Portal:Key Stem Cell Terms

A

• Adenovirus: 90–100 nm sized, nonenveloped icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome.
• Adipocytes: a cell that has differentiated and specializes in the synthesis and storage of fat.
• Adipogenesis: a fat cell develops as internally produced lipid droplets coalesce into a single large mass
• Adult stem cells: stem cells found in tissues in adult organisms that remain in an undifferentiated state and can give rise to specialized cell types of their originating tissue.
• Alkaline Phosphotase(AP): a hydrolase enzyme that dephosphorylates molecules under alkaline conditions and is used to stain ES and iPS cells for verification of the pluripotent state.
• Allogeneic transplantation: cell, tissue or organ transplants from one member of a species to a genetically different member of the same species.
• Amphotropic Virus: a virus usually associated with retroviruses that may not produce disease in its natural host but does replicate in tissue culture cells of host species as well as in cells from other species.
• Angiogenesis: the process involving the growth of new blood vessels from pre-existing blood vessels .
• Antigen: any substance that can stimulate the production of antibodies and specifically combine with them.
• Apoptosis: programmed cell death.

B

• B Cell: a lymphocyte derived from stem cells in the bone marrow. Each has a unique set of receptor molecules on its surface designed to recognize a specific antigen
• Blastocyst: the early human embryo consisting of about 100 cells. It has a fluid-filled cavity, an internal cluster of cells called the inner cell mass and an outer layer of cells called the trophoblast.
• Bone Marrow Stromal Cells: stem cells in bone marrow that do not generate blood cells, but give rise to bone, cartilage, fat, and connective tissue.
• Bone Morphogenetic Protein (BMP): a protein that is essential for the self-renewal of mouse embryonic stem cells, but promotes differentiation in human embryonic stem cells.

C

• Capsid: a coiled structure that encloses the nucleic acid of a virus.
• Cell Culture: growth of cells in vitro under controlled conditions.
• Cell Division: method by which a single cell divides to create two cells.
• vCell Passaging: in order to grow cells for extended periods scientists passage or split groups up. In the case of embryonic stem cells, passaging helps to keep the cells in their primitive state.
• Cell Proliferation: an increase in the number of cells resulting from cell growth and division.
• Cell Signaling: cell Signaling is part of a complex system of communications that govern basic cellular activities and cell action.
• Chimeric: an animal that has two or more different populations of genetically distinct cells that originated in different zygotes.
• Chondryocyte: the cell from which cartilage develops.
• Chromatin: a complex of DNA and protein that makes up chromosomes.
• Clevage: the process of cell division before an embryo becomes a blastocyst.
• Clone: a line of cells that is genetically identical to the precursor cell.
• CMV promoter: the enhancer of cytomegalovirus (CMV promoter) is one of the most commonly used promoters for expression of transgenes in eukaryotic cells.
• Concatemer: a long molecule of DNA that contains multiple copies of the same DNA sequences linked in a series.
• Confluency: the coverage or proliferation that the cells are allowed throughout the culture medium.
• Cytokines: a category of signaling molecules that regulate immunity, inflammation and hematopoiesis.
• Cytotoxicity: the quality or state of being directly toxic to cells.

D

• Dendritic cells: function to process antigen material and present it on the surface of other cells.
• Differentiation: the process where an undifferentiated cell acquires a more specialized function and increases its level of organization.
• Direct Reprogramming: induced pluripotent stem cell (iPS) generation via ectopic expression of required transcription factors (Oct4, Sox2, c-Myc, Klf4).
• DNA demethylation: is a process of removal of methyl group from nucleotide in DNA.
• Doxycycline: a drug that when added to iPS cells, switches on the four genes (Oct4, Sox2, c-Myc, Klf4) in the cells.

E

• Ectoderm: outermost germ layer of cells giving rise to the nervous system, skin and sensory organs.
• Electroporation: the application of a current to a living surface to pass another material through a pore or channel.
• Embryonic Stem Cells: derived from the inner cell mass of developing blastocytes that can replicate themselves and can form other cell types in the body.
• Embryoid Bodies: clumps of cells that arise during embryonic cell culture that have tissue from all three germ layers.
• EMT: Epithelial-mesenchymal transition is a program of development of biological cells characterized by loss of cell adhesion, repression of E-cadherin expression, and increased cell mobility.
• Endoderm: innermost layer of cells giving rise to respiratory and digestive organs.
• Endogenous: originate from within an organism, tissue, or cell.
• Epigenetic: changes in the appearance or gene expression caused by something other than changes in DNA sequence.
• Exogenous: derived or developed from outside the body; originating externally.

F

• Feeder Cells: provide nutrients for growth of mouse and human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells.
• Feeder Layer: cells used in cell culture that maintains pluripotent stem cells.
• Fibroblast: a type of cell found in connective tissue which produces collagen.
• Flow Cytometry: used to identify/characterize the cell types by the proteins the cells express, and can be used to determine the percentage of a certain cell type in the overall cell population. Different types of cells produce different intracellular and secretable proteins.

