So where are these genes expressed in the fruit fly brain?

Antibody staining indicates that the mushroom bodies contain the molecular components that are key for learning:

•Adenylyl cyclase •PKA•cAMP phosphodiesterase

Proposed CS-US and behavior pathways

Fruit fly and sea slugs appear to use common mechanisms

Characterizing different forms of memory using modern molecular genetic techniques

•Fruit flies can learn and remember odor-shock relationships•There are a number of mutant fly strains that have been produced which have a variety of learning and memory related deficits:

•Dunce •Amnesiac•Rutabaga •Radish•Cabbage •Turnip

Transgenic animals: Organisms that have had genes inserted into their genome

•GFP: an array of different genetically encoded florescence

Red and green great star corals

Their GFPs can be expressed in bacteria

http://www.whitney.ufl.edu/index.htm

GFP-like fluorescent proteins as biotechnology tools

The first application of fluorescent proteins from reef organisms for dual-color in vivo labeling: tracing the cell progeny of left and right dorsal blastomeres in a developing tadpole.

Transgenic animals:

Transgenic animals: Its not just for GFPsExpression of foreign or native genes can be controlled via insertion of

promoter genes• Heat shock promoter (hsp70)

• Can be inserted next to a gene of interest (even another inserted gene)

• Is activated by warming the animal above a threshold temperature

Experiment:1. Associate a hsp70 with a PKA-inhibitor gene in fruit fly2. Heat flies

• PKA-inhibitor expression increases within 1h• Learning is disrupted

1. Associate a hsp70 with a mutated (dysfunctional) PKA-inhibitor gene in fruit fly

2. Heat flies• Dysfunctional PKA-inhibitor expression increases • Learning is NOT disrupted

This tells us SPECIFICALLY that disruption of PKA disrupts learning

Consolidation of memory and the role of gene transcription

Behavioral data: different training regimes produce different amounts of retention •Shock avoidance conditioning:

•Spaced= 10 trials, 15 min between trials•Massed= 10 trials, in rapid succession •1 trial

Results:All produced evidence of strong initial learning but:

•1 trial group showed little retention @ 1 day•Massed group showed little retention @ 4 days•Spaced showed persistent retention even @ 7 days

•These results suggest that spaced training provides an added benefit specifically relating to longer term retention.

Consolidation of memory and the role of gene transcription

Cyclohexamide (CXM) blocks protein synthesis •Eliminated the additive effects of spaced training trials•Does not affect the aspect of memory related to massed trials

Consolidation of memory and the role of gene transcription

CXM does not affect short term memory (or single trial learning)

Does not affect cold-shock or anesthesia-resistant memory (ARM)

Consolidation of memory and the role of gene transcription

ASM vs ARM•ASM:

•Earlier retention phase •ARM:

•Follows ASM •Insensitive (resistant) to cold-shock•Lasts for 4 days•Insensitive to CXM (no protein synthesis required)•Not present in the radish mutant

Consolidation of memory and the role of gene transcription

Massed training produces ONLY ARM Experiment: Radish vs wild-type and spaced vs massed

•Radish mutants display no apparent ARM (which is produced by massed trials)•Thus to parse ARM from CXM consolidation we simply need to mix treatments

Predictions:1. Wild-type spaced:

• ARM+LTM2. Wild-type massed:

• ARM but no LTM3. Wild-type CXM+spaced

• Only ARM4. Radish spaced

• No ARM but LTM5. Radish massed

• No ARM/LTM6. Radish CXM+spaced

• No ARM/LTM

LTM is CREB-dependent:Transgenic HS-promoted negative CREB disrupts:

•Normal CREB •The added effects of spaced trials•All behavioral evidence of LTM

ARM -CREB

ARM+CREB

ARM -CREB

Double mutant radish + negative CREB transgene combinations establish ARM and LTM are functionally distinct processes.

Results of 1-day Posttest

Model describing the phases of learning and memory consolidation