Knockdown of Clock in the ventral tegmental area through RNA interference results in a mixed state of mania and depression-like behavior.
BACKGROUND
Circadian rhythm abnormalities are strongly associated with bipolar disorder; however the role of circadian genes in mood regulation is unclear. Previously, we reported that mice with a mutation in the Clock gene (ClockDelta19) display a behavioral profile that is strikingly similar to bipolar patients in the manic state.


METHODS
Here, we used RNA interference and viral-mediated gene transfer to knock down Clock expression specifically in the ventral tegmental area (VTA) of mice. We then performed a variety of behavioral, molecular, and physiological measures.


RESULTS
We found that knockdown of Clock, specifically in the VTA, results in hyperactivity and a reduction in anxiety-related behavior, which is similar to the phenotype of the ClockDelta19 mice. However, VTA-specific knockdown also results in a substantial increase in depression-like behavior, creating an overall mixed manic state. Surprisingly, VTA knockdown of Clock also altered circadian period and amplitude, suggesting a role for Clock in the VTA in the regulation of circadian rhythms. Furthermore, VTA dopaminergic neurons expressing the Clock short hairpin RNA have increased activity compared with control neurons, and this knockdown alters the expression of multiple ion channels and dopamine-related genes in the VTA that could be responsible for the physiological and behavioral changes in these mice.


CONCLUSIONS
Taken together, these results suggest an important role for Clock in the VTA in the regulation of dopaminergic activity, manic and depressive-like behavior, and circadian rhythms.
Mukherjee
Shibani
S
Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, 75390, USA.
Coque
Laurent
L
Cao
Jun-Li
JL
Kumar
Jaswinder
J
Chakravarty
Sumana
S
Asaithamby
Aroumougame
A
Graham
Ami
A
Gordon
Elizabeth
E
Enwright
John F
JF
DiLeone
Ralph J
RJ
Birnbaum
Shari G
SG
Cooper
Donald C
DC
McClung
Colleen A
CA
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D001007:Anxiety / Q000235:genetics; D001714:Bipolar Disorder / Q000235:genetics*; D056926:CLOCK Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics; D000229:Dependovirus / Q000235:genetics; D003863:Depression / Q000235:genetics; D004298:Dopamine / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques / Q000379:methods; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL / Q000235:genetics; D009474:Neurons / Q000502:physiology; D034622:RNA Interference; D017557:Ventral Tegmental Area / Q000378:metabolism*
D056926:CLOCK Proteins; C538944:Clock protein, mouse; D004298:Dopamine