Hematopoietic Stem Cells: Progenitor cells from which all blood cells derive.Hematopoietic Stem Cell Transplantation: Transfer of HEMATOPOIETIC STEM CELLS from BONE MARROW or BLOOD between individuals within the same species (TRANSPLANTATION, HOMOLOGOUS) or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS). Hematopoietic stem cell transplantation has been used as an alternative to BONE MARROW TRANSPLANTATION in the treatment of a variety of neoplasms.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.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Hematopoiesis: The development and formation of various types of BLOOD CELLS. Hematopoiesis can take place in the BONE MARROW (medullary) or outside the bone marrow (HEMATOPOIESIS, EXTRAMEDULLARY).Cell Lineage: The developmental history of specific differentiated cell types as traced back to the original STEM CELLS in the embryo.Stem Cell Transplantation: The transfer of STEM CELLS from one individual to another within the same species (TRANSPLANTATION, HOMOLOGOUS) or between species (XENOTRANSPLANTATION), or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS). The source and location of the stem cells determines their potency or pluripotency to differentiate into various cell types.Embryonic Stem Cells: Cells derived from the BLASTOCYST INNER CELL MASS which forms before implantation in the uterine wall. They retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.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.Bone Marrow Cells: Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells.Stem Cell Niche: A particular zone of tissue composed of a specialized microenvironment where stem cells are retained in a undifferentiated, self-renewable state.Antigens, CD34: Glycoproteins found on immature hematopoietic cells and endothelial cells. They are the only molecules to date whose expression within the blood system is restricted to a small number of progenitor cells in the bone marrow.Adult Stem Cells: Cells with high proliferative and self renewal capacities derived from adults.Transplantation, Homologous: Transplantation between individuals of the same species. Usually refers to genetically disparate individuals in contradistinction to isogeneic transplantation for genetically identical individuals.Hematopoietic Stem Cell Mobilization: The release of stem cells from the bone marrow into the peripheral blood circulation for the purpose of leukapheresis, prior to stem cell transplantation. Hematopoietic growth factors or chemotherapeutic agents often are used to stimulate the mobilization.Mice, Inbred C57BLColony-Forming Units Assay: A cytologic technique for measuring the functional capacity of stem cells by assaying their activity.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Pluripotent Stem Cells: Cells that can give rise to cells of the three different GERM LAYERS.Stem Cell Factor: A hematopoietic growth factor and the ligand of the cell surface c-kit protein (PROTO-ONCOGENE PROTEINS C-KIT). It is expressed during embryogenesis and is a growth factor for a number of cell types including the MAST CELLS and the MELANOCYTES in addition to the HEMATOPOIETIC STEM CELLS.Multipotent Stem Cells: Specialized stem cells that are committed to give rise to cells that have a particular function; examples are MYOBLASTS; MYELOID PROGENITOR CELLS; and skin stem cells. (Stem Cells: A Primer [Internet]. Bethesda (MD): National Institutes of Health (US); 2000 May [cited 2002 Apr 5]. Available from: http://www.nih.gov/news/stemcell/primer.htm)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 Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Bone Marrow: The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.Mesenchymal Stromal Cells: Bone-marrow-derived, non-hematopoietic cells that support HEMATOPOETIC STEM CELLS. They have also been isolated from other organs and tissues such as UMBILICAL CORD BLOOD, umbilical vein subendothelium, and WHARTON JELLY. These cells are considered to be a source of multipotent stem cells because they include subpopulations of mesenchymal stem cells.Cell SeparationGraft vs Host Disease: The clinical entity characterized by anorexia, diarrhea, loss of hair, leukopenia, thrombocytopenia, growth retardation, and eventual death brought about by the GRAFT VS HOST REACTION.Neural Stem Cells: Self-renewing cells that generate the main phenotypes of the nervous system in both the embryo and adult. Neural stem cells are precursors to both NEURONS and NEUROGLIA.Fetal Blood: Blood of the fetus. Exchange of nutrients and waste between the fetal and maternal blood occurs via the PLACENTA. The cord blood is blood contained in the umbilical vessels (UMBILICAL CORD) at the time of delivery.Transplantation Conditioning: Preparative treatment of transplant recipient with various conditioning regimens including radiation, immune sera, chemotherapy, and/or immunosuppressive agents, prior to transplantation. Transplantation conditioning is very common before bone marrow transplantation.Hematopoietic System: The blood-making organs and tissues, principally the bone marrow and lymph nodes.Bone Marrow Transplantation: The transference of BONE MARROW from one human or animal to another for a variety of purposes including HEMATOPOIETIC STEM CELL TRANSPLANTATION or MESENCHYMAL STEM CELL TRANSPLANTATION.Induced Pluripotent Stem Cells: Cells from adult organisms that have been reprogrammed into a pluripotential state similar to that of EMBRYONIC STEM CELLS.