Abstract
Circadian rhythms, which measure time on a scale of 24 h, are genetically generated by the circadian clock, which plays a crucial role in the regulation of almost every physiological and metabolic process in most organisms. This review gathers all the available information about the circadian clock in a small Malagasy primate, the gray mouse lemur (Microcebus murinus), and reports 30 years data from the historical colony at Brunoy (France). Although the mouse lemur has long been seen as a “primitive” species, its clock displays high phenotypic plasticity, allowing perfect adaptation of its biological rhythms to environmental challenges (seasonality, food availability). The alterations of the circadian timing system in M. murinus during aging show many similarities with those in human aging. Comparisons are drawn with other mammalian species (more specifically, with rodents, other non-human primates and humans) to demonstrate that the gray mouse lemur is a good complementary and alternative model for studying the circadian clock and, more broadly, brain aging and pathologies.
Highlights
Circadian rhythms are biological rhythms that display an endogenous period of approximately 24 h
We focus on the gray mouse lemur (Microcebus murinus, Figure 1), a Malagasy non-human primate belonging to the suborder Strepsirhini and to the Cheirogaleidae family, which includes small, omnivorous primates
The mouse lemur expresses two completely opposite seasonal phenotypes that are a particularity of Cheirogaleus and Microcebus, two Malagasy cheirogaleid primates, and are only determined by photoperiod length and driven by the plastic biological clock (Kobbe et al, 2011)
Summary
Circadian rhythms are biological rhythms that display an endogenous period of approximately 24 h. The endogenous clock controls vital physiological, metabolic and behavioral processes such as hormone secretions, temperature, cellular metabolism and locomotor activity (LA) (Aschoff, 1983; Dvornyk et al, 2003; Lin et al, 2009; Bass and Takahashi, 2010) It synchronizes these functions to light-dark cycles to anticipate the environmental changes associated with the solar day. Both physiological and behavioral parameters show a decrease after 5.5 years (Aujard and Perret, 1998; Némoz-Bertholet and Aujard, 2003), allowing the discrimination of young and aged animals This species is nocturnal, M. murinus is a convenient model for studying chronobiology because its behaviors, biological rhythms and physiological functions depend strongly on photoperiod. Table drawing up a comparison of gray mouse lemur, rodents, human and other primate species’ circadian features, is available in Supplementary Table S1
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