Apoptosis in Embryos Flashcards
What are four differences between apoptosis and necrosis?
- Necrosis involves disruption of organelles whereas apoptosis involves preservation of organelles.
- Necrosis results from lack of oxygen (causing swelling/bursting) whereas apoptosis involves rapid engulfment by neighboring cells to prevent inflammation.
- Necrosis damages neighboring cells.
- Hallmark of apoptosis is DNA fragmentation (chromatin condenses and cell shrinks; plasma and nuclear membrane “blebs”).
What are seven morphological features indicating apoptosis of a cell is occurring?
- Scattered single cells
- Chromatin condensation
- Indentation of nuclear membrane
- Cytoplasmic vacuoles
- Nuclear fragmentation
- Cytoplasmic fragmentation and apoptotic body formation
- Phagocytosis or extraction and secondary necrosis
What are six biochemical features indicating apoptosis of a cell is occurring?
- Separation of cell from neighbors
- Increased endonucleases
- Lamin disassembly
- Caspase activation
- Lamin disassembly
- Expression of surface triggers of phagocytosis
What are six diseases related to decreased rates of apoptosis?
- Cancer (follicular lymphomas, carcinomas with p53 mutations)
- Breast cancer
- Prostate cancer
- Ovarian cancer
- Autoimmune disorders (mixed increase and decrease)
- Viral infections
What are three types of diseases/injuries related to increased rates of apoptosis?
- AIDS (non-infected cells increase apoptosis)
- Neurodenerative disorders (Alzheimer’s, Parkinson’s, Ischemic injury, Toxin-induced liver disease)
- Other conditions (sarcopenia, atrophy, fiber loss, myocyte loss?)
How was apoptosis discovered and in what creature was it originally found?
In nematode worms exactly 1090 somatic cells were formed during development, of which 131 undergo programmed death during embryogenesis and larval development (leaving exactly 959 cells).
What are four important nematode genes involved in apoptosis and why are they important?
- Ced-9 “life gene” prevents apoptosis in certain cells (countering ced-3 and ced-4).
- Caspases ced-3 and ced-4 “death genes” downstream of ced-9 (when they lose function, 131 cells remain living).
- Ced-1 and ced-2 control engulfment of the dead cell by a neighbor.
- Nuc-1 codes for a DNA endonuclease to digest the dead cell nucleus.
What three mammal genes homologous to nematode genes involved in apoptosis have been discovered?
- Human bcl-9 (oncogene - can mutate and cause cancer) homologous to nematode ced-9.
- IL-1 converting enzyme or “ICE” or “caspase-1” in mammals homologous to nematode ced-3.
- Apaf-1 in mammals is a regulator that is homologous to nematode ced-4 (facilitates caspase activation).
What does the earliest event of apoptosis in human embryos appear in the form of?
Membrane changes; apoptotic cell rounds up and separates from neighboring cells.
Cells that are excluded between other blastomeres and the zona pellucida in a human embryo (with poor gap junctions) indicate what?
Apoptosis.
What are two ways to mark early evidence of apoptosis in human embryos?
- Phosphatidylserine in apoptotic cells is not in the inner membrane leaflet like in healthy cells–it’s found on the outside of the cell membrane.
- Anticoagulant protein annexin V binds to phosphatidylserine in apoptotic cells but not in healthy cells with full membrane integrity.
NOTE: Some studies showed no labeling of annexin V (conflict in results).
What is one common feature of pre-implantation human embryos that also may indicate the presence of apoptosis?
- Vacuoles (transluscent cytoplasmic vacuoles in apoptotic cells).
How is chromatin condensation observed in apoptotic embryos?
By staining with DNA dyes.
Chromatin condensation and nuclear fragmentation have been detected in apoptotic embryos of what stages?
Cleavage stage embryos and blastocysts.
What is considered to be the hallmark of apoptosis?
DNA degradation into oligonucleosomal fragments.
