Synaptotagmin-7 is a key factor for bipolar-like behavioral abnormalities in mice

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Bipolar disorder (BD) pathogenesis remains unclear, with animal models often failing to replicate core mood cycling symptoms.
• Induced pluripotent stem cell (iPSC) studies suggest signaling cascade dysfunction is crucial in some BD patients.
• A potential link between behavioral and metabolic abnormalities in BD warrants investigation.

Purpose of the Study:

• To investigate shared molecular mechanisms underlying behavioral and metabolic abnormalities in bipolar disorder.
• To identify genes involved in both synaptic function and insulin signaling that may be implicated in BD.
• To explore the role of synaptotagmin-7 (Syt7) in the pathogenesis of bipolar disorder.

Main Methods:

• Generated neurons from iPSCs of BD patients to analyze gene expression.
• Created mice with hippocampus-specific silencing of candidate genes.
• Generated and analyzed synaptotagmin-7 (Syt7) knockout (KO) mice for behavioral phenotypes.
• Administered clinical BD drugs (olanzapine, lithium) to Syt7 KO mice.
• Measured Syt7 mRNA levels in plasma samples from BD patients and healthy controls.

Main Results:

• Identified synaptotagmin-7 (Syt7) as a candidate risk factor for behavioral abnormalities.
• Syt7 KO mice exhibited nocturnal manic-like and diurnal depressive-like behavioral fluctuations, mimicking BD mood cycling.
• Olanzapine and lithium treatments effectively regulated behavioral abnormalities in Syt7 KO mice.
• BD patients showed significantly attenuated Syt7 mRNA levels in plasma compared to healthy controls.

Conclusions:

• Synaptotagmin-7 (Syt7) is implicated as a key factor in bipolar-like behavioral abnormalities.
• Syt7 deficits may contribute to the pathogenesis of bipolar disorder in a subset of patients.
• Syt7 represents a potential therapeutic target for bipolar disorder.