G

• Gene Expression: the conversion of information encoded in a gene to mRNA and then a protein.
• Gene Therapy: the science of gene transfer into individuals for therapeutic purposes by altering cell structure or function.
• Genome: the entire hereditary information of an organism encoded in their DNA.
• Germ Layer: one of the three layers of cells that originate during cell division after fertilization of an egg.
• GFP (Green Fluorescent Protein): The gene for GFP has been isolated and has become a useful tool for making chimeric proteins of GFP linked to other proteins where it functions as a fluorescent protein tag. As a noninvasive fluorescent marker in living cells, it allows for a wide range of applications where it may function as a cell lineage tracer, reporter of gene expression, or as a measure of protein-protein interactions.

H

• Hela cells: cells that can divide an unlimited amount of times on a cell culture plate as long as basic survival conditions are met.
• Hematopoietic stem cells: stem cells that give rise to blood cells.
• Hypotoxic: oxygen deficient.

I

• In vitro: describes a state or condition that occurs and /or exists outside the body. This term often refers to testing conditions that occur in a laboratory environment.
• In vivo: describes a state or condition that occurs and/or exists within the body. This term is often used to describe testing conditions that occur within humans and/or animals.
• Immunocytochemistry (ICC): used to visualize protein expression on cell surface or to locate proteins within cells with the assistance of a microscope.
• Immunogenicity: capable of causing an immune response.
• Induced Pluripotent Stem Cell (iPS): adult cells that have been reprogrammed to behave like embryonic stem cells.
• Integrins: receptors on a cells surface that interact with the extracellular matrix and mediate intracellular signals.
• Isogenic: genetically equivalent.
• Isotype Control antibodies: used to estimate the non-specific binding of target primary antibodies to cell surface antigens.

J

K

• Klf4: a transcription factor that plays a role in cell proliferation and survival and acts as a transcriptional activator or repressor.

L

• Lentiviral vectors: an RNA viral vector that integrates in non-dividing cells without immunogenicity.
• Lentivirus: integrates into actively dividing cells and non-dividing cells
• Leukemia Inhibitory Factor (LIF): a signaling molecule that affects the self renewal of ES cells by activating STAT signaling through a membrane bound receptor.
• Long Term Self-Renewal: the ability of cells to renew themselves by dividing into the same type of specialized cell over a certain length of time.
• Luciferase: measures the transfection activity by quantifying the total amount of luciferase protein produced by that cell.
• Lysis: cell death by breaking the cellular membrane.

M

• Mesenchymal stem cells: cells originating from immature embryonic connective tissue.
• Mesoderm: the middle layer of cells that give rise to muscle, bone, kidneys and connective tissue.
• Multipotent: ability of a cell to develop into more than one cell type.
• Morphology: the status of cell health and differentiation in cell culture.

N

• Neoplasm: the abnormal proliferation of cells.
• Niche: the cellular environment that provides support and stimuli to sustain self renewal.
• Notch: a protein involved in cell division, differentiation, adhesion and cell death.
• Nucleotide: structural units of DNA and RNA and play a role in cellular signaling and metabolism. These organic compounds consist of joined structures: a nitrogenous base, a sugar, and a phosphate group.
• Nuclear Transfer: the process in which the nucleus is removed from an egg and replaced with a nucleus of an older cell.

O

• Oct4: a transcription factor critically involved in the self-renewal of undifferentiated stem cells and is frequently used as a marker for undifferentiated cells.
• Oligopotent: able to form more than one lineage within a tissue.
• Oncoretrovirus: the most widely used retroviral factors for gene therapy that can transduce only dividing cells.

P

• Pantrophic: ability to thrive in many different environments
• Paracrine factors: the growth of differentiation factors.
• Passage: a round of cell growth and proliferation during cell culture.
• Phosphorylation: the addition of a phosphate (PO4) group to a protein or other organic molecule that plays a significant role in a wide range of cellular processes.
• piggyBac: a transposon that has been used to deliver dox-inducible transcription factors into a cell that can be removed after reprogramming.
• Plasmid: a linear or circular double-stranded DNA that is capable of replicating independently of the chromosomal DNA.
• Plasticity: the ability of adult stem cells from one tissue to generate differentiated cell types of another tissue.
• Pleiotrophic: one gene that is responsible for more than one phenotypic characteristic.
• Pluripotency: developmental potential to differentiate into different cell types from each of the primary germ layers.
• Pluripotency markers: antigenic and molecular markers specific to pluripotent cells including; Oct-4, Nanog, Rex1, SSEA-3, SSEA-4, Tra-1-60, Tra 1-80.
• Polycomb: a class of proteins that maintains stable and heritable repression of genes.
• Precursors: a compound that participates in the chemical reaction that produces another compound
• Precursor cells: cells that contribute to tissue formation that do not have self-renewal ability.
• Progenitor cell: a descendant of a stem cell that can differentiate but cannot self-renew.
• Proliferation: cell expansion by continuous division of single cells into two identical cells.
• Propagation: maintenance of stem cell self-renewal.
• Pseudotyped: phenotypic mixing in retroviruses results in a genome from a parent with a defective envelope, contained within the envelope capsid from a helper retrovirus.
• Puromycin selection: an antibiotic that inhibits cell growth by interfering with protein synthesis and is used to select cells modified by genetic engineering.

