1. Fus1 KO female mice have olfactory and spatial memory impairments and
sleep/wake cycle disturbances in adult age: a new model for sAD
Coronas-Samano G, Baker KL, Winston JT, Ivanova AV, Verhagen JV.
The John B. Pierce Laboratory, Department of Surgery and Neuroscience, Yale University, New Haven, CT.
Sleep/wake cycle
INTRODUCTION
METHODS
Association
memory
Working
memory
Circadian
rhythm
The majority of current animal models of Alzheimer’s disease (AD) express human genes with mutations associated with familial AD (fAD, early onset AD), even though fAD represents only the 5% of AD cases. In contrast, sporadic AD (sAD, late onset AD) represents 95% of the remaining AD population.
Aging is a high risk factor for developing sAD. Aging is itself related to the production of free radicals and excess of free radicals may contribute to amyloid beta aggregation. Impairments in odor detection and recognition are the earliest symptoms of AD, even before the onset of minor cognitive impairments.
Here, we introduce a Fus1 KO mouse that lacks the mitochondrial protein Fus1/Tusc2 as a novel model for sAD that combines premature aging, chronic oxidative stress due to high ROS production and inadequate anti-oxidant machinery, mitochondrial dysfunction, low grade chronic inflammation and aberrant acute inflammatory response.
To establish sAD relevance, we assessed sAD related deficits in Fus1 KO and WT mice of 4-5 months old, equivalent to the human age when the earliest cognitive and olfactory sAD symptoms arise.
Fus1 KO mice showed oxidative stress (increased levels of ROS, decreased levels of PRDX1), disruption of metabolic homeostasis (decreased levels of LC3-II), PKC (decreased levels of RACK1) and calcium signaling (decreased levels of Calb2) in the olfactory bulb and/or hippocampus.
Fus1 KO showed deficits in olfactory memory (decreased habituation/cross-habituation in the short and long term), olfactory guided navigation memory (inability to reduce the latency to find the hidden cookie), spatial memory (learning impairments when finding the platform in the Morris water maze), and showed more sleep time during the diurnal cycle.
These neurobehavioral deficits of the Fus1 KO mice at this relatively young age are highly relevant to sAD, making them an effective model for research into pharmacological targets in the context of early intervention of sAD.
More details about this research:
Coronas-Samano G., Baker KL, Winston JT, Ivanova AV and Verhagen JV. (2016) Fus1 KO mouse as a model of oxidative stress-mediated sporadic Alzheimer’s disease: circadian disruption and long-term spatial and olfactory memory impairments. Front. Aging Neurosci. 8:268.
Olfactory A
Depression
Anxiety B
SPT
OFT
PAT
MWM
S/W
HaXha
LTM 1 3 4 5 7 9 11 2 8 10 6 NB
STM
HCT
D/L
A. In the sleep/wake test during both cycles, the Fus1 KO spent a larger fraction of time asleep during the dark cycle of the first day and the second day, also in the dark light cycle of the second day.
B. Differences between groups were observed in the total of time asleep in the dark and light cycles across two days.
HaXha: Habituation/Cross-habituation
STM: Short term olfactory memory
LTM: Long term olfactory memory
HCT: Hidden cookie test
SPT: Sucrose preference test
NB: Nestlet building
OFT: Open field test
D/L: dark/light box
PAT: Passive avoidance test
MWM: Morris water maze
S/A: Sleep/wake cycle
Noldus videotracking throughout
♀Fus1 KO n=19-22
♀WT n=14
Hidden cookie test
Short term olfactory memory
Long term olfactory memory A A A B B C C D C D B *
A. The WT group reduced their urine exploration time by the second trial and 24 hours later compared with the initial exposure. Further, the exploration time between the urine and control was significant.
B. The KO mice explored the urine more than the water control. However, they did not habituate to the stimulus.
C. The exploration time for the urine between groups was not significant.
D. No differences were found on the water exploration time between groups.
A. Only the WT group showed a reduction in the latency to find the hidden cookie over 2 days.
B. The intra-day average in latency on day 2 was significantly lower than on day 1 for the WT group.
C. Fus1 KO did not show differences in the latency over trials and between the intra-day averages from day 1 compared to day 2.
A. The WT mice habituated to the urine odor from the third exposure. They did not show any effect when investigating the water control.
B. Fus1 KO mice habituated to the urine odor on the second trial , but showed cross-habituation by the third trial. The KO did not show effect on the water control.
C. The Fus1 showed higher exploration time during the third exposure compared with the WT.
D. No difference between groups related to the amount of time spend exploring the water stimulus.
Western immunoblot analysis
4 days training session
(hidden platform)
Test day (without platform)
Morris water maze NW NE SW SE A C A B * E * * C D F
Western blot analysis of aging-related proteins in the olfactory bulbs and hippocampi of WT and Fus1 KO mice. Proteins involved in energy homeostasis, antioxidant machinery, autophagy, apoptosis and brain activities are presented as a relative expression or phosphorylation index. B D
CONCLUSIONS
The Fus1 KO mice:
-showed a mild impairment of short-term odor memory.
-did not habituate in the long term olfactory memory task.
-did not improve their odor guided foraging, in contrast to WT mice.
-showed spatial memory deficits
-slept more
-showed alterations in energy homeostasis, antioxidant, autophagy, OKC and calcium signaling proteins in the olfactory bulb and (or) hippocampus.
A. The distance traveled (cm). The WT traveled further than the Fus1 KO.
B. Reduction in velocity (cm/sec) of the Fus1 KO compared to the WT.
C. The latency to the platform zone was higher on the Fus1 KO.
D. The number of times each group crossed into the NW quadrant (in which the platform was submerged during the training session).
E. Heat maps of the swimming paths of two mice. The KO does not show preference for the NW.
F. Average of time spent in the center or periphery of the maze. The Fus1 spent more time in the periphery.
A. The average of swimming velocity (cm/sec) over the training days.
B. The average distance traveled (cm) over the training days.
C. The average latency to find the hidden platform. The Fus1 KO showed higher latency.
D. Only the WT mice reduced the latency over trials (were able to learn the platform zone location).
ACKNOWLEDGEMENTS
Supported by NIH/NIDCD grants R01D and R01DC to J.V. Verhagen and R21DC to A.V. Ivanova.