Comorbidity between Alzheimer's disease and Major Depression: a behavioural and transcriptomic characterization study in mice

Background: Major Depression (MD) is the most prevalent psychiatric disease in the population and is considered a prodromal stage of the Alzheimer's disease (AD). Despite both diseases having a robust genetic component, the common transcriptomic signature remains unknown. Method: In this regard, we investigated the cognitive and emotional behavioural responses in 3- (n=16 per group) and 6-month-old (n=14 per group) in APP/PSEN1-Tg mutant mice, before ?-amyloid plaques were detected in comparison with non-transgenic mice. Then, we studied the deregulation of genes and pathways in prefrontal cortex, striatum, hippocampus and amygdala of mice at both ages, using transcriptomic and functional data analysis. Results: We found that depressive-like and anxiety-like behaviours, as well as memory impairments are already present at 3-month-old APP/PSEN1-Tg mutant mice together with the deregulation of several genes such as Ciart, Chrm5, Aldh1a, Grin3b, Nr1d1 and Mc4r, and gene sets, including components of the circadian rhythms, electronic transport chain, neuroinflammation and neurotransmission. Then, we extended these results to human data performing GSEA analysis using DisGeNET database, which is specific for diseases and disease-related phenotypes and provides translational support for common deregulated gene sets related to MD and AD. Conclusion: The present study shed further light on the genetic bases shared between MD and AD, illustrating a wide characterization from the behavioural to transcriptomic level in APP/PSEN1-Tg mutant mouse model. These findings could indicate that late MD could be an early manifestation of AD. Overall design: Transcriptomic analysis comparison between APP/PSEN1 and non-transgenic mice in four different brain regions at two different ages.