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Mice, SCID: Mice homozygous for the mutant autosomal recessive gene "scid" which is located on the centromeric end of chromosome 16. These mice lack mature, functional lymphocytes and are thus highly susceptible to lethal opportunistic infections if not chronically treated with antibiotics. The lack of B- and T-cell immunity resembles severe combined immunodeficiency (SCID) syndrome in human infants. SCID mice are useful as animal models since they are receptive to implantation of a human immune system producing SCID-human (SCID-hu) hematochimeric mice.Cell Culture Techniques: Methods for maintaining or growing CELLS in vitro.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Transplantation, Autologous: Transplantation of an individual's own tissue from one site to another site.Mesonephros: One of a pair of excretory organs (mesonephroi) which grows caudally to the first pair (PRONEPHROI) during development. Mesonephroi are the permanent kidneys in adult amphibians and fish. In higher vertebrates, proneprhoi and most of mesonephroi degenerate with the appearance of metanephroi. The remaining ducts become WOLFFIAN DUCTS.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.Hematologic Neoplasms: Neoplasms located in the blood and blood-forming tissue (the bone marrow and lymphatic tissue). The commonest forms are the various types of LEUKEMIA, of LYMPHOMA, and of the progressive, life-threatening forms of the MYELODYSPLASTIC SYNDROMES.Mesenchymal Stem Cell Transplantation: Transfer of MESENCHYMAL STEM CELLS between individuals within the same species (TRANSPLANTATION, HOMOLOGOUS) or transfer within the same individual (TRANSPLANTATION, AUTOLOGOUS).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.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.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.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Fetal Stem Cells: Cells derived from a FETUS that retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.Proto-Oncogene Proteins c-kit: A protein-tyrosine kinase receptor that is specific for STEM CELL FACTOR. This interaction is crucial for the development of hematopoietic, gonadal, and pigment stem cells. Genetic mutations that disrupt the expression of PROTO-ONCOGENE PROTEINS C-KIT are associated with PIEBALDISM, while overexpression or constitutive activation of the c-kit protein-tyrosine kinase is associated with tumorigenesis.Time Factors: Elements of limited time intervals, contributing to particular results or situations.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Cell Survival: The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.Mice, Inbred NOD: A strain of non-obese diabetic mice developed in Japan that has been widely studied as a model for T-cell-dependent autoimmune insulin-dependent diabetes mellitus in which insulitis is a major histopathologic feature, and in which genetic susceptibility is strongly MHC-linked.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Antigens, CD: Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation.Transplantation Chimera: An organism that, as a result of transplantation of donor tissue or cells, consists of two or more cell lines descended from at least two zygotes. This state may result in the induction of donor-specific TRANSPLANTATION TOLERANCE.Lentivirus: A genus of the family RETROVIRIDAE consisting of non-oncogenic retroviruses that produce multi-organ diseases characterized by long incubation periods and persistent infection. Lentiviruses are unique in that they contain open reading frames (ORFs) between the pol and env genes and in the 3' env region. Five serogroups are recognized, reflecting the mammalian hosts with which they are associated. HIV-1 is the type species.Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.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.