March 3, 2010

Introduction to developmentGene 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_02_DNA.jpg

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