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Retinoic Acid
Retinoic acid (simplified nomenclature for all-''trans''-retinoic acid) is a metabolite of vitamin A1 (all-''trans''-retinol) that is required for embryonic development, male fertility, regulation of bone growth and immune function. All-''trans''-retinoic acid is required for chordate animal development, which includes all higher animals from fish to humans. During early embryonic development, all-''trans''-retinoic acid generated in a specific region of the embryo helps determine position along the embryonic anterior/posterior axis by serving as an intercellular signaling molecule that guides development of the posterior portion of the embryo. It acts through Hox genes, which ultimately control anterior/posterior patterning in early developmental stages. In adult tissues, the activity of endogenous retinoic acid appears limited to immune function and male fertility. All-''trans''-retinoic acid is the major occurring retinoic acid, while isomers like 13-''cis''- and 9-''cis''-r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinol
Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family that is found in food and used as a dietary supplement. Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and mucous membranes, immune function and reproductive development. Dietary sources include fish, dairy products, and meat. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophthalmia. It is taken by mouth or by intramuscular injection, injection into a muscle. As an ingredient in skin-care products, it is used to reduce wrinkles and other effects of skin aging. Retinol at normal doses is well tolerated. High doses may cause hepatomegaly, enlargement of the liver, dry skin, and hypervitaminosis A. High doses during pregnancy may harm the fetus. The body converts retinol to retinal and retinoic acid, through which it acts. Retinol was discovered in 1909, isolated in 1931, and first m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAR-beta
Retinoic acid receptor beta (RAR-beta), also known as NR1B2 (nuclear receptor subfamily 1, group B, member 2) is a nuclear receptor that in humans is encoded by the ''RARB'' gene. Function This gene encodes retinoic acid receptor beta, a member of the thyroid-steroid hormone receptor superfamily of nuclear transcriptional regulators. This receptor localizes to the cytoplasm and to subnuclear compartments. It binds retinoic acid, the biologically active form of vitamin A which mediates cellular signalling in embryonic morphogenesis, cell growth and differentiation. It is thought that this protein limits growth of many cell types by regulating gene expression. The gene was first identified in a hepatocellular carcinoma where it flanks a hepatitis B virus integration site. A deregulation of this gene has also been detected in uterine cervical carcinoma preneoplastic lesions. The gene expresses at least two transcript variants; one additional transcript has been described, but its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALDH1A1
Aldehyde dehydrogenase 1 family, member A1, also known as ALDH1A1 or retinaldehyde dehydrogenase 1 (RALDH1), is an enzyme that is encoded by the ''ALDH1A1'' gene. Function This protein belongs to the aldehyde dehydrogenases family of proteins and is a member of the ALDH1 subfamily (including ALDH1A2, ALDH1A3, ALDH1B1, ALDH2). Aldehyde dehydrogenase isozymes are NAD(P)-dependent dehydrogenases that catalyze the oxidation of an aldehyde into the corresponding carboxylic acid while reducing NAD+ or NADP+. ALDH1A1 is the only ALDH1 isozyme known to oxidize 9-cis retinaldehyde into 9-cis retinoic acid and thus serve as the only known activator of the Retinoid X receptor alpha, rexinoid nuclear receptor pathway. ALDH1A1 has also been described with activity against other substrates in living systems, including All-Trans-Retinaldehyde, all-trans retinaldehyde as well as oxazaphosphorine, a cyclophosphamide metabolite. Unique among the ALDH1 isozymes, ALDH1A1 is known to possess estera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinaldehyde Dehydrogenase
In enzymology, a retinal dehydrogenase, also known as retinaldehyde dehydrogenase (RALDH), catalyzes the chemical reaction converting retinal to retinoic acid. This enzyme belongs to the family of oxidoreductases, specifically the class acting on aldehyde or oxo- donor groups with NAD+ or NADP+ as acceptor groups, the systematic name being retinal:NAD+ oxidoreductase. This enzyme participates in retinol metabolism. The general scheme for the reaction catalyzed by this enzyme is: retinal + NAD+ + H2O \rightleftharpoons retinoic acid + NADH + H+ Structure Retinal dehydrogenase is a tetramer of identical units, consisting of a dimer of dimers. Retinal dehydrogenase monomers are composed of three domains: a nucleotide-binding domain, a tetramerization domain, and a catalytic domain. The dimer can be pictured as an "X" with the dimers forming upper and lower halves that cross over each other. Interestingly, the nucleotide-binding domain of retinal dehydrogenase contains 5 instead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinol Dehydrogenase
In enzymology, a retinol dehydrogenase (RDH) () is an enzyme that catalysis, catalyzes the chemical reaction :retinol + NAD+ \rightleftharpoons retinal + NADH + H+ Sometimes, in addition to or along with nicotinamide adenine dinucleotide, NAD+, Nicotinamide adenine dinucleotide phosphate, NADP+ can act as a preferred cofactor in the reaction as well. The substrate of the enzyme can be all-''trans''- or -''cis''- retinol. Some 20 enzymes with RDH activity had been found and studied by 2006. Thus, the two substrate (biochemistry), substrates of this enzyme are retinol and nicotinamide adenine dinucleotide, NAD+, whereas its 3 product (chemistry), products are retinal, nicotinamide adenine dinucleotide, NADH (or NADPH in the case where Nicotinamide adenine dinucleotide phosphate, NADP+ is a cofactor), and hydrogen ion, H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The List of enzymes, sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulation Of Gene Expression