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Cell Movement: The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.Transduction, Genetic: The transfer of bacterial DNA by phages from an infected bacterium to another bacterium. This also refers to the transfer of genes into eukaryotic cells by viruses. This naturally occurring process is routinely employed as a GENE TRANSFER TECHNIQUE.Cord Blood Stem Cell Transplantation: Transplantation of STEM CELLS collected from the fetal blood remaining in the UMBILICAL CORD and the PLACENTA after delivery. Included are the HEMATOPOIETIC STEM CELLS.Graft Survival: The survival of a graft in a host, the factors responsible for the survival and the changes occurring within the graft during growth in the host.Whole-Body Irradiation: Irradiation of the whole body with ionizing or non-ionizing radiation. It is applicable to humans or animals but not to microorganisms.Myeloid Progenitor Cells: Stem cells derived from HEMATOPOIETIC STEM CELLS. Derived from these myeloid progenitor cells are the MEGAKARYOCYTES; ERYTHROID CELLS; MYELOID CELLS; and some DENDRITIC CELLS.Leukemia: A progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow. Leukemias were originally termed acute or chronic based on life expectancy but now are classified according to cellular maturity. Acute leukemias consist of predominately immature cells; chronic leukemias are composed of more mature cells. (From The Merck Manual, 2006)Genetic Vectors: DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.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).Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Regeneration: The physiological renewal, repair, or replacement of tissue.Cell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Coculture Techniques: A technique of culturing mixed cell types in vitro to allow their synergistic or antagonistic interactions, such as on CELL DIFFERENTIATION or APOPTOSIS. Coculture can be of different types of cells, tissues, or organs from normal or disease states.Retroviridae: Family of RNA viruses that infects birds and mammals and encodes the enzyme reverse transcriptase. The family contains seven genera: DELTARETROVIRUS; LENTIVIRUS; RETROVIRUSES TYPE B, MAMMALIAN; ALPHARETROVIRUS; GAMMARETROVIRUS; RETROVIRUSES TYPE D; and SPUMAVIRUS. A key feature of retrovirus biology is the synthesis of a DNA copy of the genome which is integrated into cellular DNA. After integration it is sometimes not expressed but maintained in a latent state (PROVIRUSES).Neoplastic Stem Cells: Highly proliferative, self-renewing, and colony-forming stem cells which give rise to NEOPLASMS.Stromal Cells: Connective tissue cells of an organ found in the loose connective tissue. These are most often associated with the uterine mucosa and the ovary as well as the hematopoietic system and elsewhere.Granulocyte Colony-Stimulating Factor: A glycoprotein of MW 25 kDa containing internal disulfide bonds. It induces the survival, proliferation, and differentiation of neutrophilic granulocyte precursor cells and functionally activates mature blood neutrophils. Among the family of colony-stimulating factors, G-CSF is the most potent inducer of terminal differentiation to granulocytes and macrophages of leukemic myeloid cell lines.Gene Expression Profiling: The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.T-Lymphocytes: Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.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.Lymphopoiesis: Formation of LYMPHOCYTES and PLASMA CELLS from the lymphoid stem cells which develop from the pluripotent HEMATOPOIETIC STEM CELLS in the BONE MARROW. These lymphoid stem cells differentiate into T-LYMPHOCYTES; B-LYMPHOCYTES; PLASMA CELLS; or NK-cells (KILLER CELLS, NATURAL) depending on the organ or tissues (LYMPHOID TISSUE) to which they migrate.Chimerism: The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from different individuals. This contrasts with MOSAICISM in which the different cell populations are derived from a single individual.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Osteoblasts: Bone-forming cells which secrete an EXTRACELLULAR MATRIX. HYDROXYAPATITE crystals are then deposited into the matrix to form bone.Hematopoiesis, Extramedullary: The formation and development of blood cells outside the BONE MARROW, as in the SPLEEN; LIVER; or LYMPH NODES.