Circadian desynchrony in early life leads to enduring autistic-like behavioral changes in adulthood.

Circadian rhythm regulates a variety of biological processes in almost all living organisms. Modern lifestyles, e.g. transmeridian travel, night shift, light at night, etc., frequently disrupt people's regular sleep-wake cycles and create a misalignment (circadian desynchrony) between the natural environment and the endogenous body clock, and between different circadian oscillators within the body. The long-term consequences of circadian desynchrony on neurodevelopment and adult behavior remain elusive. Increasing clinical evidence supports a correlation between the disruption of the circadian system and neurodevelopmental disorders, such as autism spectrum disorders. Despite clinical correlations, experimental evidence is yet to establish a link between circadian disturbance in early life and adult behavioral changes. Here, using a "short day" (SD) mouse model, in which mice were exposed to an 8 h/8 h light/dark (LD) cycle mimicking a "shift work" schedule from gestation day 1 to postnatal day 21, we performed a battery of behavioral tests to assess changes in adult behaviors, including sociability, affective behaviors, stereotypy, cognition and locomotor functions. In contrast to the control mice kept in a 12 h/12 h LD cycle, the adult SD mice entrained to the 8 h/8 h LD cycle, but their free running rhythms remained normal in constant darkness. Interestingly, however, the SD mice displayed diminished sociability, a reduced preference for social novelty, excessive repetitive behaviors, and compromised cognitive functions, all of which resemble characteristics of autism-like behavioral alterations. In addition, the SD mice exhibited significant anxiety- and depressive-like behaviors and impaired motor functions. By western blotting and immunostaining analyses, hyperactivation of the mTORC1/S6K1 pathway was detected in multiple forebrain regions of SD mice. These findings underscore the enduring impact of early-life circadian disruption on neurochemical signaling and behavioral patterns into adulthood, highlighting a pivotal role for circadian regulation in neurodevelopment.