results in developmental defects.Low Density Lipoprotein Receptor-Related Protein-5: LDL-receptor related protein that combines with FRIZZLED RECEPTORS at the cell surface to form receptors that bind WNT PROTEINS. The protein plays an important role in the WNT SIGNALING PATHWAY in OSTEOBLASTS and during EMBRYONIC DEVELOPMENT.Proto-Oncogene Proteins: Products of proto-oncogenes. Normally they do not have oncogenic or transforming properties, but are involved in the regulation or differentiation of cell growth. They often have protein kinase activity.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.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.Cytoskeletal Proteins: Major constituent of the cytoskeleton found in the cytoplasm of eukaryotic cells. They form a flexible framework for the cell, provide attachment points for organelles and formed bodies, and make communication between parts of the cell possible.Embryo, Nonmammalian: The developmental entity of a fertilized egg (ZYGOTE) in animal species other than MAMMALS. For chickens, use CHICK EMBRYO.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.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.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.Transcription Factor 7-Like 2 Protein: A transcription factor that takes part in WNT signaling pathway. The activity of the protein is regulated via its interaction with BETA CATENIN. Transcription factor 7-like 2 protein plays an important role in the embryogenesis of the PANCREAS and ISLET CELLS.Mesoderm: The middle germ layer of an embryo derived from three paired mesenchymal aggregates along the neural tube.Trans-Activators: Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.T Cell Transcription Factor 1: A TCF transcription factor that was originally identified as a DNA-binding protein that interacts with the enhancers of T-CELL RECEPTOR ALPHA GENES. It plays a role in T-LYMPHOCYTE development.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Receptors, G-Protein-Coupled: The largest family of cell surface receptors involved in SIGNAL TRANSDUCTION. They share a common structure and signal through HETEROTRIMERIC G-PROTEINS.Xenopus: An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Adaptor Proteins, Signal Transducing: A broad category of carrier proteins that play a role in SIGNAL TRANSDUCTION. They generally contain several modular domains, each of which having its own binding activity, and act by forming complexes with other intracellular-signaling molecules. Signal-transducing adaptor proteins lack enzyme activity, however their activity can be modulated by other signal-transducing enzymesGastrulation: 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.Adenomatous Polyposis Coli Protein: A negative regulator of beta-catenin signaling which is mutant in ADENOMATOUS POLYPOSIS COLI and GARDNER SYNDROME.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.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.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).Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Cell Line, Tumor: A cell line derived from cultured tumor cells.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.Lithium Chloride: A salt of lithium that has been used experimentally as an immunomodulator.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.Cell Lineage: The developmental history of specific differentiated cell types as traced back to the original STEM CELLS in the embryo.HEK293 Cells: A cell line generated from human embryonic kidney cells that were transformed with human adenovirus type 5.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Repressor Proteins: Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.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.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.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.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.Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.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 Polarity: Orientation of intracellular structures especially with respect to the apical and basolateral domains of the plasma membrane. Polarized cells must direct proteins from the Golgi apparatus to the appropriate domain since tight junctions prevent proteins from diffusing between the two domains.PhosphoproteinsGlycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.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).Ectoderm: The outer of the three germ layers of an embryo.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Gene Expression Regulation, Neoplastic: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in neoplastic tissue.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Embryonic Development: Morphological and physiological development of EMBRYOS.Osteoblasts: Bone-forming cells which secrete an EXTRACELLULAR MATRIX. HYDROXYAPATITE crystals are then deposited into the matrix to form bone.Animals, Genetically Modified: ANIMALS whose GENOME has been altered by GENETIC ENGINEERING, or their offspring.Gene Knockdown Techniques: The artificial induction of GENE SILENCING by the use of RNA INTERFERENCE to reduce the expression of a specific gene. It includes the use of DOUBLE-STRANDED RNA, such as SMALL INTERFERING RNA and RNA containing HAIRPIN LOOP SEQUENCE, and ANTI-SENSE OLIGONUCLEOTIDES.