Biomaterial Database

Vertebrate limb development. 1995

C Tickle

Department of Anatomy and Developmental Biology, University College and Middlesex School of Medicine, University College London, UK.

The recent identification of Wnt-7a as a signalling molecule in dorsal/ventral patterning means that we now have a known signal for control of each of the three limb axes. Fibroblast growth factors can allow proximal/distal patterning and Sonic hedgehog gene expression signals anterior/posterior patterning. Networks of these signals not only coordinate cell responses, but also mutually maintain each other. A positive feedback loop is established which coordinates expression of Sonic hedgehog in mesenchyme cells of the polarizing region and Fgf-4 expression in overlying apical ridge ectoderm. Wnt-7a expression in dorsal ectoderm also influences Sonic hedgehog expression in the polarizing region. Initiation of development of a complete limb can be achieved with just one signal, a growth factor.

UI	MeSH Term	Description	Entries
D011506	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.	Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D004627	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).	Embryonic Inductions,Induction, Embryonic,Inductions, Embryonic
D005121	Extremities	The farthest or outermost projections of the body, such as the HAND and FOOT.	Limbs,Extremity,Limb
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014714	Vertebrates	Animals having a vertebral column, members of the phylum Chordata, subphylum Craniata comprising mammals, birds, reptiles, amphibians, and fishes.	Vertebrate
D015398	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.	Cell Signaling,Receptor-Mediated Signal Transduction,Signal Pathways,Receptor Mediated Signal Transduction,Signal Transduction Pathways,Signal Transduction Systems,Pathway, Signal,Pathway, Signal Transduction,Pathways, Signal,Pathways, Signal Transduction,Receptor-Mediated Signal Transductions,Signal Pathway,Signal Transduction Pathway,Signal Transduction System,Signal Transduction, Receptor-Mediated,Signal Transductions,Signal Transductions, Receptor-Mediated,System, Signal Transduction,Systems, Signal Transduction,Transduction, Signal,Transductions, Signal
D015534	Trans-Activators	Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.	Nuclear Trans-Acting Factor,Trans-Acting Factors,Trans-Acting Factor,Trans-Activator,Transactivator,Transactivators,Factor, Nuclear Trans-Acting,Factor, Trans-Acting,Factors, Trans-Acting,Nuclear Trans Acting Factor,Trans Acting Factor,Trans Acting Factors,Trans Activator,Trans Activators,Trans-Acting Factor, Nuclear
D053823	Hedgehog Proteins	A family of intercellular signaling proteins that play an 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.	Hedgehog Protein,Hedgehog Protein, Vertebrate,Banded Hedgehog Protein,Desert Hedgehog Protein,Indian Hedgehog Protein,Sonic Hedgehog Protein,Vertebrate Hedgehog Protein,Hedgehog Protein, Banded,Hedgehog Protein, Desert,Hedgehog Protein, Indian,Hedgehog Protein, Sonic,Protein, Hedgehog
D018507	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.	Developmental Gene Expression Regulation,Embryologic Gene Expression Regulation,Gene Expression Regulation, Embryologic,Regulation of Gene Expression, Developmental,Regulation of Gene Expression, Embryologic,Regulation, Gene Expression, Developmental,Regulation, Gene Expression, Embryologic
D018878	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.	Limb Bud,Bud, Limb,Buds, Limb