Q

R

• Ras Proteins: a group of GTP binding proteins that that control cell proliferation and differentiation.
• Recombinase: an enzyme that catalyzes the exchange of short pieces of DNA between two longer strands.
• Regenerative Medicine: reconstruction of diseased or injured tissue by activation of endogenous cells or by cell transplantation.
• Reprogramming: conversion of somatic/adult cell to the ES-like pluripotent state.
• Retinoic Acid: a transcriptional regulator of differentiation during embryogenesis.
• Retroviral vectors: RNA viral vectors that can integrate into hosts’ DNA where upon integration, the transgene of interest is copied and results in prolonged transgene expression.
• Retrovirus: integrates into actively dividing cells upon cell division.
• rtTA (tetracycline reverse transcriptional activator): binds to tetracycline operator elements (TetO) in the presence of doxycycline causing transcriptional activation of genes downstream of TetO.

S

• Self renewal: the ability of stem cells to produce more stem cells with identical characteristics.
• Somatic Cells: cells from the body other than sperm or egg cells.
• Somatic Cell Nuclear Transfer (SCNT): a process involving the removal of the nucleus of an unfertilized egg cell and replacing it with the nucleus of a somatic cell and directing this cell to begin cell division.
• Sonic Hedgehog (SHH): protein that controls cell division of adult stem cells.
• Sox2: a transcription factor essential to maintain self-renewal of undifferentiated embryonic stem cells.
• Stem Cells: cells that have the ability to divide as well as differentiate into specialized cells
  • Adult stem cell: an undifferentiated cell found in a differentiated tissue that can renew itself and (with certain limitations) differentiate to yield all the specialized cell types of the tissue from which it originated.
  • Endogenous stem cells: stem cells that are already present in the body.
  • Embryonic stem cells: primitive (undifferentiated) cells from the embryo that have the potential to become a wide variety of specialized cell types.
• Stem Cell Line: stem cells that have been growing in cell culture for six or more months without becoming specialized and appear genetically normal.
• Stromal Cells: non-blood cells derived from blood organs that can support growth of blood cells in vitro.
• Subculturing: the transfer of cultured cells from one vessel to another.

• Subventricular zone (SVZ): the region in the brain that harbors neural stem and progenitor cells during and after nervous system development.
• Surface Markers: proteins, located on the outside of a cell, unique to a certain cell type and can be seen with the use of antibodies.

T

• T Cell: derived from the bone marrow, these cells are principal agents of cell-mediated immunity and play different roles in the immune response.
• Teratoma: tumors that contain a variety of differentiated cells from all three primary germ layers.
• Teratocarcinomas: tumors that are derived from undifferentiated ESCs.
• TGF-β: transforming growth factor beta, controls proliferation, cellular differentiation, and other functions in most cells.
• Tet-regulatable system: a tool for controlling gene expression by encoding within the viral vectors.
• Totipotent: the ability to differentiate into any kind of cell.
• Transcription: the synthesis of RNA under the direction of DNA.
• Transcription Factors: a group of proteins that regulate gene activity by increasing or decreasing the binding of RNA polymerases to DNA. Transcription factors are part of the system that controls the transfer (or transcription) of genetic information from DNA to RNA.
• Transdifferentiation: the process where stem cells of one tissue differentiate in to cells of a different tissue.
• Transduction: the process of which foreign DNA is introduced into another cell via a viral vector.
• Transfection: the process of introducing nucleic acids into cells by non-viral methods.
• Trophectoderm: the outer layer of a blastocyst.
• Tropism: the orientation of an organism to an external stimulus.
• Trophoblast: a layer of the ectoderm that provides nourishment to the embryo or develops into a fetal membrane.

U

• Undifferentiated: a cell that has not yet obtained characteristics of a specialized cell type.
• Unipotent: cells that can self-renew but only produce one cell type. It's self-renewal that distinguishes them from non-stem cells.

V

• Vasculogenesis: a type of angiogenesis involving the spontaneous formation of blood vessels.
• Vector: is a vehicle for transferring genetic material into a cell.
• Virus: is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell.
• Viral Vector: is a virus that has been modified to transduct specific genetic material into a cell.
• VSV-G: glycoprotein of vesicular stomatitis virus.

W

• Western Blot: used to identify specific proteins in a given sample of cells from a cell lysate separated by gel electrophoresis. Used to identify cell lysate proteins that are separated by gel electrophoresis to detect specific proteins in a given sample of cells.
• Wnt Proteins: a highly conserved family of signaling molecules that regulate cell to cell interactions during embyogenesis.

X

• Xenograph: a tissue graft taken from a donor of one species and grafted to a recipient of another species.

Y

Z

• Zygote: the cell that results from fertilization between the ovum from a female and the sperm cell from a male.