Experimental Cell Biology II: Apoptosis
Apoptosis is the controlled and programmed In further studies, they treated C. elegans with
cell death. It is used during embryonic mutagenic chemicals to induce random mutations.
development where cells or tissues need to be The goal was to study mutants that showed
removed. slowed-down apoptosis to better investigate the
phenomenon. They looked at the wild-type and
How is apoptosis discovered? mutants under the microscope and found a
In 1972, researchers found “apoptotic bodies” decrease in apoptotic cells in the mutant, so cells
in tissues of several organisms. According to that should have been removed by apoptosis
the researchers, the cells were packaged, during embryogenesis were still present.
shrunk down and taken up for degradation by
macrophages. Apoptosis differs from necrosis, Wild type
because it is programmed and a clean process.
During necrosis there is often spillage of cell
material in the tissue which causes
Mutant
inflammation reactions. Necrosis happens as a
result from injury, such as a papercut. After
this discovery the following questions arose:
• How is apoptosis important for tissue In 1988 they discovered that the gene unc-86
development? coded for a transcription factor that was involved
• How is apoptosis initiated? in apoptosis. They sequenced it and found that the
• Which signal transduction routes are sequence was similar to known transcription
involved? factors. This was an indication that the mutated
To answer these questions, a model organism genes that were involved in apoptosis were also
was used, the nematode C. elegans. This is a important in the transcription of the
simple multi-cellular eukaryote with a fixed developmental genes. This links apoptosis and
number of cells (959), the defined number of development/embryogenesis together.
cells ~100 are removed during embryogenesis.
After 1980 gene identification/sequencing/ Researchers in 1990 discovered that the main
cloning technology was discovered which made initiation of apoptosis was caused by
working with the C. elegans easier. mitochondria. They used lymphocytes from mice
as a model. They stained the cells with two
fluorescent dyes (DiOC) which stains
mitochondria when they
show proton motive force. They
applied flow cytometry and found
that cells with PBS had a high peak
Later they found out that there are certains comparing to normal mitochondria.
cells in C. elegans that change position during Cells with DEX, which is an apoptotic
development. Mutants lead to the change of chemical, showed less fluorescence
this behaviour. This was one of the first and thus, the proton motive force
indications that apoptosis may depend on decreased after the treatment with this chemical.
certain factors. They found that certain There are two hypothesis for this, 1 the proton
mutations in the cell of the second generation motive force went down, but the mitochondria
behave like the parent were still there or 2, the sye could
line. That meant that decrease the number of mitochondria.
the development of To find out which one it is, they labeled
certain cells is sup- antibodies with fluorescent labels that
pressed by this bind to ATP synthase (immuno-
mutation. This lead to fluorescence) and compare it to the
the concept of cells that were treated with the
“programmed cell apoptotic chemical. Both cells had the
death”. same fluorescence, so inducing
apoptosis with DEX does not decrease
the number of mitochondria or ATP synthase.
Apoptosis is the controlled and programmed In further studies, they treated C. elegans with
cell death. It is used during embryonic mutagenic chemicals to induce random mutations.
development where cells or tissues need to be The goal was to study mutants that showed
removed. slowed-down apoptosis to better investigate the
phenomenon. They looked at the wild-type and
How is apoptosis discovered? mutants under the microscope and found a
In 1972, researchers found “apoptotic bodies” decrease in apoptotic cells in the mutant, so cells
in tissues of several organisms. According to that should have been removed by apoptosis
the researchers, the cells were packaged, during embryogenesis were still present.
shrunk down and taken up for degradation by
macrophages. Apoptosis differs from necrosis, Wild type
because it is programmed and a clean process.
During necrosis there is often spillage of cell
material in the tissue which causes
Mutant
inflammation reactions. Necrosis happens as a
result from injury, such as a papercut. After
this discovery the following questions arose:
• How is apoptosis important for tissue In 1988 they discovered that the gene unc-86
development? coded for a transcription factor that was involved
• How is apoptosis initiated? in apoptosis. They sequenced it and found that the
• Which signal transduction routes are sequence was similar to known transcription
involved? factors. This was an indication that the mutated
To answer these questions, a model organism genes that were involved in apoptosis were also
was used, the nematode C. elegans. This is a important in the transcription of the
simple multi-cellular eukaryote with a fixed developmental genes. This links apoptosis and
number of cells (959), the defined number of development/embryogenesis together.
cells ~100 are removed during embryogenesis.
After 1980 gene identification/sequencing/ Researchers in 1990 discovered that the main
cloning technology was discovered which made initiation of apoptosis was caused by
working with the C. elegans easier. mitochondria. They used lymphocytes from mice
as a model. They stained the cells with two
fluorescent dyes (DiOC) which stains
mitochondria when they
show proton motive force. They
applied flow cytometry and found
that cells with PBS had a high peak
Later they found out that there are certains comparing to normal mitochondria.
cells in C. elegans that change position during Cells with DEX, which is an apoptotic
development. Mutants lead to the change of chemical, showed less fluorescence
this behaviour. This was one of the first and thus, the proton motive force
indications that apoptosis may depend on decreased after the treatment with this chemical.
certain factors. They found that certain There are two hypothesis for this, 1 the proton
mutations in the cell of the second generation motive force went down, but the mitochondria
behave like the parent were still there or 2, the sye could
line. That meant that decrease the number of mitochondria.
the development of To find out which one it is, they labeled
certain cells is sup- antibodies with fluorescent labels that
pressed by this bind to ATP synthase (immuno-
mutation. This lead to fluorescence) and compare it to the
the concept of cells that were treated with the
“programmed cell apoptotic chemical. Both cells had the
death”. same fluorescence, so inducing
apoptosis with DEX does not decrease
the number of mitochondria or ATP synthase.
