March 3, 2010
Introduction to development
Gene expression
What cellular functions are needed to carry out development?
What cellular functions are needed to carry out development?
DivideGrowDifferentiateDieMoveAdhereSecreteSignal
Cell biological properties need to be coordinated in space and time
Where is the “program” for development encoded?
Where is the “program” for development encoded?
In the genes
Why do different cells behave differently?
Why do different cells behave differently?
Have different genes?Have different histories?Experience different environments?Chance?Have different gene expression states?
Why do different cells behave differently?
Have different genes?Have different histories?Experience different environments?Chance?Have different gene expression states?
05_10_Genes_info.jpgGenes
Carry out functions
07_37_Protein.produc.jpgSteps in gene expression
08_03_control.steps.jpg
mRNA localization control(tether mRNA to localized proteins)
mRNA turnover control(microRNAs)
Protein turnover control(ubiquitylation and proteasome digestion)
Protein localization control
Regulation of gene expression
08_03_control.steps.jpg
mRNA localization control(tether mRNA to localized proteins)
mRNA turnover control(microRNAs)
Protein turnover control(ubiquitylation and proteasome digestion)
Protein localization control
Regulation of gene expression
coding strand
Regulation of transcription:Parts of a gene
08_13_gene.activation.jpgRegulation of transcription
Transcription factors
05_24_Chromatin pack.jpgNucleosomes (histones) package DNA
05_30_histone tails.jpgHistone modifications affect gene expression
Can affect recruitment of transcription factors to promoter
08_14_chromatin.struc.jpgSome transcription factors affect histones
08_15_Reg. proteins.jpgMultiple transcription factors regulate most genes
08_18_reporter.gene.jpgModularity of the Drosophila even-skipped promoter
Coordinated regulation of multiple genes
Developmental functions
Signals can regulate activity of transcription factors
08_23_cell.memory.jpgMaintaining gene expression states
(a positive feedback loop)
08_24_chromatin.state.jpgMaintaining gene expression states
The histone code also needs to be maintained in daughter cells
Maintaining gene expression states – DNA methylation
How does one monitor which genes a particular cell expresses?
10_14_1_Southrn.blotting.jpgSouthern blot
10_14_2_Southrn.blotting.jpgSouthern blot – DNA on blotNorthern blot – RNA on blot
Northern blot hybridization
(tests one gene at a time)
In situ hybridization of developing flowers with ARF6 probe
From Wildwater et al., Cell 123: 1337-1349 (2005)
Rb-Related expression in Arabidopsis embryosby in situ hybridization
08_18_reporter.gene.jpgPromoter:reporter fusion gene in a transgenic fly embryo
PARF6::ARF6::GUS fusion expression in flowers and ovules
Promoter:protein:reporter fusion gene – reveals protein location
Kosman et al., Science 254: 118-122 (1991)
anti-Snailanti-Twist
Immunolocalization of Snail and Twist proteins in Drosophila embryos
Utility of looking at expression of single genes at a time:
Markers of cell type, differentiation
Visualization of regulatory events
Utility of looking at expression of many genes at once:
Global view of tissue identity
Comparing different tissues or states
Global view of regulatory events