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Peripheral Blood Stem Cell Transplantation: Transplantation of stem cells collected from the peripheral blood. It is a less invasive alternative to direct marrow harvesting of hematopoietic stem cells. Enrichment of stem cells in peripheral blood can be achieved by inducing mobilization of stem cells from the BONE MARROW.Tissue Donors: Individuals supplying living tissue, organs, cells, blood or blood components for transfer or transplantation to histocompatible recipients.Antigens, Differentiation: Antigens expressed primarily on the membranes of living cells during sequential stages of maturation and differentiation. As immunologic markers they have high organ and tissue specificity and are useful as probes in studies of normal cell development as well as neoplastic transformation.Radiation Chimera: An organism whose body contains cell populations of different genotypes as a result of the TRANSPLANTATION of donor cells after sufficient ionizing radiation to destroy the mature recipient's cells which would otherwise reject the donor cells.Cell Line, Tumor: A cell line derived from cultured tumor cells.Green Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.Granulocytes: Leukocytes with abundant granules in the cytoplasm. They are divided into three groups according to the staining properties of the granules: neutrophilic, eosinophilic, and basophilic. Mature granulocytes are the NEUTROPHILS; EOSINOPHILS; and BASOPHILS.Biological Markers: Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.Myeloid Cells: The classes of BONE MARROW-derived blood cells in the monocytic series (MONOCYTES and their precursors) and granulocytic series (GRANULOCYTES and their precursors).Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Thrombopoietin: A humoral factor that stimulates the production of thrombocytes (BLOOD PLATELETS). Thrombopoietin stimulates the proliferation of bone marrow MEGAKARYOCYTES and their release of blood platelets. The process is called THROMBOPOIESIS.Immunophenotyping: Process of classifying cells of the immune system based on structural and functional differences. The process is commonly used to analyze and sort T-lymphocytes into subsets based on CD antigens by the technique of flow cytometry.Clone Cells: A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed)Antigens, CD38: A bifunctional enzyme that catalyzes the synthesis and HYDROLYSIS of CYCLIC ADP-RIBOSE (cADPR) from NAD+ to ADP-RIBOSE. It is a cell surface molecule which is predominantly expressed on LYMPHOID CELLS and MYELOID CELLS.Antigens, Ly: A group of lymphocyte surface antigens located on mouse LYMPHOCYTES. Specific Ly antigens are useful markers for distinguishing subpopulations of lymphocytes.Genetic Therapy: Techniques and strategies which include the use of coding sequences and other conventional or radical means to transform or modify cells for the purpose of treating or reversing disease conditions.Transplantation, Heterologous: Transplantation between animals of different species.Leukemia, Myeloid, Acute: Clonal expansion of myeloid blasts in bone marrow, blood, and other tissue. Myeloid leukemias develop from changes in cells that normally produce NEUTROPHILS; BASOPHILS; EOSINOPHILS; and MONOCYTES.Myelopoiesis: Formation of MYELOID CELLS from the pluripotent HEMATOPOIETIC STEM CELLS in the BONE MARROW via MYELOID STEM CELLS. Myelopoiesis generally refers to the production of leukocytes in blood, such as MONOCYTES and GRANULOCYTES. This process also produces precursor cells for MACROPHAGE and DENDRITIC CELLS found in the lymphoid tissue.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.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.Antigens, Thy-1: A group of differentiation surface antigens, among the first to be discovered on thymocytes and T-lymphocytes. Originally identified in the mouse, they are also found in other species including humans, and are expressed on brain neurons and other cells.Mice, Mutant Strains: Mice bearing mutant genes which are phenotypically expressed in the animals.B-Lymphocytes: Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.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.Megakaryocytes: Very large BONE MARROW CELLS which release mature BLOOD PLATELETS.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Mice, Inbred BALB CGonads: The gamete-producing glands, OVARY or TESTIS.Yolk Sac: The first of four extra-embryonic membranes to form during EMBRYOGENESIS. In REPTILES and BIRDS, it arises from endoderm and mesoderm to incorporate the EGG YOLK into the DIGESTIVE TRACT for nourishing the embryo. In placental MAMMALS, its nutritional function is vestigial; however, it is the source of INTESTINAL MUCOSA; BLOOD CELLS; and GERM CELLS. It is sometimes called the vitelline sac, which should not be confused with the VITELLINE MEMBRANE of the egg.Chemokine CXCL12: A CXC chemokine that is chemotactic for T-LYMPHOCYTES and MONOCYTES. It has specificity for CXCR4 RECEPTORS. Two isoforms of CXCL12 are produced by alternative mRNA splicing.Lymphoid Progenitor Cells: Stem cells from which B-LYMPHOCYTES; T-LYMPHOCYTES; NATURAL KILLER CELLS; and some DENDRITIC CELLS derive.Receptors, Notch: A family of conserved cell surface receptors that contain EPIDERMAL GROWTH FACTOR repeats in their extracellular domain and ANKYRIN repeats in their cytoplasmic domains. The cytoplasmic domain of notch receptors is released upon ligand binding and translocates to the CELL NUCLEUS where it acts as transcription factor.Busulfan: An alkylating agent having a selective immunosuppressive effect on BONE MARROW. It has been used in the palliative treatment of chronic myeloid leukemia (MYELOID LEUKEMIA, CHRONIC), but although symptomatic relief is provided, no permanent remission is brought about. