Paper 1: Embryonic Stem Cell Lines Derived from Human Blastocysts

Alpha-fetoprotein (AFP)

A plasma protein found abundantly in fetuses that in humans is encoded by the AFP gene.

Alkaline phosphatase

An enzyme commonly expressed in almost all living organisms. In humans and other mammals, it is a marker for pluripotent stem cells.

BeWo

A placental cell line derived from a choriocarcinoma (a malignant tumor of the uterus that originates in the cells of the chorion of a fetus).

Carcinoma

A malignant and invasive epithelial tumor that spreads by metastasis and often recurs after excision; cancer

Chimera

An organism made up of cells or tissues with different genotypes. An organism with genetically distinct cells from two different zygotes.

Chorion

The outermost membrane surrounding an embryo. In mammals (including humans), it contributes to the formation of the placenta.

Confluence

Number of cells on a dish given as a percent coverage of the dish. 50% confluence means about 50% of the dish is covered. 100 percent confluence means the surface is completely covered by the cells, and no more room is left for the cells to grow as a monolayer.

Ectoderm

Outermost of three layers of embryo, giving rise to epidermis and neural tissue

Endoderm

Innermost of three layers of embryo, giving rise to internal tissues

Epitope

The part of an antigen molecule that an antibody binds to

Feeder layer

In order to culture some cells, particularly at low or clonal density, it is necessary to use a layer of less fastidious cells to condition the medium.

Often the cells of the feeder layer are irradiated or otherwise treated so that they will not proliferate. In some cases the feeder layer may be producing growth factors or cytokines.

Fibroblast

Resident cell of connective tissue, mesodermally derived, that secretes fibrillar procollagen, fibronectin and collagenase.

Human chorionic gonadotropin (hCG)

A hormone produced during pregnancy that is made by the developing placenta after conception, and later by the placental component syncytiotrophoblast. It indirectly stimulates production of progesterone which enriches the uterus and helps it sustain the fetus.

Immunosurgery

A specialized laboratory technique in developmental biology used to selectively isolate the inner cell mass (ICM) from an early-stage embryo (blastocyst). It works by using antibodies and complement proteins to chemically destroy the outer protective cell layer (trophectoderm) without harming the inner pluripotent stem cells.

Karyotype

An individual’s collection of chromosomes

Leukemia inhibitory factor (LIF)

An interleukin 6 class cytokine that affects cell growth by inhibiting differentiation. It is a primary component used in stem cell culture to prevent them from differentiating. Normally expressed in the trophectoderm of the developing embryo, with its receptor LIFR expressed throughout the inner cell mass. As embryonic stem cells are derived from the inner cell mass at the blastocyst stage, removing them from the inner cell mass also removes their source of LIF.

Use in stem cell culture:

Removal of LIF pushes stem cells toward differentiation, but they retain their proliferative potential or pluripotency. Therefore LIF is used in mouse embryonic stem cell culture. It is necessary to maintain the stem cells in an undifferentiated state. LIF is not required for culture of human embryonic stem cells.

Mesoderm

Middle of three layers of embryo, giving rise to connective tissue, bone and cartilage, muscle, blood and blood vessels, lymphatics and lymphoid organs, notochord, pleura, pericardium, peritoneum, kidneys, and gonads.

Passage

Passaging a cell line means dividing cells in culture into fresh medium. It gives an approximate number of cell divisions. A cell line that’s at passage 20 has gone through approximately 20 rounds of cell division.

SCID mice

Mice that lack T and B cells, and therefore do not reject non-self tissue or cells.

Stage specific embryonic antigen (SSEA)

Cell surface markers expressed on surface of embryonic cells. Embryos of different stages express different markers and these are hallmarks of developing embryo. Using these markers, a given embryonic cell can be identified to be of a particular stage.

Telomeres

A repeating sequence of double-stranded DNA located at the ends of chromosomes. Greater telomere length is associated with immortalized cell lines such as embryonic stem cells and cancer cells. As cells divide and differentiate throughout the lifespan of an organism or cell line, the telomeres become progressively shortened and lose the ability to maintain their length.

Telomerase

An enzyme that lengthens telomeres by adding on repeating sequences of DNA. It binds to the ends of the telomere via an RNA template that is used for the attachment of a new strand of DNA. It adds several repeated DNA sequences then releases and a second enzyme, DNA Polymerase, attaches the opposite or complementary strand of DNA completing the double stranded extension of the chromosome ends. High levels of telomerase activity are detected in embryonic stem cells and cancer cells, whereas little or no telomerase activity is present in most mature, differentiated cell types. The functions of telomeres and telomerase appear to be important in cell division, normal development, and aging.

Teratocarcinoma / teratoma

Tumor that contains multiple tissue types—for example, tissue derived from endoderm and mesoderm; typically, tissues not found at tumor site

Totipotent

Ability of a cell to differentiate into every single type of tissue, including placental tissue

TRAP Assay (Telomere Repeat Amplification Protocol)

A sensitive, PCR-based laboratory technique used to detect and measure the activity of telomerase.

Trapeze

Highly sensitive in vitro assay system for detecting telomerase activity (commercialized/optimized kit)

Zona pellucida

A glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but not extraneous to it.

This structure binds spermatozoa, and is required to initiate the acrosome reaction.

The zona glycoprotein, ZP3, is responsible for sperm binding, adhering to proteins on the sperm plasma membrane. There is evidence that ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle.