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BIOL30001 reproductive physiology
Molecular techniques for reproductive research
Hongshi YuResearch AssociateDepartment of ZoologyUniversity of Melbourne
Reading and References
• Green M.R. and Sambrook J. Molecular Cloning: A Laboratory Manual (4th Edition) 2012 Cold Spring Harbor Laboratory Press
• Nicholl D.S.T. An Introduction to Genetic Engineering. 2013 (3rd Edition). Cambridge University Press
• Current protocols | Book series |Wiley• Methods in Cell Biology | Book series | Elsevier• Methods in Molecular Biology | Book series |
Springer
The discovery of the SRY gene
• sex chromosome was discovered in 1921XX, female XY, male
• Y chromosome determines sex was recognized in 1960sXO [Turner] XXY [Klinefelter]
• Mutation, Sequencing and DNA analysis to discover SRY in 1990
“Three men” with XX; “”a woman” with XY
Materials
Genomic DNA
RNA
Protein
cell functions
transcription
translation
Isolation of DNA, RNA and protein
Homogenization Separation
Aqueous phase
Interphase
Organic phase
RNA
DNA
Protein
Precipitation
TRI Reagent® protocol
PCR
• Polymerase Chain Reaction– Amplifies small amounts of DNA so we have
enough to use in tests.– Can assess if a gene present
• eg SRY in males or females• eg is gene present in different species?
Sequence toamplify
5’3’ 5’
3’
Polymerase Chain Reaction (PCR)5’3’ 5’
3’
5’ 3’5’
3’ 5’
5’
Denature to separateAnneal to add primers
Add Taq polymerase
5’ 3’3’ 5’
+ 3’ 5’5’ 3’
Denature to separateAnneal to add primers
5’ 3’
3’ 5’
5’5’
3’ 5’
5’5’ 3’
5’
Add Taq polymerase
5’3’ 5’
3’ 5’5’ 3’
3’ 5’5’
5’ 3’5’
Amplifications of target
Repeat cycles
Cycles Copies1 22 4
4 1610 1,024
15 32,76820 1,048,576
25 33,554,43230 1,073,741,824
Real-time PCR
Assessing gene transcription
• mRNA present?• How much?
• mRNA breaks down quickly
• mRNA cDNA (stable) PCR
mRNA to cDNA: Reverse transcriptase
AAA(A)n
5’-CapmRNA
(dT)12~18 primer anneal
5’-Cap
AAA(A)n
3’ 5’
Reverse transcriptasedNTP
5’-Cap
AAA(A)n
5’
cDNA:mRNA hybrid
Koopman et al (1990) Nature 348(6300):450-452.
Mouse Sry gene expression pattern
RT-PCR Northern blot
When is it expressed?
Where is it expressed?
SRY expression in tammar
Pask, Calatayud, Shaw and Renfree BMC Biol.2010
0
1
2
3
4
-4 -2 0 2 4 6 8
SR
Y m
RN
A e
xpre
ssio
n re
lativ
e to
β-A
ctin birth
days from birth
Testis differentiates
mRNA in situ hybridization
Target RNA
Hybridize withLabeled probe (complementary sequence)
Detect probeReveal cellCell interest
Which cells / tissues express the gene of interest?
Swain et al (1998) Nature 391(6669):761-767.
Whole mount in situ hybridization of Sry gene
male female
SRY expressed in testis, starting at posterior, and not it ovary
Day 25 fetal testis
Tammar SRY in situ hybridisation
Day 2 PY testis
50µm
Meso
50µm
Meso
Setoli Cell
Germ Cell
Sem
inife
rous
tubu
les
Unpublished data, Yu et al
gonadtestis
SRY expressed in Sertoli cells, starting just before onset of differentiation
Tammar SRY in situ
Day 8 PY testis
Day 17 PY testis
Seminiferous tubuleSeminiferous tubules
Sertoli cells
Germ cells
Sertoli cells
Germ cells
Unpublished data, Yu et al
Immunohistochemistry
Hopefully antibody is specific to particular protein
or part of protein
Kashimada and Koopman (2010) Development 137:3921-3930
SRY immunofluorescence
Western blot
Is the antibody detectingjust one band, and of the appropriate size?
quantitation.
Molecular techniques
• PCR to determine if gene is absent or present
• Real-time PCR to quantify how much mRNA present
• mRNA in situ hybridization to show mRNA spatio-temporal
expression
• Northern blot to check RNA sizes, abundance,
and expression
• Immunohistochemistry to localize protein distribution
• Western blot to confirm identity (correct protein size), and
assess abundance
Microscopical analysis: Geoff Shaw
Structure Function
Gross anatomy (macroscopic) tells us what is happening on a gross scale
Microscopical anatomy tells us what is happening on a cellular scale
BIOL30002 Experimental Reproductive Physiology
MicroscopyScale limited by detection method
visible light: wavelength ~ 0.38 – 0.74 μm cannot reveal structures less than about 1 μm
(organelles)
Electron beam: at 10kV 0.00 001 μm(large molecules)
Synchrotron beam: 0.000 001 μm(small molecules)
Atomic force microscopy atomic scale
Types of microscopyLight microscopy
thin sections – paraffin; frozen – 4-10 μmgood for tissue/cellular levelrelatively low costmany ways to stain to highlight things of interest
Confocal microscopylight microscopy with special opticscan get higher resolutioncan build up 3-D structure
Transmission Electron microscopyextremely thin sections (0.05 μm)good for cellular and subcellular levelexpensive machinerymore limited staining options (heavy metals)
Scanning EMshows surface structures
Interpreting Microscope Slides
• 2-D vs
oblique
TS
longitudinal,sagittal
central tangential
oblique
TS
longitudinal,sagittal
central tangential
transverse sectionstransverse sections
histology
• light microscopy vs TEM vs SEM vs confocal• stains
– haematoxylin & eosin - good general purpose– trichrome - good connective tissue discrimination– PAS - sugar containing components– lipophilic dyes - fats and oils– nucleic acid stains– enzyme histochemistry– immunohistochemistry
• Resources: – Kerr (2000) Atlas of Functional Histology– Wheater et al, (1987) Functional Histology
Basic tissue types
• blood
• connective tissue, bone
• fat (adipose tissue)
• muscle
• nerves
• epithelium (epithelia)
epithelia• columnar• cuboidal• squamous• …
uterine luminal epithelium
lumen
Junctions between cells barrier
pituitary
posterior(nerve ends)
anterior
stalk (with blood vessels)
testis
testisepididymis
epididymis
fat
seminiferous tubules
germ cells
lumenblood
ovaryantral follicle
oocyte
Drawings
• Use a SHARP pencil• Tissue outlines – don’t
attempt elaborate shading unless you are very skilled
• Use appropriate size scales
• Don’t spend forever replicating fine detail – just do a bit to show
• Label and annotate with observations and info from reference material
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