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), busulfan is listed as a known carcinogen.Spleen: An encapsulated lymphatic organ through which venous blood filters.Down-Regulation: A negative regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.Histocompatibility Testing: Identification of the major histocompatibility antigens of transplant DONORS and potential recipients, usually by serological tests. Donor and recipient pairs should be of identical ABO blood group, and in addition should be matched as closely as possible for HISTOCOMPATIBILITY ANTIGENS in order to minimize the likelihood of allograft rejection. (King, Dictionary of Genetics, 4th ed)Bromodeoxyuridine: A nucleoside that substitutes for thymidine in DNA and thus acts as an antimetabolite. It causes breaks in chromosomes and has been proposed as an antiviral and antineoplastic agent. It has been given orphan drug status for use in the treatment of primary brain tumors.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.Interleukin-3: A multilineage cell growth factor secreted by LYMPHOCYTES; EPITHELIAL CELLS; and ASTROCYTES which stimulates clonal proliferation and differentiation of various types of blood and tissue cells.Stem Cell Research: Experimentation on STEM CELLS and on the use of stem cells.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Blood Cells: The cells found in the body fluid circulating throughout the CARDIOVASCULAR SYSTEM.Antigens, CD45: High-molecular weight glycoproteins uniquely expressed on the surface of LEUKOCYTES and their hemopoietic progenitors. They contain a cytoplasmic protein tyrosine phosphatase activity which plays a role in intracellular signaling from the CELL SURFACE RECEPTORS. The CD45 antigens occur as multiple isoforms that result from alternative mRNA splicing and differential usage of three exons.GATA2 Transcription Factor: An essential GATA transcription factor that is expressed primarily in HEMATOPOIETIC STEM CELLS.Cell Aging: The decrease in the cell's ability to proliferate with the passing of time. Each cell is programmed for a certain number of cell divisions and at the end of that time proliferation halts. The cell enters a quiescent state after which it experiences CELL DEATH via the process of APOPTOSIS.Core Binding Factor Alpha 2 Subunit: A transcription factor that dimerizes with the cofactor CORE BINDING FACTOR BETA SUBUNIT to form core binding factor. It contains a highly conserved DNA-binding domain known as the runt domain. Runx1 is frequently mutated in human LEUKEMIAS.Thymus Gland: A single, unpaired primary lymphoid organ situated in the MEDIASTINUM, extending superiorly into the neck to the lower edge of the THYROID GLAND and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat.Plant Stems: Parts of plants that usually grow vertically upwards towards the light and support the leaves, buds, and reproductive structures. (From Concise Dictionary of Biology, 1990)Tumor Cells, Cultured: Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.Basic Helix-Loop-Helix Transcription Factors: A family of DNA-binding transcription factors that contain a basic HELIX-LOOP-HELIX MOTIF.Mice, Congenic: Mouse strains constructed to possess identical genotypes except for a difference at a single gene locus.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Histocompatibility: The degree of antigenic similarity between the tissues of different individuals, which determines the acceptance or rejection of allografts.Up-Regulation: A positive regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.Severe Combined Immunodeficiency: Group of rare congenital disorders characterized by impairment of both humoral and cell-mediated immunity, leukopenia, and low or absent antibody levels. It is inherited as an X-linked or autosomal recessive defect. Mutations occurring in many different genes cause human Severe Combined Immunodeficiency (SCID).Erythropoiesis: The production of red blood cells (ERYTHROCYTES). In humans, erythrocytes are produced by the YOLK SAC in the first trimester; by the liver in the second trimester; by the BONE MARROW in the third trimester and after birth. In normal individuals, the erythrocyte count in the peripheral blood remains relatively constant implying a balance between the rate of erythrocyte production and rate of destruction.Hematologic Diseases: Disorders of the blood and blood forming tissues.Hematopoietic Cell Growth Factors: These growth factors comprise a family of hematopoietic regulators with biological specificities defined