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from Transcriptional regulation, transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network. Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (''Ac'') and Dissociator (''Ds''), in the color f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinaldehyde
Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision). Some microorganisms use retinal to convert light into metabolic energy. One study suggests that approximately three billion years ago, most living organisms on Earth used retinal, rather than chlorophyll, to convert sunlight into energy. Because retinal absorbs mostly green light and transmits purple light, this gave rise to the Purple Earth hypothesis. Retinal itself is considered to be a form of vitamin A when eaten by an animal. There are many forms of vitamin A, all of which are converted to retinal, which cannot be made without them. The number of different molecules that can be converted to retinal varies from species to species. Retinal was originally called retinene, and was renamed after it was discovered to be vitamin A aldehyde. Vertebrate animals ingest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulatory T Cell
The regulatory T cells (Tregs or Treg cells), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain immune tolerance, tolerance to self-antigens, and prevent autoimmune disease. Treg cells are immunosuppression, immunosuppressive and generally suppress or downregulation and upregulation, downregulate induction and proliferation of effector T cells. Treg cells express the biomarkers CD4, FOXP3, and CD25 and are thought to be derived from the same cell lineage, lineage as naïve T helper cell, CD4+ cells. Because effector T cells also express CD4 and CD25, Treg cells are very difficult to effectively discern from effector CD4+, making them difficult to study. Research has found that the cytokine Transforming growth factor beta, transforming growth factor beta (TGF-β) is essential for Treg cells to differentiate from naïve CD4+ cells and is important in maintaining Treg cell homeostas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HOXD4
Homeobox protein Hox-D4 is a protein that in humans is encoded by the ''HOXD4'' gene. Function This gene belongs to the homeobox family of genes. The homeobox genes encode a highly conserved family of transcription factors that play an important role in morphogenesis in all multicellular organisms. Mammals possess four similar homeobox gene clusters, HOXA, HOXB, HOXC and HOXD, located on different chromosomes, consisting of 9 to 11 genes arranged in tandem. This gene is one of several homeobox HOXD genes located at 2q31-2q37 chromosome regions. Deletions that removed the entire HOXD gene cluster or 5' end of this cluster have been associated with severe limb and genital abnormalities. The protein encoded by this gene may play a role in determining positional values in developing limb buds. Alternatively spliced variants have been described but their full length nature has not been determined. See also * Homeobox References Further reading * * * * * * * * * * * * Ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HOXB4
Homeobox protein Hox-B4 is a protein that in humans is encoded by the ''HOXB4'' gene. Function This gene is a member of the Antp homeobox family and encodes a nuclear protein with a homeobox DNA-binding domain. It is included in a cluster of homeobox B genes located on chromosome 17. The encoded protein functions as a sequence-specific transcription factor that is involved in development. Intracellular or ectopic expression of this protein expands hematopoietic stem and progenitor cells in vivo and in vitro, making it a potential candidate for therapeutic stem cell expansion. See also * Homeobox A homeobox is a Nucleic acid sequence, DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of ... References Further reading * * * * * * * * * * * * * * * * * External links * Transcription fac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HOXB1
Homeobox protein Hox-B1 is a protein that in humans is encoded by the ''HOXB1'' gene. Function This gene belongs to the homeobox family of genes. The homeobox genes encode a highly conserved family of transcription factors that play an important role in morphogenesis in all multicellular organisms. Mammals possess four similar homeobox gene clusters, HOXA, HOXB, HOXC and HOXD, located on different chromosomes, consisting of 9 to 11 genes arranged in tandem. This gene is one of several homeobox HOXB genes located in a cluster on chromosome 17 Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 84 million base pairs (the building material of DNA) and represents between 2.5 and 3% of the total DN .... Interactions HOXB1 has been shown to interact with PBX1. See also * Tandemly arrayed genes References Further reading * * * * * * * * * * * * * * * * * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HOXA1
Homeobox protein Hox-A1 is a protein that in humans is encoded by the ''HOXA1'' gene. Gene Two transcription (genetics), transcript variants encoding two different protein isoform, isoforms have been found for this gene, with only one of the isoforms containing the homeodomain fold, homeodomain region. Function In vertebrates, the genes encoding the class of transcription factors called homeobox genes are found in clusters named A, B, C, and D on four separate chromosomes. Expression of these proteins is spatially and temporally regulated during embryogenesis, embryonic development. This gene is part of the A cluster on chromosome 7 and encodes a DNA-binding transcription factor which may regulate gene expression, morphogenesis, and cellular differentiation. The homeobox protein Hox-A1 may be involved in the placement of hindbrain segments in the proper location along the anterior-posterior axis during development. Clinical significance A common polymorphism in the HOXA1 ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
