2. Presented by Justin P. Smith
AKT/GSK-3 β / β -CATENIN SIGNALLING WITHIN HIPPOCAMPUS AND AMYGDALA REFLECTS GENETICALLY DETERMINED DIFFERENCES IN POSTTRAUMATIC STRESS DISORDER LIKE SYMPTOMS
Presented by Justin P. Smith

3. PTSD Review Traumatic Event
Persistent exaggerated fear responses, avoidance behavior, hyper-arousal, and emotional numbing
.33% of PTSD patients have symptoms for 10+ years despite therapeutic interventions

4. Background Evidence for genetic & environmental factors
β-catenin required in amygdala for normal consolidation, but not acquisition of fear memories*
Suggesting β-catenin modulates synaptic remodeling and stabilization of long-term memory*
*Maguschak & Ressler Nat Neurosci 2008

5. Background cont. Inescapable foot shock- their model of PTSD
Maternal inexperience as potential risk factor
B6N – PTSD susceptible, increased contextual and sensitized fear response
B6JOIa – PTSD resilient
Maguschak and Ressler paper suggests that the transcription factor β-catenin plays a similarly important role in consolidation of fear memories at the level of the basolateral amygdala

6. Mechanism GSK-3 β (glycogen synthase kinase -3 β) controls β-catenin
“Normal” conditions: GSK-3 β phosphorylates (℗) β-catenin to decrease activity
AKT ℗ inactivates GSK-3 β ℗ which stabilizes β-catenin
Stabilized levels of β-catenin then mediates gene transcription

7. Wada 2009

8. Why-What
Evidence for role of kinases and transcription factors, little info about activity changes that last more than a couple of hours (exempli gratia PTSD)
This study looks at AKT/GSK-3 β / β -catenin-cascades within the dorsal hippocampus and basolateral amygdala (BLA) in the long-term aftermath of exposure to an inescapable foot shock

9. Animals Male B6N (N) & B6JOIa (J) mice Embryo-transfers
(Donor/Recipients)
(Embryo/Mom)
B6N donors and B6N recipients (N/N), B6N donors and B6JOla recipients (N/J), B6JOla donors and B6JOla recipients (J/J), B6JOla donors and B6N recipients (J/N)

10. Experiments Experiment 1. Male B6N Experiment 2. Male B6N and B6JOla
Groups: foot shock, unshocked (cage control).
tested for sensitized and contextual fear (28 days after shock) before brain removal (42 days after shock)
Experiment 2. Male B6N and B6JOla
Within-strain (N/N, J/J) and between-strain (N/J, J/N) embryo transfers
Shocked, tested for sensitized and contextual fear (28 days after shock), Western blot analysis hippocampus and amygdala
Limited yield of the transfers did not allow inclusion of unshocked controls (no cage controls!)

11. Box plot Maximum Upper quartile (75th percentile) Median
Dr. John Tukey
Maximum
Upper quartile (75th percentile)
Median
Lower quartile (25th percentile)
Minimum

12. Fig 1. B6N mice purchased from commercial breeders
Fig 1. B6N mice purchased from commercial breeders. Western blot, shock/no shock. Relative to mean levels of non-shock controls.
PTSD-like symptoms coincide with changes
in kinase and transcription factor activities
at remote time points
Amygdala

13. -within-strain (N/N, J/J) -between-strain (N/J, J/N) -N- PTSD mice
Fig.2 Fear behavior in mice originating from commercial breeders or within-strain and between-strain embryo transfers. 28 days after shock.
Back in box (Morning)
Embryo transfers
-within-strain (N/N, J/J)
-between-strain (N/J, J/N)
-N- PTSD mice
-J- Resilient mice
Maternal effect
Tone (Afternoon)
Maternal effect
Maternal effect

14. Fig 3
Fig 4
Embryo
Mother
Donor
Effect

15. Fig 5
Fig 6
Recipient
Effect

16. Fig. 7. Changes in signaling cascades within the hippocampus.

17. Fig. 8. Changes in signaling cascades within the amygdala.

18. Discussion Behavior influenced by both genetic and maternal factors
Molecular level results influenced by embryo genotype, not maternal genotype
Unclear as to when after foot shock changes occur (different waves of kinase activity?)

19. Discussion cont.
It is tempting to speculate that the changes in kinase activity observed in the present study contribute to this phenotype, similarly to the role of PKA/adenylate cyclase 1, NMDA receptor NR1 subunits and CaMKII in development and/or maintenance of remote contextual fear memory.
Are they speculating???

20. Discussion cont. Fig 2C- _/J had higher sensitized fear than _/N
Not statistically secured were separately analyzed (Fig 5C & 6C)
AKT/GSK-3 β /β -catenin pathway
decreased rather than increased GSK-3 β activity within the amygdala coincides with sustained PTSD-like symptoms
the same pathway appears to be regulated in the opposite manner in the amygdala and hippocampus

21. Take home
Identifies lasting changes in AKT/GSK-3 β / β -catenin-cascades in the amygdala and hippocampus
B6N’s showed long-term contextual & sensitized fear
dHippocampus: increased phosphorylated AKT
In BLA:
higher levels of phosphorylated AKT and GSK-3 β
Increased β -catenin levels
Embryo transfer did not alter effect (mother’s genotype had no effect)
Shocked B6N levels of phosphorylated GSK-3 β and β -catenin levels were decreased in dHippocampus but increased in BLA compared to shocked B6JOIa

22. Thank you