by their ability to support proliferation and differentiation of blood cells of different lineages. ERYTHROPOIETIN and the COLONY-STIMULATING FACTORS belong to this family. Some of these factors have been studied and used in the treatment of chemotherapy-induced neutropenia, myelodysplastic syndromes, and bone marrow failure syndromes.Erythroid Precursor Cells: The cells in the erythroid series derived from MYELOID PROGENITOR CELLS or from the bi-potential MEGAKARYOCYTE-ERYTHROID PROGENITOR CELLS which eventually give rise to mature RED BLOOD CELLS. The erythroid progenitor cells develop in two phases: erythroid burst-forming units (BFU-E) followed by erythroid colony-forming units (CFU-E); BFU-E differentiate into CFU-E on stimulation by ERYTHROPOIETIN, and then further differentiate into ERYTHROBLASTS when stimulated by other factors.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Myelodysplastic Syndromes: Clonal hematopoietic stem cell disorders characterized by dysplasia in one or more hematopoietic cell lineages. They predominantly affect patients over 60, are considered preleukemic conditions, and have high probability of transformation into ACUTE MYELOID LEUKEMIA.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Cytokines: Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Cell Transformation, Neoplastic: Cell changes manifested by escape from control mechanisms, increased growth potential, alterations in the cell surface, karyotypic abnormalities, morphological and biochemical deviations from the norm, and other attributes conferring the ability to invade, metastasize, and kill.Cell Transplantation: Transference of cells within an individual, between individuals of the same species, or between individuals of different species.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Tretinoin: An important regulator of GENE EXPRESSION during growth and development, and in NEOPLASMS. Tretinoin, also known as retinoic acid and derived from maternal VITAMIN A, is essential for normal GROWTH; and EMBRYONIC DEVELOPMENT. An excess of tretinoin can be teratogenic. It is used in the treatment of PSORIASIS; ACNE VULGARIS; and several other SKIN DISEASES. It has also been approved for use in promyelocytic leukemia (LEUKEMIA, PROMYELOCYTIC, ACUTE).Oligonucleotide Array Sequence Analysis: Hybridization of a nucleic acid sample to a very large set of OLIGONUCLEOTIDE PROBES, which have been attached individually in columns and rows to a solid support, to determine a BASE SEQUENCE, or to detect variations in a gene sequence, GENE EXPRESSION, or for GENE MAPPING.Cell Adhesion: Adherence of cells to surfaces or to other cells.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Interleukin Receptor Common gamma Subunit: An interleukin receptor subunit that was originally discovered as a component of the INTERLEUKIN 2 RECEPTOR. It was subsequently found to be a component of several other receptors including the INTERLEUKIN 4 RECEPTOR, the INTERLEUKIN 7 RECEPTOR, the INTERLEUKIN-9 RECEPTOR, the INTERLEUKIN-15 RECEPTOR, and the INTERLEUKIN-21 RECEPTOR. Mutations in the gene for the interleukin receptor common gamma chain have been associated with X-LINKED COMBINED IMMUNODEFICIENCY DISEASES.Mice, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations, or by parent x offspring matings carried out with certain restrictions. All animals within an inbred strain trace back to a common ancestor in the twentieth generation.Trans-Activators: Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.Fibroblasts: Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Lymphocyte Activation: Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.Octamer Transcription Factor-3: An octamer transcription factor that is expressed primarily in totipotent embryonic STEM CELLS and GERM CELLS and is down-regulated during CELL DIFFERENTIATION.Cellular Microenvironment: Local surroundings with which cells interact by processing various chemical and physical signals, and by contributing their own effects to this environment.Gene Transfer Techniques: The introduction of functional (usually cloned) GENES into cells. A variety of techniques and naturally occurring processes are used for the gene transfer such as cell hybridization, LIPOSOMES or microcell-mediated gene transfer, ELECTROPORATION, chromosome-mediated gene transfer, TRANSFECTION, and GENETIC TRANSDUCTION. Gene transfer may result in genetically transformed cells and individual organisms.Real-Time Polymerase Chain Reaction: Methods used for detecting the amplified DNA products from the polymerase chain reaction as they accumulate instead of at the end of the reaction.Leukemia, Myelogenous, Chronic, BCR-ABL Positive: Clonal hematopoetic disorder caused by an acquired genetic defect in PLURIPOTENT STEM CELLS. It starts in MYELOID CELLS of the bone