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Biomolecular Gradient
A biomolecular gradient is established by a difference in the concentration of molecules in a biological system such as individual cells, groups of cells, or an entire organism. A biomolecular gradient can exist intracellularly (within a cell) or extracellularly (between groups of cells). The purposes of such gradients in biological systems vary, but include chemotaxis and functions in development. These types of gradients play a role in many different types of signaling as well as recently being implicated in cancer metastasis. Development Cells themselves can create biomolecular gradients by releasing signaling molecules that diffuse outwardly. These gradients are critical for cellular identity and cell relocation. Similarly, the gradients produced by cells may influence cellular fate by their temporal and spatial characteristics. In certain organisms, the choice of cell fate can be determined by a gradient, a binary choice, or through a relay of molecules released by a cell. If ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Polarity
Cell polarity refers to spatial differences in shape, structure, and function within a cell. Almost all cell types exhibit some form of polarity, which enables them to carry out specialized functions. Classical examples of polarized cells are described below, including epithelial cells with apical-basal polarity, neurons in which signals propagate in one direction from dendrites to axons, and migrating cells. Furthermore, cell polarity is important during many types of asymmetric cell division to set up functional asymmetries between daughter cells. Many of the key molecular players implicated in cell polarity are well conserved. For example, in metazoan cells, the PAR-3/PAR-6/aPKC complex plays a fundamental role in cell polarity. While the biochemical details may vary, some of the core principles such as negative and/or positive feedback between different molecules are common and essential to many known polarity systems. Examples of polarized cells Epithelial cells Epitheli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotaxis
Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming toward the highest concentration of food molecules, or to flee from poisons (e.g., phenol). In multicellular organisms, chemotaxis is critical to early development (e.g., movement of sperm towards the egg during fertilization) and development (e.g., migration of neurons or lymphocytes) as well as in normal function and health (e.g., migration of leukocytes during injury or infection). In addition, it has been recognized that mechanisms that allow chemotaxis in animals can be subverted during cancer metastasis. The aberrant chemotaxis of leukocytes and lymphocytes also contribute to inflammatory diseases such as atherosclerosis, asthma, and arthr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morphogens
A morphogen is a substance whose non-uniform distribution governs the pattern of tissue development in the process of morphogenesis or pattern formation, one of the core processes of developmental biology, establishing positions of the various specialized cell types within a tissue. More specifically, a morphogen is a signaling molecule that acts directly on cells to produce specific cellular responses depending on its local concentration. Typically, morphogens are produced by source cells and diffuse through surrounding tissues in an embryo during early development, such that concentration gradients are set up. These gradients drive the process of differentiation of unspecialised stem cells into different cell types, ultimately forming all the tissues and organs of the body. The control of morphogenesis is a central element in evolutionary developmental biology (evo-devo). History The term was coined by Alan Turing in the paper "The Chemical Basis of Morphogenesis", where he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonic Hedgehog
Sonic hedgehog protein (SHH) is encoded for by the ''SHH'' gene. The protein is named after the character ''Sonic the Hedgehog''. This signaling molecule is key in regulating embryonic morphogenesis in all animals. SHH controls organogenesis and the organization of the central nervous system, limbs, digits and many other parts of the body. Sonic hedgehog is a morphogen that patterns the developing embryo using a concentration gradient characterized by the French flag model. This model has a non-uniform distribution of SHH molecules which governs different cell fates according to concentration. Mutations in this gene can cause holoprosencephaly, a failure of splitting in the cerebral hemispheres, as demonstrated in an experiment using SHH knock-out mice in which the forebrain midline failed to develop and instead only a single fused telencephalic vesicle resulted. Sonic hedgehog still plays a role in differentiation, proliferation, and maintenance of adult tissues. Abnormal activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angiogenesis
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splitting. Vasculogenesis is the embryonic formation of endothelial cells from mesoderm cell precursors, and from neovascularization, although discussions are not always precise (especially in older texts). The first vessels in the developing embryo form through vasculogenesis, after which angiogenesis is responsible for most, if not all, blood vessel growth during development and in disease. Angiogenesis is a normal and vital process in growth and development, as well as in wound healing and in the formation of granulation tissue. However, it is also a fundamental step in the transition of tumors from a benign state to a malignant one, leading to the use of angiogenesis inhibitors in the treatment of cancer. The essential role of angiogenesis in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pom1
Pom1 is a polarity protein kinase in fission yeast, ''Schizosaccharomyces pombe'' (''S. pombe''), that localizes to cell ends and regulates cell division. As the cell lengthens, the level of Pom1 in the middle declines, which triggers mitosis.Bahler, J., and Pringle, J.R. “Pom1p, a fission yeast protein kinase that provides positional information for both polarized growth and cytokinesis.” Genes and Development 12, 1356-1370 (1998). The genebr>''pom1''codes for a protein 1087 amino acids long with the protein kinase domain likely located at the carboxyl terminus. Pom1 regulates a signaling pathway that includes Cdk1 and ultimately regulates mitotic entry.Moseley, J.B., Mayeux, A., Paoletti, A. and Nurse, P. “A spatial gradient coordinates cell size and mitotic entry in fission yeast.” Nature 459, 857-861 (2009). Cells with mutant pom1 form a septa and growth zone, but show a host of abnormalities including misplaced or misoriented septa, bi-polar growth replaced with r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
