Transcript Model key paper ppt presentation

Give full reference information
Decrease in actin gene expression in
melanoma cells compared to melanocytes
is partly counteracted by BrdU-induced cell
adhesion and antagonized by L-tyrosine
induction of terminal differentiation.
Gomez LA, Rieber MS, Rieber M. 995
Biochem and Biophys Res Comm 216:84-89
Bob Smith and Alicia Applegate
Fall 2011
Purpose of study
What factors are important to the metastasis
of melanoma cells
Key Question
Do the effects of BrdU on cell shape involve
changes to the actin cytoskeleton
Purpose: is the broadest reason for performing the
investigation
Key Question: specific topic of the investigation
Experimental system
• Used normal mouse melanocytes and
B16 melanoma cells
• Cultured
• Studied effects of BruU and/or tyrosine on
actin gene expression
Description of the experimental system is broad and
generally applies to all experiments in the study
Why do researchers
study effects of BrdU?
• Bromodeoxyuridine (BrdU)
• Thymidine nucleoside analog
• Causes mutations
– Induced by UV radiation
• Previous Studies have shown BrdU
– Effects cell adhesion
– Change melanocyte shape and invasiveness
– Potential treatment?
Give enough background information for
your audience to understand key terms
and concepts
Why is L-Tyrosine studied?
• Amino Acid
• Involved in melanin pigment synthesis
- Characteristic of melanocytes
• Induces differentiation of melanoma cells
Supplement with relevant
graphics whenever possible
pdrhealth.com
In the following presentation of different experiments
each section includes the relevant
Methodology, Results, and Interpretations
Avoid unnecessarily using slide titles like “Procedures”
“Results”
“Description”
(especially big ugly titles that take up an
entire slide or a large portion of one)
Introduce each experiment with the
specific question it seeks to answer
It is generally obvious what will be procedures, results etc.
How did BrdU and tyrosine
affect cell attachment?
No need for “Procedures” label – you can simply state
it.
• To cultures of B16 melanoma cells were
added:
– BrdU, L-tyrosine, or BrdU + L-tyrosine
• Treated cultures with trypsin to cause
detachment
Results
1) % attachment
reduced by BrdU
2) Effect inhibited or
reversed by tyrosine
Combine Description of Results
and Interpreations on same slide
(whenever possible)
Explanation:
Tyrosine believed to cause differentiation
of cells, reducing BrdU incorporation
State key results (above), and
point out data in Figure to the
audience as you do so.
Explanations of results are
essential.
How did BrdU and tyrosine
affect actin gene expression?
• BrdU, L-tyrosine or BrdU + L-tyrosine treated B16
• Compared to normal melanocytes
– BrdU, L-tyrosine or BrdU + L-tyrosine
You must be very judicious
in the level of detail included
• After 5 days
with procedures
– total RNA extracted
– Ethidium bromide staining (total RNA)
Include what is necessary
for your audience to
Actin mRNA
understand the results
– Actin mRNA identified with actin probe
– Labeled with P32
You can verbally add
procedural details
– Northern blot performed
– Autoradiaography and densitometry
Results
C = untreated B16
mel = normal melanocytes
Notice that Figures do not have
lengthy legends, as would be
found in original article
You may need to supply a key to
abbreviations (as above), but you
should talk through rest of figure
details
EtBr stained
actin mRNA
Quantification of mRNA expression data
Notice additional
labels added to this
figure for clarity
mel
Northern blot subject to
densitometry
Results
BrdU
-- BrdU increased actin
mRNA
-- Tyr or BrdU + Tyr
similar to control
-- not as much mRNA
as in normal cells
Explanation
• Effect of BrdU is to increased actin mRNA expression in B16
• Reversed again by Tyr induced differentiation
How does UV light exposure effect
actin mRNA expression?
• BrdU treated cells exposed to UV light
• Relative expression of actin mRNA
• GAPDH mRNA used as a control
Results
UV light treatment
Increased the amount
of actin expressed in
the BrdU cells vs. the
BrdU/UV cells.
Explanation
BrdU treated cells are
more sensitive to UV
light induced damage
Overall conclusions
Effect of BrdU
• BrdU affects actin cytoskeleton
• BrdU increases actin gene expression
• UV light affect
Effect of tyrosine
• cell differentiation
• less cell division
• less BrdU incorporation
The overall conclusions
summarize findings for all
experiments
And indicate how those
results relate back to broad
purpose of the article
Thus, changes in gene expression may be
important factor in melanoma metastasis
Critique of Investigation
• Cell attachment methodology and
measurements not clearly explained
• Which type of actin is probed?
• No statistical analysis performed
• Medical significance of UV treatment is unclear
• BrdU is a mutagen; thus seems unlikely
candidate as drug
Critique of the article reflects how well you really understand it.
Avoid shallow critiques like:
“It was confusing”
“Not much background was given about…”
“They did not explain their results…”
Overall Conclusions
• BrdU exposed to UV light decreases actin
expression
• BrdU increases actin expression and
cellular adhesion
• L-tyrosine with BrdU decreases actin
expression
• Conclusions support idea that actin gene
involved in melanoma growth.