marrow, invades the blood and then other organs. The condition progresses from a stable, more indolent, chronic phase (LEUKEMIA, MYELOID, CHRONIC PHASE) lasting up to 7 years, to an advanced phase composed of an accelerated phase (LEUKEMIA, MYELOID, ACCELERATED PHASE) and BLAST CRISIS.Receptors, Thrombopoietin: Cell surface receptors that are specific for THROMBOPOIETIN. They signal through interaction with JANUS KINASES such as JANUS KINASE 2.RNA, Small Interfering: Small double-stranded, non-protein coding RNAs (21-31 nucleotides) involved in GENE SILENCING functions, especially RNA INTERFERENCE (RNAi). Endogenously, siRNAs are generated from dsRNAs (RNA, DOUBLE-STRANDED) by the same ribonuclease, Dicer, that generates miRNAs (MICRORNAS). The perfect match of the siRNAs' antisense strand to their target RNAs mediates RNAi by siRNA-guided RNA cleavage. siRNAs fall into different classes including trans-acting siRNA (tasiRNA), repeat-associated RNA (rasiRNA), small-scan RNA (scnRNA), and Piwi protein-interacting RNA (piRNA) and have different specific gene silencing functions.Leukemia, Myeloid: Form of leukemia characterized by an uncontrolled proliferation of the myeloid lineage and their precursors (MYELOID PROGENITOR CELLS) in the bone marrow and other sites.Blood Cell Count: The number of LEUKOCYTES and ERYTHROCYTES per unit volume in a sample of venous BLOOD. A complete blood count (CBC) also includes measurement of the HEMOGLOBIN; HEMATOCRIT; and ERYTHROCYTE INDICES.Receptor, Notch1: A notch receptor that interacts with a variety of ligands and regulates SIGNAL TRANSDUCTION PATHWAYS for multiple cellular processes. It is widely expressed during EMBRYOGENESIS and is essential for EMBRYONIC DEVELOPMENT.Receptors, CXCR4: CXCR receptors with specificity for CXCL12 CHEMOKINE. The receptors may play a role in HEMATOPOIESIS regulation and can also function as coreceptors for the HUMAN IMMUNODEFICIENCY VIRUS.Graft vs Leukemia Effect: Immunological rejection of leukemia cells following bone marrow transplantation.Osteogenesis: The process of bone formation. Histogenesis of bone including ossification.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.Transgenes: Genes that are introduced into an organism using GENE TRANSFER TECHNIQUES.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.Mesoderm: The middle germ layer of an embryo derived from three paired mesenchymal aggregates along the neural tube.Myeloablative Agonists: Agents that destroy bone marrow activity. They are used to prepare patients for BONE MARROW TRANSPLANTATION or STEM CELL TRANSPLANTATION.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Cell- and Tissue-Based Therapy: Therapies that involve the TRANSPLANTATION of CELLS or TISSUES developed for the purpose of restoring the function of diseased or dysfunctional cells or tissues.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.ADP-ribosyl Cyclase: A membrane-bound or cytosolic enzyme that catalyzes the synthesis of CYCLIC ADP-RIBOSE (cADPR) from nicotinamide adenine dinucleotide (NAD). This enzyme generally catalyzes the hydrolysis of cADPR to ADP-RIBOSE, as well, and sometimes the synthesis of cyclic ADP-ribose 2' phosphate (2'-P-cADPR) from NADP.Regenerative Medicine: A field of medicine concerned with developing and using strategies aimed at repair or replacement of damaged, diseased, or metabolically deficient organs, tissues, and cells via TISSUE ENGINEERING; CELL TRANSPLANTATION; and ARTIFICIAL ORGANS and BIOARTIFICIAL ORGANS and tissues.Erythroid Cells: The series of cells in the red blood cell lineage at various stages of differentiation.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.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Chimera: An individual that contains cell populations derived from different zygotes.Myeloproliferative Disorders: Conditions which cause proliferation of hemopoietically active tissue or of tissue which has embryonic hemopoietic potential. They all involve dysregulation of multipotent MYELOID PROGENITOR CELLS, most often caused by a mutation in the JAK2 PROTEIN TYROSINE KINASE.Nerve Tissue ProteinsSex Differentiation: The process in developing sex- or gender-specific tissue, organ, or function after SEX DETERMINATION PROCESSES have set the sex of the GONADS. Major areas of sex differentiation occur in the reproductive tract (GENITALIA) and the brain.Adipogenesis: The differentiation of pre-adipocytes into mature ADIPOCYTES.RNA Interference: A gene silencing phenomenon whereby specific dsRNAs (RNA, DOUBLE-STRANDED) trigger the degradation of homologous mRNA (RNA, MESSENGER). The specific dsRNAs are processed into SMALL INTERFERING RNA (siRNA) which serves as a guide for cleavage of the homologous mRNA in the RNA-INDUCED SILENCING COMPLEX. DNA METHYLATION may also be triggered during this process.