Ephrins: Signaling proteins that are ligands for the EPH FAMILY RECEPTORS. They are membrane-bound proteins that are attached to the CELL MEMBRANE either through a GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR or through a transmembrane domain. Many of the ephrins are considered important intercellular signaling molecules that control morphogenic changes during embryogenesis.Receptors, Eph Family: A large family of receptor protein-tyrosine kinases that are structurally-related. The name of this family of proteins derives from original protein Eph (now called the EPHA1 RECEPTOR), which was named after the cell line it was first discovered in: Erythropoietin-Producing human Hepatocellular carcinoma cell line. Members of this family have been implicated in regulation of cell-cell interactions involved in nervous system patterning and development.Ephrin-A5: A GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR containing ephrin found in developing tectum. It has been shown to mediate the bundling of cortical axons and repel the axonal growth of retinal ganglia axons. It is found in a variety of adult tissues of BRAIN; HEART; and KIDNEY.Ephrin-B1: A transmembrane domain containing ephrin that is specific for EPHB1 RECEPTOR; EPHB2 RECEPTOR and EPHB3 RECEPTOR. It is widely expressed in a variety of developing and adult tissues.Receptor, EphA3: An eph family receptor that is found primarily in adult BRAIN and variety of tissues in the developing embryo tissues. During embryonic development high levels of EphA3 receptor expression is seen in the nervous system and coincides with neuronal cell migration, suggesting a role for this protein in axonal pathfinding.Ephrin-A2: A GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR-containing ephrin with a high affinity for the EPHA3 RECEPTOR. Early in embryogenesis it is expressed at high levels in the MESENCEPHALON; SOMITES; branchial arches, and LIMB BUDS.Ephrin-B2: A transmembrane domain containing ephrin that binds with high affinity to EPHB1 RECEPTOR; EPHB3 RECEPTOR; and EPHB4 RECEPTOR. Expression of ephrin-B2 occurs in a variety of adult tissues. During embryogenesis, high levels of ephrin-B2 is seen in the PROSENCEPHALON; RHOMBENCEPHALON; developing SOMITES; LIMB BUD; and bronchial arches.Receptor, EphA4: An eph family receptor found in variety of tissues including BRAIN. During embryogenesis, EphA4 receptor exhibits a diverse spatial and temporal patterns of expression suggesting its role in multiple developmental processes.Ephrin-A4: A GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR containing ephrin found in variety of adult tissue such as KIDNEY; LUNG; COLON and OVARY. During embryonic development, ephrin-A4 is expressed in the HIPPOCAMPUS and CEREBRAL CORTEX. It binds preferentially to ephA receptors (EPH FAMILY RECEPTORS) with the exception of the EPHA1 RECEPTOR.Ephrin-A3: A GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR containing ephrin with a high affinity for the EPHA3 RECEPTOR; EPHA5 RECEPTOR; EPHA6 RECEPTOR; EPHA7 RECEPTOR; and EPHA8 RECEPTOR. It is found primarily in NERVE TISSUE.Receptor, EphA7: An eph family receptor found widely expressed in embryo tissues, including the NERVOUS SYSTEM. In the BRAIN high levels of EphA7 expression occurs in the anterior tectum, medulla, RHOMBENCEPHALON, and SUBCOMMISSURAL ORGAN. Several isoforms of the protein occur due to multiple alternative spicing of the EphA7 mRNA.Receptor, EphB4: An eph family receptor found in a variety of adult and embryonic tissues. Unlike the majority of proteins in this class there is little or no expression of EphB4 receptor in the BRAIN. It has been found at high levels in developing mammary glands and in invasive mammary tumors.Receptor, EphA1: The founding member of the EPH FAMILY RECEPTORS. It was first cloned from an erythropoietin-producing human hepatocellular carcinoma cell line and is highly conserved among many mammalian species. Overproduction of the EphA1 receptor is associated with tumors and tumor cells of epithelial origin. It is also expressed at high levels in LIVER; LUNG; and KIDNEY; which is in contrast to many other members of the Eph receptor that are found primarily in tissues of the nervous system.Ephrin-A1: An ephrin that was originally identified as the product of an early response gene induced by TUMOR NECROSIS FACTORS. It is linked to the CELL MEMBRANE via a GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR and binds EPHA2 RECEPTOR with high affinity. During embryogenesis high levels of ephrin-A1 are expressed in LUNG; KIDNEY; SALIVARY GLANDS; and INTESTINE.Ephrin-B3: A transmembrane domain containing ephrin. Although originally found to be specific for the EPHB3 RECEPTOR it has since been shown to bind a variety of EPH FAMILY RECEPTORS. During embryogenesis ephrin-B3 is expressed at high levels in the ventral neural tube. In adult tissues, it is found primarily in the BRAIN and HEART.Receptor, EphB2: An eph family receptor found widely expressed in embryonic and adult tissues. High levels of EphB2 receptor are observed in growing AXONS and NERVE FIBERS. Several isoforms of the protein exist due to multiple alternative mRNA splicing.Receptor, EphB3: An eph family receptor found in a number of tissues including BRAIN; LUNG; KIDNEY; PANCREAS; INTESTINE; and HEART. During embryogenesis EphB3 receptor is expressed at high levels in the brain.Receptor, EphB1: An eph family receptor found primarily in the nervous system. In the embryonic BRAIN EphB1 receptor expression occurs in the mantle layer and increases with the progression of embryogenesis. In adult brain it is found in the several regions including the CEREBELLUM; CEREBRAL CORTEX; and CAUDATE NUCLEUS; and PUTAMEN.Receptor, EphA2: An Eph family receptor found abundantly in tissues of epithelial origin. It is expressed in a diverse array of tissues during embryonic development, suggesting that it may play a role in embryogenesis. In adult tissues high levels of the receptor are expressed in the LUNG; SKIN; SMALL INTESTINE and OVARY.Receptor, EphA5: An eph family receptor found primarily in differentiated neuronal tissues. Several isoforms of EphA5 receptor occur due to multiple alternative RNA splicing. The protein is prominently expressed in the NEURONS of the LIMBIC SYSTEM during development and throughout adult life, suggesting its role in the plasticity of limbic structure and function.Fetal Proteins: Proteins that are preferentially expressed or upregulated during FETAL DEVELOPMENT.Receptor Protein-Tyrosine Kinases: A class of cellular receptors that have an intrinsic PROTEIN-TYROSINE KINASE activity.Growth Cones: Bulbous enlargement of the growing tip of nerve axons and dendrites. They are crucial to neuronal development because of their pathfinding ability and their role in synaptogenesis.Syntenins: Intracellular signaling adaptor proteins that play a role in the coupling of SYNDECANS to CYTOSKELETAL PROTEINS.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Protein Tyrosine Phosphatase, Non-Receptor Type 13: A subtype of non-receptor protein tyrosine phosphatases that is characterized by the presence of an amino-terminal FERM domain, an intervening region containing five different PDZ domains, and a carboxyl-terminal phosphatase domain. In addition to playing a role as a regulator of the FAS RECEPTOR activity this subtype interacts via its PDZ and FERM domains with a variety of INTRACELLULAR SIGNALING PROTEINS and CYTOSKELETAL PROTEINS.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Ligands: A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)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.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.Superior Colliculi: The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.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.